A multitracer dopaminergic PET study of YOPD patients with and without parkin mutations

Objectives To characterize with ¹⁸FDOPA, ¹¹C-PE2I and ¹¹C-Raclopride the pattern of dopaminergic lesions in young onset Parkinson’s disease patients (YOPD) carrying or not mutations of the parkin gene.

Methods 35 YOPD patients were enrolled (16 with parkin mutation, 19 without). The uptake constant (K_i) of ¹⁸FDOPA and the binding potential (BP) of ¹¹C-PE2I (BP_DAT) and ¹¹C-Raclopride (BP_D2) were calculated in the striatum. Comparisons were made between the two groups of YOPD and between controls and patients. For each radiotracer, parametric images were obtained and a statistical parametric analysis (SPM5) was performed. Correlations between the cognitive and motor status and PET were analysed.

Results In YOPD patients, K_i values were reduced to 67% (putamen, Pu) and 39% (caudate, Cd) of normal values (p<0.0001). This decrease was symmetrical and comparable for both patient's groups. No correlation was found between K_i and cognitive or motor status. BP_DAT in YOPD, was decreased to 56% (Pu) and 41% (Cd) of normal values (p<0.0001), and did not differ between the two YOPD populations. BP_D2 values were reduced (p<0.02) to 17% (Pu) and 28% (Cd) and did not differ between the non-parkin and parkin patients. Moreover, SPM shows a decrease of ¹⁸FDOPA and ¹¹C-PE2I uptake in the substantia nigra bilaterally (p<0.001).

Conclusions Carriers of parkin mutations are indistinguishable on PET markers of dopaminergic dysfunction, from other YOPD patients with long disease duration.