Acute disseminated encephalomyelitis (ADEM) is also known as or subsumes Postinfectious encephalomyelitis and Parainfectious encephalomyelitis. -ed.
Approximately 25% of all children with an acute inflammatory demyelinating attack in the central nervous system will meet consensus criteria for a diagnosis of acute disseminated encephalomyelitis. Acute disseminated encephalomyelitis is clinically defined by polyfocal neurologic deficits and encephalopathy, and is radiographically characterized by multifocal areas of increased signal in both white and gray matter of the brain and spinal cord visible on T2/FLAIR-weighted magnetization resonance images. Acute disseminated encephalomyelitis is primarily a pediatric disorder, though adults can be affected. Though the etiologic mechanisms have not been fully elucidated, acute disseminated encephalomyelitis is thought to be an immune-mediated process and is often precipitated by viral infection. Acute disseminated encephalomyelitis is typically a monophasic illness, but multiphasic forms have been reported. There are no laboratory features diagnostic of acute disseminated encephalomyelitis. A small proportion of children ultimately diagnosed with multiple sclerosis or neuromyelitis optica experience an acute disseminated encephalomyelitis—like first clinical attack. Features more strongly associated with a monophasic acute disseminated encephalomyelitis illness will be presented. In this updated review, Drs. Sona Narula and Brenda Banwell of the Children’s Hospital of Philadelphia discuss clinical and imaging features, etiology, pathogenesis, differential diagnosis, and management of acute disseminated encephalomyelitis.