Summary of Acute Disseminated Encephalomyelitis
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When considering intradural intramedullary
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lesions in children,
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we should consider the possibility of ADEM.
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Remember that this was originally described as a
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monophasic disease, but we now know that it,
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too, may be polyphasic.
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It occurs classically two to four weeks after
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viral illnesses, most commonly,
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immunizations, much less commonly.
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It is a delayed type hypersensitivity type IV
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reaction to the myelin basic protein.
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So it's an autoimmune disorder,
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and you may have both brain and spine lesions.
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There is a hemorrhagic aggressive form that only
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occurs in the brain, not in the spinal cord.
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Where does ADEM occur? As you can see,
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predominantly in the brain.
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However, the cord lesions occur in 50% of patients who
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are children and 10% of adult lesions, so
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much more likely to occur in the brain.
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But you may see manifestations in the cord
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in children after viral illnesses.
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The typical ADEM appearance in the brain shows
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both white matter confluent lesions, as well as
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deep gray matter lesions, distinguishing
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it from multiple sclerosis.
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And these lesions may or may not
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show contrast enhancement.
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As I mentioned, sometimes you will have multiphasic
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disseminated encephalomyelitis,
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and this may be a precursor to the development
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as an adult of multiple sclerosis.
David M Yousem, MD, MBA
Professor of Radiology, Vice Chairman and Associate Dean
Johns Hopkins University
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