Parkinsonism, L-Dopa and Intelligence

Although many patients with parkinsonism undergo a significant amount of intellectual impairment, several investigators, including the authors, have observed an improvement in intellectual functioning during the first year of treatment with L-dopa. Upon reexamining subjects after 30 months of treatment, however, the authors found that most of their patients did not maintain this improvement. The reasons for the decline are not yet clear, but probably involve the waning influence of L-dopa, the onset or progression of the intellectual impairment common to parkinsonism and the normal aging process, and the impact of other physical illnesses.