L-2-BETA-CARBOMETHOXY-3-BETA-(4-IODOPHENYL)TROPANE SPECT IN HEALTHY CONTROLS AND EARLY-STAGE, DRUG-NAIVE PARKINSONS-DISEASE

The aims of this study were to investigate whether the loss of striata l dopamine transporters in early and drug-naive patients with Parkinso n's disease could be demonstrated by means of I-123-N-omega-fluoroprop yl-2 beta-carbomethoxy-3 beta-(4-iodophenyl)tropane (I-123-FP-CIT) SPE CT 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) an d 14 healthy controls (age range 28-83 yr; mean age 53.6 yr) were exam ined, SPECT image acquisition was always performed at 3 hr postinjecti on. The ratio of specific to nonspecific striatal I-123-FP-CIT binding was used as the outcome measure, Results: All striatal I-123-FP-CIT r atios were significantly lower in the Parkinson's disease group compar ed to those in the control group. The mean reduction in the putamen wa s 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 I-123-FP-CIT binding. Discriminant functi on analysis, using the I-123-FP-CIT SPECT data of the ipsilateral and contralateral putamen, predicted group membership in all cases; the co ntralateral putamen accounted for the greatest difference between the Parkinson's disease patients and the controls, In the control group, a clear decline in I-123-FP-CIT binding was found with aging, amounting to 9.6%/decade, Unexpectedly, in the Parkinson's disease group, regre ssion analysis revealed that neither severity of disease nor age accou nted for a significant part of the variance in striatal SPECT measures . Conclusion: Our findings indicate that I-123-FP-CIT SPECT is a relia ble method to discriminate between early, drug-naive Parkinson's disea se patients and healthy controls and to identify patients in the precl inical phase of Parkinson's disease. Possibly due to the relatively ho mogeneous group of Parkinson's disease patients and the use of a subop timal outcome measure, no significant correlations were found between striatal I-123-FP-CIT binding ratios and disease severity, such as wer e established earlier with I-123-beta-CIT. Further research is necessa ry to interpret these findings.