Young-onset Parkinson disease with and without parkin gene mutations: a fluorodopa F 18 positron emission tomography study.

BACKGROUND Mutations of the parkin gene are frequently encountered in patients with young-onset Parkinson disease (YOPD), but the effects of this mutation on the nigrostriatal dopaminergic degeneration are not well established. OBJECTIVE To analyze, using positron emission tomography and fluorodopa F 18, the severity and profile of striatal dopaminergic metabolism in YOPD patients with and without parkin gene mutations. METHODS We performed positron emission tomography with fluorodopa F 18 in 19 YOPD patients with parkin gene mutations (parkin patients), 6 YOPD patients without parkin gene mutations (nonparkin patients), and 9 healthy controls. Putamen and caudate nucleus fluorodopa F 18 uptake was assessed using regions of interest analysis. RESULTS In parkin patients, the striatal fluorodopa F 18 uptake reduction was 36.3%, 51.3%, and 66.7%, respectively, for the caudate nucleus, anterior putamen, and posterior putamen compared with controls. In nonparkin patients, this reduction was 23.0%, 43.6%, and 73.0%, respectively. This reduction was asymmetrical according to the most affected hemibody for the anterior and posterior putamen in parkin patients and for the posterior putamen in nonparkin patients. A rostrocaudal gradient was observed with a severe decrease in fluorodopa F 18 uptake in the putamen and relative sparing of the caudate nucleus. There was no significant difference of striatal fluorodopa F 18 uptake between our 2 YOPD populations. In parkin patients, no significant correlation was found among fluorodopa F 18 uptake, motor disability, and the type of mutations. In nonparkin patients, there was a significant correlation between fluorodopa F 18 uptake and clinical severity. CONCLUSIONS The pattern of fluorodopa F 18 uptake in the striatum of YOPD patients is similar to that of patients with idiopathic Parkinson disease and does not depend on the presence or absence of mutations of the parkin gene.