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  1. L Bennetto,
  2. N Scolding
  1. Institute of Clinical Neurosciences, Department of Neurology, University of Bristol, Frenchay Hospital, Bristol, UK
  1. Correspondence to:
 Professor Neil J Scolding
 Institute of Clinical Neurosciences, Department of Neurology, University of Bristol, Frenchay Hospital, Bristol BS16 1LE, UK;

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Post-infectious and inflammatory encephalomyelitis are broadly represented by the syndrome acute disseminated encephalomyelitis (ADEM). ADEM forms one of several categories of primary inflammatory demyelinating disorders of the central nervous system. Others include multiple sclerosis (MS), acute transverse myelitis, and Devic’s disease. It should be remembered that these are syndromically defined diseases at present. There are no diagnostic tests presently available short of brain biopsy, but future advances may reveal diagnostic biological markers of disease and in so doing dramatically advance the pathophysiological and therapeutic understanding of these conditions. A wholesale change in classification and nomenclature may well follow. In the meantime clinicians must remain keenly appreciative of subtle shades of grey: ADEM, first MS relapse, or ultimately benign clinically isolated syndrome? The answers are relevant to prognosis and, more recently, selection of the correct therapeutic strategy.


ADEM is an inflammatory demyelinating disorder of the central nervous system that is usually monophasic, but a relapsing variant distinct from MS—multiphasic disseminated encephalomyelitis (MDEM) is well-described. ADEM is predominantly, though by no means exclusively, a disease of children and in particular infants. Historically it includes post-infectious encephalomyelitis and post-vaccination encephalomyelitis. While these two syndromes were distinguished by their precipitant it was realised that clinically and pathologically they were very similar. As there were also a significant proportion of cases in which no antecedent infectious or inflammatory event is identifiable historically, microbiologically, or serologically the term ADEM has become clinically useful. ADEM has a more severe and aggressive phenotype than acute events or relapses in MS; it is, however, less severe than the often fatal acute haemorrhagic leucoencephalomyelitis. ADEM (and MDEM) does not share the relentless progressive phase evident in MS, and providing the initial insult is withstood, ultimately has a better prognosis.


Post-infectious encephalomyelitis is associated with an antecedent or concomitant infection, usually …

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