BENZODIAZEPINE RECEPTOR-BINDING IN CEREBELLAR DEGENERATIONS STUDIED WITH POSITRON EMISSION TOMOGRAPHY

We used positron emission tomography with [C-11]flumazenil to study ga mma-aminobutyric acid type A/benzodiazepine receptor binding quantitat ively in the cerebral hemispheres, basal ganglia, thalamus, cerebellum , and brainstem of 72 subjects, including 14 with multiple system atro phy of the ataxic (olivopontocerebellar atrophy) type, 5 with multiple system atrophy of the extrapyramidal/autonomic (Shy-Drager syndrome) type, 18 with sporadic olivopontocerebellar atrophy, 15 with dominantl y inherited olivopontocerebellar atrophy, and 20 normal control subjec ts with similar age and sex distributions. In comparison with data obt ained from the normal control subjects, we found significantly decreas ed ligand influx in the cerebellum and brainstem of multiple system at rophy patients of the olivopontocerebellar atrophy type and in patient s with sporadic olivopontocerebellar atrophy, but not in patients with multiple system atrophy of the Shy-Drager syndrome type. Despite thes e differences in ligand influx, benzodiazepine binding was largely pre served in the cerebral hemispheres, basal ganglia, thalamus, cerebellu m, and brainstem in patients with multiple system atrophy of both type s as well as those with sporadic or dominantly inherited olivopontocer ebellar atrophy as compared with normal control subjects. The finding of relative preservation of benzodiazepine receptors indicates that th ese sites are available for pharmacological therapy in these disorders .