Acute disseminated encephalomyelitis (ADEM)

Acute disseminated encephalomyelitis is a sudden, usually one-time burst of inflammation and demyelination across the brain and spinal cord. It's understood as an immune reaction, often triggered after a viral infection or, rarely, a vaccination, in which the immune system attacks myelin, the insulating coating around nerve fibers, in the central nervous system. It is more common in children and is most often monophasic, a single event rather than a recurring illness, though relapsing forms have been reported and can be hard to distinguish from multiple sclerosis.

Research describes ADEM as a rare condition, with one widely cited estimate placing overall incidence around 0.4 per 100,000 people per year and no particular gender, age group, or region disproportionately affected. Outcomes in children are generally favorable, though cognitive effects can persist even when other symptoms resolve.

Common signs

A fairly rapid onset of confusion or altered consciousness (encephalopathy) along with fever, headache, and multiple neurological problems such as weakness, vision changes, unsteadiness, and sometimes seizures.

This is a plain-language summary for orientation, not a diagnosis. Mechanisms are described as current understanding, not settled fact. Work with your own clinician for your care.