What are the earliest signs of acute disseminated encephalomyelitis (ADEM)?

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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The first signs of ADEM usually include abrupt onset encephalopathy (alteration in consciousness or behavioral change unexplained by fever, systemic illness or postictal symptoms. [59] Rapid-onset encephalopathy is typically associated with multifocal neurologic symptoms.

  • In most cases, the clinical course is rapidly progressive and typically develops over hours to maximum deficits within days (mean of 4.5 days). [85] A minority of cases show continued deterioration of function for periods as long as 4 weeks.

  • Strictly speaking, encephalopathy, unexplained by fever, should be present for a diagnosis of ADEM, though it may not be the presenting sign. A single institution follow-up study (at least 5.5 y for each individual) of 52 young individuals (age range 10 mo to 19 y) who presented with their first bout of an acute central nervous system demyelinating disease included 26 children ultimately diagnosed with MS and 24 diagnosed with ADEM. Encephalopathy was the presenting sign in 42% of those with a follow-up diagnosis of ADEM but none of the individuals with a follow-up diagnosis of MS. [7]

  • Convulsive seizures occur around the onset of ADEM in as many as 35% of cases. [85]

  • Meningismus may be present and has been reported in up to 30% of cases. [63]

  • Although almost any portion of the CNS may be clinically involved, certain systems appear to be particularly prone to dysfunction; thus, the descending white matter motor tracts, optic nerves, and spinal cord are particularly commonly involved.

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