Acute disseminated encephalomyelitis.

Acute disseminated encephalomyelitis (ADEM) is a demyelinating syndrome of the central nervous system. It is considered to be an autoimmune response to an antecedent antigenic stimulus, most frequently a prior infectious illness (postinfectious encephalitis) or immunization (postvaccination encephalitis) occurring in the days or weeks before neurologic illness. Clinically, ADEM is characterized by encephalopathy, or focal/multifocal neurologic signs; brain MRI is characterized by diffuse multifocal or patchy areas of demyelination. The differentiation between ADEM and a first episode of multiple sclerosis, a chronic central nervous system demyelinating disease, may be difficult but has important prognostic and treatment implications. Although no clinical trials have assessed the efficacy of treatment modalities in patients with ADEM, immunomodulators, including corticosteroids and intravenous immunoglobulin, are frequently used empirically. ADEM outcome is generally favorable, with resolution over weeks to months.