PRKN and Parkinson disease: Importantly, [18F]FDOPA PET uptake was reduced in the pineal gland and hypothalamus in patients with advanced PD, possibly related to intrinsic amine synthesis for the pineal gland [228], whereas it was preserved in PD patients with Parkin mutation and in non-symptomatic single parkin mutation carriers [229], who may also have less frequent sleep-related non-motor symptoms [230].