Cognitive impairments in Parkinson's disease

It is now recognized that many patients with Parkinson's disease will experience cognitive and intellectual decline in the course of their illness. Selective visuospatial and memory impairment, executive dysfunction, slowed information processing, and depression are consistently observed in a high proportion of patients. Language abilities appear to be relatively spared. Current age, age of onset, disease duration, and predominant motor symptoms all exert important differential effects on the expression of the dementing process. Although these patterns point to a subcortical origin, it is probable that Parkinson's disease is composed of several dementia syndromes.