Parkinson disease, dementia, and Alzheimer disease: clinicopathological correlations.

Clinical records and neuropathological specimens from 36 patients with autopsy-demonstrated idiopathic Parkinson disease (PD) were reviewed independently and the results compared. Nine (31%) of the 29 patients with adequate clinical data had severe dementia and 7 (24%) had mild dementia. The cerebral cortex showed senile plaques and fibrillary tangles in 15 of the 36 patients (42%). These changes were found in all 9 patients with severe dementia, in 3 of the 7 with mild dementia, and in 3 of the 13 patients with normal mental status. The prevalence of pathologically established Alzheimer changes and dementia among the patients with PD (33%) was over six times that found in an age-matched population (5.1%). Survival after the onset of PD with Alzheimer disease was shorter than in PD without Alzheimer disease.