DECREASED STRIATAL MONOAMINERGIC TERMINALS IN OLIVOPONTOCEREBELLAR ATROPHY AND MULTIPLE SYSTEM ATROPHY DEMONSTRATED WITH POSITRON EMISSION TOMOGRAPHY

We used [C-11]dihydrotetrabenazine, a new ligand for the type 2 vesicu lar monoamine transporter (VMAT2), with positron emission tomography t o study striatal monoaminergic presynaptic terminals in 4 patients wit h multiple system atrophy, 8 with sporadic olivopontocerebellar atroph y, and 9 normal control subjects. Specific binding in the striatum was significantly reduced in the multiple system atrophy patients as comp ared with the normal control group, with average reductions of 61% in the caudate nucleus (p = 0.002) and 58% in the putamen (p = 0.009). Sm aller reductions were found in the sporadic olivopontocerebellar atrop hy group, averaging 26% in the caudate nucleus (p = 0.05) and 24% in t he putamen (p = 0.11). Mean blood-to-brain [C-11]dihydrotetrabenazine transport (K-1) was significantly different between groups only in the cerebellum, with values for the sporadic olivopontocerebellar atrophy group diminished compared with the normal control group. Cerebellar K -1 was not significantly decreased in the multiple system atrophy grou p. The finding of reduced striatal VMAT2 in sporadic olivopontocerebel lar atrophy patients suggests nigrostriatal pathology, indicating that some may later develop symptomatic extrapyramidal disease.