What are the pathophysiologic mechanisms 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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Answer

The mechanisms of these demyelinating illnesses remain incompletely understood despite the extraordinary richness and complexity of immunologic abnormalities that have been identified after more than a century of clinical, pathological, and laboratory studies. Experimental observations have depended greatly on EAE, a research model that may be more pertinent to ADEM than MS.

However, the possibility of provoking spontaneously recurrent demyelination with this model further supports the concept that ADEM and MS represent a continuum. Basic studies have shown that, in the earliest stages of inflammation, both MS and ADEM are likely to be mediated by stimulated clones of T-helper cells sensitized to auto-antigens such as myelin proteins. Some studies have even identified serum autoantibodies to various myelin proteins that help to differentiate ADEM from MS. In particular, ADEM appears to be characterized by class-switched IgG autoantibodies, supporting the hypothesis of an antigen-driven immune response in ADEM cases; whereas, MS cases are characterized by serum IgM autoantibodies. [49] The complex ensuing inflammatory cascade entails the local action of cytokines and chemokines as well as lymphokine-induced chemotaxis of other cellular mediators of inflammation (eg, other T cell lines, B cells, microglia, phagocytes).


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