Relationship of motor symptoms to intellectual deficits in Parkinson disease.

We studied 60 patients with idiopathic Parkinson disease with motor and neuropsychologic tests to ascertain whether the severity of motor symptoms was associated with the degree of neuropsychologic deficity. Significant correlations were found between the severity of brady kinesia and impaired performance on tests assessing visual-spatial reasoning and psychomotor speed. More severe tremor was associated with better performance on a spatial orientation memory test. There relationships remained when age, age at onset, and self-rated depression were controlled. The findings suggested that cognitive impairment may result from the same subcortical lesions that cause motor symptoms.