Iodine-123-N-omega-fluoropropyl-2beta-carbomethoxy-3beta-(4-iod ophenyl)tropane SPECT in healthy controls and early-stage, drug-naive Parkinson's disease

Abstract

The aims of this study were to investigate whether the loss of striatal dopamine transporters in early and drug-naive patients with Parkinson's disease could be demonstrated by means of 123I-N-omega-fluoropropyl-2beta-carbomethoxy-3beta-(4-iodoph enyl)tropane (123I-FP-CIT) SPECT in a 1-day protocol and whether the SPECT measures were correlated with disease severity.

Methods: Twenty-one early-stage and drug-naive Parkinson's disease patients (age range 42-73 yr; mean age 55.5 yr) and 14 healthy controls (age range 28-83 yr; mean age 53.6 yr) were examined. SPECT image acquisition was always performed at 3 hr postinjection. The ratio of specific to nonspecific striatal 123I-FP-CIT binding was used as the outcome measure.

Results: All striatal 123I-FP-CIT ratios were significantly lower in the Parkinson's disease group compared to those in the control group. The mean reduction in the putamen was 57% of the control mean, and that in the caudate nucleus was 29% of the control mean. Patients with unilateral Parkinson's disease showed a bilateral loss of striatal 123I-FP-CIT binding. Discriminant function analysis, using the 123I-FP-CIT SPECT data of the ipsilateral and contralateral putamen, predicted group membership in all cases; the contralateral putamen accounted for the greatest difference between the Parkinson's disease patients and the controls. In the control group, a clear decline in 123I-FP-CIT binding was found with aging, amounting to 9.6%/decade. Unexpectedly, in the Parkinson's disease group, regression analysis revealed that neither severity of disease nor age accounted for a significant part of the variance in striatal SPECT measures.

Conclusion: Our findings indicate that 123I-FP-CIT SPECT is a reliable method to discriminate between early, drug-naive Parkinson's disease patients and healthy controls and to identify patients in the preclinical phase of Parkinson's disease. Possibly due to the relatively homogeneous group of Parkinson's disease patients and the use of a suboptimal outcome measure, no significant correlations were found between striatal 123I-FP-CIT binding ratios and disease severity, such as were established earlier with 123I-beta-CIT. Further research is necessary to interpret these findings.