SPECT measurement of iodine-123-beta-CIT binding to dopamine and serotonintransporters in Parkinson's disease: Correlation with symptom severity

Iodine-123-beta-CIT (2 beta-carbomethoxy-3 beta-(4-iodophenyl/tropane) bind s with high affinity to dopamine (DA) and serotonin (5-HT) transporters. Th is study examined the correlation of single-photon emission computed tomogr aphic (SPECT) measures of [(123)1]beta-CIT binding to DA and 5-HT transport ers with symptom severity in Parkinson's disease (PD). Forty six L-dopa-res ponsive PD patients (Hoehn-Yahr stage 1-3) had SPECT scans at 20-24 h after injection of [(123)1]beta-CIT. Specific to nondisplaceable uptake ratios ( designated V-3") were calculated in the striatum and hypothalamic/midbrain region, where the binding of [1231]beta-CIT is associated primarily with DA and 5-HT transporters, respectively. Striatal V-3" was significantly corre lated with Hoehn-Yahr stage and total, motor and activities of daily living scores of Unified Parkinson's Disease Rating Scale (UPDRS). There was a si gnificant correlation between the sum of lateralizing motor UPDRS subscores (tremor, rigidity, bradykinesia) calculated for each side of limbs and V-3 " values in the contralateral striatum. No significant correlation was foun d between striatal V-3" and UPDRS rating of mentation, behavior, and mood. Hypothalamic/midbrain V-3" uas not significantly correlated with either Hoe hn-Yahr stage or UPDRS scores including both motor and nonmotor measures. T he significant correlation of SPECT measures of striatal [(123)1]beta-CIT b inding with motor severity suggests that [(123)1]beta-CIT binding to striat al DA transporters can serve as an in vivo indicator of disease severity in PD, with potential utility in the serial monitoring of disease progression .