Distribution and dynamic process of neuronal cytoplasmic inclusion (NCI) in MSA: correlation of the density of NCI and the degree of involvement of the pontine nuclei.

MSA is a sporadic degenerative disease that occurs in striatonigral degeneration (SND), SDS and most cases of sporadic OPCA. Oligodendroglial inclusion is a hallmark of MSA. Recently there have been a small number of reports of neuronal argyrophilic inclusions. To clarify the distribution and dynamic process of neuronal cytoplasmic inclusions (NCI), 31 cases of MSA were studied using histology, immunohistochemistry, and electron microscopy. The inclusions were exclusively found in the pontine nucleus and there was a correlation between the incidence of NCI and the severity of OPCA, but not of SND. NCI were increased to some extent in the cases with moderate OPCA and decreased in number in proportion to devastation of the pontine nuclei. Immunohistochemical and ultrastructural features of NCI were virtually identical to those of glial cytoplasmic inclusions (GCI), which gives some clues to the pathogenesis of MSA. It is tempting to interpret this as NCI playing a significant role in the degenerative changes of the neurons at least in the pons. Further systematic studies on NCI in the other brain regions are necessary to elucidate the pathogenesis of neuronal degeneration in MSA.