ABSTRACT
Parkinsonism is a symptom complex which is seen in association with a variety of illnesses, either intrinsic to the nervous system or systemic in nature. The commonest cause is idiopathic Parkinson’s disease (PD). The major underlying pathology in PD is neuronal cell loss in the pigmented nuclei of the brain stem, most notably in the substantia nigra pars compacta. The nigral neurons project to the caudate and putamen and utilize dopamine as a neurotransmitter. The neurochemical mechanisms underlying nigrostriatal plasticity are thought to involve both pre- and postsynaptic mechanisms. On the basis of post-mortem neurochemical studies, an age-related deterioration in nigrostriatal function has been postulated. Positron emission tomography studies with these tracers have provided in vivo confirmation of this change and provide a method to follow these changes with increasing age. Patients with more advanced PD characterized by the “on-off” phenomena have a more marked depression of striatal radioactivity than do patients with less advanced disease.
