Acute Disseminated Encephalomeylitis (ADEM)
Acute Disseminated Encephalomyelitis (ADEM)

ADEM is an intense autoimmune disease that produces multiple inflammatory lesions in the brain and spinal cord that damage nerve fibers. ADEM occurs in fewer than 1 (0.8) per 100,000 people per year.


Symptoms of fever, headache, drowsiness, nausea and vomiting and, in severe cases, seizures and coma usually begin 1 to 3 weeks after infection or rarely after vaccination. Although initially the symptoms may be mild, they worsen rapidly over the course of hours to days. The average time to maximum severity is about 4 to 5 days. Symptoms such as visual loss, difficulty walking and paralysis can occur. The symptoms are sometimes misdiagnosed as a severe first attack of multiple sclerosis.


ADEM often occurs after a viral infection, or rarely after certain vaccinations, bacterial or parasitic infections, or it can even appear spontaneously.

Diagnostic Tests

Imaging techniques, such as MRI (magnetic resonance imaging), may be used to search for telltale areas of inflammatory damage in the brain and spinal cord. Rarely, a brain biopsy may be performed.


Aggressive treatment with high doses of intravenous corticosteroids is aimed at rapidly reducing inflammation of the brain and spinal cord. Alternative therapies, used when corticosteroids cannot be used or fail to show an effect, include intravenous immunoglobulins or plasmapheresis.


If treated, most patient with ADEM begin recovery within days. Between 50 to 70% of patients recover completely. Some patinets may have some degree of lifelong impairment, ranging from mild clumsiness to paralysis. Severe cases of ADEM can be fatal. Some who are first diagnosed with ADEM later are discovered to have multiple sclerosis.