Background: Many cases of seizure are obvious, and many cases of syncope are obvious, but some fall into the grey zone in between. Witnesses often think a patient has had a seizure because there were jerking movements during the episode, and it can be tricky for us to figure out what really happened after the fact. That is, it was tricky until this lovely little paper came along…

 

The paper: This was a comparison of the videotape recordings of 65 cases of syncope and 50 cases of seizure. The first group were undergoing tilt table testing for suspected vasovagal syncope, while the second were being evaluated for epilepsy. The authors focused primarily on motor phenomena, looking for patterns to differentiate syncope from seizure. The results are shown in the table below. (Neurology, April 2018)

 

   Syncope   

   Seizure   

Myoclonic jerks?          

51%

100%

Bilateral?

78%

100%

Synchronous?

48%

90%

Median number

2

48

Duration of jerking

3.6s

29s

Tonic posture

65%

100%

Loss of tone

100%

0%

 

The bottom line: The following phenomena favour syncope rather than seizure as the diagnosis: no myoclonic jerks, or a few myoclonic jerks that are unilateral or asynchronous, and loss of tone. The authors coin the 10/20 rule – 10 jerks or less is syncope; 20 jerks or more is seizure.