Compartmental loss of striatal medium spiny neurons in multiple system atrophy of parkinsonian type.

Topographical or compartmental involvement of the putamen and caudate nucleus has not been fully elucidated in multiple system atrophy predominantly presenting with Parkinsonism (MSA-P). We carried out immunohistochemical studies using antibodies to calbindin (CALB) and calcineurin (CaN) as neurochemical markers for striatal medium spiny neurons. We found that in the caudal and dorsolateral putamen, the area most affected in MSA-P, the medium spiny neurons positive for CALB were severely depleted, while CaN-positive neurons were relatively spared in a mosaic pattern. In the dorsal caudate nucleus, an area less affected in MSA, residual CALB-positive neurons exhibited a compartmentalized distribution that corresponded with the striosomal arrangement visualized by Met-enkephalin immunostaining. Our findings suggest that there is a compartmental difference in the susceptibility of striatal medium spiny neurons to neurodegeneration in MSA-P.