Primary involvement of the motor area in association with the nigrostriatal pathway in multiple system atrophy: neuropathological and morphometric evaluations

To evaluate the changes that occur in the motor and supplementary motor cor tices in cases of multiple system atrophy (MSA), we carried out morphologic al and morphometric studies in 7 cases of MSA and 11 age-matched controls. Neuropathological study revealed presence of glial cytoplasmic inclusions ( GCIs) in the cortex and subcortical white matter of the motor and supplemen tary motor areas, loss of small to medium-sized pyramidal neurons, and astr ocytosis in the motor cortex in all cases of MSA, showing a definite predil ection in the cortical layers V and VI. The severity of neuronal loss in th e motor cortex was highly correlated with the incidence of GCIs and the inv olvement of the nigrostriatal pathway. Morphometrically, significant reduct ions of both the thickness of motor cortical layers V and VI and the number of neurons were observed. In addition, a reduction in the number of neuron s in the supplementary motor cortex was detected in three out of the seven MSA cases. The results of this study suggest that the motor area is a cardi nal target in MSA, and that in association with the nigrostriatal pathway i t forms a motor loop degeneration in this disease.