What is the pathognomonic histopathologic lesion of multiple system atrophy (MSA)?

Updated: Sep 24, 2018
  • Author: Stephen M Bloomfield, MD; Chief Editor: Selim R Benbadis, MD  more...
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Answer

Many neurodegenerative disorders have been associated with a distinctive pathognomonic histopathologic lesion that can assist in diagnosis. Until 1989, no such distinctive lesion was associated with MSA, and the histopathologic diagnosis was based on nonspecific and variable neuronal-system atrophy, cell loss, myelin pallor, and astrocytosis. In 1989, GCIs were described in patients with MSA.

GCIs are argyrophilic and have various shapes (eg, triangular, sickle, half-moon, oval, conical). They are occasionally flame shaped and may superficially resemble neurofibrillary tangles. However, cytoplasmic location, size, ultrastructure, immunocytochemical profile, and regional distribution of GCIs are distinctive. GCIs vary in size; they may fill the cytoplasm completely and push the nucleus to the side. The distribution of GCIs follows the suprasegmental motor system, supraspinal autonomic system, and their targets. This distribution includes the primary and secondary motor cortices, the pyramidal and extrapyramidal tracts, and the corticocerebellar systems.

The density of GCIs correlates with the severity of symptoms of patients with MSA. The distribution of GCIs correlates with the subtypes of MSA: putaminal lesions are prevalent in patients with the MSA-P subtype, and corticopontine lesions are prevalent in patients with the MSA-C subtype. Pyramidal lesions correlate with the severity of symptoms in both subtypes.


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