Decrease in neuronal density in the cerebral cortex in multiple system atrophy

The presence of argyrophilic oligodendroglial cytoplasmic inclusions (GCIs) is a pathognomonic feature of multiple system atrophy (MSA), which has established MSA as a nosological entity, and serves as a diagnostic criterion. As a neurodegenerative disease, MSA exhibits neuronal degeneration and loss from several regions of the central nervous system. Recent mapping studies of the distribution of GCIs have shown their presence in regions of the brain previously thought not to be affected in MSA, for example the cerebral cortex. This study has used stereological techniques to establish whether neuronal loss is related to the presence of GCIs in three regions of the cerebral cortex. In the prefrontal cortex, in which GCIs are sparse, there is no significant difference in either neuronal or glial cell numerical density in MSA cases compared to controls. However in two cortical regions which are both GCI rich, the anterior central gyrus and the supplementary motor cortex, there is a marked reduction in neuronal density of 18.7% and 21.4% respectively, which is statistically significant only in the supplementary motor cortex. In both of these regions there is a concomitant increase in glial cell numerical density which results in a significant change in the ratio of neurons to glial cells. These results indicate that there is a regional reduction in the neuronal density in the cortex in multiple system atrophy which is associated with the presence of GCIs.