Dopamine Turnover Rate as Surrogate Parameter for Diagnosis of Early Parkinson's Disease

The study is designed to measure the difference of dopamine turnover rate measured by Fluoro-Dopa-PET in the putamen between patients with Parkinson's disease treated with cabergoline and levodopa for 3 months. The study protocol includes an initial Fluoro-Dopa-PET scan before treatment and after three months double-blind treatment with cabergoline or levodopa. The hypothesis for this study is that the dopamine turnover rate is a more sensitive marker for the early diagnosis of Parkinson's disease compared to the standard Fluoro-Dopa-PET measuring only the Fluoro-Dopa uptake into the striatum. For the interventional part of the study, the hypothesis is that levodopa has larger effects on striatal dopamine turnover compared to dopamine agonists by providing more dopamine precursor. Enhancement of compensatory mechanisms for dopamine loss in early PD such as increased dopamine turnover could have several beneficial implications such as improvement or prolongation of symptomatic treatment responses, but might also produce therapeutic problems such as the development of levodopa-induced motor complications.