Acute encephalitis describes a rapidly developing inflammation of the brain. It is a life-threatening disease with a mortality rate of up to 15%. However, the cause of 37 to 62% of encephalitis cases is not identified, even after a thorough diagnostic investigation. Mark Ellul is a Specialist Registrar in Neurology and Clinical Research Fellow funded by the Association of British Neurologists at IGH. He recently published a paper in Clinical Medicine “Acute encephalitis – diagnosis and management” (http://www.clinmed.rcpjournal.org/content/18/2/155.abstract). He came to talk to us about acute encephalitis and his work searching for new diagnostic tools to help doctors in the emergency room.