Neuronal cell loss of the striatonigral system in multiple system atrophy.

We investigated the longitudinal as well as lateral loss of striatal and nigral cells and its distribution in 7 cases of multiple system atrophy. Loss of striatal small cells and nigral pigmented cells was more prominent in the caudal part than in the rostral and mid-parts. Cell loss was especially high in the dorsolateral zone of the caudal putamen and in the lateral zone of the caudal nigra. These findings indicate that MSA predominantly disturbs the striatal and nigral efferent systems, which interlink the caudal and dorsolateral putamen with the caudolateral nigra. In less severe cases, the rostral to mid-parts of the putamen or substantia nigra were almost intact while its caudal portion was clearly affected. The degenerative process of MSA seems to occur initially in the caudal parts of the putamen and substantia nigra, extending later to the rostral parts. Thus striatal small cells and nigral pigmented cells degenerate according to anatomical relationship. In MSA, degeneration of the striatonigral system could well be explained as being transsynaptic.