Constant involvement of the Betz cells and pyramidal tract in multiple system atrophy: a clinicopathological study of seven autopsy cases

We investigated clinicopathologically the pyramidal signs, including spasti city, hyperreflexia, and Babinski's sign, and the involvement of the pyrami dal tract and primary motor cortex, in seven Japanese autopsy cases of mult iple system atrophy (MSA). Pyramidal signs were observed in six (86%) of th e seven autopsy cases. Hyperreflexia;md Babinski's sign were each evident i n five patients. but spasticity was observed in only one patient. Loss of B etz cells and presence of glial cytoplasmic inclusions in the primary motor cortex were noticed in all seven cases. Astrocytosis in the fifth layer of the primary motor cortex was noticed in five cases, but its presence was n ot related to the duration of the disease. Involvement of the pyramidal tra ct in the spinal cord, particularly of the small myelinated fibers, was obs erved in all seven cases, but no involvement of the pyramidal tract in the midbrain was evident in any of the six cases in which this structure was ex amined. In MSA, pyramidal signs were shown to be present more frequently th an believed before, and the clinicopathological correlation between pyramid al signs and involvement of the pyramidal tract was obvious. Constant invol vement of Betz cells in MSA has not been reported. Our clinicopathological findings may also make a contribution to the understanding of the clinicopa thological hallmarks of MSA.