What is the frequency of a prodrome in 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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Answer

A cause-and-effect relationship between a possible prodrome and ADEM is more difficult to establish in cases where longer or very short intervals exist between a possible exogenous stimulus and inflammatory result.

  • Latencies longer than 50 days have been suggested for infections or vaccines but are difficult to prove. [6]

  • Relationships are also difficult to determine when a febrile systemic process is rapidly followed by neurologic deterioration because such cases may represent meningoencephalitis.

    • Approximately 25% of cases lack a clearly-defined prodrome. [47, 58, 85]

    • Some of these cases are possible examples of longer than 20 days of latency from prodrome to ADEM, especially in prepubertal children, with imaging changes suggesting ADEM, with negative CSF immune profile, and with rapid and complete recovery.

    • Another subgroup with poorly-defined prodrome but low risk for recurrence are children or adolescents manifesting subacute-onset syndromes that combine neuropsychiatric abnormalities and movement disorders and imaging changes suggestive of ADEM. The course in these cases, which could be termed Johnson syndrome, is often prolonged or even progressive, improving with high-dose intravenous corticosteroids.


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