Putaminal dopamine turnover in de novo Parkinson disease predicts later motor complications.

OBJECTIVE: To investigate the predictive value of striatal dopamine turnover in patients with de novo Parkinson disease (PD) for the onset of later motor complications.

METHODS: This retrospective, observer-blinded cohort study followed up 31 patients with early PD who completed quantitative (18)F-dopa PET imaging to measure striatal (18)F-dopa uptake (Kocc) and effective distribution volume ratio (EDVR) as the inverse of dopamine turnover prior to antiparkinsonian treatment. The onset of wearing-off and dyskinesias was determined based on blinded clinical assessments and patient records. The predictive value of baseline PET measures for motor complications was evaluated using Cox proportional hazard models.

RESULTS: During a mean follow-up time of 6.8 years, 18 (58.1%) patients developed wearing-off, 11 (35.5%) dyskinesia, and 20 (64.5%) any motor complication. Patients with dyskinesia and any motor complication showed lower baseline EDVR (higher dopamine turnover) in the putamen than those without dyskinesias and any motor complication, with differences most markedly present in the posterior putamen. Baseline EDVR in the whole and the posterior putamen predicted development of motor complications with an increasing risk with lower EDVR (higher dopamine turnover), whereas EDVR in other regions and Kocc did not correlate with motor complications. Correspondingly, Kaplan-Meier curves showed reduced survival from motor complications in patients with lower baseline EDVR (higher dopamine turnover) in the posterior putamen with ongoing levodopa treatment and disease duration.

CONCLUSIONS: Elevated putaminal dopamine turnover in de novo PD is associated with an increased risk for later motor complications and comprises a disease-intrinsic predisposing factor for their development.