How are acute disseminated encephalomyelitis (ADEM)-associated lesions distinguished from lesions caused by other conditions in the differential diagnosis?

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

Many of the diseases that constitute the differential diagnosis of ADEM produce MRI abnormalities that emulate various ADEM-associated lesions.

  • Some cases of encephalitis result in the development of multiple tiny or small patches of bright signal on T2-weighted images that have been mislabeled as ADEM, but response to corticosteroid therapy is poor and follow-up scans may show severe encephalomalacia.

  • HSV-2 encephalitis or Lyme disease may be difficult to distinguish from ADEM and may involve ADEM mechanisms in pathogenesis.

  • Pial enhancement does not occur in ADEM and suggests meningoencephalitis.

  • Metazoal parasitic diseases of the brain (eg, cysticercosis), neoplasia, and ADEM are occasionally mistaken for one another.

  • Metabolic leukdystrophies may appear similar on MRI but often exhibit symmetric abnormalities in the white matter (as opposed to the asymmetric abnormalities seen in ADEM).


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