The distribution and dynamic density of oligodendroglial cytoplasmic inclusions (GCIs) in multiple system atrophy: a correlation between the density of GCIs and the degree of involvement of striatonigral and olivopontocerebellar systems.

The distribution and dynamic density of oligodendroglial cytoplasmic inclusions (GCIs) were studied based on 30 cases of multiple system atrophy (MSA), including striatonigral degeneration (SND), olivopontocerebellar atrophy (OPCA) and Shy-Drager syndrome. GCIs were widely spread throughout the central nervous system, including the striatonigral and olivopontocerebellar systems. Inclusion-bearing cells appeared to be oligodendrocytes which usually had larger and lighter nuclei than those of normal-looking oligodendrocytes. The distribution of GCIs was similar in all cases, irrespective of the degrees of OPCA and SND, but the frequency of GCIs varied from case to case. We classified all the cases into two categories based on the degree of neuropathological changes of SND (mild and severe) and, independently, into three groups based on that of OPCA (minimal, moderate and severe), i.e., a total of six groups. An association between the frequency of GCIs and the severity of the lesions was obtained. For example, many GCIs were seen the cerebellar white matter in the cases in which OPCA was not histologically confirmed. More GCIs were seen in the cases with moderate OPCA. In the cases with severe OPCA, GCIs were rarer and smaller, in proportion to the devastation of fibers; no GCIs were seen in the cases with more severe OPCA. The incidence of GCIs showed a positive correlation to the severity of OPCA but not that of SND in the corticopontine tracts, of both OPCA and SND in the pyramidal tracts, and of SND but not of OPCA in the pencil fibers of the putamen. It is suggested that GCIs may represent either a change synchronous with neuronal degeneration or a phenomenon preceding neuronal changes, especially in the cerebellar white matter. Thus, they may represent the early changes in MSA and may be a useful neuropathological hallmark for diagnosis of MSA, even in cases with minimal OPCA and SND.