Intellectual changes in patients with MPTP-induced parkinsonism.

We studied six patients with MPTP-induced parkinsonism to assess intellectual function, attention, reaction time, and depression. Eight controls with a similar history of drug abuse also participated. General intellectual function, construction, category naming, and frontal lobe function were worse in the patients; other aspects of performance were comparable. All affected women but none of the men were depressed, usually before onset of parkinsonism. The pattern of intellectual deficit in the MPTP patients was similar to that of idiopathic Parkinson's disease. Since MPTP-induced parkinsonism probably represents a purely dopaminergic deficiency, these findings suggest that changes in the dopamine system are responsible for at least some of the intellectual changes of idiopathic Parkinson's disease.