Can early dopamine transporter imaging serve as a predictor of Parkinson's disease progression and late motor complications?

Background: The role of nuclear imaging in predicting Parkinson's disease (PD) progression is unclear. This study investigated whether the degree of reduced striatal dopamine transporter binding at diagnosis of PD predicts later motor complications and time to disease progression. Methods: We retrospectively studied 41 patients with early PD who underwent I-123-FP-CIT SPECT and were followed thereafter with a mean disease duration of 9.51 +/- 3.18 years. The association of quantitatively analyzed I-123-FP-CIT binding in striatal subregions with the development of motor fluctuations, dyskinesias, freezing of gait (FOG) and falls as well as the time to Hoehn and Yahr (H&Y) stage 3 was evaluated. Results: Logistic regression models controlling for age at diagnosis, sex, disease duration, and L-dopa dose revealed that I-123-FP-CIT binding in the putamen and striatum significantly predicted FOG (OR = 0.02, p = 0.03; OR = 0.01, p = 0.04; respectively) but not falls. Cox proportional hazard analysis did not reveal significant relationship between I-123-FP-CIT binding and motor fluctuations, dyskinesias, or H&Y stage 3. Conclusions: Our results suggest that a more severe depletion of presynaptic dopamine in early PD is a bad prognostic sign in terms of FOG development. These findings, if replicated, may point to dopaminergic transmission as part of the mechanism underlying FOG in PD.