Acute Disseminated Encephalomyelitis

Acute disseminated encephalomyelitis (ADEM) is an inflammatory demyelinating syndrome with encephalopathy. ADEM typically affects young children, is often postinfectious, and is typically monophasic. MRI neuroimaging, which shows new lesions with poorly demarcated borders, but not old and established lesions, is essential to diagnosis. Autoantibodies against myelin oligodendrocyte glycoprotein (MOG) are found in ∼40% of ADEM patients, and these patients have different clinical and neuroimaging features to seronegative patients. Treatment in the acute phase is typically with high-dose corticosteroids and intravenous immunoglobulin or plasma exchange for refractory patients. Outcome is usually good, but residual cognitive, inattentive, and executive issues are likely underestimated. In patients who have a relapse, biomarkers and imaging should help differentiate multiphasic ADEM, neuromyelitis optica spectrum disorder, anti-MOG antibody–associated relapsing demyelination, and multiple sclerosis.