A 35 year-old woman presented with fever, headache and confusion. Over the next week she continued to deteriorate neurologically, eventually becoming comatose with bilateral long tract signs.

ADEM is a monophasic demyelinating syndrome that occurs as an autoimmune phenomenon typically following a viral infection or immunization. It is characterized clinically by rapid development of focal or multifocal neurological dysfunction. Clinical features include encephalopathy ranging from lethargy to coma, seizures, and focal or multifocal signs reflecting involvement of the cerebrum (hemiparesis), brainstem (cranial nerve palsies), and spinal cord (paraparesis). ADEM presents acutely, with features similar to encephalitis (fever, headache, seizures and coma). In some cases, it may not be possible to distinguish ADEM from the first episode of multiple sclerosis (MS). The mortality rate varies between 10% and 30%, with complete recovery in 50%.