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Spontaneous intracranial hypotension reflects a disruption of the normal continuous production, circulation, and reabsorption of CSF. Diagnosis requires the recognition of common and uncommon presentations, careful selection and scrutiny of brain and spine imaging, and, frequently, referral to specialist centers.

In this episode, Gordon Smith, MD, FAAN speaks with Jill C. Rau, MD, PhD, author of the article "Clinical Features and Diagnosis of Spontaneous Intracranial Hypotension" in the Continuum® June 2025 Disorders of CSF Dynamics issue.

Dr. Smith is a Continuum® Audio interviewer and a professor and chair of neurology at Kenneth and Dianne Wright Distinguished Chair in Clinical and Translational Research at Virginia Commonwealth University in Richmond, Virginia.

Dr. Rau is an assistant professor of clinical neurology at the University of Arizona, School of Medicine-Phoenix in Phoenix, Arizona.

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Full episode transcript available here

Interview with Jill Rau, MD

Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum. Thank you for listening to Continuum Audio. Be sure to visit the links in the episode notes for information about earning CME, subscribing to the journal, and exclusive access to interviews not featured on the podcast.

Dr Smith: This is Dr Gordon Smith. Today I'm interviewing Dr Jill Rau about her article on clinical features and diagnosis of spontaneous intracranial hypotension, which she wrote with Dr Jeremy Cutsworth-Gregory from the Mayo Clinic. This article appears in the 2025 Continuum issue on disorders of CSF dynamics. I'm really excited to welcome you to the Continuum podcast. Maybe you can start by just telling our listeners a little bit about yourself?

Dr Rau: Hi, thanks for having me. I'm really honored to be here, and I really enjoyed writing the paper with Dr Cutsforth-Gregory. I hope you guys enjoy it. I am the director of headache medicine at the Baba Bay Neuroscience Institute at Honor Health in Scottsdale, Arizona. I'm also currently the chair of the special interest group in CSF Dynamics at the American Headache Society, and I've had a special interest in this field since I first watched Dr Linda Gray speak at a conference where she talked about spinal CSF leaks and their different presentations. And they were so different than what I had been taught in residency. They're not just the post-LP headache. They have such a wide variety of presentations and how devastating they can be, and how much impact there is on someone's life when you find it and fix it. And I've been super interested in the field and involved in research since that time. And, yeah. Love it.

Dr Smith: Well, thanks for sharing your story. And as I reflected on our conversation ahead of time and have been thinking about this issue… this is a cool topic, and every time I read one of these manuscripts and have the opportunity to speak with one of the authors, I learn a ton, because this was something that wasn't even on the radar when I trained back in the 1800's. So, really looking forward to the conversation. I wonder if you could really briefly just summarize or remind for everyone the normal physiology about CSF dynamics, you know, production, absorption, and so forth?

Dr Rau: So, the CSF is the fluid that surrounds the brain and the spinal cord, and it's contained by the dura, which is like a canvas or a sac that covers that whole brain and spinal cord. And within the ventricles of the brain, the choroid plexus produce CSF. It's constantly producing and then being reabsorbed by the arachnoid granulations and pushed into the venous space, the cerebral sinuses, venous sinuses. And also some absorption and push into the lymphatics that we've just learned about in the past year. This is kind of new data coming out, so always learning more and more about CSF, but we know that it bathes the brain and the spinal cord, helps keep some buoyancy of the brain as well as pushing nutrients in and pulling out metabolic waste. And it sort of keeps the brain in the state of homeostasis that's happy. And so, when there's a disruption of that flow and the amount of fluid there, that disrupts that, that can cause lots of different symptoms and problems for people.

Dr Smith: One of the many new things I learned is that even the name of this---spontaneous intracranial hypotension---is misleading. And I think this is clinically relevant, as we'll probably get to in a moment, but can you talk a little bit about this? Is this really like a pressure disorder or a volume disorder?

Dr Rau: Yeah. It's almost certainly a volume disorder. We do see in some people that they have low pressure, and it's still part of the diagnostic criteria. But it's there because if you have a low pressure, if you measure an opening pressure and it's below six, if you're measuring it in the spine in the right place, then you have indication that there's low volume. But there's over 50% of people's opening pressure who have a spinal CSF leak, have all the symptoms and can be fixed. So, they have normal pressure in 50% of the people. So, it is an inaccurate term, hypotension, but it was originally discovered because of the thought that it was a low-pressure situation. Some of the findings would suggest low pressure, but ultimately, we are pretty sure it's a low-volume condition.

Dr Smith: Another new thing that I learned that really blew me away is how bad this can be. I did a podcast with Mark Burish about cluster, and I was reminded many cluster patients are pushed to the point of suicidal ideation or committing suicide by the severity of pain. And this sounds like for many patients it's equally severe. Can you maybe paint a picture for our listeners why this is so clinically important?

Dr Rau: A large number of people, even people who are known to have leaks because they've had them before or they've releaked, they have a lot of brain fog and cognitive impairment. They often have severe headaches when they're upright. So, orthostatic headache is probably the number one most common symptom, and those headaches are one of the worst headaches out there. When people stand up, their fluid is not supporting the brain and there's an intense amount of pain. And so, they spend a large portion of their lives horizontal. And there's associated symptoms with that, it's not just headache pain and brain fog. There's neck pain. There's often subsequent disorders that accompany this, like partial orthostatic tachycardia syndrome. We don't know if that's because of deconditioning or an actual sequela of the disease, but it's a frequent comorbidity. We have patients that have extreme dizziness with their symptoms, but many patients are limited to hours, if that, upright per day, combined, total. And so they live their lives, often, just in the dark, lots of photophobia, sensitive to the light, really unable to function. It's also very hard to find and so underrecognized that a lot of patients, especially if they don't have that really clinical symptom of orthostatic headache. So, it's often missed. So, they're just debilitated. You know, treatments don't work because it's not a migraine and it's not a typical headache. It's a mechanical issue as well as a metabolic issue and not found, not a lot helps it.

Dr Smith: So, you know, I have always thought about this as really primarily an orthostatic symptom. I wonder if you can talk about the complexity of this; in particular, kind of how this evolves over time, because it's not quite that simple. And maybe in doing so, you can give our listeners some pearls on when they should be thinking about this disorder?

Dr Rau: A large portion of people do have headache with spinal CSF leak, in particular, spontaneous intracranial hypertension- hypotension, excuse me. And that's something to be thought about, is that there are spontaneous conditions where people have either rupture of the dural sac, or an erosion of the dural sac, or a development of a connection between the dura and the venous system. And that is taking away or allowing CSF to escape. In these instances that patients have spontaneous, there may be a different presentation than if they have, like, a postdural puncture or a chronic traumatic or iatrogenic leak. And we're not sure of that yet, but we're looking into that. Still, the largest presentation is headache, and orthostatic headache is very dominant in the headache realm. But over time, patients' brains can compensate for that lack of CSF and start overproducing---or at least we think that's probably what's happening. And you may see a reduction in the orthostatic symptoms over time, and you may see an improvement in the radiographic findings. So, there are some interesting papers that have been published that look at these changes over time, and we do see that sometimes within that first three to four months; this is the most common time to see that change. Other patients may worsen. You may actually see someone going from looking sort of normal radiographically to developing more of a SIH-type of picture on the brain. And so it's not predictable which patients have gone from orthostatic to improvement or the other way around, both radiographically and clinically.

So, it can be quite difficult to tell. So, for me, if I have a patient that comes to me and they're struggling with headache… if it's orthostatic, very clearly orthostatic: I lay down, I get considerably better or my headache completely goes away. And then when I stand up, it comes on relatively quickly, within an hour. And sometimes it's a worsening-throughout-the-day type of thing, it's lowest in the morning and it worsens throughout the day. These are the times that it's most obvious to think about CSF leak. Especially if that headache onset relatively suddenly, if it onset after a small trauma. Like I've had patients that say, you know, I was doing yoga and I did some twists and I felt kind of a pop. And then I've had this headache that is horrible when I'm upright but is better when I lay down ever since, you know, since that time. That's kind of a very classic presentation of spinal CSF leak or spontaneous intracranial hypotension. Maybe a less common presentation would be someone who comes to you, they've had a persistent headache for a couple years, they kind of remember it started in March of a couple years ago, but they don't know. Maybe it's, you know, it's a little better when they lay down. It may be a little worse when they're up moving around, but so is migraine, and it's a migrainous headache. But they've tried every migraine drug you can think of. Nothing is responding, nothing helps. I'm always looking at patients who are new daily, persistent headaches and patients who aren't responding to meds even if it's not new daily, but they have just barely any response. I will always go back and examine their brain imaging and get full spine to make sure I'm not missing. And you can never be 100% sure, but it's always good to consider those patients to the best of your ability, if that- have that in the back of your mind.

Dr Smith: So obviously, goes without saying, this is something people need to have on their radar and think about. And then we'll talk more about diagnostic tools here in a second. But how common is this? If you're a headache doc, you see a lot of patients who have intractable headaches. And how often do you see this in your headache practice? Now you're- this is your thing, so probably a little more than others, but, you know, how common will someone who sees a lot of headache encounter these patients?

Dr Rau: If you see a lot of headache, I mean, currently the thought is it's about 5 in 100,000. That was from a study before we were finding CSF venous fistulas. I think a lot of us think it's more common than that, but it's not super common. We don't have good estimates, but I would guess between 5 and 10 for 100,000 persons, not "persons who come to a tertiary headache clinic with intractable headaches". So, it's hard to gauge how frequent it is, but I would say it's considerably more frequent than we currently think it is. There's still a group of people with orthostatic headaches that we can't find leaks on; that, once you treat other things that can cause or look for other things that can cause orthostatic headaches. So, there may be even still a pathophysiology out there that is still a leak type. Before 2014, we didn't even know about CSF venous fistulas. And now here we are; like, 50% of them are CSF venous fistulas. So, you know, we're still in a huge learning curve right now.

Dr Smith: So, I definitely want to talk about the fistulas in a second. But before moving on, one of the things that I found really interesting is the wide spectrum of clinical phenotype. And we obviously don't have a lot of time to get into all of these different ones, but the one that I was hoping you might talk about---and there's a really great case, and you're on bunch of great case, a great case of this---is brain sagging dementia, not a term I've used before. Can you really briefly just tell our listeners about that, because that's a really interesting story and a great case in your article?

Dr Rau: Yeah. So, brain sag dementia is a… almost like an extreme version of a spontaneous intracranial hypotension. Where there is clear brain sag in the imaging---so that's helpful---but the patients present kind of like a frontotemporal dementia. And when this was first started to being determined, you could turn the patient into Trendelenburg, and sometimes they would improve. There are some practitioners that have introduced fluid into the thecal sac and had temporary improvement. Patching has improvement, then they leak again, sometimes not. But the clinical changes with this have been pretty tremendous to be able to identify that that's a real thing. And in some cases, out of Cedars Sinai, you know, who does a lot of the best research in this, they've had lots of cases where they can't find the leak, but there's clear brain sag that fits with our clinical picture of CSF leaks. So, we're on a learning curve. But yeah, this- they really present. They have disinhibition and cognitive impairment that is very similar to frontotemporal dementia.

Dr Smith: Well, so let's talk about what causes this. You mentioned CSF venous fistulas. I mean, that was reported now just over a decade ago, it's pretty amazing. That accounts for about half of cases, if I understand correctly. What are the other causes? And then we'll talk more about therapy in a minute, but what causes this?

Dr Rau: So, within the realm of spontaneous, you know, we say it's spontaneous. But the spontaneous cases we account for, they can be tears in the dura, which are usually sort of lateral tears in the dura. They can be little places that rubbed a hole, often on an osteophyte from the spine. They can come from these spinal diverticuli. So, I always describe it to my patients like those balls that have mesh and squishy, and you squeeze them in the- through the mesh, there's the extra little bubbling out. If you think of like the dura bubbling, out in some cases, through the framing of the spine, right where the spinal nerve roots come out, they should poke out like wires from the dura. But in many cases they poke out with this extra dura surrounding them, and we call that spinal diverticuli. And if you imagine like the weakening of where you squeeze that, you know, balloon through your fingers, in those locations, that's a very common place to find a CSF leak, and you can imagine that the integrity of the dura there may be less than it would be if it were not being expanded in that direction. And that's often the most common place we see these CSF venous fistulas.

So, you can get minor traumas; like I said, it can be spontaneous, like someone just develops a leak one day. It can be rubbed off, and it can be a development of a connection between the dura and the venous system. There are also iatrogenic causes, but we don't consider them spontaneous. But when you're considering your patients for spontaneous cases, you should consider if they've ever had chronic---even long, long time ago---had any spinal implementation, procedures near the spine, spinal injections, LPs in the past, and especially women who've had epidurals in pregnancy.

Dr Smith: All right, so we see a patient, positional severe headache, who meets the clinical criteria. Next step, MRI scan?

Dr Rau: Yeah. So, the first thing is always to get the brain MRI with and without contrast. Most places will have a SIH or a spinal CSF leak protocol, but you should get contrast because one of the most pathognomonic findings on brain MRI is that smooth diffuse dural enhancement. And that's a really fantastic thing when you find it, because it's kind of a slam dunk. If you find it, then you will see other findings. It almost never exists alone. But if you see that, it's pretty much a spinal CSF leak. But you're also looking for subdural collections, any indication of brain sag. We do have these new algorithms that have come out in the past couple of years that are helpful. They're not exclusionary---you can have negative findings on the brain and still have spinal CSF leak---but the brain MRI is extremely helpful. If it's positive for the findings, it really does help you nudge you in the direction of further investigations and treatments.

Dr Smith: And what about those further investigations and treatments, right? So, you see that there's findings consistent with low pressure, and I guess I should say low intracranial CSF volume. Be that as it may, what's the next step after that?

Dr Rau: Depends on where you are and what you can do. I almost always will get a full spine MRI: so, C spine, T spine, and L spine separately. Not, you know, we don't want it all in one picture, because we want to get the full view. And you want to get that with at least T2 highly- heavily T2 weighted with fat saturation in at least the sagittal and axial planes. It's really helpful if you can get it in the coronal planes, but we have to have- often have good talks with your radiologist to get the coronal plane. I spoke about the spinal diverticuli earlier, and I want to clarify a little bit of something. The coronal image will show those really nicely. It's interesting, but 44% of people have those. So just having the spinal diverticuli does not indicate that you have a leak. But if you have a lot of those, there may be more likelihood of having leak than if you don't have any of those.

So, I will get all of those and I will look at them myself, but I've been looking at them myself for a long time. But a lot of radiologists in community hospitals, especially not- nonneuroradiologists, but even neuroradiologists, this isn't something that's that everybody's been educated about, and we've been learning so much about it so rapidly in the past ten years. It's not easy to do and it's often missed. And if it's not protocoled properly, the fat saturation's not there, it's very hard to see… you can have a leak and not see it. Even the best people, like- it's not always something that's visible. And these CSF venous fistulas that we talked about are never visible on normal MRI imaging. Nonetheless, I will run those because if I can find a leak---and 90% of the ones that are found on MRI imaging are in the thoracic spine. So that's where I spend the most of my time looking. But if you find it, that's another thing to take to your team to say, hey, look, here it is, let's try and do this, or, let's try and do that, or, I've got more evidence. And there are other findings on the spine; not just the leak, but other findings, sometimes, you can see on spine that maybe help you push you towards, yes, this is probably a leak versus not.

Dr Smith: So, your article has a lot of great examples and detail about kind of advanced imaging to, like, find the fistula and what not. I guess I'm thinking most of our listeners are probably practicing in a location where they don't have a team that really focuses on that. So, let's say we do the imaging of the spine and you don't find a clear cause. Is the next step to just do a blood patch? Do you send them to someone like you? What's the practical next step?

Dr Rau: Yeah, if your- regardless of whether you find a leak or not, if your clinical acumen is such that you think this patient has a leak or I've treated them for everything else and it's not working and I have at least a high enough suspicion that I think the risk of getting a patch is lower than the benefit that if they got a patch and it worked, I do send my patients for non-directed blood patches, because it currently does take a long time to get them to a center that can do CT myelograms or any kind of advanced imaging to look for sort of a CSF venous fistula or to get treated outside of a nondirected patch. You know, sometimes nondirected patches are beneficial for patients, and there's some good papers out there that sort of explain the low risks of doing these if done properly versus the extreme benefit for patients when it works. And, I mean, I can't tell you how many people come in and tell me how their lives are changed because they finally got a blood patch. And sometimes it works. And it's life-changing for those people. You know, they go back to work. They can interact with their kids again. Before, they didn't know what was wrong, just had this headache that started. So it's worth doing if you have a strong clinical suspicion.

Dr Smith: Yeah. I mean, that was great. And, you know, to go back to where we began, this is severe. It's something like 60% of patients with this problem have thought about suicide, right? And you take this patient and cure the problem. I feel really empowered having read the article and talked to you today. And so, I'm ready to go out and look for this. Thank you so much for a really engaging conversation. This has been terrific.

Dr Rau: Thank you. I appreciate it. I enjoyed being here.

Dr Smith: Again, today I've been interviewing Dr Jill Rau about her article on clinical features and diagnosis of spontaneous intracranial hypotension---which I guess I should say hypovolemia after having talked to you---which she wrote with Dr Jeremy Cutsworth-Gregory. This article appears in the most recent issue of Continuum on disorders of CSF dynamics. Please be sure to check out Continuum Audio episodes from this really interesting issue and other interesting issues. And thank you, our listeners, again for listening to us today.

Dr Monteith: This is Dr Teshamae Monteith, Associate Editor of Continuum Audio. If you've enjoyed this episode, you'll love the journal, which is full of in-depth and clinically relevant information important for neurology practitioners. Use the link in the episode notes to learn more and subscribe. AAN members, you can get CME for listening to this interview by completing the evaluation at continpub.com/audioCME. Thank you for listening to Continuum Audio.

In this episode, Lyell K. Jones Jr, MD, FAAN, speaks with Jeremy K. Cutsforth-Gregory, MD, FAAN, who served as the guest editor of the June 2025 Disorders of CSF Dynamics issue. They provide a preview of the issue, which publishes on June 2, 2025.

Dr. Jones is the editor-in-chief of Continuum: Lifelong Learning in Neurology® and is a professor of neurology at Mayo Clinic in Rochester, Minnesota.

Dr. Cutsforth-Gregory is an associate professor in the department of neurology at Mayo Clinic in Rochester, Minnesota.

Additional Resources

Read the issue: continuumjournal.com

Subscribe to Continuum®: shop.lww.com/Continuum

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More about the American Academy of Neurology: aan.com

Social Media

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Host: @LyellJ

Guest: @JCGneuro

Full episode transcript available here

Interview with Jeremy Cutsforth-Gregory, MD

Dr Jones: Most of the time when neurologists think about cerebrospinal fluid or CSF, we're thinking about getting a sample so we can test it for biomarkers of infection or inflammation, tumors, more recently neurodegenerative diseases. But there are many patients for whom the CSF isn't a clue to the problem---it is the problem. Today I have the opportunity to interview Dr Jeremy Cutsforth-Gregory, who is the guest editor of our first-ever issue at Continuum on disorders of CSF dynamics.

Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum. Thank you for listening to Continuum Audio. Be sure to visit the links in the episode notes for information about subscribing to the journal, listening to verbatim recordings of the articles, and exclusive access to interviews not featured on the podcast.

Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum: Lifelong Learning in Neurology. Today I'm interviewing Dr Jeremy Cutsforth-Gregory, who recently served as Continuum's guest editor for our latest issue, which covers disorders of CSF dynamics. Dr Cutsforth-Gregory is an associate professor in the Department of Neurology at Mayo Clinic in Rochester, Minnesota, where he's also the director of the Mayo Clinic CSF Dynamics Clinic and an assistant dean of career advising at the Mayo Clinic School of Medicine. Dr Cutsforth-Gregory, welcome, and thank you for joining us today. Why don't you introduce yourself to our listeners?

Dr Cutsforth-Gregory: Thank you so much, Dr Jones. I'm excited to be here and really privileged to have served as the guest editor for this first issue devoted to CSF dynamics. You mentioned my title as director of the CSF Dynamics Clinic, in which we brought together what we think of as the full spectrum of disorders where pressure or flow of the fluid around the central nervous system is off. So, we do CSF leaks, we do intracranial hypertension and normal pressure hydrocephalus, and from that have been able to gain quite a few insights that I'm excited to share with you today.

Dr Jones: Yeah. And I'm really grateful for your time. I'm really grateful for this issue. You know, we all learn about disorders of CSF flow in training, but my impression---and maybe you share it, Dr Cutsforth-Gregory---is that many of these patients fall through the cracks. I think there's probably many reasons for this. I think it's in part because some aspects of this practice are relatively new or they're changing rapidly, or some of the disorders are uncommon. And I think many of these require a high degree of coordination between neurologists and neurosurgeons and radiologists. So we thought a Continuum issue dedicated to this would help close some practice gaps that we're pretty confident are out there. I'm really grateful for your leadership of it, and I think it'll come in handy for junior readers and even our more experienced listeners as well. And let's get right to it. You've had a chance now to review all of the articles in the issue and, you know, the latest in the field. What's the biggest thing that you would like to see change in the care of these patients?

Dr Cutsforth-Gregory: I think you're right that there is often delay in diagnosis, incorrect diagnosis, misdiagnosis, really across the spectrum of the low pressure, high pressure and normal pressure disorders. And that's what I'd like to see change with this issue, is increased awareness of the really myriad presentations that spontaneous intracranial hypotension can have. It's not all orthostatic headache, although that's common. Similarly, idiopathic intracranial hypertension is misdiagnosed in a third or more cases presenting to ophthalmology clinics. So, it's not just papilledema, high pressure in a certain demographic. And I think the article by Dr Aileen Antonio really goes into the details on how to make an accurate diagnosis and not miss these and not mistreat them. And normal pressure hydrocephalus, the pendulum has really swung between whether this is an entity or isn't an entity. It is. It's patients we can help. The imaging findings are surprisingly common, and the disorder is probably somehow both overcalled on CT scans of the head---cannot rule out normal pressure hydrocephalus, clinical correlation required, we've all seen that report---but also missed opportunities to help patients who have treatable gait, cognitive and bladder disorders. So, if we could improve awareness and increase the accuracy of diagnosis on these three disorders, I will say the mission has really been moved forward.

Dr Jones: Thanks for that. Let's start with NPH because again, over my career, I have seen the pendulum swing back and forth in terms of awareness of this disorder and thresholds for diagnosis. What's our latest in terms of the understanding of normal pressure hydrocephalus and how should our listeners think about the approach to diagnosing these patients?

Dr Cutsforth-Gregory: I think we all learn that NPH is dementia, gait disorder and urinary incontinence, and that hasn't changed. A good chunk of these patients, perhaps half or more, don't have the full triad, and you do not have to have the full triad for the diagnosis or to justify intervention with permanent CSF diversion through shunt placement. And so, being open to the diagnosis in a patient with a gate apraxia, which is usually the first leading present presenting change which is a gait disorder. Cognitive changes follow that, bladder comes along the way. So, I think anytime you see someone with an unexplained gait disorder that has apraxic features, short steps, three steps to turn, can look a little Parkinsonian but you don't have other Parkinsonism on exam necessarily, we should be thinking about NPH and ordering a good-quality head imaging to look for those features.

Dr Jones: Yeah, thanks for that point, Jeremy. It does seem like the pendulum has swung back and forth on the diagnosis of this disorder. And I think in many ways it comes down to having good diagnostic biomarkers. A term that I know… I was only made aware of it a few years ago: disproportionately enlarged subarachnoid space hydrocephalus, or DESH. So, tell us a little bit more about that. It's not just about the ventricles, right?

Dr Cutsforth-Gregory: That's exactly right. So, we think hydrocephalus, that means ventriculomegaly, and it does, but DESH, as you said, the mouthful "disproportionately enlarged subarachnoid space hydrocephalus", is basically CSF accumulation around the brain outside the ventricles. Common features would be enlarged Sylvian fissures, focally dilated sulci, and then at the same time, up high on the convexity, tight sulci. So, it's this combination; there's clearly a flow problem where CSF is being trapped in certain areas outside the brain and excluded from others. And that is a common feature. And that alone predicts a positive response to shunt surgery.

Dr Jones: I remember the first time one of my colleagues pointed that out to me on an image, and it just made me wonder how many times I had missed it before that point in my career. But that's the point, is to learn and move forward. One of the common themes, I think, in this practice, one of the common themes in this issue, is the interdisciplinary work that's necessary not just for treating patients with CSF dynamics disorders, but also the diagnosis. We really do have to work carefully and closely with neurosurgeons and with radiologists. And to reflect that we had a pretty diverse group of authors. Moreso, I think, that we usually do for Continuum, given the overlap with the radiology and surgical practice. As you were reviewing these articles, were there any unique or distinctive perspectives that you saw come through?

Dr Cutsforth-Gregory: Absolutely. And I have to say, I'm so proud of the diverse author panel we were able to put together: as you said, including clinicians, but also neuroradiologists; neurosurgeons, both adult and pediatric; as well as a couple- an ENT surgeon to talk about those cranial skull base leaks. So, we really brought together what we think is necessary to take care of these patients. As far as unique perspectives here, I would point to the article on diagnosis, surgical treatment, the long term implications of atraumatic cranial CSF leaks. So, these are the patients who present with CSF otorrhea or rhinorrhea and do not have a history of skull base surgery or trauma to explain it. That is often a chronic intracranial hypertension patient who, instead of staying sealed up and building up pressure and presenting with papilledema and headaches, had a leak. And that's relevant because, after it's fixed, that patient needs to come to us in neurology to be monitoring for papilledema, measure lumbar puncture, open pressure. And we've developed that as part of our workflow with our colleagues in neurosurgery and ENT who seal those leaks, because that's a patient who is at high risk of recurrent leak if we don't treat the underlying high pressure disorder. That's a new concept, I think, for many of us. And so, to be able to put that front and center in an article, in an issue for practicing neurologists, I think, is really important, and it's something we haven't been able to do before.

Similarly, the article by Dr Olga Fermo on the treatment of persistent symptoms after normalization of CSF pressure. We've all taken care of patients who had a CSF leak or had hypertension, and it seems like those issues are resolved, and yet they still have headaches. The IIH treatment trial taught us that that happens in perhaps two thirds of patients with IIH. And so, to have Dr Fermo's article on how to help those patients manage the headaches when the CSF disorder seems to have been resolved, I think it's super useful. The last one I would mention is just the final one by Dr Shenandoah Robinson, a pediatric neurosurgeon, talking about child onset hydrocephalus. And so, NPH is the focus of most of those other articles. But the patients who we will take care of as adult neurologists, child neurologists, whose issue really started early on, it's important that we stay involved and how to do that, what things we should be watching for, when to suspect shunt malfunction, it's all covered in Dr Robinson's article, and it's a unique one for this issue.

Dr Jones: It's always interesting to read articles, as a neurologist, that are written by a neurosurgeon because, you know, they have a different perspective, right? T're intervening on the anatomy, and just hearing how they think about these things was illuminating for me. The article on atraumatic cranial skull base CSF leaks, that connection with intracranial hypertension, I was unaware of that. So that was a good learning point for me. And while we're still on the too-high-pressure problem of idiopathic intracranial hypertension, do we have any more insight into what causes that? What's the mechanism of that disease? Do we know any more than we used to?

Dr Cutsforth-Gregory: We know more than we used to. We certainly don't understand all of it. But rather than just a disease of reproductive-age women carrying extra weight, it is now recognized as, really, a metabolic and hormonal-driven condition. And it's relevant because it really highlights new ways to intervene and to treat these patients. The GLP-1 inhibitors may have a role, considering some of the comorbidities like polycystic ovary syndrome and the hormonal connections. The patients who perhaps are female-to-male trans, who then can present with intranial hypertension, and how we can help them without needing to take them off gender confirming hormone therapy, is all really relevant to help us help more patients by having that broader understanding of the cause of disease, that it's not just weight gain/weight loss.

Dr Jones: Fantastic, and very useful to know. Thinking of the other end of the spectrum, right, rather than too much CSF or too much CSF pressure… I know this has been a focus of your academic work, Dr Cutsforth-Gregory. We also have disorders of CSF hypotension where the pressure is too low, and that this is usually reflective of a dural defect. I know in my own practice, sometimes, these are very difficult to find, and that's really- as you said, diagnosis is the first step, but then we have to find the problem and try to direct surgeons where to go to repair it. Do you have any tips for our listeners on how to approach the hunt for the source of CSF leaks?

Dr Cutsforth-Gregory: Absolutely. And I first have to give a call out to my mentor, Dr Bahram Mokri, who is the one who first reported the diffuse sterile enhancement, back in the early 1990s, that marks some, but not all, patients with spontaneous intracranial hypotension. He would also remind me that that's not a good term to call it, even though I just did and I will continue to do it intermittently. Because really, this is an underlying spinal CSF leak or a CSF venous fistula. And the problem is not too-low pressure, which is why hypotension is probably not the best word, but too-low volume. It's intracranial CSF hypovolemia. You know, with the opportunity that Dr Mokri gave me to see some of those patients with him and become intrigued by it, it is the bulk of my clinical practice, my research focus, and the conversations I get to have every single day with neuroradiologists and neurosurgeons. I tell patients, it is a field that is moving incredibly quickly and that, when I see them again in a few months or the next year, for whatever reason, I always joke and I say, I reserve the right to have different recommendations, because it is moving. I finished residency in 2014, which is the year CSF fistulas were first reported. I'm sure they existed before that. So, it was a lack of awareness. And so, look for what you know. Now we know to look for fistulas. You find what you look for; we've developed a number of new myographic techniques to find these things, and they are now the majority of the type of leak that we find. So, it is a patient population where we were missing more than we were hitting ten years ago. And now maybe that's still true, but we're certainly finding a lot more than we used to because of those collaborations.

Dr Jones: Thinking back to DESH, right? Once you're aware that it is something that can be identified, you start to see it more and more. And again, that's how we move the field forward. And again, the CSF venous fistula story is one that I know was relatively new to me and something I learned a lot about reading through the issue. And hopefully our readers and our listeners find some insights and benefits there. This is a rapidly changing field. This may be a hard question to answer, but when you look into the future, what are some of the changes on the horizon in this practice?

Dr Cutsforth-Gregory: See, I'll probably point to the- both diagnosis and treatment. We're recognizing that it's, like I said earlier, not all orthostatic headache, but some of the other manifestations, such as frontotemporal brain sagging syndrome, can be a manifestation of leak. So, suspected leak is the first step. Then you have to look for it. And MRI will change, you know, incrementally, I'm sure; we'll get higher resolution pictures. But the C wave of change is going to be in how to do the myelogram, what imaging modality we use; and the newest kit on the block, if you will, is photon-counting detector CT myelography. That's a different kind of CT scanner than we've been used to over the last few decades. It detects light energy differently. It allows better signal-to-noise ratio, faster acquisition of scans. And so, using that allows us to get thinner slices through the spine to look for leaks and fistulas. I think photon CT will become more widespread because it has applications well beyond neurology and just myelograms.

And so, as those scanners become more available, everyone will get to be better at finding these leaks. And then treatment, I'll highlight a procedure called transvenous paraspinal vein embolization. You know, a CSF venous fistula is an abnormal connection between a nerve root sleeve and a vein. And the CSF is escaping up through the that vein in an unregulated fashion. And historically when those were found, the treatment was to ligate the nerve root. Get rid of the nerve root sleeve, you get rid of the abnormal connection, you get rid of the vein, you stop the leak. And that is effective. A number of studies have shown that. But it's also invasive; it requires a laminectomy and losing a nerve root. You can't do that at every level of the spine, right? This is predominantly thoracic, and only if you're away from the artery of Adamkiewicz. But a few years ago, Dr Walid Benjigchi pioneered a procedure of going through the vein and embolizing it, putting in a liquid embolic agent that seals it off. The nerve root stays attacked. We can do it at every level of the spine, and it's an outpatient, endovascular procedure to fix fistulas. That kind of minimally invasive procedure for fistulas has been a major shift away from the open surgeries. We will, I think, make advances with new catheters and new needles to be able to do some other kind of minimally invasive procedures for the other kinds of leaks. I think that's what we'll be seeing, is less and less invasive procedures on the leak side.

Dr Jones: Great summary there. Thank you. So, it sounds like a combination of hopefully improved clinician awareness, which will improve diagnostic recognition; more sensitive tools like the photon counting CTS; and less invasive definitive therapies, which I think is promising for the field. And you've led a lot of that work, Dr Cutsforth-Gregory, over the last few years. When you see these patients, I'm sure it's rewarding to see patients with previously poorly-recognized or misunderstood symptoms get better. Is that the most rewarding part of this practice for you, or what can you tell me about your experience in the care of these patients?

Dr Cutsforth-Gregory: You know, I'm a curious person. I like to learn. So, I will say it is really rewarding to develop a new technique and put it into practice and see it increase our hit rate on finding these leaks and helping these patients. But nothing beats the feeling of taking a patient who's been stuck in bed or saying that they can't function and they're out of work or out of their family life, and getting that Christmas card or that hug that says they're back. But, you know, we're here to help our patients, and nothing can beat that feeling.

Dr Jones: I think that's a great point to end on. Dr Cutsforth-Gregory, thank you for joining us. Thank you for such a detailed discussion of a broad, diverse topic. I learned a lot today---some things that I wasn't aware of, having read the issue---and hopefully our listeners did, too.

Dr Cutsforth-Gregory: Thank you so much, Dr Jones.

Dr Jones: Again, we've been speaking with Dr Jeremy Cutsforth-Gregory, Guest Editor of Continuum's first-ever issue focusing on CSF dynamics. Please check it out. And thank you to our listeners for joining today.

Dr Monteith: This is Dr Teshamae Monteith, Associate Editor of Continuum Audio. If you've enjoyed this episode, you'll love the journal, which is full of in-depth and clinically relevant information important for neurology practitioners. Use the link in the episode notes to learn more and subscribe. Thank you for listening to Continuum Audio.

As artificial intelligence (AI) tools become increasingly mainstream, they can potentially transform neurology clinical practice by improving patient care and reducing clinician workload. Critically evaluating these AI tools for clinical practice is important for successful implementation.

In this episode, Katie Grouse, MD, FAAN speaks with Peter Hadar, MD, MS, coauthor of the article "Clinical Applications of Artificial Intelligence in Neurology Practice" in the Continuum® April 2025 Neuro-ophthalmology issue.

Dr. Grouse is a Continuum® Audio interviewer and a clinical assistant professor at the University of California San Francisco in San Francisco, California.

Dr. Hadar is an instructor of neurology at Harvard Medical School and an attending physician at the Massachusetts General Hospital in Boston, Massachusetts.

Additional Resources

Read the article: Clinical Applications of Artificial Intelligence in Neurology Practice

Subscribe to Continuum®: shop.lww.com/Continuum

Continuum® Aloud (verbatim audio-book style recordings of articles available only to Continuum® subscribers): continpub.com/Aloud

More about the American Academy of Neurology: aan.com

Social Media

facebook.com/continuumcme

@ContinuumAAN

Guest: @PeterNHadar

Full episode transcript available here

Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum. Thank you for listening to Continuum Audio. Be sure to visit the links in the episode notes for information about subscribing to the journal, listening to verbatim recordings of the articles, and exclusive access to interviews not featured on the podcast.

Dr Grouse: This is Dr Katie Grouse. Today I'm interviewing Dr Peter Hadar about his article on clinical applications of artificial intelligence in neurology practice, which he wrote with Dr Lydia Moura. This article appears in the April 2025 Continuum issue on neuro-ophthalmology. Welcome to the podcast, and please introduce yourself to our audience.

Dr Hadar: Hi, thanks for having me on, Katie. My name is Dr Peter Hadar. I'm currently an instructor over at Mass General Hospital, Harvard Medical School, and I'm excited to talk more about AI and how it's going to change our world, hopefully for the better.

Dr Grouse: We're so excited to have you. The application of AI in clinical practice is such an exciting and rapidly developing topic, and I'm so pleased to have you here to talk about your article, which I found to be absolutely fascinating. To start, I'd like to hear what you hope will be the key takeaway from your article with our listeners.

Dr Hadar: Yeah, thank you. The main point of the article is that AI in medicine is a tool. It's a wonderful tool that we should be cautiously optimistic about. But the important thing is for doctors, providers to be advocates on their behalf and on behalf of their patients for the appropriate use of this tool, because there are promises and pitfalls just with any tool. And I think in the article we detail a couple ways that it can be used in diagnostics, in clinical documentation, in the workflow, all ways that can really help providers. But sometimes the devil is in the details. So, we get into that as well.

Dr Grouse: How did you become interested in AI and its application, specifically in the practice of neurology?

Dr Hadar: When I was a kid, as most neurologists are, I was- I nerded out on a lot of sci-fi books, and I was really into Isaac Asimov and some of his robotics, which kind of talks about the philosophy of AI and how AI will be integrated in the future. As I got into neurology, I started doing research neurology and a lot of folks, if you're familiar with AI and machine learning, statistics can overlap a lot with machine learning. So slowly but surely, I started using statistical methods, machine learning methods, in some of my neurology research and kind of what brought me to where I am today.

Dr Grouse: And thinking about and talking about AI, could you briefly summarize a few important terms that we might be talking about, such as artificial intelligence, generative AI, machine learning, etcetera?

Dr Hadar: It's a little difficult, because some of these terms are nebulous and some of these terms are used in the lay public differently than other folks would use it. But in general, artificial intelligence is kind of the ability of machines or computers to communicate independently. It's similar to as humans would do so. And there are kind of different levels of AI. There's this very hard AI where people are worried about with kind of terminator-full ability to replicate a human, effectively. And there are other forms of narrow AI, which are actually more of what we're talking about today, and where it's very kind of specific, task-based applications of machine learning in which even if it's very complex, the AI tools, the machine learning tools are able to give you a result. And just some other terms, I guess out there. You hear a lot about generative AI. There's a lot of these companies and different algorithms that incorporate generative AI, and that usually kind of creates something, kind of from scratch, based on a lot of data. So, it can create pictures, it can create new text if you just ask it. Other terms that can be used are natural language processing, which is a big part of some of the hospital records. When AI tools read hospital records and can summarize something, if it can translate things. So, it turns human speech into these results that you look for. And I guess other terms like large language models are something that also have come into prominence and they rely a lot on natural language processing, being able to understand human speech, interpret it and come up with the results that you want.

Dr Grouse: Thank you, that's really helpful. Building on that, what are some of the current clinical applications of AI that we may already be using in our neurologic practice and may not even be aware that that's what that is?

Dr Hadar: It depends on which medical record system you use, but a very common one are some of the clinical alerts that people might get, although some of them are pretty basic and they can say, you know, if the sodium is this level, you get an alert. But sometimes they do incorporate fancier machine learning tools to say, here's a red flag. You really should think about contacting the patient about this. And we can talk about it as well. It might encourage burnout with all the different flags. So, it's not a perfect tool. But these sorts of things, typically in the setting of alerts, are the most common use. Sorry, and another one is in folks who do stroke, there are a lot of stroke algorithms with imaging that can help detect where the strokes occur. And that's a heavy machine learning field of image processing, image analysis for rapid detection of stroke.

Dr Grouse: That's really interesting. I think my understanding is that AI has been used specifically for radiology interpretation applications for some time now. Is that right?

Dr Hadar: In some ways. Actually, my background is in neuroimaging analysis, and we've been doing a lot of it. I've been doing it for years. There's still a lot of room to go, but it's really getting there in some ways. My suspicion is that in the coming years, it's going to be similar to how anesthesiologists at one point were actively bagging people in the fifties, and then you develop machines that can kind of do it for you. At some point there's going to be a prelim radiology read that is not just done by the resident or fellow, but is done by the machine. And then another radiologist would double check it and make sure. And I think that's going to happen in our lifetime.

Dr Grouse: Wow, that's absolutely fascinating. What are some potential applications of AI in neurologic practice that may be most high-yield to improve patient care, patient access, and even reduce physician burnout?

Dr Hadar: These are separate sort of questions, but they're all sort of interlinked. I think one of the big aspects of patient care in the last few years, especially with the electronic medical record, is patients have become much more their own advocates and we focus a lot more on patient autonomy. So, they are reaching out to providers outside of appointments. This can kind of lead to physician burnout. You have to answer all these messages through the electronic medical record. And so having, effectively, digital twins of yourself, AI version of yourself, that can answer the questions for the patient on your off times is one of the things that can definitely help with patient care. In terms of access, I think another aspect is having integrated workflows. So, being able to schedule patients efficiently, effectively, where more difficult patients automatically get one-hour appointments, patients who have fewer medical difficulties might get shorter appointments. That's another big improvement. Then finally, in terms of physician burnout, having ambient intelligence where notes can be written on your behalf and you just need to double-check them after allows you to really have a much better relationship with the patients. You can actually talk with them one on one and just focus on kind of the holistic care of the patient. And I think that's- being less of a cog in the machine and focusing on your role as a healer would be actually very helpful with the implementation of some of these AI tools.

Dr Grouse: You mentioned ambient technology and specifically ambient documentation. And certainly, this is an area that I feel a lot of excitement about from many physicians, a lot of anticipation to be able to have access to this technology. And you mentioned already some of the potential benefits. What are some of the potential… the big wins, but then also potential drawbacks of ambient documentation?

Dr Hadar: Just to kind of summarize, the ambient intelligence idea is using kind of an environmental AI system that, without being very obtrusive, just is able to record, able to detect language and process it, usually into notes. So, effectively like an AI scribe that is not actually in the appointment. So, the clear one is that---and I've seen this as well in my practice---it's very difficult to really engage with the patient and truly listen to what they're saying and form that relationship when you're behind a computer and behind a desk. And having that one-on-one interaction where you just focus on the patient, learn everything, and basically someone else takes notes for you is a very helpful component of it.

Some of the drawbacks, though, some of it has to do with the existing technology. It's still not at the stage where it can do everything. It can have errors in writing down the medication, writing down the exact doses. It can't really, at this point, detect some of the apprehensions and some of the nonverbal cues that patients and providers may kind of state. Then there's also the big one where a lot of these are still done by startups and other companies where privacy may be an issue, and a lot of patients may feel very uncomfortable with having ambient intelligence tools introduced into their clinical visit, having a machine basically come between the doctor and the patient. But I think that over time these apprehensions will lessen. A lot of the security will improve and be strengthened, and I think that it's going to be incorporated a lot more into clinical practice.

Dr Grouse: Yeah, well, we'll all be really excited to see how that technology develops. It certainly seems like it has a lot of promise. You mentioned in your article a lot about how AI can be used to improve screening for patients for certain types of conditions, and that certainly seems like an obvious win. But as I was reading the article, I couldn't help but worry that, at least in the short term, these tools could translate into more work for busy neurologists and more demand for access, which is, you know, already, you know, big problems in our field. How can tools like these, such as, like, for instance, the AI fundoscopic screening for vascular cognitive risk factors help without adding to these existing burdens?

Dr Hadar: It's a very good point. And I think it's one of the central points of why we wanted to write the article is that these AI in medicine, it's, it's a tool like any other. And just like when the electronic medical record came into being, a lot of folks thought that this was going to save a lot of time. And you know, some people would say that it actually worsened things in a way. And when you use these diagnostic screening tools, there is an improvement in efficiency, there is an improvement in patient care. But it's important that doctors, patients advocate for this to be value-based and not revenue-based, necessarily. And it doesn't mean that suddenly the appointments are shorter, that now physicians have to see twice as many patients and then patients just have less of a relationship with their provider. So, it's important to just be able to integrate these tools in an appropriate way in which the provider and the patient both benefit.

Dr Grouse: You mentioned earlier about the digital twin. Certainly, in your article you mentioned, you know, that idea along with the idea of the potential of development of virtual chatbot visits or in-person visits with a robot neurologist. And I read all this with equal parts, I think excitement, but horror and and fear. Can you tell us more about what these concepts are, and how far are we from seeing technology like this in our clinics, and maybe even, what are the risks we need to be thinking about with these?

Dr Hadar: Yeah. So, I mean, I definitely think that we will see implementation of some of these tools in our lifetime. I'm not sure if we're going to have a full walking, talking robot doing some of the clinical visits. But I do think that, especially as we start doing a lot more virtual visits, it is very easy to imagine that there will be some sort of video AI doctor that can serve as, effectively, a digital twin of me or someone else, that can see patients and diagnose them. The idea behind the digital twin is that it's kind of like an AI version of yourself. So, while you only see one patient, an AI twin can go and see two or three other patients. They could also, if the patients send you messages, can respond to those messages in a way that you would, based on your training and that sort of thing. So, it allows for the ability to be in multiple places at once.

One of the risks of this is, I guess, overreliance on the technology, where if you just say, we're just going to have a chatbot do everything for us and then not look at the results, you really run the risk of the chatbot just recommending really bad things. And there is training to be had. Maybe in fifty years the chatbot will be at the same level as a physician, but there's still a lot of room for improvement. I personally, I think that my suspicion as to where things will go are for very simple visits in the future and in our lifetime. If someone is having a cold or something like that and it goes to their primary care physician, a chatbot or something like that may be of really beneficial use. And it'll help segment out the different groups of simple diagnosis, simple treatments can be seen by these robots, these AI, these machine learning tools; and some of the more complex ones, at least for the early implementation of this will be seen by more specialized providers like neurologists and subspecialist neurologists too.

Dr Grouse: That certainly seems reasonable, and it does seem that the more simple algorithmic things are always where these technologies will start, but it'll be interesting to see where things can go with more complex areas. Now I wanted to switch gears a little bit in the article- and I thought this was really important because I see it as being certainly one of the bigger drawbacks of AI, is that despite the many benefits of artificial intelligence, AI can unfortunately perpetuate systemic bias. And I'm wondering if you could tell us a little bit more about how this happened?

Dr Hadar: I know I'm beating a dead horse on this, but AI is a tool like any other. And the problem with it is that what you put in is very similar to what you get out. And there's this idea in computer science of "garbage in, garbage out". If you include a lot of data that has a lot of systemic biases already in the data, you're going to get results that perpetuate these things. So, for instance, if in dermatologic practices, if you just had a data set that included people of one skin color or one race and you attempted to train a model that would be able to detect skin cancer lesions, that model may not be easily applicable to people of other races, other ethnicities, other skin colors. And that can be very damaging for care. And it can actually really, really hurt the treatments for a lot of the patients.

So that is one of the, kind of, main components of the systemic biases in AI. The way we mitigate them is by being aware of it and actually implementing, I guess, really hard stops on a lot of these tools before they get into practice. Being sure, did your data set include this breakdown of sex and gender, of race and ethnicity? So that the stuff you have in the AI tool is not just a very narrow, focused application, but can be generalized to a large population, not just of one community, one ethnic group, racial group, one country, but can really be generalized throughout the world for many patients.

Dr Grouse: The first step is being aware of it, and hopefully these models will be built thoughtfully to help mitigate this as much as possible. I wanted to ask as well, another concern about AI is the safety of private data. And I'm wondering, as we're starting to do things like use ambient documentation, AI scribe, and other types of technologies like this, what can we tell our patients who are concerned about the safety of their personal data collected via these programs, particularly when they're being stored or used with outside companies that aren't even in our own electronic medical records system?

Dr Hadar: Yeah, it's a very good question, and I think it's one of the major limitations of the current implementation of AI into clinical practice, because we still don't really have great standards---medical standards, at least---for storing this data, how to analyze this data. And my suspicion is that at some point in the future, we're going to need to have a HIPAA compliance that's going to be updated for the 21st century, that will incorporate the appropriate use of these tools, the appropriate use of these data storage, of data storage beyond just PHI. Because there's a lot more that goes into it. I would say that the important thing for how to implement this, and for patients to be aware of, is being very clear and very open with informed consent. If you're using a company that isn't really transparent about their data security and their data sharing practices, that needs to be clearly stated to the patient. If their data is going to be shared with other people, reanalyzed in a different way, many patients will potentially consider not participating in an AI implementation in clinic. And I think the other key thing is that this should be, at least initially, an opt-in approach as opposed to an opt-out approach. So patients really have- can really decide and have an informed opinion about whether or not they want to participate in the AI implementation in medicine.

Dr Grouse: Well, thank you so much for explaining that. And it does certainly sound like there's a lot of development that's going to happen in that space as we are learning more about this and the use of it becomes more prevalent. Now, I also wanted to ask, another good point that you made in your article---and I don't think comes up enough in this area, but likely will as we're using it more---AI has a cost, and some of that cost is just the high amount of data and computational processing needed to use it, as well as the effects on the environment from all this energy usage. Given this drawback of AI, how can we think about potential costs versus the benefits, the more widespread use of this technology? Or how should we be thinking about it?

Dr Hadar: It's part of a balance of the costs and benefits, effectively, is that AI---and just to kind of name some of them, when you have these larger data centers that are storing all this data, it requires a lot of energy consumption. It requires actually a lot of water to cool these things because they get really hot. So, these are some of the key environmental factors. And at this point, it's not as extreme as it could be, but you can imagine, as the world transitions towards an AI future, these data centers will become huge, massive, require a lot of energy. And as long as we still use a lot of nonrenewable resources to power our world, our civilization, I think this is going to be very difficult. It's going to allow for more carbon in the atmosphere, potentially more climate change.

So, being very clear about using sustainable practices for AI usage, whether it be having data centers specifically use renewable resources, have clear water management guidelines, that sort of thing will allow for AI to grow, but in a sustainable way that doesn't damage our planet. In terms of the financial costs… so, AI is not free. However, on a given computer, if you want to run some basic AI analysis, you can definitely do it on any laptop you have and sometimes even on your phone. But for some of these larger models, kind of the ones that we're talking about in the medical field, it really requires a lot of computational power. And this stuff can be very expensive and can get very expensive very quickly, as anyone who's used any of these web service providers can attest to. So, it's very important to be clear-eyed about problems with implementation because some of these costs can be very prohibitive. You can run thousands and you can quickly rack up a lot of money for some very basic analysis if you want to do it in a very rapid way, in a very effective way.

Dr Grouse: That's a great overview. You know, something that I think we're all going to be having to think about a lot more as we're incorporating these technologies. So, important conversations I hope we're all having, and in our institutions as we're making these decisions. I wanted to ask, certainly, as some of our listeners who may be still in the training process are hearing you talk about this and are really excited about AI and implementation of technology in medicine, what would you recommend to people who want to pursue a career in this area as you have done?

Dr Hadar: So, I think one of the important things for trainees to understand are, there are different ways that they can incorporate AI into their lives going forward as they become more seasoned doctors. There are clinical ways, there are research ways, there are educational ways. A lot of the research ways, I'm one of the researchers, you can definitely incorporate AI. You can learn online. You can learn through books about how to use machine learning tools to do your analysis, and it can be very helpful. But I think one of the things that is lacking is a clinician who can traverse both the AI and patient care fields and be able to introduce AI in a very effective way that really provides value to the patients and improves the care of patients. So that means if a hospital system that a trainee is eventually part of wants to implement ambient technology, it's important for physicians to understand the risks, the benefits, how they may need to adapt to this. And to really advocate and say, just because we have this ambient technology doesn't mean now we see fifty different patients, and then you're stuck with the same issue of a worse patient-provider relationship. One of the reasons I got into medicine was to have that patient-provider interaction to not only be kind of a cog in the hospital machine, but to really take on a role as a healer and a physician. And one of the benefits of these AI tools is that in putting the machine in medicine, you can also put the humanity back in medicine at times. And I think that's a key component that trainees need to take to heart.

Dr Grouse: I really appreciate you going into that, and sounds like there's certainly need. Hoping some of our listeners today will consider careers in pursuing AI and other types of technologies in medicine. I really appreciate you coming to talk with us today. I think this is just such a fascinating topic and an area that everybody's really excited about, and hoping that we'll be seeing more of this in our lives and hopefully improving our clinical practice. Thank you so much for talking to us about your article on AI in clinical neurology. It was a fascinating topic and I learned a lot.

Dr Hadar: Thank you very much. I really appreciate the conversation, and I hope that trainees, physicians, and others will gain a lot and really help our patients through this.

Dr Grouse: So again, today I've been interviewing Dr Peter Hadar about his article on clinical applications of artificial intelligence in neurology practice, which he wrote with Dr Lydia Moura. This article appears in the most recent issue of Continuum on neuro-ophthalmology. Be sure to check out Continuum Audio episodes from this and other issues. And thank you to our listeners for joining today.

Dr Monteith: This is Dr Teshamae Monteith, Associate Editor of Continuum Audio. If you've enjoyed this episode, you'll love the journal, which is full of in-depth and clinically relevant information important for neurology practitioners. Use the link in the episode notes to learn more and subscribe. Thank you for listening to Continuum Audio.

Neuro-ophthalmic deficits significantly impair quality of life by limiting participation in employment, educational, and recreational activities. Low-vision occupational therapy can improve cognition and mental health by helping patients adjust to visual disturbances.

In this episode, Katie Grouse, MD, FAAN, speaks with Sachin Kedar, MD, FAAN, author of the article "Symptomatic Treatment of Neuro-ophthalmic Visual Disturbances" in the Continuum® April 2025 Neuro-ophthalmology issue.

Dr. Grouse is a Continuum® Audio interviewer and a clinical assistant professor at the University of California San Francisco in San Francisco, California.

Dr. Kedar is the Cyrus H Stoner professor of ophthalmology and a professor of neurology at Emory University School of Medicine in Atlanta, Georgia.

Additional Resources

Read the article: Symptomatic Treatment of Neuro-ophthalmic Visual Disturbances

Subscribe to Continuum®: shop.lww.com/Continuum

Earn CME (available only to AAN members): continpub.com/AudioCME

Continuum® Aloud (verbatim audio-book style recordings of articles available only to Continuum® subscribers): continpub.com/Aloud

More about the American Academy of Neurology: aan.com

Social Media

facebook.com/continuumcme

@ContinuumAAN

Guest: @AIIMS1992

Full episode transcript available here

Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum. Thank you for listening to Continuum Audio. Be sure to visit the links in the episode notes for information about earning CME, subscribing to the journal, and exclusive access to interviews not featured on the podcast.

Dr Grouse: This is Dr Katie Grouse. Today I'm interviewing Dr Sachin Kedar about his article on symptomatic treatment of neuro-ophthalmic visual disturbances, which appears in the April 2025 Continuum issue on neuro-ophthalmology. Welcome to the podcast, and please introduce yourself to our audience.

Dr Kedar: Thank you, Katie. This is Sachin Kedar. I'm a neuro-ophthalmologist at Emory University, and I've been doing this for more than fifteen years now. I trained in both neurology and ophthalmology, with a fellowship in neuro-ophthalmology in between. It's a pleasure to be here.

Dr Grouse: Well, we are so happy to have you, and I'm just so excited to be discussing this article with you, which I found to be a real treasure trove of useful clinical information on a topic that many find isn't covered enough in their neurologic training. I strongly recommend all of our listeners who work with patients with visual disturbances to check this out. I wanted to start by asking you what you hope will be the main takeaway from this article for our listeners?

Dr Kedar: The most important takeaway from this article is, just keep vision on your radar when you are evaluating your patients with neurological disorders. Have a list of a few symptoms, do a basic screening vision, and ask patients about how their vision is impacting the quality of life. Things like activities of daily living, hobbies, whether they can cook, dress, ambulate, drive, read, interact with others. It is very important for us to do so because vision can be impacted by a lot of neurological diseases.

Dr Grouse: What in the article do you think would come as the biggest surprise to our listeners?

Dr Kedar: The fact that impairment of vision can magnify and amplify neurological deficits in a lot of what we think of as core neurological disorders should come as a surprise to most of the audience.

Dr Grouse: On that note, I think it's probably helpful if you could remind us about the types of visual disturbances we should be thinking about and screening for in our patients?

Dr Kedar: Patients who have neurological diseases can have a whole host of visual deficits. The simplest ones are deficits of central vision. They can have problems with their visual field. They can have abnormalities of color vision or even contrast sensitivity. A lot of our patients also complain of light sensitivity, eyes feeling tired when they're doing their usual stuff. Some of our patients can have double vision, they can have shaky vision, which leads to their sense of imbalance and maybe a fall risk to them.

Dr Grouse: It's really helpful to think about all the different aspects in which vision can be affected, not just sort of the classic loss of vision. Now, your article also serves as a really important reminder, which you alluded to earlier, about how impactful visual disturbances can be on daily activities. Could you elaborate a little further on this, and particularly the various domains that can be affected when there are visual disturbances present?

Dr Kedar: So, when I look at how visual disturbances affect quality of life, I look at two broad categories. One is activities of basic daily living. These would be things like, are you able to cook? Are you able to ambulate not just in your home, but in your neighborhood? Are you able to drive to your doctor's appointment or to visit with your family? Are you able to dress yourself appropriately? Are you able to visualize the clothing and choose them appropriately? And then the second category is recreational activities. Are you able to read? Are you able to watch television? Are you able to visit the theatre? Are you able to travel? Are you able to participate in group activities, be it with your family or be it with your social group? It is very important for us to ask our patients if they have problems doing any of this because it really can adversely impact the quality of life.

Dr Grouse: I think, certainly with all the things we try to get through talking with our patients, this may not be something that we do spend a lot of time on. So, I think it's it is a good reminder that when we can, being able to ask about these are going to be really important and help us hit on a lot of other things we may not even realize or know to ask about. Now, I was really struck when I was reading your article by the meta-analysis that you had quoted that had showed 47% higher risk of developing dementia among the visually impaired compared to those without visual impairments. Should we be doing more in-depth visual testing on all of our patients with cognitive symptoms?

Dr Kedar: This is actually the most interesting part of this article, and kind of hones in on the importance of vision in neurological disorders. Now I want to clarify that patients with visual disorders, it's not a causative influence on dementia, but if you have a patient with an underlying cognitive disorder, any kind of visual disturbance will significantly make it worse. And this has been shown in several studies, both in the neurologic and in the ophthalmological literature. So, I quoted one of the big meta-analysis over there, but studies have clearly shown that if you have these patients and treat them for their visual deficits, their cognitive indices can actually significantly improve.

To answer your question, I would say a neurologist should include basic vision screening as part of every single evaluation. Now, I know it's a hard thing in, you know, these days when we are literally running on the hamster wheel, but I can assure you that it won't take you more than 2 to 3 minutes of your time to do this basic screening; in fact, you can have one of your assistants included as part of the vital signs assessment. What are these basic screening tools? Measure the visual acuity for both near and distance. Check and see if their visual field's off with the confrontation. Look at their eye movements. Are they able to move their eyes in all directions? Are the eyes stable when they're trying to fixate on a particular point? I think if you can do these basic things, you will have achieved quite a bit.

Dr Grouse: That's really helpful, and thanks for going through some of the standard, or really, you know, solid basic foundation of visual testing we should be thinking about doing. I wanted to move on to some more details about the visual disturbances. You made an excellent point that there are many types of primary ophthalmologic conditions that can cause visual disturbances that we should keep in mind. So maybe not things that we think about a lot on a day-to-day basis, but, you know, are still there and very common. What are some of the most common ones, and when should we be referring them to see an ophthalmologist?

Dr Kedar: So, it depends on the age group of your patient population. Now, the majority of us are adult neurologists, and so the kinds of ophthalmic conditions that we see in this population is going to be different from the pediatric age group. So in the adult population, we might see patients with uncorrected refractive error, presbyopia, patients who have cataracts creep on them, they may have glaucoma, they may have macular degeneration, and these tend to have a slightly higher incidence in the older age group. Now for those of us who are taking care of the younger population, uncorrected refractive errors, strabismus and amblyopia tend to be fairly common causes of visual deprivation in this age group.

What I would encourage all of our neurologists is, make sure that your patients get a basic eye examination at least once a year. Just like you want them to go to their primary care and get an annual maintenance visit, everybody should go to the ophthalmologist or the optometrist and get a basic examination. And, if you're resourceful enough, have your patients bring a copy of that assessment. Whether it is normal or there's some abnormality, it is going to help you in the management.

Dr Grouse: Absolutely. I think that's a great piece of advice, to think of it almost, like, them seeing their primary care doctor, which of course we offer encourage our patients to do, thinking of this as another very important piece of standard primary care. If a patient comes to you reporting difficulty reading due to possible visual disturbances, I'm curious, can you walk us through how you would approach this evaluation?

Dr Kedar: It is not a very common presenting complaint of our patients, even in the neuro-ophthalmology clinic. It's a very rare patient that I see who comes and says, I cannot read or, I have difficulty reading. Most of the patients will come saying, oh, I cannot see. And then you have to dig in to find out, what does that actually mean? What can you not see? Is it a problem in your driving? Is it a problem in your reading? Or is it a problem that occurs at all times? Now you asked me, how do you approach this evaluation? One of the things that all of us, whether we are neurologists, ophthalmologists, or neuro-ophthalmologists, forget to do is to actually have the patient read a paragraph, a sentence, when they are in clinic. And that will give you a lot of ideas about what might actually be going wrong with the patient.

Now, as far as how do I approach this evaluation, I will do a basic screening examination to make sure that their visual acuity is good for both distance and near. A lot of us tend to do either distance or near and we will miss the other parameter. You want to do a basic confrontation visual field to make sure that they do not have any subtle deficits that's impacting their ability to read. Examine the eye movements, do a fundoscopic examination. Now, once you've done this basic screening, as a neurologist, you already have some idea of whether your patient has a lesion along the visual pathways. If you suspect that this is a problem with, say, the visual pathways, ask your ophthalmology colleague to do a formal visual field assessment, and that'll pick up subtle deficits of central visual field.

And lastly, don't forget higher visual function testing or cortical visual function testing. So basically, you're looking for neglect, phenomenon, or simultanagnosia, all of which tends to have an impact on reading. So, in the manuscript I have a schema of how you can approach a patient with reading difficulties, and in that ischemia you will see categories of where things can go wrong during the process of reading. And if you can approach your patient systematically through one of those domains, there's a fairly good chance that you'll be able to pick up a problem.

Dr Grouse: Going a little further on to when you do identify problems with loss of central or peripheral vision, what are some strategies for symptomatic management of these types of visual disturbances?

Dr Kedar: As a neurologist, if you pick up a problem with the vision, you have to send this patient to an eye care provider. The vast majority of people who have visual disturbances, it's from an eye disease. You know, as I alluded to earlier, it can be something as simple as uncorrected refractive error, and that can be fixed easily. A lot of patients in our older age group will have dry eye syndrome, which means they are unable to adequately lubricate the surface of the eye, and as a result, it degrades the quality of their vision. So, they tend to get intermittent episodes of blurred vision, or they tend to get glare. They tend to get various forms of optical aberration. Patients can have cataracts, patients can have glaucoma or macular degeneration. And in all of those instances, the goal is to treat the underlying disease, optimize the vision, and then see what the residual deficit is. By and large, if a patient has a problem with the central vision, then magnification will help them for activities that they perform at near; say, reading.

Now for patients with peripheral vision problem, it's a different entity altogether. Again, once you've identified what the underlying cause is, your first goal is to treat it. So, for example, if your patient has glaucoma, which is affecting peripheral vision, you're going to treat glaucoma to make sure that the visual field does not progress. Now a lot of what happens after that is rehabilitation, and that is always geared towards the specific activities that are affected. Is it reading? Is it ambulating? Is it watching television? Is it driving? And then you can advise as a neurologist, you can advise your occupational therapist or low vision specialist and say, hey, my patient is not able to do this particular activity. Can we help them?

Dr Grouse: Moving on from that, I wanted to also hit on your approach when patients have disorders of ocular motility. What are some things you can do for symptomatic management of that?

Dr Kedar: So, patients with ocular motility can have two separate symptoms. Two, you know, two disabling symptoms, as they would call it. One is double vision and the other is oscillopsia, or the feeling or the visualization of the environment moving in response to your eyes not being able to stay still. Typically, you would see this in nystagmus. Now, let's start with diplopia. Diplopia is a fairly common presenting complaint for neurologists, ophthalmologists, and the neuro-ophthalmologist. The first aspect in the management of diplopia is to differentiate between monocular diplopia and binocular diplopia. Now, monocular diplopia is when the double vision persists even after covering one eye. And that is never a neurological issue. It's almost always an ophthalmic problem, which means the patient will then have to be assessed by an eye care provider to identify what's causing it. And again, refractive error, cataracts, opacities, they can do it.

Now, if the patient is able to see single vision by covering one eye at a time, that's binocular diplopia. Now, in patients with binocular diplopia in the very early stages of the disease, the standard treatment regimen is just monocular occlusion. Cover one eye, the diplopia goes away, and then give it time to improve on its own. So, this is what we would typically do in a patient with, say, acute sixth nerve palsy or fourth nerve palsy or third nerve palsy, maybe expect spontaneous improvement in a few months. Now if the double vision does not improve and persists long term, then the neuro-ophthalmologist or the ophthalmologist will monitor the amount of deviation to see if it fluctuates or if it stays the same. So, what are the treatment options that we have in a patient who absolutely refuses any intervention or is not a candidate for any intervention? Monocular occlusion still remains the viable option. Now, patients who have stable ocular deviation can benefit from using prisms in their glasses, or they can be sent to a surgeon to have a strabismus surgery that can realign their eyes. So, again, a broad answer, but there are options available that we can use.

Dr Grouse: Thank you for that overview. I think that's just really helpful to keep in mind as we're working with these patients and thinking about what their options are. And then finally, I wanted to touch on patients with higher-order vision processing and attention difficulties. What are some strategies for them?

Dr Kedar: These are frankly the most difficult patients that I get to manage in my clinic, simply because there is no effective therapies for managing them. In fact, I think neurologists are far better at this than ophthalmologists or even neuro-ophthalmologists. In patients with attentional disorders, everything boils down to the underlying cause, whether you can treat it or whether it is a slowly progressive, you know, condition, such as from neurodegenerative diseases. And that tailors our goals towards therapy. The primary goal is for safety. A lot of these patients who have visual disturbances from vision processing or attention, they are at accident and fall risk. They have problems with social interactions. And, importantly, there is a gap of understanding of what's going on, not just from their side but also from the family's side. So, I tend to approach these patients from a safety perspective and social interaction perspective.

Now, I have a table listed in the manuscript which will go into details of what the specific things are. But in a nutshell, if your patient has neglect in a specific part of the visual field, they have accident risk on that side. Simple things like walking through a doorway, they can hurt their shoulders or their knees when they bang into the wall on that side because they are unable to judge what's on the other side. Another example would be a patient who has simultanagnosia or a downgaze policy, such as from progressive super nuclear policy. They are unable to look down fast enough, or they are simply unable to look down and appreciate things that are on the floor, and so they can trip and fall. Walking downstairs is also not a huge risk because they are unable to judge distances as they walk down. A lot of what we see in these patients are things that we have to advise occupational therapists and help them improve these safety parameters at home.

Another thing that we often forget is patients can inadvertently cause a social incident when they tend to ignore people on their affected side. So, if there is a family gathering, they tend to consistently ignore a group of people who are sitting on the affected side as opposed to the other side. And I've had more than a few patients who've come and said that, I may have offended some of my friends and family. In those instances, it's always helpful when they are in clinic to demonstrate to the family how this can be awkward and how this can be mitigated. So, having everybody sit on one side is a useful strategy. Advise your family and friends before a gathering that, hey, this may happen. And it is not because it is deliberate, but it's because of the medical condition. And that goes a lot, you know, further in helping our patients come out of social isolation because they are also afraid of offending people, you know. And they can also participate socially, and it can overall improve their quality of life.

Dr Grouse: That's a really helpful tip, and something I'll keep in mind with my patients with neglect and visual field cuts. Thank you so much for coming to talk with us today. Your article has been so helpful, and I urge everybody listening today to take a look.

Dr Kedar: Thank you, Katie. It was wonderful talking to you.

Dr Grouse: I've been interviewing Dr Sachin Kedar about his article on symptomatic treatment of neuro-ophthalmic visual disturbances, which appears in the most recent issue of Continuum on neuro-ophthalmology. Be sure to check out Continuum Audio episodes from this and other issues. And thank you to our listeners for joining today.

Dr Monteith: This is Dr Teshamae Monteith, Associate Editor of Continuum Audio. If you've enjoyed this episode, you'll love the journal, which is full of in-depth and clinically relevant information important for neurology practitioners. Use the link in the episode notes to learn more and subscribe. AAN members, you can get CME for listening to this interview by completing the evaluation at continpub.com/audioCME. Thank you for listening to Continuum Audio.

Dysfunction of the supranuclear ocular motor pathways typically causes highly localizable deficits. With sophisticated neuroimaging, it is critical to better understand structure-function relationships and precisely localize pathology within the brain.

In this episode, Lyell K. Jones Jr, MD, FAAN, speaks with Gregory P. Van Stavern, MD, author of the article "Supranuclear Disorders of Eye Movements" in the Continuum® April 2025 Neuro-ophthalmology issue.

Dr. Jones is the editor-in-chief of Continuum: Lifelong Learning in Neurology® and is a professor of neurology at Mayo Clinic in Rochester, Minnesota.

Dr. Van Stavern is the Robert C. Drews professor of ophthalmology and visual sciences at Washington University in St Louis, Missouri.

Additional Resources

Read the article: Internuclear and Supranuclear Disorders of Eye Movements

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Host: @LyellJ

Full episode transcript available here

Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum. Thank you for listening to Continuum Audio. Be sure to visit the links in the episode notes for information about earning CME, subscribing to the journal, and exclusive access to interviews not featured on the podcast.

Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum: Lifelong Learning in Neurology. Today I'm interviewing Dr Gregory Van Stavern, who recently authored an article on intranuclear and supranuclear disorders of eye movements for our latest Continuum issue on neuro-ophthalmology. Dr Van Stavern is the Robert C Drews professor of ophthalmology and visual sciences at Washington University in Saint Louis. Dr Van Stavern, welcome, and thank you for joining us today. Why don't you introduce yourself to our audience?

Dr Van Stavern: Hi, my name is Gregory Van Stavern. I'm a neuro-ophthalmologist located in Saint Louis, and I'm pleased to be on this show today.

Dr Jones: We appreciate you being here, and obviously, any discussion of the visual system is worthwhile. The visual system is important. It's how most of us and most of our patients navigate the world. Roughly 40% of the brain---you can correct me if I'm wrong---is in some way assigned to our visual system. But it's not just about the sensory experience, right? The afferent visual processing. We also have motor systems of control that align our vision and allow us to accurately direct our vision to visual targets of interest. The circuitry is complex, which I think is intimidating to many of us. It's much easier to see a diagram of that than to describe it on a podcast. But I think this is a good opportunity for us to talk about the ocular motor exam and how it helps us localize lesions and, and better understand diagnoses for certain disorders. So, let's get right to it, Dr Van Stavern. If you had from your article, which is outstanding, a single most important message for our listeners about recognizing or treating patients with ocular motor disorders, what would that message be?

Dr Van Stavern: Well, I think if we can basically zoom out a little to the big picture, I think it really emphasizes the continuing importance of the examination. History as well, but the examination. I was reading an article the other day that was essentially downplaying the importance of the physical examination in the modern era with modern imaging techniques and technology. But for neurology, and especially neuro-ophthalmology, the history and the examination should still drive clinical decision-making. And doing a careful assessment of the ocular motor system should be able to tell you exactly where the lesion is located, because it's very easy to order a brain MRI, but the MRI is, like Forrest Gump might say, it's like a box of chocolates. You never know what you're going to find. You may find a lot of things, but because you've done the history and the examination, you can see if whatever lesion is uncovered by the MRI is the lesion that explains what's going on with the patient. So even today, even with the most modern imaging techniques we have, it is still really important to know what you're looking for. And that's where the oculomotor examination can be very helpful.

Dr Jones: I did not have Forrest Gump on my bingo card today, Dr Van Stavern, but that's a really good analogy, right? If you order the MRI, you don't know what you're going to get. And then- and if you don't have a really well-formed question, then sometimes you get misleading information, right?

Dr Van Stavern: Exactly.

Dr Jones: We'll get into some technology here in a minute, because I think that's relevant for this discussion. I think most of our listeners are going to agree with us that the exam is important in neuro-ophthalmology, and neurology broadly. So, I think you have some sympathetic listeners there. Again, the point of the exam is to localize and then lead to a diagnosis that we can help patients with. When you think about neurologic disorders where the ocular motor exam helps you get to the right diagnosis, obviously disorders of eye movements, but sometimes it's a clue to a broader neurologic syndrome. And you have some nice discussions in your article about the ocular motor clues to Parkinson disease or to progressive supranuclear palsy. Tell us a little more about that. In your practice, which neurologic disorders do you find the ocular motor exam being most helpful?

Dr Van Stavern: Well, just a very brief digression. So, I started off being an ophthalmology resident, and I do two years of ophthalmology and then switch to neurology. And during neurology residency, I was debating which subspecialty to go into, and I realized that neuro-ophthalmology touches every other subspecialty in neurology. And it goes back to the fact that the visual system is so pervasive and widely distributed throughout the brain. So, if you have a neurologic disease, there is a very good chance it is going to affect vision, maybe in a minor way or a major way. That's why careful assessment of the visual system, and particularly the oculomotor system, is really helpful for many neurologic diseases. Neuromuscular disease, obviously, myasthenia gravis and certain myopathies affect the eye movements. Neurodegenerative diseases, in particular Parkinson's disease and parkinsonian conditions, often affect the eye movements. And in particular, when you're trying to differentiate, is this classic Parkinson's disease? Or is this progressive supranuclear palsy? Is it some broad spectrum multisystem atrophy? The differences between the eye movement disorders, even allowing for the fact that there's overlap, can really help point in one direction to the other, and again, prevent unnecessary testing, unnecessary treatment, and so on.

Dr Jones: Very good. And I think, to follow on a thread from that concept with patients who have movement disorders, in my practice, seeing older patients who have a little bit of restriction of vertical gaze is not that uncommon. And it's more common in patients who have idiopathic Parkinson disease. And then we use that part of the exam to help us screen patients for other neurodegenerative syndromes like progressive nuclear- supranuclear palsy. So, do you have any tips for our listeners to- how to look at, maybe, vertical gaze and say, this is maybe a normal age-related degree of change. This is something that might suggest idiopathic Parkinson disease. Or maybe something a little more progressive and sinister like progressive super nuclear palsy?

Dr Van Stavern: Well, I think part of the issue- and it's harder to do this without the visual aspect. One of my colleagues always likes to say for a neurologist, the eye movement exam begins and ends with the neurology benediction, just doing the sign of the cross and checking the eye movements. And that's a good place to start. But I think it's important to remember that all you're looking at is smooth pursuit and range of eye movements, and there's much more to the oculomotor examination than that. There's other aspects of eye movement. Looking at saccades can be really helpful; in particular, classically, saccadic movements are selectively abnormal in PSP versus Parkinson's with progressive supranuclear palsy. Saccades, which are essentially rapid movements of the eyes---up and down, in this case---are going to be affected in downward gaze. So, the patient is going to have more difficulty initiating downward saccades, slower saccades, and less range of movement of saccades in downgaze. Whereas in Parkinson's, it's classically upward eye movements and upgaze. So, I think that's something you won't be able to see if you're just doing, looking at, you know, your classic, look at your eye movements, which are just assessing, smooth pursuit. Looking carefully at the eye movements during fixation can be helpful.

Another aspect of many parkinsonian conditions is saccadic intrusions, where there's quick movements or saccades of the eye that are interrupting fixation. Much, much more common in PSP than in Parkinson's disease. The saccadic intrusions are what we call square-wave jerks because of what they look like. Eye movement recordings are much larger amplitude in PSP and other multisystem atrophy diseases than with Parkinson's. And none of these are perfect differentiators, but the constellation of those findings, a patient with slow downwards saccades, very large amplitude, and frequent saccadic intrusions might point you more towards this being PSP rather than Parkinson's.

Dr Jones: That's a great pearl, thinking about the saccades in addition to the smooth pursuit. So, thank you for that. And you mentioned eye movement measurements. I think it's simultaneously impressive and a little scary that my phone can tell when I'm looking at it within a few degrees of visual attention. So, I imagine there are automated tools to analyze eye movement. Tell us, what's the state of the art there, and what should our listeners be aware of in terms of tools that are available and what they can and can't do?

Dr Van Stavern: Well, I could tell you, I mean, I see neuro-ophthalmic patients with eye movement disorders every day and we do not have any automated tools for eye movement. We have a ton of imaging techniques for imaging the optic nerve and the retina in different ways, but we don't routinely employ eye movement recording devices. The only time we usually do that is in somebody where we suspect they have a central or peripheral vestibular disease and we send them for vestibular testing, for eye movement recordings. There is interest in using- I know, again, sort of another digression, but if you're looking at the HINTS technique, which is described in the chapter to differentiate central from peripheral disease, which is a very easy, useful way to differentiate central from peripheral or peripheral vestibular disease. And again, in the acute setting, is this a stroke or not a stroke? Is it the brain or is it the inner ear? Part of the problem is that if you're deploying this widespread, the people who are doing it may not be sufficiently good enough at doing the test to differentiate, is a positive or negative test?

And that's where some people have started introducing this into the emergency room, these eye movement recording devices, to give the- using, potentially, AI and algorithms to help the emergency room physicians say, all right, this looks like a stroke, we need to admit the patient, get an MRI and so on, versus, this is vestibular neuritis or an inner ear problem, treat them symptomatically, follow up as an outpatient. That has not yet been widely employed. It's a similar way that a lot of institutions are having fundus photography and OCT devices placed in the emergency room to aid the emergency room physician for patients who present with acute vision issues. So, I think that could be the future. It probably would be something that would be AI-assisted or AI-driven. But I can tell you at least at our institution and most of the ones I know of, it is not routinely employed yet.

Dr Jones: So maybe on the horizon, AI kind of facilitated tools for eye movement disorder interpretation, but it's not ready for prime time yet. Is that a fair summary?

Dr Van Stavern: In my opinion, yes.

Dr Jones: Good to know. This has struck me every time I've read about ocular motor anatomy and ocular motor disorders, whether they're supranuclear or intranuclear disorders. The anatomy is complex, the circuitry is very complicated. Which means I learn it and then I forget it and then I relearn it. But some of the anatomy isn't even fully understood yet. This is a very complex real estate in the brainstem. Why do you think the neurophysiology and neuroanatomy is not fully clarified yet? And is there anything on the horizon that might clarify some of this anatomy?

Dr Van Stavern: The very first time I encountered this topic as an ophthalmology resident and later as a neurology resident, I just couldn't understand how anyone could really understand all of the circuitry involved. And there is a lot of circuitry that is involved in us simply having clear, single binocular vision with the afferent and efferent system working in concert. Even in arch. In my chapter, when you look at the anatomy and physiology of the smooth pursuit system or the vertical gaze pathways, there's a lot of, I'll admit it, there's a lot of hand waving and we don't completely understand it. I think a lot of it has to do with, in the old days, a lot of the anatomy was based on lesions, you know, lesion this area either experimentally or clinically. And that's how you would determine, this is what this region of the brain is responsible for.

Although we've gotten more sophisticated with better imaging, with functional connectivity MRI and so on, all of those have limitations. And that's why I still don't think we completely understand all the way this information is integrated and synthesized, and, to get even more big level and esoteric, how this makes its way into our conscious mind. And that has to do with self-awareness and consciousness, which is a whole other kettle of fish. It's just really complicated. I think when I'm at least talking to other neurologists and residents, I try to keep it as simple as possible from a clinical standpoint. If you see someone with an eye movement problem, try to see if you can localize it to which level you're dealing with. Is it a muscle problem? Is it neuromuscular junction? Is it nerve? Is it nucleus? Is it supranuclear? If you can put it at even one of those two levels, you have eliminated huge territories of neurologic real estate, and that will definitely help you target and tailor your workup. So, again, you're not costing the patient in the healthcare system hundreds of thousands of dollars.

Dr Jones: Great points in there. And I think, you know, if we can't get it down to the rostral interstitial nucleus of the medial longitudinal fasciculus, if we can get it to the brainstem, I think that's obviously- that's helpful in its own right. And I imagine, Dr Van Stavern, managing patients with persistent ocular motor disorders is a challenge. We take foveation for granted, right, when we can create these single cortical images. And I imagine it's important for daily function and difficult for patients who lose that ability to maintain their ocular alignment. What are some of the clinical tools that you use in your practice that our listeners should be aware of to help patients that have a persistent supranuclear disorder of ocular movement?

Dr Van Stavern: Well, I think you tailor your treatment to the symptoms, and if it's directly due to underlying condition, obviously you treat the underlying condition. If they have sixth nerve palsy because of a skull base tumor, obviously you treat the skull base tumor. But from a practical standpoint, I think it depends on what the symptom is, what's causing it, and how much it's affecting their quality of life. And everyone is really different. Some patients have higher levels of tolerance for blurred vision and double vision. For things- for patients who have double vision, depending upon the underlying cause we can sometimes use prisms and glasses. Prisms are simply- a lot of people just think prism is this, like, mystical word that means a lot. It's simply just an optical device that bends light. So, it essentially bends light to allow the eyes- basically, the image to fall on the fovea in both eyes. And whether the prisms help or not is partly dependent upon how large the misalignment is. If somebody has a large degree of misalignment, you're not going to fix that with prism. The amount of prism you'd need to bend the light enough to land on the fovea in both eyes would cause so much blur and distortion that it would essentially be a glorified patch. So, for small ranges of misalignment, prisms are often very helpful, that we can paste over glasses or grind into glasses. For larger degrees of misalignment that- let's say it is due to some skull base tumor or brain stem lesion that is not going to get better, then eye muscle surgery is a very effective option. We usually like to give people a long enough period of time to make sure there's no change before proceeding with eye muscle surgery.

Dr Jones: Very helpful. So, prisms will help to a limited extent with misalignment, and then surgery is always an option if it's persistent. That's a good pearl for, I think, our listeners to take away.

Dr Van Stavern: And even in those circumstances, even prisms and eye muscle surgery, the goal is primarily to cause single binocular vision and primary gaze at near. Even in those cases, even with the best results, patients are still going to have double vision, eccentric gaze. For most people, that's not a big issue, but we have had a few patients… I had a couple of patients who were truck drivers who were really bothered by the fact that when they look to the left, let's say because it's a 4th nerve palsy on the right, they have double vision. I had a patient who was a golfer who was really, really unhappy with that. Most people are okay with that, but it all depends upon the individual patient and what they use their vision for.

Dr Jones: That's a great point. There's not enough neurologists in the world. I know for a fact there are not enough neuro-ophthalmologists in the world, right? There's just not many people that have that dual expertise. You mentioned that you started with ophthalmology and then did neurology training. What do you think the pipeline looks like for neuro-ophthalmology? Do you see growing interest in this among trainees, or unchanged? What are your thoughts about that?

Dr Van Stavern: No, that's a continuing discussion we're having within our own field about how to attract more residents into neuro-ophthalmology. And there's been a huge shift. In the past, this was primarily ophthalmology-driven. Most neuro-ophthalmologists were trained in ophthalmology initially before doing a fellowship. The last twenty years, it switched. Now there's an almost 50/50 division between neurologists and ophthalmologists, as more neurologists have become more interested. This is probably a topic more for the ophthalmology equivalent of Continuum. One of the perceptions is this is not a surgical subspecialty, so a lot of ophthalmology residents are disincentivized to pursue it. So, we have tried to change that. You can do neuro-ophthalmology and do eye muscle surgery or general ophthalmology. I think it really depends upon whether you have exposure to a neuro-ophthalmologist during your neurology residency. If you do not have any exposure to neuro-ophthalmology, this field will always seem mysterious, a huge black box, something intimidating, and something that is not appealing to a neurologist. I and most of my colleagues make sure to include neurology residents in our clinic so they at least have exposure to it.

Dr Jones: That's a great point. If you never see it, it's hard to envision yourself in that practice. So, a little bit of a self-fulfilling prophecy. If you don't have neuro-ophthalmologists, it's hard to expose that practice to trainees.

Dr Van Stavern: And we're also trying; I mean, we make sure to include medical students, bring them to our meetings, present research to try to get them interested in this field at a very early stage.

Dr Jones: Dr Van Stavern, great discussion, very helpful. I want to thank you for joining us today. I want to thank you for not just a great podcast, but also just a wonderful article on ocular motor disorders, supranuclear and intranuclear. I learned a lot, and hopefully our listeners did too.

Dr Van Stavern: Well, thanks. I really appreciate doing this. And I love Continuum. I learn something new every time I get another issue.

Dr Jones: Well, thanks for reading it. And I'll tell you as the editor of Continuum, I learn a lot reading these articles. So, it's really a joy to get to read, up to the minute, cutting-edge clinical content for neurology. Again, we've been speaking with Dr Gregory Van Stavern, author of a fantastic article on intranuclear and supranuclear disorders of eye movements in Continuum's most recent issue on neuro-ophthalmology. Please check it out, and thank you to our listeners for joining today.

Dr Monteith: This is Dr Teshamae Monteith, Associate Editor of Continuum Audio. If you've enjoyed this episode, you'll love the journal, which is full of in-depth and clinically relevant information important for neurology practitioners. Use the link in the episode notes to learn more and subscribe. AAN members, you can get CME for listening to this interview by completing the evaluation at continpub.com/audioCME. Thank you for listening to Continuum Audio.

Double vision is a symptom often experienced by patients with neurologic disease. An organized systematic approach to evaluating patients with diplopia needs a foundational understanding of the neuroanatomy and examination of eye movements and ocular alignment.

In this episode, Teshamae Monteith, MD, FAAN, speaks with Devin Mackay, MD, FAAN, author of the article "Approach to Diplopia" in the Continuum® April 2025 Neuro-ophthalmology issue.

Dr. Monteith is the associate editor of Continuum® Audio and an associate professor of clinical neurology at the University of Miami Miller School of Medicine in Miami, Florida.

Dr. Mackay is an associate professor of neurology, ophthalmology, and clinical neurosurgery at Indiana University School of Medicine in Indianapolis, Indiana.

Additional Resources

Read the article: Approach to Diplopia

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Full episode transcript available here

Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum. Thank you for listening to Continuum Audio. Be sure to visit the links in the episode notes for information about earning CME, subscribing to the journal, and exclusive access to interviews not featured on the podcast.

Dr Monteith: This is Dr Teshamae Monteith. Today I'm interviewing Dr Devin Mackay about his article on approach to diplopia, which appears in the April 2025 Continuum issue on neuro-ophthalmology. Welcome to the podcast. How are you?

Dr Mackay: Thank you. It's great to be here.

Dr Monteith: Congratulations on your article.

Dr Mackay: Thank you. I appreciate that.

Dr Monteith: Why don't you start off with introducing yourself to our audience?

Dr Mackay: So, yeah, my name is Devin Mackay. I'm a neuro-ophthalmologist at Indiana University. I did my residency at what was used to be known as the Partners Healthcare Program in Boston, and I did a fellowship in neuro-ophthalmology in Atlanta. And I've been in practice now for about ten years.

Dr Monteith: Oh, wow. Okay. Tell us a little bit about your goals when you were writing the chapter.

Dr Mackay: So, my goal with the approach to double vision was really to demystify double vision. I think double vision is something that as trainees, and even as faculty members and practicing neurologists, we really get intimidated by, I think. And it really helps to have a way to approach it that demystifies it and allows us to localize, just like we do with so many other problems in neurology.

Dr Monteith: I love that, demystification. So why don't you tell us what got you interested in neuro-ophthalmology?

Dr Mackay: Yeah, so neuro-ophthalmology I stumbled on during a rotation during residency. We rotated in different subspecialties of neurology and I did neuro-ophthalmology, and I was just amazed by the exam and how intricate it was, the value of neuroanatomy and localization, the ability to take a complicated problem and kind of approach it as a diagnostic specialist and really unravel the layers of it to make it better. To, you know, figure out what the problem is and make it better.

Dr Monteith: Okay, so you had a calling, clearly.

Dr Mackay: I sure did.

Dr Monteith: You talked about latest developments in neuro-ophthalmology as it relates to diplopia. Why don't you share that with our listeners?

Dr Mackay: Yeah. So, you know, double vision is something that's really been around since the beginning of time, essentially. So that part hasn't really changed a lot, but there are some changes that have happened in how we approach double vision. Probably one of the bigger ones has been, we used to teach that with a, you know, patient over the age of fifty with vascular risk factors who had a cranial nerve palsy of cranial nerves 3, 4, or 6, we used to automatically assume that was a microvascular palsy and we just wouldn't do any more testing and we'd just, you know, wait to see how they did. And it turns out we're missing some patients who have significant pathologies, sometimes, with that approach. And so, we've really shifted our teaching with that to emphasize that it's a lot easier to get an MRI, for example, than it ever has been. And it can be important to make sure we're not missing important pathology in patients, even if they have vascular risk factors over the age of fifty and they just have a cranial nerve 3, 4, or 6 palsy. So that's been one change.

Dr Monteith: Interesting. And why don't you tell us a little bit about the essential points that you want to get across in the article?

Dr Mackay: Yeah. So, I think one is to have a systematic approach to double vision. And a lot of that really revolves around localization. And it even begins with the history that we take from the patients. There's lots of interesting things we can ask about double vision from the patient. For example, the most important thing you can ever ask someone with double vision is, does it go away when you cover either eye? And that really helps us figure out the first question for us as neurologists, which is, is it neurologic or non-neurologic? If it's still there when covering one eye, then it is not neurologic and that's usually a problem for an ophthalmologist to sort out. So that's really number one. And then if it is binocular double vision, then we get into details about, is it horizontal or vertical misalignment? Is it- what makes it better and worse? Is there an associated ptosis or other symptoms? And based on all of that, we can really localize the abnormality with the double vision and get into details about further testing if needed, and so forth. I also love that that approach really reduces our need to rely on things like neuroimaging sometimes when we may not need it, or on other tests. So, I think it really helps us be more efficient and really take better care of patients.

Dr Monteith: So definitely that cover/uncover test, top thing there. Your approach- and you mentioned, are you really getting that history, and are there any other kind of key factors when you're approaching diplopia before getting into some of the details?

Dr Mackay: Yeah, that's a good question. I think also having some basics of how to examine the patient, because double vision is such a challenging thing. A lot of us aren't as familiar with the exam toolkit, so to speak, of what you would do with a patient with double vision. And so, I go over in the article a bit about a Maddox rod, which is a handy little tool that I always keep in my pocket of my lab coat. It allows you to assign a red line to one eye and a light to the other eye, and you can see if the eyes line up or not. And you don't need any other special equipment, you just need the light in that Maddox rod. That really helps us understand a lot about the pattern of misalignment, which is really important for evaluating double vision. So, for example, if someone has a right 6th nerve palsy, I'll expect a horizontal misalignment of the eyes that worsens when the patient looks to the right and improves when they look to the left. And especially if it's a partial palsy, it's not always easy to see that just by looking at their eye movements. And having a way to really measure the eye alignment and figure out, is it worse or better in certain directions, is really essential to localization, I think, in a lot of cases.

Dr Monteith: You caught me. I skipped over that Maddox rod part, even though you spent a lot of time talking about Maddox rods. Kind of skipped over it. So, you're saying that I need one.

Dr Mackay: Everyone needs one. I've converted some of our residents here to carry one with them. And yeah, I realize it's a daunting tool at first, but when you have a patient with double vision and their eye movements look normal, I feel like a lot of neurologists are- kind of, their hands seem like they're tied and they're like, oh, I don't know, I don't know what to do at this point. And if you can get some more details with a simple object like that, it can really change things.

Dr Monteith: So, we've got to talk to the AAN store and make sure that they have enough of these, because now there's going to be lots of…

Dr Mackay: We're going to sell out on Amazon today now because of this podcast.

Dr Monteith: Cyber Monday. So, let's talk about the H pattern. And I didn't know it had the- well, yeah, I guess the official name is "H pattern." In medical school, I mean, that's what I learned. But as a resident and, you know, certainly as an attendee, I see people doing all sorts of things. You're pro-H pattern, but are there other patterns that you also respect?

Dr Mackay: It depends on what you're looking for, I think. The reason I like the H pattern is because you get to look at upgaze and downgaze in two different directions. So, you get to look at upgaze and downgaze when looking to the left, and up- and downgaze when looking to the right. And the reason that matters is because vertical movements of the eyes are actually controlled by different eye muscles depending on whether the eye is adducted toward the nose or abducted away from the nose. And so that's why I love the H pattern, is because it allows you to see that. If you just have them look up and down with just a cross pattern, for example, then you really lose that specificity of looking at both the adduction and abduction aspects. So, it's not wrong to do it another way with, like, the cross, for example, but I just think there are some cases where we'll be missing some information, and sometimes that can actually make a difference.

Dr Monteith: Well, there you have it. Let's talk a little bit about eliciting diplopia during the neurologic exam. What other things should we be looking out for?

Dr Mackay: So, in terms of eliciting diplopia, it really starts with the exam and again, figuring out, are we covering one eye? And figuring out, is this patient still having double vision? It's tricky because sometimes the patients won't even know the answer to that question or they've never done it, they've never covered one eye. And so, if that's the case, I really make them do it in the office with me and it's like, okay, well, are we having double vision right now? Well, great, okay, we are, then we're going to figure this out right now. And we cover one eye and say, is it still double? And that way we can really figure out, are we monocular or binocular? That's always step one. And then if we've established that it's binocular diplopia, then that's when we get into the other details that I mentioned before. And then as far as other things to look for, we're always in tune to other things that are going on in terms of symptoms, like ptosis, or if there's bulbar weakness, or some sensory change or motor problem that seems to be associated with it. Obviously, those will give us clues in the localization as well.

Dr Monteith: And what about ocular malalignment?

Dr Mackay: Yeah. So ocular malalignment, really, the cardinal symptom of that is going to be double vision. And so, if a patient has a misalignment of the eyes and they don't have double vision, then usually that means either we're wrong and they don't have double vision, or they do have double vision and they, you know, haven't said it correctly. Or it could be that the vision is poor in one eye. Sometimes that can happen. Or, some patients were actually born with an eye misalignment and their brain has learned in a way to kind of tune out or not allow the proper development of vision in one eye. And so that's also known as amblyopia, also known as the lazy eye, some people call it. But that finding can also make someone not experience double vision. But otherwise, if someone's had normal vision kind of throughout their life, they'll usually be pretty aware of when they first notice double vision. It'll be an obvious event for them in in most cases.

Dr Monteith: And then the Cogan lid twitch?

Dr Mackay: Oh yes, the Cogan lid twitch. So, the Cogan lid twitch is a feature of myasthenia gravis. The way you elicit it is, you have the patient look down. I'm not sure there's a standardization for how long; you want to have it long enough that you're resting the levator muscle, which is the muscle that pulls the upper lid open. And so, you rest that by having them look down for… I usually do about ten or fifteen seconds. And then I have them look up to looking straight forward. And you want to pay careful attention to their lid position as their eye settles in that straight-forward position. What will happen with a Cogan's lid twitch is, the lid will overshoot, and then it'll come back down and settle into its, kind of, proper position. And what we think is happening there is, it's almost like a little mini "rest test" in a way, where you're resting that muscle just long enough to allow some of the neurotransmission to recover. You get a normal contraction of the muscle, but it fades very quickly and comes back down. And that's experienced as a twitch.

Dr Monteith: So, the patient can feel it. And it's something you can see?

Dr Mackay: Yeah, the patient may not feel it as much. It's usually it's going to be something that the clinician can see if they're looking for it. And I would say that's one of the physical exam findings that can be a hallmark of myasthenia gravis, but certainly not the only one. Some others that we often look for are fatigable ptosis with sustained upgaze. You have the patient look up for a prolonged time and you'll see the lid droop down. So that can be one. Ice pack test is very popular nowadays, and it has pretty good sensitivity and specificity for myasthenia. So, you keep an ice pack over the closed eyes for two minutes and you compare the lid position before and after the ice pack test. And in the vast majority of myasthenia patients, if they have ptosis, the ptosis will have resolved, or at least significantly improved, in those patients. And yet one more sign is, if you find the patient's eye with ptosis and you lift open the eye manually, you'll often see that the other eyelid and the other eye will lower down. So, I'm not sure there's a name for that, but that can be a helpful sign as well.

Dr Monteith: Since you're going through some of these, kind of, key features of different neurologic disease, why don't you tell us about a few others?

Dr Mackay: Yeah, so another I mentioned in the in the article is measurement of levator function, which is really a test of eyelid strength. And so, that can be helpful if we have- someone has ptosis, or we're not sure if they have ptosis and we're trying to evaluate that to see if it's linked to the double vision, because that really changes the differential if ptosis is part of the clinical situation. So, the way that's measured is you have a patient look down as far as they can. And you get out a little ruler---I usually use a millimeter ruler---and I set the zero of the ruler at the upper lid margin when they're looking down. So, I hold the ruler there, and then I ask the patient to look up as far as they can without moving their head. Where the lid position stops of the upper lid is the new point on the ruler. And so, you measure that and see how much that is. And so, a normal patient may have a value somewhere between, I don't know, twelve or thirteen millimeters up to seventeen or eighteen millimeters, probably, in most cases. Especially if there is an asymmetric lid position, if you find that the levator function is symmetric, then it tells you that the muscle is working fine and that the ptosis is not from the muscle. So then the ptosis may be from dehiscence of the lid margin from the muscle. And so, that's a really common cause of ptosis, and that's often age-related or trauma-related. And we can dismiss that as being part of the symptom constellation of double vision. So, it can be really helpful to clarify, is this a muscle problem, which you'd expect with myasthenia or a third nerve palsy, or is this a mechanical problem with the lid, which is non-neurologic and really should be dismissed? So that can be a really helpful exam tool.

Dr Monteith: So, you're just now getting into a little localization. So why don't we kind of start from the most proximal pistol with localization. Give us a little bit of tips. I know they just got to read your article, but give us a few tips.

Dr Mackay: So, in terms of most proximal causes, there are supranuclear causes of ocular misalignment. For example, a skew deviation would qualify as that. Anything that's happening from some deficient input before you get to the cranial nerve nuclei, that we would consider supranuclear. So, we also see that with things like progressive supranuclear policy and certain other conditions. And then there can be lesions of the cranial nerve nuclei themselves. So, cranial nerves 3, 4, and 6 all have nuclei, and if they're lesioned they will cause double vision in specific patterns. And then there's also another subgroup, which is known as intranuclear problems with eye alignment. And so, the most common of that is going to be intranuclear ophthalmoplegia. And so that's very common in patients with demyelinating disorders, or it can also happen with strokes and tumors and other causes.

And then there's infranuclear problems, which are from the cranial nerve nuclei out, and so those would be the cranial nerves themselves. So that's where your microvascular palsies, any tumor pressing on the nerve in those locations can cause palsies like that, any inflammatory disorder along that course. Then as we get more distal, we get into the orbit, we have the neuromuscular junction---so, the connection between the nerve and the muscle. And of course, that's our myasthenia gravis. And there are rare causes, things like botulinum and tick borne illnesses and certain other things that are more rare. And then, of course, we get to the muscle itself, and there can be different muscular dystrophies, different things like myositis or inflammatory disorders of the orbit or even physical trauma. So, if a patient, you know, had a trauma in trapping an extraocular muscle, that can be a localization. So really, anywhere along that pathway you can have double vision. So, I love to approach it from that perspective to help narrow down the diagnostic possibilities.

Dr Monteith: Okay, just like everything?

Dr Mackay: Just like all of the rest of the neurology. See, it's not that scary.

Dr Monteith: You know, and so, yeah. And then you do a lot more than, you know, a few cranial nerves, right?

Dr Mackay: Right. That's right. There's a lot more to double vision than that. I think as neurologists, we get lost if it's not a cranial nerve palsy, we're like, oh, I don't know what this is. And if it's not myasthenia, not a cranial nerve palsy. But it's worth also considering that there are ophthalmologic causes of someone having double vision that we often don't consider. So maybe someone who was born with strabismus, or maybe they have a little bit of a tendency toward an eye misalignment that their brain compensates, for and then it decompensates someday and that now they have a little bit of double vision intermittently, so that those can be causes to consider as well.

Dr Monteith: Yeah, well, we'll just have to, you know, request those records from forty years ago. No problem.

Dr Mackay: That's right.

Dr Monteith: Why don't you also give us a little bit of tip when we're on the wards and we want to teach either a medical student or a resident, or if it's a resident listening, may want to teach a junior resident and seem like a star when approaching a patient with diplopia. Give us some teaching pearls.

Dr Mackay: Yeah. So, I would love people teaching more about this at the bedside. I'd say probably the first thing to do would be to equip yourself by recognizing what some of the pertinent questions are to ask someone with double vision. Those things would include, is the double vision worse when looking in a certain direction? Does the double vision go away or not when you cover one eye? What happens when you tilt your head one direction or the other? Is it intermittent or constant? What makes it better? What makes it worse? Those kinds of things can really help us narrow down the possibilities. And then the other thing would be to equip yourself with some tools for examining. And it doesn't have to be physical tools. These can actually be things like, you mentioned the cross-cover test or cover/uncover test. That's described in the article. And I think knowing how to do that properly, knowing how to examine the eye movements properly and how to check for subtle things like a subtle intranuclear ophthalmoplegia, which is also mentioned in the article, being familiar with those things can be a really useful exercise in allowing you to teach others later on.

Dr Monteith: Cool. Why don't you tell us about some of the things you're most excited about in the field?

Dr Mackay: One of the things about our subspecialty for so long is we really haven't had big data with, you know, big trials and all these things that all the stroke people have. And that's starting to change slowly. There's been, for example, the idiopathic intracranial hypertension treatment trial that was published back in, I think it was 2014. You know, of course we had the optic neuritis treatment trial, back a few decades ago now. Some of the exciting ones coming up, there's going to be a randomized controlled trial looking at different treatments for idiopathic intracranial hypertension that are surgically based. So, for example, comparing venous sinus stenting with optic nerve sheath fenestration. And so, figuring out, is there a best practice for surgical intervention for patients with IIH? So, we're starting to have more trials like that now than I think we've had in the past. And so, it's exciting to get to have an evidence base for some of the things that we recommend and do.

Dr Monteith: And what about some of the treatment for diplopia? Like prisms, and where are we with some of that?

Dr Mackay: Yeah, great. So, it's a pretty simple concept, but still kind of difficult in practice. I kind of say there are four different ways to treat double vision: you can ignore it, you can patch or cover one eye, you can treat with prisms, and you can treat with eye muscle surgery. And so, those are the main ways other than, of course, treating the underlying disorder if there's a disorder causing double vision. So those are the main ways to treat. In terms of knowing if someone's going to be a candidate for prism therapy, we also have to remember that prisms are really going to be most helpful for when someone's looking straight forward. So, we need to make sure that their double vision is happening when they look straight forward. So, for example, if they're only having double vision looking to the left or to the right, that patient may not benefit from prisms as much as someone who is having double vision when they look straight forward. So that's one thing I look for. And then strabismus surgery is something to be considered if someone is not tolerating prisms and they're not helping and their eye alignment is stable. So, if you think about it, if someone's eye alignment is changing a lot, you're probably not going to want to do surgery for that patient because it's going to keep changing after surgery. And so, if someone's eye alignment is stable for six months or more and they're not getting the benefit they'd like from prisms, then maybe referral to a strabismus surgeon might be something to consider.

Dr Monteith: Great. And then, I guess another question is just popping up in my head selfishly. What are your thoughts about patients that get referrals for exercises? Say they have, like, a convergence efficiency or something causing diplopia, maybe after a concussion. Maybe there's not a lot of evidence, but what is your take on exercising?

Dr Mackay: Yeah, excellent question. So, there actually is evidence for exercises for convergence insufficiency. So, we know that those do work. Now where exercises are probably not as helpful, or at least not- there isn't an evidence base for them, is really with just about every other kind of eye misalignment in adults. We hear a lot about eye movement therapies for concussion and barely any other acquired misalignment of the eyes as well. And really, the evidence really hasn't shown us that that's helpful; again, with the exception being convergence insufficiency. So, we know that an office-based vision therapy type program for convergence insufficiency does work, but of course it's kind of inconvenient. It can cost money that may or may not be covered by insurance. And so, there are difficulties even with doing that. And so, I often recommend that patients with convergence insufficiency at least try something called pencil push-ups, where they take a pencil at arm's length and they bring it in and exercise that convergence ability. You know, that's a cheap, easy way to try to treat that initially. So yeah, there can be some limited utility for eye muscle exercises in certain conditions.

Dr Monteith: My one example. I was- it was fuzzy, but in a different way. So, what do you do for fun? I mean, it sounds like you like to see a lot of eyeballs?

Dr Mackay: I do. I like to see a lot of eyeballs.

Dr Monteith: When you're not doing these things, what do you do for fun?

Dr Mackay: So, people ask me what my hobbies are, and I laugh because my hobby is actually raising children.

Dr Monteith: Oh, okay!

Dr Mackay: So, my wife and I have eight kids-

Dr Monteith: Oh, wow!

Dr Mackay: Ages three to thirteen. So, kind of doesn't allow me to have other things right now. I'm sure I'll have more hobbies later on, but no, I really love my kids. And I- they give me plenty to do. There's no shortage of- in fact, they were really, they were really excited about this podcast today. They're so excited that Dad gets to be on a podcast, and so I'm going to have to show this to them later. They're going to be thrilled about it.

Dr Monteith: Excellent. Well, thank you so much for being on the podcast.

Dr Mackay: Thank you. It's been my pleasure.

Dr Monteith: Again, today I've been interviewing Dr Devin Mackay about his article on approach to diplopia, which appears in the most recent issue of Continuum on neuro-ophthalmology. Be sure to check out Continuum Audio episodes from this and other issues. And thank you to our listeners for joining today.

Dr Monteith: This is Dr Teshamae Monteith, Associate Editor of Continuum Audio. If you've enjoyed this episode, you'll love the journal, which is full of in-depth and clinically relevant information important for neurology practitioners. Use the link in the episode notes to learn more and subscribe. AAN members, you can get CME for listening to this interview by completing the evaluation at continpub.com/audioCME. Thank you for listening to Continuum Audio.

Papilledema describes optic disc swelling (usually bilateral) arising from raised intracranial pressure. Due to its serious nature, there is a fear of underdiagnosis; hence, one major stumbling points is correct identification, which typically requires a thorough ocular examination including visual field testing.

In this episode, Kait Nevel, MD speaks with Susan P. Mollan, MBChB, PhD, FRCOphth, author of the article "Papilledema" in the Continuum® April 2025 Neuro-ophthalmology issue.

Dr. Nevel is a Continuum® Audio interviewer and a neurologist and neuro-oncologist at Indiana University School of Medicine in Indianapolis, Indiana.

Dr. Mollan is a professor and neuro-ophthalmology consultant at University Hospitals Birmingham in Birmingham, United Kingdom.

Additional Resources

Read the article: Papilledema

Subscribe to Continuum®: shop.lww.com/Continuum

Earn CME (available only to AAN members): continpub.com/AudioCME

Continuum® Aloud (verbatim audio-book style recordings of articles available only to Continuum® subscribers): continpub.com/Aloud

More about the American Academy of Neurology: aan.com

Social Media

facebook.com/continuumcme

@ContinuumAAN

Host: @IUneurodocmom

Guest: @DrMollan

Full episode transcript available here

Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum. Thank you for listening to Continuum Audio. Be sure to visit the links in the episode notes for information about earning CME, subscribing to the journal, and exclusive access to interviews not featured on the podcast.

Dr Nevel: Hello, this is Dr Kait Nevel. Today I'm interviewing Dr Susan Mollan about her article Papilledema Diagnosis and Management, which appears in the April 2025 Continuum issue on neuro-ophthalmology. Susie, welcome to the podcast, and please introduce yourself to our audience.

Dr Mollan: Thank you so much, Kait. It's a pleasure to be here today. I'm Susie Mollan, I'm a consultant neuro-ophthalmologist, and I work at University Hospitals Birmingham- and that's in England.

Dr Nevel: Wonderful. So glad to be talking to you today about your article. To start us off, can you please share with us what you think is the most important takeaway from your article for the practicing neurologist?

Dr Mollan: I think really the most important thing is about examining the fundus and actually trying to visualize the optic nerves. Because as neurologists, you're really acutely trained in examining the cranial nerves, and often people shy away from looking at the eyes. And it can give people such confidence when they're able to really work out straightaway whether there's going to be a problem or there's not going to be a problem with papilledema. And I guess maybe a little bit later on we can talk about the article and tips and tricks for looking at the fundus. But I think that would be my most important thing to take away.

Dr Nevel: I'm so glad that you started with that because, you know, that's something that I find with trainees in general, that they often find one of the more daunting or challenging aspects of learning, really, how to do an excellent neurological exam is examining the fundus and feeling confident in diagnosing papilledema. What kind of advice do you give to trainees learning this skill?

Dr Mollan: So, it really is practice and always carrying your ophthalmoscope with you. There's lots of different devices that people can choose to buy. But really, if you have a direct ophthalmoscope, get it out in the ward, get it out in clinic. Look at those patients that you'd know have alternative diagnosis, but it gives you that practice. I also invite everybody to come to the eye clinic because we have dilated patients there all the time. We have diabetic retinopathy clinics, and it makes it really easy to start to acquire those skills because I think it's very tricky, because you're getting a highly magnified view of the optic nerve and you've got to sort out in your head what you're actually looking at. I think it's practice. and then use every opportunity to really look at the fundus, and then ask your ophthalmology colleagues whether you can go to clinic.

Dr Nevel: Wonderful advice. What do you think is most challenging about the evaluation of papilledema and why?

Dr Mollan: I think there are many different aspects that are challenging, and these patients come from lots of different areas. They can come from the family doctor, they can come from an optician or another specialist. A lot of them can have headache. And, as you know, headache is almost ubiquitous in the population. So, trying to pull out the sort of salient symptoms that can go across so many different conditions. There's nothing that's pathognomonic for papilledema other than looking at the optic nerves. So, I think it's difficult because the presentation can be difficult. The actual history can be challenging. There are those rare patients that don't have headache, don't have pulsatile tinnitus, but can still have papilledema. So, I think it- the most challenging thing is actually confirming papilledema. And if you're not able to confirm it, getting that person to somebody who's able to help and confirm or refute papilledema is the most important thing.

Dr Nevel: Yeah, right. Because you talk in your article the importance of distinguishing between papilledema and some other diagnoses that can look like papilledema but aren't papilledema. Can you talk about that a little bit?

Dr Mollan: Absolutely. I think in the article it's quite nice because we were able to spend a bit of time on a big table going through all the pseudopapilledema diagnoses. So that includes people with shortsightedness, longsightedness, people with optic nerve head drusen. And we've been very fortunate in ophthalmology that we now have 3D imaging of the optic nerve. So, it makes it quite clear to us, when it's pseudopapilledema, it's almost unfair when you're using the direct ophthalmoscope that you don't get a cross sectional image through that optic nerve. So, I'd really sort of recommend people to delve into the article and look at that table because it nicely picks out how you could pick up pseudopapilledema versus papilledema.

Dr Nevel: Perfect. In your article, you also talk about what's important to think about in terms of causes of papilledema and what to evaluate for. Can you tell us, you know, when you see someone who you diagnose with papilledema, what do you kind of run through in terms of diagnostic tests and things that you want to make sure you're evaluating for or not missing?

Dr Mollan: Yeah. So, I think the first thing is, is once it's confirmed, is making sure it's isolated or whether there's any additional cranial nerve palsies. So that might be particularly important in terms of double vision and a sixth nerve palsy, but also not forgetting things like corneal sensation in the rest of the cranial nerves. I then make sure that we have a blood pressure. And that sounds a bit ridiculous in this day and age because everybody should have a blood pressure coming to clinic or into the emergency room. But sometimes it's overlooked in the panic of thinking, gosh, I need to investigate this person. And if you find that somebody does have malignant hypertension, often what we do is we kind of stop the investigational pathway and go down the route of getting the medics involved to help with lowering the blood pressure to a safe level. I would then always think about my next thing in terms of taking some bloods. I like to rule out anemia because anemia can coexist in a lot of different conditions of raised endocranial pressure.

And so, taking some simple blood such as a complete blood count, checking the kidney function, I think is important in that investigational pathway. But you're not really going to stop there. You're going to move on to neuroimaging. It doesn't really matter what you do, whether you do a CT or an MRI, it's just getting that imaging pretty much on the same day as you see the patient. And the key point to that imaging is to do venography. And you want to rule out a venous sinus thrombosis cause that's the one thing that is really going to cause the patient a lot of morbidity. Once your neuroimaging is secure and you're happy, there's no structural lesion or a thrombosis, it's then reviewing that imaging to make sure it's safe to proceed with lumbar puncture. And so, we would recommend the lumbar puncture in the left lateral decubitus position and allowing the patient to be as calm and relaxed as possible to be able to get that accurate opening pressure. Once we get that, we can send the CSF for contents, looking for- making sure they don't have any signs of meningitis or raised protein. And then, really, we're at that point of saying, you know, we should have a secure diagnosis, whether it would be a structural lesion, venous sinus thrombosis, or idiopathic intracranial hypertension.

Dr Nevel: Wonderful. Thank you for that really nice overview and, kind of, diagnostic pathway and stepwise thought process in the evaluations that we do. There are several different treatments for papilledema that you go through in your article, ranging from surgical to medication options. When we're taking care of an individual patient, what factors do you use to help guide you in this decision-making process of what treatment is best for the patient and how urgent treatment is?

Dr Mollan: I think that's a really important question because there's two things to consider here. One is, what is the underlying diagnosis? Which, hopefully, through the investigational save, you'll have been able to achieve a secure diagnosis. But going along that investigational pathway, which determines the urgency of treatment, is, what's happening with the vision? If we have somebody where we're noting that the vision is affected- and normally it's actually through a formal visual field. And that's really challenging for lots of people to get in the emergency situation because syndromes of raised endocranial pressure often don't cause problems with the visual acuity or the color vision until it's very late. And also, you won't necessarily get a relative afferent papillary defect because often it's bilateral. So I really worry if any of those signs are there in somebody that may have papilledema.

And so, a lot rests on that visual field. Now, we're quite good at doing confrontational visual fields, but I would say that most neurologists should be carrying pins to be able to look at the visual fields rather than just pointing fingers and quadrants if you're not able to get a formal visual field early. It's from that I would then determine if the vision is affected, I need to step up what I'm going to do. So, I think the sort of next thing to think about is that sort of vision. So, if we have somebody who, you know, you define as have severe sight loss at the point that you're going through this investigational pathway, you need to get an ophthalmologist or a neuro-ophthalmologist on board to help discuss either the surgery teams as to whether you need to be heading towards an intervention. And there are a number of different types of intervention. And the reason why we discuss it in the article---and we'll also be discussing it in a future issue of Continuum---is there's not high-class evidence to suggest one surgery over another surgery. We may touch on this later.

So, we've got our patients with severe visual loss who we need to do something immediately. We may have people where the papilledema is moderate, but the vision isn't particularly affected. They may just have an enlarged blind spot. For those patients, I think we definitely need to be thinking about medical therapy and talking to them about what the underlying cause is. And the commonest medicine to use for raised endocranial pressure in this setting is acetazolamide, a carbonic anhydrous inhibitor. And I think that should be started at the point that you believe somebody has moderate papilledema, with a lot of discussion around the side effects of the medicine that we go into the article and also the fact that a lot of our patients find acetazolamide in an escalating dose challenging. There are some patients with very mild papilledema and no visual change where I might say, hey, I don't think we need to start treatment immediately, but you need to see somebody who understands your disease to talk to you about what's going on. And generally, I would try and get somebody out of the emergency investigational pathway and into a formal clinic as soon as possible.

Dr Nevel: Thank you so much for that. One thing that I was wondering that we see clinically is you get a consult for a patient, maybe, who had an isolated episode of vertigo, back to their normal self, completely resolved… but incidentally, somebody ordered an MRI. And that MRI, in the report, it says partially empty sella, slight flattening of the posterior globe, concerns for increased intracranial pressure. What should we be doing with these patients who, you know, normal neurological exam, maybe we can't detect any definite papilledema on our endoscopic exam. What do you think the appropriate pathway is for those patients?

Dr Mollan: I think it's really important. The more neuroimaging that we're doing, we're sort of seeing more people with signs that are we don't believe are normal. So, you've mentioned a few, the sort of partially empty sella, empty sella, tortuosity of the optic nerves, flattening of the globes, changes in transverse sinus. And we have quite a nice, again, table in the article that talks about these signs. But they have really low sensitivity for a diagnosis of raised endocranial pressure and isolation. And so, I think it's about understanding the context of which the neuroimaging has been taken, taking a history and going back and visiting that to make sure that they don't have escalating headache. And also, as you said, rechecking the eye nerves to make sure there's no papilledema.

I think if you have a good examination with the direct ophthalmoscope and you determine that there's no papilledema, I would be confident to say there's no papilledema. So, I don't think they need to necessarily cry doubt. The ophthalmology offices, we certainly are having quite a few additional referrals, particularly for this, which we kind of called IIH-RAD, where patients are coming to us for this exclusion. And I think, in the intervening time, patients can get very anxious about having a sort of MRI artifact picked up that may necessarily mean a different diagnosis. So, I guess it's a little bit about reassurance, making sure we've taken the appropriate history and performed the examination. And then knowing that actually it's really a number of different signs that you need to be able to confidently diagnose raised ICP, and also the understanding that sometimes when people have these signs, if the ICP reduces, those signs remain. You know, we're learning an awful lot more about MRI imaging and what's normal, what's within normal limits. So, I think reassurance and sensible medical approach.

Dr Nevel: Absolutely. In the section in your article on idiopathic intracranial hypertension, you spend a little bit of time talking about how important it is that we sensitively approach the topic of potential weight loss for those patients who are overweight. How do you approach that discussion in your clinic? Because I think it's an important part of the holistic patient care with that condition.

Dr Mollan: I think this is one of the things that we've really listened to the patients about over the last number of years where we recognize that in an emergency situation, sometimes we can be quite quick to sort of say, hey, you have idiopathic endocranial hypertension and weight loss is, you know, the best treatment for the condition. And I think in those circumstances, it can be quite distressing to the patient because they feel that there's a lot of stigma attached around weight management. So, we worked with the patient group here at IIH UK to really come up with a way of a signposting to our patients that we have to be honest that there is a link, you know, a strong evidence that weight gain and body shape change can cause someone to fall into a diagnosis of IIH. And we know that weight loss is really effective with this condition. So, I think where I've learned from the patients is trying to use language that's less stigmatizing. I definitely signpost that I'm going to talk about something sensitive. So, I say I'm going to talk about something sensitive and I'm going to say, do you know that this condition is related to body shape change? And I know that if I listen to this podcast in a couple of years, I'm sure my words will have changed. And I think that's part of the process, is learning how to speak to people in an ever-changing language. And they think that sort of signpost that you're going to talk about something sensitive and you're going to talk about body shape change. And then follow up with, are you OK with me talking about this now? Is it something you want to talk about? And the vast majority of people say, yes, let's talk about it. There'll be a few people that don't want to talk about it. And I usually come in quite quickly, say, is it OK if I mention it at the next consultation? Because we have a duty of care to sort of inform our patients, but at the same time we need to take them on that journey to get them back to health, and they need to be really enlisted in that process.

Dr Nevel: Yeah, I really appreciate that. These can be really difficult conversations and uncomfortable conversations to have that are really important. And you're right, we have a duty as medical providers to have these conversations or inform our patients, but the way that we approach it can really impact the way patients perceive not only their diagnosis, but the relationship that we have with our patients. And we always want that to be a positive relationship moving forward so that we can best serve our patients.

Dr Mollan: I think the other thing as well is making sure that you've got good signposts to the professionals. And that's what I say, because people then say to me, well, you know, kind of what diet should I be on? What should I be doing? And I say, well, actually, I don't have professional experience with that. I'm, I'm very fortunate in my hospital, I'm able to send patients to the endocrine weight management service. I'm also able to send patients to the dietetic service. So, it's finding, really, what suits the patient. Also what's within licensing in your healthcare system to be able to provide. But not being too prescriptive, because when you spend time with weight management professionals, they'll tell you lots of different things about diets that people have championed and actually, in randomized controlled trials, they haven't been effective. I think it's that signpost really.

Dr Nevel: Yeah, absolutely. So, could you talk a little bit about what's going on in research in papilledema or in this area, and what do you think is up-and-coming?

Dr Mollan: I think there's so much going on. Mainly there's two parts of it. One is image analysis, and we've had some really fantastic work out of the Singapore group Bonsai looking at a machine learning decision support tool. When people take fundal pictures from a normal fundus camera, they're able to say with good certainty, is this papilledema, is this not papilledema? But more importantly, if you talk to the investigators, something that we can't tell when we look in is they're able to, with quite a high level of certainty, say, well, this is base occupying lesion, this is a venous sinus thrombosis, and this is IIH. And you know, I've looked at thousands and thousands of people's eyes and that I can't tell why that is. So, I think the area of research that is most exciting, that will help us all, is this idea about decision support tools. Where, in your emergency pathway, you're putting a fundal camera in that helps you be able to run the image, the retina, and also to try and work out possibly what's going on. I think that's where the future will go. I think we've got many sort of regulatory steps and validation and appropriate location of a learning to go on in that area. So, that's one side of the imaging.

I think the other side that I'm really excited about, particularly with some of the work that we've been doing in Birmingham, is about treatment. The surgical treatments, as I talked about earlier… really, there's no high-class evidence. There's a number of different groups that have been trying to do randomized trials, looking at stenting versus shunting. They're so difficult to recruit to in terms of trials. And so, looking at other treatments that can reduce intracranial pressure. We published a small phase two study looking at exenatide, which is a glucagon-like peptide receptor agonist, and it showed in a small group of patients living with IIH that it could reduce the intracranial pressure two and a half hours, twenty-four hours, and also out to three months. And the reason why this is exciting is we would have a really good acute therapy---if it's proven in Phase III trials---for other diseases, so, traumatic brain injury where you have problems controlling ICP. And to be able to do that medically would be a huge breakthrough, I think, for patient care.

Dr Nevel: Yeah, really exciting. Looking forward to seeing what comes in the future then. Wonderful. Well, thank you so much for chatting with me today about your article. I really enjoyed learning more from you during our conversation today and from your article, which I encourage all of our listeners to please read. Lots of good information in that article.

So again, today I've been interviewing Dr Susie Mollan about her article Papilledema Diagnosis and Management, which appears in the most recent issue of Continuum on neuro-ophthalmology.Please be sure to check out Continuum episodes from this and other issues. And thank you to our listeners for joining us today. Thank you, Susie.

Dr Mollan: Thank you so much.

Dr Monteith: This is Dr Teshamae Monteith, Associate Editor of Continuum Audio. If you've enjoyed this episode, you'll love the journal, which is full of in-depth and clinically relevant information important for neurology practitioners. Use the link in the episode notes to learn more and subscribe. AAN members, you can get CME for listening to this interview by completing the evaluation at continpub.com/audioCME. Thank you for listening to Continuum Audio.

The inflammatory and infectious optic neuropathies are a broad, heterogeneous, and common group of diseases producing visual loss. Although many now-distinct syndromes have been previously combined as "typical or atypical optic neuritis," recent developments highlight the importance of precision terminology as well as an individualized evaluation and treatment approach.

In this episode, Gordon Smith, MD, FAAN speaks with Eric Eggenberger, DO, MS, FAAN, author of the article "Optic Neuritis" in the Continuum® April 2025 Neuro-ophthalmology issue.

Dr. Smith is a Continuum® Audio interviewer and a professor and chair of neurology at Kenneth and Dianne Wright Distinguished Chair in Clinical and Translational Research at Virginia Commonwealth University in Richmond, Virginia.

Dr. Eggenberger is a professor of ophthalmology, neurology, and neurosurgery at the Mayo Clinic in Jacksonville, Florida.

Additional Resources

Read the article: Optic Neuritis

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More about the American Academy of Neurology: aan.com

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Host: @gordonsmithMD

Full episode transcript available here

Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum. Thank you for listening to Continuum Audio. Be sure to visit the links in the episode notes for information about earning CME, subscribing to the journal, and exclusive access to interviews not featured on the podcast.

Dr Smith: This is Dr Gordon Smith. Today I'm interviewing someone who really needs no introduction, Dr Eric Eggenberger, about his article on optic neuritis, which appears in the April 2025 Continuum issue on neuro-ophthalmology. Eric, welcome to the podcast, and maybe you can introduce yourself to our audience.

Dr Eggenberger: Thank you. Thanks for having me. So, my name is Eric Eggenberger. I work at Mayo Clinic Florida, and I am involved exclusively in neuro-ophthalmology.

Dr Smith: I just had the pleasure, Eric, of talking yesterday with Lindsey De Lott about non-optic neuritis causes of optic neuropathy. And so, I'm going to kind of reference a little bit what I learned yesterday. She was great. I wonder if you might begin by talking a little bit about nomenclature. You talk about the need for use of precise terminology in your article. And yesterday she taught me a lot about the risk of misdiagnosis and other causes of optic neuropathy, and the two seem related. So, I wonder if you can maybe lay the foundation for our conversation by talking about terminology?

Dr Eggenberger: I think that's a great point. So, we are in an era now where, instead of lumping all these different diagnoses together, we have learned to split apart some of these clinical entities. And so, I think it's really important that we focus on precise terminology and recognize that all optic neuritis is not the same. And we have very different, distinct clinical pathways for these imaging pathways, treatment pathways, for these different types of optic neuritis, whether that's MS related, whether it's MOG related or aquaporin-4 related.

Dr Smith: So, I wonder maybe we can begin by just, you know, giving our listeners wisdom, pearls, and pitfalls about, how do you recognize when someone with a suspected optic neuropathy has optic neuritis versus a noninflammatory optic neuropathy?

Dr Eggenberger: So, that's a really important issue because there's a lot of clinical overlap in terms of exam findings. So, for instance, in any optic neuropathy, let's say it's unilateral, you typically are going to see decreases in acuity and field and color, and you're going to see a relative afferent pupillary defect. And then it's really the context that that occurs in that helps us distinguish different disease entities. So, with optic neuritis, typically you're going to have pain. And that's oftentimes going to be in the younger populations compared to some of the other common optic neuropathies we see, like ischemic optic neuropathy, for instance.

Dr Smith: Right. So maybe we can talk a little bit about, kind of, your overall diagnostic approach, right? A lot of this is, of course, based on age and context, but young people get ischemic lesions and older people can have inflammatory lesions. So, what's your overall approach to the patient you just described? Let's say it's a forty-eight-year-old woman who comes to the emergency department with subacute unilateral vision loss and there's dyschromatopsia, APD, reduced acuity. And, you know, let's just say a fairly, you know, benign-looking fundoscopic exam. What do you do to evaluate that patient?

Dr Eggenberger: In that particular context, I think we're looking at other contextual clues. Is there other vascular risk factors or other things to point you in one direction or the other? One of the important parts you mentioned was the fundus exam. So, we know with ischemic optic neuropathy, 100% of the time with AIOM, you're going to see disc edema. And so, in the context of that story, we want to confirm on our exam an optic neuropathy, and then we can kind of focus on the retrobulbar courses or different types of optic neuropathies. From an exam perspective, in that particular patient we'd be looking to measure the acuity, quantify that. And in the ER, you're not going to be able to do a perfect field, but you'll get some sense of the field and how much field loss there is. And then as you mentioned, the afferent pupillary defect is critical. And we're going to get a little bit of the historical features in terms of pain. With typical retrobulbar optic neuritis, most of those patients are going to experience some pain, and usually it's pain on eye movements. And those would be the clinical things to focus on. Other exposures the patient may or may not have had, any other concomitant conditions, would all help point you in different directions, perhaps, and then we're probably on towards imaging.

Dr Smith: Yeah, maybe you can talk a little bit about that? What's the appropriate use of imaging? I mean, presumably the patients, like the one I just threw out there, are pretty much all going to get neuroimaging. What's your approach to that? How do you protocol the study? What should we be looking for?

Dr Eggenberger: In our clinic, we would typically be ordering an MRI orbit and brain, and each of those has a specific purpose. The orbit is going to show us the extent of the optic neuropathy. So, we're particularly looking for a longitudinally extensive optic nerve lesion or more than half of the optic nerve involved. And most patients acutely, if it isn't an "itis" situation, we'll see enhancement. And then the MR brain is going to be useful for looking for other evidence of demyelination within the central nervous system. We may at some point get down to doing an MR cord, but I think acutely it's going to be brain and orbit that most of our patients are getting.

Dr Smith: Let's say that we did the scan and, sure enough, there's sort of a shorter segment, so less than half the length of the nerve region of enhancement. What's the rest of your diagnostic evaluation look like for that patient?

Dr Eggenberger: So, in that particular case, we would look at the remainder of the brain. So, we're looking for other evidence of demyelination and any other contextual clues, systemically that would point you one direction or another. But with a shorter segment involved, one of the more common things we might encounter would be multiple sclerosis-related optic neuritis.

Dr Smith: Would you look for aquaporin-4 and MOG in a patient with what appears to be an isolated, uncomplicated short segment optic neuritis?

Dr Eggenberger: So, I think it really depends a bit on the context. I would never fault anybody for looking at MOG or an aquaporin-4 in that context because those are really treatment-altering diagnoses, but the yield in this particular case with a short segment involved and depending on the acuity and other features is probably going to be pretty low.

Dr Smith: I really liked as an aside- I wasn't going to go there next, but you kind of got me thinking about it, you have a really nice section in your article. Which, all of it's great, but talking about how to manage low titer MOG antibodies. I wonder if you could talk about that because I think that's a lesson, maybe, that is transferable to a lot of other testing that we do. in terms of pre-prior probability and titer and so forth.

Dr Eggenberger: Yeah, that's really an important point. So, we've seen this come up a number of times where the MOG antibody is a very good test, but in low titer it has a relatively low positive predictive value, perhaps 50%. In those cases, particularly without a classic clinical context, you have to be extremely alert for some other diagnosis that could mimic what you think is inflammatory demyelinating optic neuritis, but in fact is infectious or some other cause.

Dr Smith: Yeah, super, super important and helpful. In terms of aquaporin-4, how does that compare in terms of predictive values, lower titer positive results?

Dr Eggenberger: So aquaporin-4, the test has a very high specificity. So, it's quite useful if positive. You have to keep in mind there can be some false negatives, but the test otherwise is quite specific. And that is a diagnosis, you know, we never want to miss. It's a vicious disease. It tends to be a blinding disease, particularly without treatment. Bad things happen when we miss that, and we want to get on that diagnosis early and do pretty aggressive early and prophylactic treatment.

Dr Smith: Your article covers not only the common causes of optic neuritis and, you know, MS, isolated optic neuritis, MOGAD NMO, you talk about a bunch of other things. I wonder, in this patient that we've been discussing, in the absence of any other historical information that seems relevant---or maybe you can define what would seem relevant---would you do other evaluation in that individual, other serologic evaluation and so forth, just in terms of diagnosis?

Dr Eggenberger: In that particular case, without other red flags, I don't think I would initially. And follow-up is going to give you a lot of this context. So, you'd be on the lookout for other systemic conditions. So, if the patient had some arthropathy, if the patient had any pulmonary disease hints, if there was anything else that could lead you on a broader expedition. But I think in the context of this case, acutely in the ER, I probably wouldn't do a big lab plug for this. I probably would kind of go down the most likely road and start our treatments, and then follow that patient up.

Dr Smith: Yeah, I know your article does a really great job, I think, of outlining when do you need to think about some of these less common causes. Well, can we talk about treatment, Eric? Because I want to move on to some other things. But- so, we've got a patient with isolated optic neuritis, nothing else, you know, in terms of the other antibodies we've talked about. What state-of-the-care- or, state-of-the-art treatment for that patient?

Dr Eggenberger: So, the acute treatment for these inflammatory, optic neuritis-type cases is very similar Initially. High dose steroids remains kind of the standard. And then, in MS-related optic neuritis, we may or may not see a taper. So many times it's just an acute treatment of three to five days high dose. Whether that's oral or PO, we could institute either depending on the particular case. And then the taper would depend on the potential cause. So, for instance, with these antibody-driven diseases---so with MOG- or particularly with aquaporin-4---if it's a longitudinally extensive region of optic nerve involved, we tend to use a longitudinally extensive taper. And so, we use prednisone in those cases for several months while we're getting everything else set and deciding what the overall course is going to bring.

Dr Smith: What about IV versus oral? There must be something about my practice. I was telling this to Lindsey. Every time on our hospital service, we seem to have at least two patients with optic neuropathies, which I always enjoy, but I find it's a little weird to admit someone who's doing just fine otherwise to the hospital with three days of IV SOLU-MEDROL. So, I'm always trying to figure out, like, how can I get this patient home? And your article had the best term I've heard in a long time, which is "SOLU smoothies." I mean, are there other strategies that you sometimes use, other than just high-dose IV methylprednisolone?

Dr Eggenberger: So, I agree with you. It's sometimes hard to admit somebody for just an IV therapy. And we'll do this as an outpatient, high-dose IV, but we'll also use high-dose orals. And in times in the past when there's been methylprednisolone shortage, we've used high-dose oral or IV dexamethasone as well. I think the IV form, although it's the gold standard, the high-dose oral forms have pretty equivalent bioavailability and are pretty tolerable in my experience. And certainly more convenient.

Dr Smith: I wonder if we should switch and maybe talk a little bit about aquaporin-4, I mean, you emphasized that this is a vicious disease---I love the way you describe that---and often blinding. What updates do you have in terms of our therapeutic approach to NMO? That's been rapidly evolving of late.

Dr Eggenberger: Right, so these are cases we're always going to share with neuroimmunology. And it requires kind of a multidisciplinary approach, in my opinion, for ideal or for best outcomes. And so, all of these patients are going to get put on prophylactic medications. So, this is a disease you just can't leave untreated. Bad stuff will happen for sure. And we now, fortunately, have some approved, FDA-approved medications that can positively impact the course of this disease. So, that's been a welcome addition.

Dr Smith: What are the FDA-approved medications at this point for NMO?

Dr Eggenberger: So, there are several at this point, and this is an area that's in growth, fortunately. And again, these are cases we're going to be sharing with our neuroimmunology colleagues. So, these are IV medications typically aimed at complement or CD19. And they all are relatively effective at quieting the course of the disease.

Dr Smith: Maybe we can talk a little bit about MOG? I think that most of our listeners are probably pretty familiar with aquaporin-4 and NMO, what- maybe you could describe MOG a little bit and the therapeutic approach for patients with MOG-associated disease?

Dr Eggenberger: So, MOG has been a real interesting kind of condition to learn more about. We certainly see a lot of MOG, and I'm sure we saw MOG before it was formally described, but I think we just thought it was kind of a benign, maybe monophasic MS type of presentation. But MOG tends to come in with a loss of acuity that kind of rivals aquaporin-4. So, the acuity tends to be pretty, pretty depressed, but it's very steroid-responsive. So, a lot of times these are the patients, you'll see that their vision will start to improve even when they're on the initial few days of the high-dose steroids. And many times we can get their vision back to 20/20 or very close to that.

Dr Smith: And do these patients need chronic management?

Dr Eggenberger: So, that's an area of controversy to some degree. About 50% of the optic neuritis MOG-related cases are going to have a relapsing course. And because the disease is steroid-responsive, many times we'll follow these patients after a first attack to see if this is the condition that's going to declare itself to be relapsing or if this is just going to be a monophasic kind of presentation of optic neuritis. We don't have great biomarkers to separate patients who are going to be in that 50% monophasic course versus the other half. It'll be relapsing. And so, it depends on the patient. If there's somebody that's, as many of these patients are, been very steroid responsive, they get back to 20/20, we can teach them about the disease so that if they do have a relapse, we can get them high-dose steroids in a relatively rapid fashion and they're otherwise healthy, we're probably going to watch that patient. And if it's somebody that doesn't recover 100%, there's other issues with treating them with high-dose steroids potentially in the future, then we may learn more towards an earlier prophylactic approach in that patient.

Dr Smith: And what would that approach look like? Is it different from NMO or using more IVIG or B cell depletion as opposed to complement inhibition, for instance?

Dr Eggenberger: In MOG, we know that the B cell depletion strategies don't work as well. And so most times we're turning to IVIG, and we found that pretty effective. That's kind of our go-to at this point.

Dr Smith: Eric, it's a joy talking to you and I'd love to keep going about content, but I'll refer our listeners to your outstanding article. I mean, you're such a highly regarded neuro-ophthalmologist and educator. I wonder if you could talk to us about why you've done neuro-ophthalmology, and maybe this is an opportunity for you to convince all of our great residents that are listening or students what's great about being a neuro-ophthalmologist.

Dr Eggenberger: I think neuro-ophthalmology is by far the most interesting part of neurology. So, it's an area that I think a lot of general neurologists, in my view, don't get enough of in their residency. But it's kind of the essence of neurology, where in neurology you're localizing down to the millimeter and in neuro-ophthalmology, we're localizing down to the micron level. We have several new emerging diseases like these varieties of optic neuritis we're focused on. We're learning lots about those. You get to be involved in lots of different areas of neurology. So, we'll see not just demyelinating conditions, we'll see trauma as it relates to the visual system. And we'll see tumor, and we see all different flavors, stroke, and in any piece of neurology, commonly we'll have some vision aspect that we that we get involved in. So, we see a wide variety of conditions. So, I think it's been a really exciting place to be within neurology. And it's rapidly changing at this point. We're getting new therapeutics. So, it's, I think it's a great time to be a neuro-ophthalmologist.

Dr Smith: Yeah, listening to you talk and just reflecting on it, it's really true. Neuro-ophthalmology does cover the entire span of neurology, right? I'm a neuromuscular guy and we see a lot of ocular myasthenia, which is another super exciting area. But we've been talking about optic neuritis, and your article talks about infectious causes and the paraneoplastic and a whole host of things. So, you're a great advocate and salesperson for your field. You convinced me.

Dr Eggenberger: Efferent neuro-ophthalmology we love, we could talk about ocular myasthenia and other aspects for another hour. And we get involved in all kinds of cases: third nerve palsies, ocular myasthenia, trauma that involves the efferent system, all different aspects. It's really a great subspecialty, and you get to see a bit of all of neurology.

Dr Smith: I'm trying to remember who it was, Eric. It was an attending of mine at medical school. I went to medical school at the Mayo Clinic in Rochester, and I want to say it was Manny Gomez, who was a very famous tuberous sclerosis person, who told me that neuro-ophthalmology was the most elegant specialty within neurology. That stuck with me. Thank you so much for joining me today. I really appreciate it.

Dr Eggenberger: Thank you. I appreciate it as well.

Dr Smith: So again, today I've been interviewing Dr Eric Eggenberger about his really wonderful article on optic neuritis, which appears in the most recent issue of Continuum on neuro-ophthalmology. Be sure to check out Continuum audio episodes from the neuro-ophthalmology and other issues. And listeners, thank you very much for joining us today.

Dr Monteith: This is Dr Teshamae Monteith, Associate Editor of Continuum Audio. If you've enjoyed this episode, you'll love the journal, which is full of in-depth and clinically relevant information important for neurology practitioners. Use the link in the episode notes to learn more and subscribe. AAN members, you can get CME for listening to this interview by completing the evaluation at continpub.com/audioCME. Thank you for listening to Continuum Audio.

Optic neuropathies encompass all congenital or acquired conditions affecting the optic nerve and are often a harbinger of systemic and central nervous system disorders. A systematic approach to identifying the clinical manifestations of specific optic neuropathies is imperative for directing diagnostic assessments, formulating tailored treatment regimens, and identifying broader central nervous system and systemic disorders.

In this episode, Gordon Smith, MD, FAAN speaks with Lindsey De Lott, MD, MS, author of the article "Optic Neuropathies" in the Continuum® April 2025 Neuro-ophthalmology issue.

Dr. Smith is a Continuum® Audio interviewer and a professor and chair of neurology at Kenneth and Dianne Wright Distinguished Chair in Clinical and Translational Research at Virginia Commonwealth University in Richmond, Virginia.

Dr. De Lott is an assistant professor of neurology and ophthalmology at the University of Michigan in Ann Arbor, Michigan.

Additional Resources

Read the article: Optic Neuropathies

Subscribe to Continuum®: shop.lww.com/Continuum

Earn CME (available only to AAN members): continpub.com/AudioCME

Continuum® Aloud (verbatim audio-book style recordings of articles available only to Continuum® subscribers): continpub.com/Aloud

More about the American Academy of Neurology: aan.com

Social Media

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Host: @gordonsmithMD

Guest: @lindseydelott

Full episode transcript available here

Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum. Thank you for listening to Continuum Audio. Be sure to visit the links in the episode notes for information about earning CME, subscribing to the journal, and exclusive access to interviews not featured on the podcast.

Dr Smith: Hello, this is Dr Gordon Smith. Today I'm interviewing Dr Lindsey De Lott about her article on optic neuropathies, which appears in the April 2025 Continuum issue on neuro-ophthalmology. Lindsey, welcome to the podcast, and perhaps you can introduce yourself to our audience.

Dr De Lott: Thank you, Dr Smith. My name is Lindsey De Lott and I am a neurologist and a neuro-ophthalmologist at the University of Michigan. I also serve as the section lead for the Division of Neuro-Ophthalmology, which is actually part of the ophthalmology department rather than the neurology department. And I spend a good portion of my time as a researcher in health services research, and that's now about 60% of my practice or so.

Dr Smith: I'm super excited to spend some time talking with you. One, I'm a Michigan person. As we were chatting before this, I trained with Wayne Cornblath and John Trobe, and it's great to have you. I wonder if we maybe can begin- and by the way, your article is outstanding. It is such a huge topic and it was actually really fun to read, so I encourage our listeners to check it out. But you begin by talking about misdiagnosis as being a common problem in this patient population. I wonder if you can talk through why that is and if you have any pearls or pitfalls in avoiding it?

Dr De Lott: Yeah, I think there's been a lot of great research looking at misdiagnosis in specific types of optic neuropathies; in particular, compressive optic neuropathies and optic neuritis. A lot of that work has come out of the group at Emory and the group at Washington University. But a lot of neuro-ophthalmologists across the country really contributed to those data. And one of the statistics that always strikes me is that, you know, for example, in patients with optic nerve sheath meningiomas, something like 70% of them are actually misdiagnosed. And a lot of those errors in diagnosis, whether it's for compressive optic neuropathy or some other type of optic neuropathy, really comes down to the way that physicians are really incorporating elements of the history in the physical. For example, in optic neuritis, we know that physicians tend to anchor pretty heavily on pain in general. And that often tends to lead them astray when optic neuritis was never the diagnosis to begin with. So, it's really overindexing on certain things and not paying attention to other features of the physical exam; for example, say presence of an afferent pupillary defect. So, I think it just really highlights the need to have a really relatively structured approach to patients that you think have an optic neuropathy when you're trying to sort of plan your diagnostic testing and your treatment.

Dr Smith: I do maybe five or six weeks on our hospital service each year, and I don't know if it's just a Richmond thing, but there's always at least two people in my week who come in with an optic neuropathy or acute vision loss. How common is this in medical practice? Or neurologic practice, I should say?

Dr De Lott: Optic neuropathies themselves… if you look across, unfortunately we don't have any great data that puts together all optic neuropathies and gives us an actual sort of prevalence estimate or an incidence estimate from year to year. We do have some of those data for specific types of optic neuropathies like optic neuritis and NAION, and you're probably looking around five-ish per one hundred thousand. So, these aren't that common, but at the same time they do get funneled to- often to emergency rooms and to neurologists from our ophthalmology colleagues and optometry colleagues in particular.

Dr Smith: So, one other question I had before kind of diving into the topic at hand is how facile neurologists need to be in recognizing other causes of acute visual loss. I mean, we see acute visual loss as neurologists, we think optic neuropathy, right? Optic neuritis is sort of the go-to in a younger patient, and NAION in someone older. But what do neurologists need to know about other ophthalmologic causes? So, glaucoma or acute retinal disorders, for instance?

Dr De Lott: Yeah, I think it's really important that neurologists are able to distinguish optic neuropathies from other causes of vision loss. And so, I would really encourage the listeners to take a look at the excellent article by Nancy Newman about vision loss in this issue where she really kind of breaks it down into vision loss that is acute and chronic and how you really think through distinguishing optic neuropathies from other causes of vision loss. But it is really important. For example, a patient with a central retinal artery occlusion may potentially be eligible for treatments. And that's very different from a patient with optic neuritis and acute vision loss. So, we want to be able to distinguish these things.

Dr Smith: So maybe we can pivot to that a little bit. Just for our listeners, our focus today is going to be on- not so much on optic neuritis, although obviously we need to talk a little bit about how we differentiate optic neuritis from non-neuritis optic neuropathies. It seems like the two most common situations we encounter are ischemic optic neuropathies and optic neuritis. Maybe you can talk a little bit about how you distinguish these two? I mean, some of it's age, some of it's risk factors, some of it's exam. What's the framework, of let's say, a fifty-year-old person comes into the emergency room with acute vision loss and you're worried about an optic neuropathy?

Dr De Lott: The first step whenever you are considering an optic neuropathy is just making sure that the features are present. I think, really going back to your earlier question, making sure that the patient has the features of an optic neuropathy that we expect. So, it's not only vision loss, but it's also the presence of an apparent pupillary defect in a patient with a unilateral optic neuropathy. In a person who has a bilateral optic neuropathy, that apparent pupillary defect may not be present because it is relative. So, you really would have to have asymmetric vision loss between the two eyes. They should also have impairment of their color vision, and they're probably going to have some kind of visual field defect, whether that's central scotoma or an arcuate scotoma or an altitudinal defect that really respects the horizontal meridian.

So, you want to make sure that, first and foremost, you've got a patient that really meets most of those- most of those features. And then from there, we're looking at the other features on their history. How acute is the onset of the vision loss? What is the progression over time? Is there pain associated or not associated with the vision loss? What other medical issues does the patient have? And you know, one of the things you already brought up, for example, is, what's the age of the patient? So, I'm going to be much more hesitant to make a diagnosis of optic neuritis in a much older patient or a diagnosis on the other side, of ischemic optic neuropathy, in a much younger patient, unless they have really clear features that push me in that direction.

Dr Smith: I wonder if maybe you could talk a little bit about features that would push you away from optic neuritis, because, I mean, people who are over fifty do get optic neuritis-

Dr De Lott: They do.

Dr Smith: -and people who get ischemic optic neuropathies who are younger. So, what features would push you away from optic neuritis and towards… let's be broad, just a different type of optic neuropathy?

Dr De Lott: Sure. We know that most patients with optic neuritis do have pain, but that pain is accompanied---within a few days, typically---with vision loss. So, pain alone going on for a number of days without any visual symptoms or any of those other things I listed, like the afferent papillary defect, the visual field defect, would push me away from optic neuritis. But in general, yes, most optic neuritis is indeed painful. So, the presence of optic disc edema is unfortunately one of those things that an optic neuritis may be present, may not be present, but in somebody with ischemia that is anterior---and that's the most common type of ischemic optic neuropathy, would be anterior ischemic optic neuropathy---they have to have optic disc edema for us to be able to make that diagnosis, and that is a diagnosis of NAION, or nonarteritic ischemic optic neuropathy. An APD in this case, again, that's just a feature of an optic neuropathy. It doesn't really help you to distinguish, individual field defects are going to be relatively similar between them.

So then in patients, I'm also looking, like I said, at their history. So, in a patient where I'm entertaining a diagnosis of ischemic optic neuropathy, I want to make sure that they have vascular risk factors or that I'm actually doing things like measuring their blood pressure in the office if they haven't seen a physician recently or checking a lipid panel, hemoglobin A1c, those kinds of things, to look for vascular risk factors. One of the other features on exam that might push me more- again, in a patient with ischemic optic neuropathy, where it might suggest ischemia over optic neuritis, would be some other features on exam like a crowded optic disc that we sometimes will see in patients with ischemic optic neuropathy. I feel like that was a bit of a convoluted answer.

Dr Smith: I thought that was a great answer. And when you say crowded optic disc, that's the- is that the "disc at risk"?

Dr De Lott: That is the "disk at risk," yes. So, crowded optic disk is really a disk that is smaller than what we see in the average population, and the average cup to disk ratio is 0.3. So, I think that's where 30% of the disk should be. So, this extra wiggle room, as I sometimes will explain to my patients.

Dr Smith: And then, I wonder if you could talk a little bit about more- just more about exam, right? You raised the importance of recognizing optic disc edema. Are there aspects of that disc edema that really steer you away from optic neuritis and towards ischemia-like hemorrhages or whatnot? And then a similar question about the importance of careful visual field testing?

Dr De Lott: So, on the whole, optic disc edema is optic disc edema. And you can have very severe optic neuritis with hemorrhages, cotton wool spots, which is essentially just an infarction of the retinal nerve fiber layer either overlying the disc or other parts of the retina. And ischemia, you can have some of the same features. In patients who have giant cell arteritis, which is just one form of anterior ischemic optic neuropathy, patients can have a pallid optic disc edema where the optic disc is swollen and white-looking. But on the whole, swelling is swelling. So, I would caution anyone against using the features of the optic nerve swelling to make any type of, sort of, definitive kind of diagnosis. It's worth keeping in mind, but I just- I would caution against using specific features, optic nerve swelling.

And then for visual field testing, there are certain patterns that sometimes can be helpful. I think as I mentioned earlier, in patients with ischemic optic neuropathy, we'll often see an altitudinal defect where either the top half or, more commonly, the bottom half of the vision is lost. And that vision loss in the field corresponds to the area of swelling on the disk, which is really rewarding when you're actually able to see sectoral swelling of the disk. So, say the top half of the disk is swollen and you see a really dense inferior defect. And other types of optic neuropathy such as hereditary optic neuropathies, toxic and nutritional optic neuropathies, they often cause more central field loss. And in patients who have optic neuropathies from elevated intracranial pressure, so papilladema, those folks often have more subtle visual field loss in an arcuate pattern. And it's only once the optic nerves have sustained a pretty significant injury that you start to see other patterns of field loss and actual decline in visual acuity in those patients. I do think a detailed visual field assessment can often be pretty helpful as an adjunct to the rest of the exam.

Dr Smith: So, we haven't talked a lot about neuroimaging, and obviously, neuroimaging is really important in patients who have optic neuritis. But how about an older patient in whom you suspect ischemic optic neuropathy? Do those patients all need a MRI scan? And if so, is it orbits and brain? How do you- how do you protocol it?

Dr De Lott: You're asking such a good question, totally controversial in in some ways. And so, in patients with ischemic optic neuropathy, if you are confident in your diagnosis: the patient is over the age of fifty, they have all the vascular, you know, they have vascular risk factors. And those vascular risk factors are things like diabetes, hypertension, high blood pressure, hyperlipidemia, obstructive sleep apnea. They have a "disc at risk" in the fellow eye. They don't have pain, they don't have a cancer history. Then doing an MRI of the orbits is probably not necessary to rule out another cause. But if you aren't confident that you have all of those features, then you should absolutely do an MRI of the orbit. The MRI of the brain probably doesn't provide you with much additional information. However, if you are trying to distinguish between an ischemic optic neuropathy and, say, maybe an optic neuritis, in those patients we do recommend MRI orbits and brain imaging because the brain does provide additional information about other CNS demyelinating disorders that might be actually the cause of a patient's optic neuritis.

Dr Smith: I wonder if you could talk a little bit about posterior ischemic optic neuropathy. That's much less common, and you mentioned earlier that those patients don't have optic disk edema. So, if there's a patient who has vision loss that- in a similar sort of clinical scenario that you talked about, how do you approach that and under what circumstances do we see patients who have posterior ischemic optic neuropathy?

Dr De Lott: So, you're going to most often see patients with posterior ischemic optic neuropathy who, for example, have undergone a recent surgery. These are often associated with things like spinal surgeries, cardiac surgeries. And there are a number of risk factors that are associated with it. Things like blood pressure, drain surgery, the amount of blood loss, positioning of patient. And this is something that the surgeons and anesthesiologists are very sensitive to at this point in time, and many patients are often- this can be part of the normal informed consent process at this point in time since this is something that is well-recognized for specific surgeries. In those patients, though… again, unless you're really certain, for example, maybe the inpatient neurology attending and you've been asked to consult on a patient and it's very clear that they went into surgery normal, they came out of surgery with vision loss, and all the rest of the features really seem to be present. I would recommend that in those cases you think about orbital imaging, making sure you're not missing anything else. Again, unless all of the features really are present- and I think that's one of the themes, definitely, throughout this article, is really the importance of neuroimaging in helping us to distinguish between different types of optic neuropathy.

Dr Smith: Yeah, I think one of the things that Eric Eggenberger talks about in his article is the need to use precise nomenclature too, which I plan on talking to him about. But I think having this very structured approach- and your article does it very well, I'll tell our listeners who haven't seen it there's a series of really great tables in the article that outline a lot of these. I wonder, Lindsey, if we can switch to talk about arteritic optic neuropathy. Is that okay?

Dr De Lott: Sure. Yeah, absolutely.

Dr Smith: How do you sort that out in an older patient who comes in with an ischemic optic neuropathy?

Dr De Lott: Yeah. In patients who are over the age of fifty with an ischemic optic neuropathy, we always need to be thinking about giant cell arteritis. It is really a diagnosis we cannot afford to miss. If we do miss it, unfortunately, patients are likely to lose vision in their fellow eye about 1/3 to 1/2 the time. So, it is really one of those emergencies in neuro-ophthalmology and neurology. And so you want to do a thorough review systems for giant cell arteritis symptoms, things like headache, jaw claudication, myalgias, unintentional weight loss, fevers, things of that nature. You also want to check their inflammatory markers to look for evidence of an elevated ESR, elevated C-reactive protein. And then on exam, what you're going to find is that it can cause an anterior ischemic optic neuropathy, as I mentioned earlier. It can cause palette optic disc swelling. But giant cell arteritis can also cause posterior ischemic optic neuropathy. And so, it can be present without any swelling of the optic disc. And in fact, you know, you mentioned one of my mentors, John Trobe, who used to say that in a patient where you're entertaining the idea of posterior ischemic optic neuropathy, who is over the age of fifty with no optic disc swelling, you should be thinking about number one, giant cell arteritis; number two, giant cell arteritis; number three, giant cell arteritis. And so, I think that is a real take-home point is making sure that you're thinking of this diagnosis often in our patients who are over the age of fifty, have to rule it out.

Dr Smith: I'll ask maybe a simple question. And presumably just about everyone who you see with a presumed ischemic optic neuropathy, even if they don't have clinical features, you at least check a sed rate. Is that true?

Dr De Lott: I do. So, I do routinely check sedimentation rate and C-reactive protein. So, you need to check both. And the reason is that there are some patients who have a positive C-reactive protein but a normal sedimentation rate, so. And vice versa, although that is less common. And so both need to be checked. One other lab that sometimes can be helpful is looking at their CBC. You'll often find these patients with giant cell arteritis have elevated platelet counts. And if you can trend them over time, if you happen to have a patient that's had multiple, you'll see it sort of increasing over time.

Dr Smith: I'm just thinking about how you sort things out in the middle, right? I mean, so that not all patients with GCF, sky-high sed rate and CRP…. And I'm just thinking of Dr Trobe's wisdom. So, when you're in an uncertain situation, presumably you go ahead and treat with steroids and move to biopsy. Maybe you can talk a bit about that pathway?

Dr De Lott: Yeah, sure.

Dr Smith: What's the definitive diagnostic process? Do you- for instance, the sed rate is sky-high, do you still get a biopsy?

Dr De Lott: Yes. So, biopsy is still our gold-standard diagnosis here in the United States. I will say that is not the case in all parts of the world. In fact, many parts of Europe are moving toward using other ancillary tests in combination with labs and exam, the history, to make a definitive diagnosis of giant cell arteritis. And those tests are things like temporal artery ultrasound. We also, even though we call it temporal artery ultrasound, we actually need to image not only the temporal arteries but also the axillary arteries. The sensitivity and specificity is actually greater in those cases. And then there's high-resolution imaging of the vessels and the- both the intracranial and extracranial distributions. And both of those have shown some promise in their predictive values of patients actually having giant cell arteritis. One caution I would give to our listeners, though, is that, you know, currently in the US, temporal artery biopsy is still the gold standard. And reading the ultrasounds and the MRIs takes a really experienced radiologist. So, unless you really know the diagnostic accuracy at your institution, again, temporal artery biopsy remains the gold standard here. So, when you are considering giant cell arteritis, start the patient on steroids and- that's high dose, high dose steroids. In patients with vision loss, we use high dose intravenous methylprednisolone and then go ahead and get the biopsy.

Dr Smith: Super helpful. And are there other treatments, other than steroids? Maybe how long do you keep people on steroids? And let's say you've got a patient who's, you know, diabetic or has other factors that make you want to avoid the course of steroids. Are there other options available?

Dr De Lott: So, in the acute phase steroids are the only option. There is no other option. However, long term, yes, we do pretty quickly put patients on tocilizumab, which is really our first-line treatment. And I do that in conjunction with our rheumatology colleagues, who are incredibly helpful in managing and monitoring the tocilizumab for our patients. But when you're seeing the patients, you know, whether it's in the emergency room or in the hospital, those patients need steroids immediately. There are other steroid-sparing agents that have been tried, but the efficacy is not as good as tocilizumab. So, the American College of Rheumatology is really recommending tocilizumab as our first line steroid-sparing agent at this point.

Dr Smith: Outstanding. So again, I will refer our listeners to your article. It's just chock-full of great stuff. This has been a great conversation. Thank you so much for joining me today.

Dr De Lott: Thank you, Dr Smith. I really appreciate it.

Dr Smith: The pleasure has been all mine, and I know our listeners will be enjoying this as well. Again, today I've been interviewing Dr Lindsey De Lott about her article on optic neuropathies, which appears in the most recent issue of Continuum on neuro-ophthalmology. Be sure to check out Continuum Audio episodes from this and other issues. I already mentioned Dr Eggenberger and I will be talking about optic neuritis, which will be a great companion to this discussion. Listeners, thank you for joining us today.

Dr Monteith: This is Dr Teshamae Monteith, Associate Editor of Continuum Audio. If you've enjoyed this episode, you'll love the journal, which is full of in-depth and clinically relevant information important for neurology practitioners. Use the link in the episode notes to learn more and subscribe. AAN members, you can get CME for listening to this interview by completing the evaluation at continpub.com/audioCME. Thank you for listening to Continuum Audio.

Diagnosing and differentiating among the many possible localizations and causes of vision loss is an essential skill for neurologists. The approach to vision loss should include a history and examination geared toward localization, followed by a differential diagnosis based on the likely location of the pathophysiologic process.

In this episode, Aaron Berkowitz, MD, PhD, FAAN speaks with Nancy J. Newman, MD, FAAN, author of the article "Approach to Vision Loss" in the Continuum® April 2025 Neuro-ophthalmology issue.

Dr. Berkowitz is a Continuum® Audio interviewer and a professor of neurology at the University of California San Francisco in the Department of Neurology and a neurohospitalist, general neurologist, and clinician educator at the San Francisco VA Medical Center at the San Francisco General Hospital in San Francisco, California.

Dr. Newman is a professor of ophthalmology and neurology at the Emory University School of Medicine in Atlanta, Georgia.

Additional Resources

Read the article: Approach to Vision Loss

Subscribe to Continuum®: shop.lww.com/Continuum

Earn CME (available only to AAN members): continpub.com/AudioCME

Continuum® Aloud (verbatim audio-book style recordings of articles available only to Continuum® subscribers): continpub.com/Aloud

More about the American Academy of Neurology: aan.com

Social Media

facebook.com/continuumcme

@ContinuumAAN

Host: @AaronLBerkowitz

Full episode transcript available here

Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum. Thank you for listening to Continuum Audio. Be sure to visit the links in the episode notes for information about earning CME subscribing to the journal, and exclusive access to interviews not featured on the podcast.

Dr Berkowitz: This is Dr Aaron Berkowitz, and today I'm interviewing Dr Nancy Newman about her article on the approach to visual loss, which she wrote with Dr Valerie Biousse. This article appears in the April 2025 Continuum issue on neuro-ophthalmology. Welcome to the podcast, Dr Newman. I know you need no introduction, but if you wouldn't mind introducing yourself to our listeners.

Dr Newman: Sure. My name's Nancy Newman. I am a neurologist and neuro-ophthalmologist, professor of ophthalmology and neurology at the Emory University School of Medicine in Atlanta, Georgia.

Dr Berkowitz: You and your colleague Dr Biousse have written a comprehensive and practical article on the approach to visual loss here. It's fantastic to have this article by two of the world's leading experts and best-known teachers in neuro-ophthalmology. And so, readers of this article will find extremely helpful flow charts, tables and very nuanced clinical discussion about how to make a bedside diagnosis of the cause of visual loss based on the history exam and ancillary testing. We'll talk today about that important topic, and excited to learn from you and for our listeners to learn from you. To begin, let's start broad. Let's say you have a patient presenting with visual loss. What's your framework for the approach to this common chief concern that has such a broad differential diagnosis of localizations and of causes? Where do you start when you hear of visual loss? How do you think about this chief concern?

Dr Newman: Well, it's very fun because this is the heart of being a neurologist, isn't it? Nowhere in the nervous system is localization as important as the complaint of vision loss. And so, the key, as any neurologist knows, is to first of all figure out where the problem is. And then you can figure out what it is based on the where, because that will limit the number of possibilities. So, the visual system is quite beautiful in that regard because you really can exquisitely localize based on figuring out where things are. And that starts with the history and then goes to the exam, in particular the first localization. So, you can whittle it down to the more power-for-your-buck question is, is the vision lost in one eye or in two eyes? Because if the vision loss clearly, whether it's transient or persistent, is in only one eye, then you only have to think about the eyeball and the optic nerve on that side. So, think about that. Why would you ever get a brain MRI? I know I'm jumping ahead here, but this is the importance of localization. Because what you really want to know, once you know for sure it's in one eye, is, is it an eyeball problem---which could be anything from the cornea, the lens, the vitreous, the retina---or is it an optic nerve problem? The only caveat is that every once in a while, although we trust our patients, a patient may insist that a homonymous hemianopia, especially when it's transient, is only in the eye with the temporal defect. So that's the only caveat. But if it's in only one eye, it has to be in that side eyeball or optic nerve. And if it's in two eyes, it's either in both eyeballs or optic nerves, or it's chiasmal or retrochiasmal. So that's the initial approach and everything about the history should first be guided by that. Then you can move on to the more nuanced questions that help you with the whats. Once you have your where, you can then figure out what the whats are that fit that particular where.

Dr Berkowitz: Fantastic. And your article with Dr Biousse has this very helpful framework, which you alluded to there, that first we figure out, is it monocular or binocular? And we figure out if it's a transient or fixed or permanent deficit. So, you have transient monocular, transient binocular, fixed monocular, fixed binocular. And I encourage our listeners to seek out this article where you have a table for each of those, a flow chart for each of those, that are definitely things people want to have printed out and at their desk or on their phone to use at the bedside. Very helpful. So, we won't be able to go through all of those different clinical presentations in this interview, but let's focus on monocular visual loss. As you just mentioned, this can be an eye problem or an optic nerve problem. So, this could be an ophthalmologic problem or a neurologic problem, right? And sometimes this can be hard to distinguish. So, you mentioned the importance of the history. When you hear a monocular visual loss- and with the caveat, I said you're convinced that this is a monocular visual problem and not a visual field defect that may appear. So, the patient has a monocular deficit, how do you approach the history at trying to get at whether this is an eye problem or an optic nerve problem and what the cause may be?

Dr Newman: Absolutely. So, the history at that point tends not to be as helpful as the examination. My mentor used to say if you haven't figured out the answer to the problem after your history, you're in trouble, because that 90% of it is history and 10% is the exam. In the visual system, the exam actually may have even more importance than anywhere else in the neurologic examination. And we need as neurologists to not have too much hubris in this. Because there's a whole specialty on the eyeball. And the ophthalmologists, although a lot of their training is surgical training that that we don't need to have, they also have a lot of expertise in recognizing when it's not a neurologic problem, when it's not an optic neuropathy. And they have all sorts of toys and equipment that can very much help them with that. And as neurologists, we tend not to be as versed in what those toys are and how to use them. So, we have to do what we can do.

Your directive thalmoscope, I wouldn't throw it in the garbage, because it's actually helpful to look at the eyeball itself, not just the back of the eye, the optic nerve and retina. And we'll come back to that, but we have in our armamentarium things we can do as neurologists without having an eye doctor's office. These include things like visual acuity and color vision, confrontation, visual fields. Although again, you have to be very humble. Sometimes you're lucky; 30% of the time it's going to show you a defect. It has to be pretty big to pick it up on confrontation fields. And then as we say, looking at the fundus. And you probably know that myself and Dr Biousse have been on somewhat of a crusade to allow the emperor's new clothes to be recognized, which is- most neurologists aren't very comfortable using the direct ophthalmoscope and aren't so comfortable, even if they can use it, seeing what they need to see. It's hard. It's really, really hard. And it's particularly hard without pupillary dilation. And technology has allowed us now with non-mydriatic cameras, cameras that are incredible, even through a small pupil can take magnificent pictures of the back of the eye. And who wouldn't rather have that? And as their cost and availability- the cost goes down and their availability goes up. These cameras should be part of every neurology office and every emergency department. And this isn't futuristic. This is happening already and will continue to happen. But over the next five years or so… well, we're transitioning into that.

I think knowing what you can do with the direct ophthalmoscope is important. First of all, if you dial in plus lenses, you can't be an ophthalmologist, but you can see media opacities. If you can't see into the back of the eye, that may be the reason the patient can't see out. And then just seeing if someone has central vision loss in one eye, it's got to be localized either to the media in the axis of vision; or it's in the macula, the very center of the retina; or it's in the optic nerve. So, if you get good at looking at the optic nerve and then try to curb your excitement when you saw it and actually move a little temporally and take a look at the macula, you're looking at the two areas. Again, a lot of ophthalmologists these days don't do much looking with the naked eye. They actually do photography, and they do what's called OCT, optical coherence tomography, which especially for maculopathies, problems in the macula are showing us the pathology so beautifully, things that used to be considered subtle like central serous retinopathy and other macula. So, I think having a real healthy respect for what an eye care provider can do for you to help screen away the ophthalmic causes, it's very, very important to have a patient complaining of central vision loss, even if they have a diagnosis like multiple sclerosis, you expect that they might have an optic neuritis… they can have retinal detachments and other things also. And so, I think every one of these patients should be seen by an eye care provider as well.

Dr Berkowitz: Thank you for that overview. And I feel certainly as guilty as charged here as one of many neurologists, I imagine, who wish we were much better and more comfortable with fundoscopy and being confident on what we see. But as you said, it's hard with the direct ophthalmoscope and a non-dilated exam. And it's great that, as you said, these fundus photography techniques and tools are becoming more widely available so that we can get a good look at the fundus. And then we're going to have to learn a lot more about how to interpret those images, right? If we haven't been so confident in our ability to see the fundus and analyze some of the subtle abnormalities that you and your colleagues and our ophthalmology colleagues are more familiar with. So, I appreciate you acknowledging that. And I'm glad to hear that coming down the pipeline, there are going to be some tools to help us there. So, you mentioned some of the things you do at the bedside to try to distinguish between eye and optic nerve. Could you go into those in a little bit more detail here? How do you check the visual fields? For example, some people count fingers, some people wiggle fingers, see when the patient can see. How should we be checking visual fields? And what are some of the other bedside tasks you use to decide this is probably going to end up being in the optic nerve or this seems more like an eye?

Dr Newman: Of course. Again, central visual acuity is very important. If somebody is older than fifty, they clearly will need some form of reading glasses. So, keeping a set of plus three glasses from cheapo drugstore in your pocket is very helpful. Have them put on their glasses and have them read an ear card. It's one of the few things you can actually measure and examine. And so that's important. The strongest reflex in the body and I can have it duke it out with the peripheral neurologists if they want to, it's not the knee jerk, it's looking for a relative afferent pupillary defect. Extremely important for neurologists to feel comfortable with that. Remember, you cut an optic nerve, you're not going to have anisocoria. It's not going to cause a big pupil. The pupils are always equal because this is not an efferent problem, it's an afferent problem, an input problem.

So basically, if the eye has been injured in the optic nerve and it can't get that information about light back into the brain, well, the endoresfol nuclei, both of them are going to reset at a bigger size. And then when you swing over and shine that light in the good optic nerve, the good eye, then the brain gets all this light and both endoresfol nuclei equally set those pupils back at a smaller size. So that's the test for the relative afferent pupillary defect. When you swing back and forth. Of course, when the light falls on the eye, that's not transmitting light as well to the brain, you're going to see the pupil dilate up. But it's not that that pupil is dilating alone. They both are getting bigger. It's an extremely powerful reflex for a unilateral or asymmetric bilateral optic neuropathy. But what you have to remember, extremely important, is, where does our optic nerve come from? Well, it comes from the retinal ganglion cells. It's the axons of the retinal ganglion cells, which is in the inner retina. And therefore inner retinal disorders such as central retinal artery occlusion, ophthalmic artery occlusion, branch retinal artery occlusion, they will also give a relative afferent pupillary defect because you're affecting the source. And this is extremely important. A retinal detachment will give a relative afferent pupillary defect. So, you can't just assume that it's optic nerve. Luckily for us, those things that also give a relative afferent pupillary defect from a retinal problem cause really bad-looking retinal disease. And you should be able to see it with your direct ophthalmoscope. And if you can't, you definitely will be able to see it with a picture, a photograph, or having an ophthalmologist or optometrist take a look for you.

That's really the bedside. You mentioned confrontation visual fields. I still do them, but I am very, very aware that they are not very sensitive. And I have an extremely low threshold to- again, I have something in my office. But if I were a general neurologist, to partner with an eye care specialist who has an automated visual field perimeter in their office because it is much more likely to pick up a deficit. Confrontation fields. Just remember, one eye at a time. Never two eyes at the same time. They overlap with each other. You're going to miss something if you do two eyes open, so one eye at a time. You check their field against your field, so you better be sure your field in that eye is normal. You probably ought to have an automated perimetry test yourself at some point during your career if you're doing that. And remember that the central thirty degrees is subserved by 90% of our fibers neurologically, so really just testing in the four quadrants around fixation within the central 30% is sufficient. You can present fingers, you don't have to wiggle in the periphery unless you want to pick up a retinal detachment.

Dr Berkowitz: You mentioned perimetry. You've also mentioned ocular coherence tomography, OCT, other tests. Sometimes we think about it in these cases, is MRI one of the orbits? When do you decide to pursue one or more of those tests based on your history and exam?

Dr Newman: So again, it sort of depends on what's available to you, right? Most neurologists don't have a perimeter and don't have an OCT machine. I think if you're worried that you have an optic neuropathy, since we're just speaking about monocular vision loss at this point, again, these are tests that you should get at an office of an eye care specialist if you can. OCT is very helpful specifically in investigating for a macular cause of central vision loss as opposed to an optic nerve cause. It's very, very good at picking up macular problems that would be bad enough to cause a vision problem. In addition, it can give you a look at the thickness of the axons that are about to become the optic nerve. We call it the peripapillary retinal nerve fiber layer. And it actually can look at the thickness of the layer of the retinal ganglion cells without any axons on them in that central area because the axons, the nerve fiber layer, bends away from central vision. So, we can see the best we can see. And remember these are anatomical measurements. So, they will lag, for the ganglion cell layer, three to four weeks behind an injury, and for the retinal nerve fiber, layer usually about six weeks behind an entry. Whereas the functional measurements, such as visual acuity, color vision, visual fields, will be immediate on an injury. So, it's that combination of function and anatomy examination that makes you all-powerful. You're very much helped by the two together and understanding where one will be more helpful than the other.

Dr Berkowitz: Let's say we've gotten to the optic nerve as our localization. Many people jump to the assumption it's the optic nerve, it's optic neuritis, because maybe that's the most common diagnosis we learn in medical school. And of course, we have to sometimes, when we're teaching our students or trainees, say, well, actually, not all optic nerve disease, optic neuritis, we have to remember there's a broader bucket of optic neuropathy. And I remember, probably I didn't hear that term until residency and thought, oh, that's right. I learned optic neuritis. Didn't really learn any of the other causes of optic nerve pathology in medical school. And so, you sort of assume that's the only one. And so you realize, no, optic neuropathy has a differential diagnosis beyond optic neuritis. Neuritis is a common cause. So how do you think about the "what" once you've localized to the optic nerve, how do you think about that? Figure out what the cause of the optic neuropathy is?

Dr Newman: Absolutely. And we've been trying to convince neuro-radiologists when they see evidence of optic nerve T2 hyperintensity, that just means damage to the optic nerve from any cause. It's just old damage, and they should not put in their read consistent with optic neuritis. But that's a pet peeve. Anyway, yes, the piece of tissue called the optic nerve can be affected by any category of pathophysiology of disease. And I always suggest that you run your categories in your head so you don't leave one out. Some are going to be more common to be bilateral involvement like toxic or metabolic causes. Others will be more likely unilateral. And so, you just run those guys. So, in my mind, my categories always are compressive-slash-infiltrative, which can be neoplastic or non-neoplastic. For example, an ophthalmic artery aneurysm pressing on an optic nerve, or a thyroid, an enlarged thyroid eye muscle pressing on the optic nerve. So, I have compressive infiltrative, which could be neoplastic or not neoplastic. I have inflammatory, which can be infectious. Some of the ones that can involve the optic nerve are syphilis, cat scratch disease. Or noninfectious, and these are usually your autoimmune such as idiopathic optic neuritis associated with multiple sclerosis, or MOG, or NMO, or even sarcoidosis and inflammation.

Next category for me would be vascular, and you can have arterial versus venous in the optic nerve, probably all arterial if we're talking about causes of optic neuropathy. Or you could have arteritic versus nonarteritic with the vascular, the arteritic usually being giant cell arteritis. And the way the optic nerve circulation is, you can have an anterior ischemic optic neuropathy or a posterior ischemic optic neuropathy defined by the presence of disc edema suggesting it's anterior, the front of the optic nerve, or not, suggesting that it's retrobulbar or posterior optic nerve.

So what category am I- we mentioned toxic, metabolic nutritional. And there are many causes in those categories of optic neuropathy, usually bilateral. You can have degenerative or inherited. And there are causes of inherited optic neuropathies such as Leber hereditary optic neuropathy and dominant optic atrophy. And then there's a group I call the mechanical optic neuropathies. The obvious one is traumatic, and that can happen in any piece of tissue. And then the other two relate to the particular anatomy of the eyeball and the optic nerve, and the fact that the optic nerve is a card-carrying member of the central nervous system. So, it's not really a nerve by the way, it's a tract. Think about it. Anyway, white matter tract. It is covered by the same fluid and meninges that the rest of the brain. So, what mechanically can happen? Well, you could have an elevated intraocular pressure where that nerve inserts. That's called glaucoma, and that would affect the front of the optic nerve. Or you can have elevated intracranial pressure. And if that's transmitted along the optic nerve, it can make the front of the optic nerve swell. And we call that specifically papilledema, optic disk edema due specifically to raised intracranial pressure. We actually even can have low intraocular pressure cause something called hypotony, and that can actually even give an optic neuropathy the swelling of the optic nerve. So, these are the mechanical. And if you were to just take that list and use it for any piece of tissue anywhere, like the heart or the kidney, you can come up with your own mechanical categories for those, like pericarditis or something like that. And then all those other categories would fit. But of course, the specific causes within that pathophysiology are going to be different based on the piece of tissue that you have. In this case, the optic nerve.

Dr Berkowitz: In our final moments here, we've talked a lot about the approach to monocular visual loss. I think most neurologists, once we find a visual field defect, we breathe a sigh of relief that we know we're in our home territory here, somewhere in the visual task base that we've studied very well. I'm not trying to distinguish ocular causes amongst themselves or ocular from optic nerve, which can be very challenging at the bedside. But one topic you cover in your article, which I realized I don't really have a great approach to, is transient binocular visual loss. Briefly here, since we're running out of time, what's your approach to transient binocular visual loss?

Dr Newman: We assume with transient binocular vision loss that we are not dealing with a different experience in each eye, because if you have a different experience in each eye, then you're dealing with bilateral eyeball or optic nerve. But if you're having the same experience in the two eyes, it's equal in the two eyes, then you're located. You're located, usually, retro chiasmally, or even chiasm if you have pituitary apoplexy or something. So, all of these things require imaging, and I want to take one minute to talk about that. If you are sure that you have monocular vision loss, please don't get a brain MRI without contrast. It's really useless. Get a orbital MRI with contrast and fat suppression techniques if you really want to look at the optic nerve. Now, let's say you you're convinced that this is chiasmal or retrochiasmal. Well then, we all know we want to get a brain MRI---again, with and without contrast---to look specifically where we could see something. And so, if it's persistent and you have a homonymous hemianopia, it's easy, you know where to look. Be careful though, optic track can fool you. It's such a small little piece, you may miss it on the MRI, especially in someone with MS. So really look hard. There's very few things that are homonymous hemianopias MRI negative. It may just be that you didn't look carefully enough. And as far as the transient binocular vision loss, again, remember, even if it's persistent, it has to be equal vision in the two eyes. If there's inequality, then you have a superimposed anterior visual pathway problem, meaning in front of the chiasm on the side that's worse.

The most common cause of transient binocular vision loss would be a form of migraine. The visual aura of migraine usually is a positive phenomenon, but sometimes you can have a homonymous hemianopic persistent defect that then ebbs and flows and goes away. Usually there's buildup, lasts maybe fifteen minutes and then it goes away, not always followed by a headache. Other things to think of would be transient ischemic attack in the vertebra Basler system, either a homonymous hemianopia or cerebral blindness, what we call cortical blindness. It can be any degree of vision loss, complete or any degree, as long as the two eyes are equal. That should last only minutes. It should be maximum at onset. There should be no buildup the way migraine has it. And it should be gone within less than ten minutes, typically. After fifteen, that's really pushing it. And then you could have seizures. Seizures can actually be the aura of a seizure, the actual ictal phenomenon of a seizure, or a postictal, almost like a todd's paralysis after a seizure. These events are typically bright colors and flashing, and they last usually seconds or just a couple of minutes at most. So, you can probably differentiate them. And then there are the more- less common but more interesting things like hyperglycemia, non-ketonic hyperglycemia can give you transient vision loss from cerebral origin, and other less common things like that.

Dr Berkowitz: Fantastic. Although we've talked about many pearls of clinical wisdom here with you today, Dr Newman, this is only a fraction of what we can find in your article with Dr Biousse. We focused here on monocular visual loss and a little bit at the end here on binocular visual loss, transient binocular visual loss. But thank you very much for your article, and thank you very much for taking the time to speak with us today. Again, today I've been interviewing Dr Nancy Newman about her article with Dr Valerie Biousse on the approach to visual loss, which appears in the most recent issue of Continuum on neuro-ophthalmology. Be sure to check out Continuum audio episodes from this and other issues. Thank you so much to our listeners for joining us today.

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