Contributions of positron emission tomography to elucidating the pathogenesis of idiopathic parkinsonism and dopa responsive dystonia

Abstract

The metabolic mapping of brain activity, using PET, confirms the conventional wisdom of neurophysiology. In studies of pathophysiology, PET has yielded evidence that has generated new hypotheses. Progression of the lesion detectable with fluorodopa, in human subjects exposed to MPTP, raises the possibility of a transient environmental event being a cause of progressive neurodegeneration. Studies with fluorodopa in Idiopathic Parkinsonism indicate that the rate of loss of neurons is faster initially, and then tends to approach the normal age-related decline. In dopa responsive dystonia: the finding of normal fluorodopa PET led to the prediction that the lesion would be functional rather than anatomical; this has been confirmed by the identification of a defect in dopamine synthesis in this disorder. Finally, new PET ligands show promise for future studies designed to unravel the pathogenesis of diseases involving the basal ganglia.