Acute disseminated encephalomyelitis (ADEM) is an autoimmune disorder of the central nervous system that is a brief but widespread inflammatory process of the brain and spinal cord. ADEM tends to have a rapid and dramatic onset with symptoms of high fever, headache, fatigue, nausea and vomiting, confusion, seizures and even sometimes, coma. Like with other neuroimmune disorders, the inflammation caused by ADEM damages myelin – the protective coating covering nerves in the brain.
ADEM primarily attacks children: over 80% of ADEM victims are younger than ten years old. Most of the rest are diagnosed between the ages of ten and twenty. Only rarely does ADEM strike adults. ADEM attacks slightly more boys than girls. It tends to appear seasonally, most frequently in spring and winter. ADEM touches all ethnic groups and geographic locations with similar prevalence – 1 in every 125,000 – 250,000. Most often, ADEM strikes after a bacterial or viral infection, and very rarely, after a measles, mumps & rubella (MMR) vaccine. In about half of all cases, ADEM is associated with the MOG antibody and in others, no trigger is found.
Treatments include intravenous corticosteroids followed by a tapering course of oral steroids. Most ADEM patients improve within days of starting treatment, and are generally fully recovered within six months. ADEM in children is most often a one-time attack, although a minority of ADEM patients continue to suffer some symptoms for their entire lives. Relapses can occur, especially in those who are older at onset and who test seropositive for the MOG antibody.
Though acute disseminated encephalomyelitis is the most common name for this disorder, it is sometimes called post-infectious encephalomyelitis or immune-mediated encephalomyelitis.
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