How are acute disseminated encephalomyelitis (ADEM) lesions characterized on MRI?

Updated: Nov 08, 2018
  • Author: J Nicholas Brenton, MD; Chief Editor: Tarakad S Ramachandran, MBBS, MBA, MPH, FAAN, FACP, FAHA, FRCP, FRCPC, FRS, LRCP, MRCP, MRCS  more...
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Answer

ADEM lesions are characteristically multiple, bilateral but asymmetric, and widespread within the CNS.

  • Typical lesions of ADEM include centrifugal at the junction of the deep cortical gray and subcortical white matter. Such lesions are found in more than 90% of children with ADEM. They are found in less than 40% of adults initially diagnosed as having ADEM, many of whom are later diagnosed as having MS.

  • Additional lesions may be found in deeper white matter, basal ganglia (30-40%), thalamus (30-40%), brainstem (45-55%), cerebellum (30-40%), and the spinal cord (16-28%). [47, 58, 54, 11] Periventricular lesions and corpus callosal lesions are uncommon in childhood ADEM compared with MS. [11]

  • The indistinct margins of childhood ADEM lesions tend to suggest a "smudged" edge rather than the crisp margin typical of the classic ellipsoid plaques of MS.

  • Though variable, as many as 90% of childhood ADEM lesions enhance with gadolinium. The degree of contrast enhancement of ADEM lesions is typically uniform and usually not very dense. In contrast, MS plaques tend to vary in degree of contrast enhancement and may at times enhance quite densely. [12, 13, 14]

    Typical childhood ADEM in 7-year-old. Note tendenc Typical childhood ADEM in 7-year-old. Note tendency to involve gray-white junction, the fact that the lesion margins are less well defined than typical MS plaques, and that the deep white matter lesions are not oriented perpendicularly to the ventricular surface as is typical in MS.
    Typical adolescent multiple sclerosis findings on Typical adolescent multiple sclerosis findings on MRI. Note the tendency of lesions to exhibit sharp margins, to be elongated, to occur in deep white matter or corpus callosum sparing the cortical gray-white junction, and to be oriented perpendicularly to the ventricular surface.

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