Acute disseminated encephalomyelitis (ADEM)
- Article
- 2021-03-02
Acute disseminated encephalomyelitis (ADEM) is characterized by a brief but widespread attack of inflammation in the brain and spinal cord that damages myelin - the protective covering of nerve fibers. ADEM often follows viral or bacterial infections, or less often follows measles, mumps, or rubella vaccination. The symptoms of ADEM are rapid, starting with encephalitis-like symptoms such as fever, fatigue, headache, nausea and vomiting, and in the most severe cases, seizures and coma. ADEM typically damages white matter (brain tissue that gets its name from the white color of myelin), leading to neurological symptoms such as loss of vision (due to inflammation of the optic nerve) in one or both eyes, weakness even to the point of paralysis and difficulty coordinating voluntary muscle movements (such as those used in walking). ADEM is sometimes misdiagnosed as a serious first bout of multiple sclerosis (MS), as the symptoms and appearance of the white matter injury on brain imaging can be similar. However, ADEM has several features that distinguish it from MS. First, unlike MS patients, individuals with ADEM will develop a rapid fever, have a history of recent infection or immunization, and some degree of loss of consciousness, perhaps even coma; these features are not usually seen in MS. Children are more likely to have ADEM than adults, while MS is a rare diagnosis in children. In addition, ADEM usually consists of a single episode or attack of widespread myelin damage, while MS has many attacks over time. Doctors will often use imaging techniques, such as magnetic resonance imaging (MRI), to look for old and new lesions (damaged areas) in the brain. The presence of older brain lesions on MRI suggests that the condition may be MS rather than ADEM, as MS can cause brain lesions before symptoms become apparent. In rare situations, a brain biopsy may be required to distinguish between ADEM and some other diseases associated with inflammation and damage to myelin.
Therapy
The treatment of ADEM is aimed at suppressing inflammation in the brain with the help of anti-inflammatory drugs. Most people respond to intravenous corticosteroids such as methylprednisolone for several days, followed by oral corticosteroid treatment. When corticosteroids don't work, plasmapheresis or intravenous immunoglobulin therapy are possible secondary treatment options that are reported to help in some severe cases. Additional treatment is symptomatic and supportive.
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