COMPLEMENTARY PET STUDIES OF STRIATAL NEURONAL FUNCTION IN THE DIFFERENTIAL-DIAGNOSIS BETWEEN MULTIPLE SYSTEM ATROPHY AND PARKINSONS-DISEASE

We used PET with the tracers [F-18]fluorodeoxyglucose (FDG), [F-18]flu orodopa (FDOPA) and [C-11]raclopride (RACLO) to study striatal glucose and dopa metabolism, and dopamine D-2 receptor binding, respectively, in nine patients with multiple system atrophy. Ten patients with clas sical Parkinson's disease were investigated with the same three PET tr acers' and three separate groups, each of 10 healthy subjects, sewed a s control populations. We found that striatal FDOPA values separated a ll healthy subjects from patients with parkinsonism but they were not useful in distinguishing multiple system atrophy from Parkinson's dise ase. Conversely, striatal RACLO as well as FDG values discriminated al l multiple system atrophy from Parkinson's disease patients as well as from healthy control subjects. Metabolic and receptor binding decreme nts in the putamen of multiple system atrophy patients were significan tly correlated Stepwise regression analysis revealed that a linear com bination of putamen RACLO and FDOPA values accurately predicted clinic al measures of disease severity in the multiple system atrophy group. Our findings suggest that striatal FDG and particularly RACLO are sens itive and effective measures of striatal function and may help charact erizing patients with multiple system atrophy. In contrast FDOPA measu rements are accurate in detecting abnormalities of the nigrostriatal d opaminergic system but may not distinguish among different forms of pa rkinsonism.