REGIONAL-ANALYSIS OF D2 DOPAMINE-RECEPTORS IN PARKINSONS-DISEASE USING SPECT AND IODINE-123-IODOBENZAMIDE

The goal of this study was to examine the relationship between D2 dopa mine receptor density and levodopa dosage, disease duration and dyskin esia in Parkinson's disease (PD). Methods: Iodine-123-iodobenzamide SP ECT scans were obtained from 14 PD patients and 12 age-matched control s using a three-headed camera in conjunction with MRI and a fiducial-b ased image registration system to define regions of interest. Basal ga nglia/cerebellum counts/voxel ratios in dorsal and ventral head of cau date and anterior and posterior putamen were measured at 30, 60, 120 a nd 180 min postinjection. As in C-11-raclopride studies, ratios obtain ed at that time when they asymptomatically approach a maximum value (1 80 min) were accepted as the best measure of receptor density. Results : Among PD patients, a trend towards an inverse correlation between re gional basal ganglia/cerebellum ratios and levodopa dosage achieved si gnificance in ventral caudate (F = 6.244, p = 0.037); similarly, an in verse correlation between these ratios and disease duration achieved s ignificance in anterior putamen (F = 13.144, p = 0.007). Ratios were s ignificantly lower in anterior putamen in patients with dyskinesia (t = 3.068, p = 0.042). Conclusion: In PD, the previously observed invers e correlation between levodopa dosage and D2-receptor density appears to be most prominent in the least dopamine-depleted region, ventral ca udate. There may be a genuine effect of disease duration on receptor d ensity in putamen and reduced receptor density in anterior putamen may be associated with dyskinesia.