Dementia in Parkinson's disease.

The prevalence of dementia, assessed on the basis of the Wechsler scale (WAIS), was determined in a group of 88 patients with idiopathic Parkinson's disease (PD) lasting longer than 4 years. In this group, 19 patients (22%) were diagnosed as demented. They were significantly older at the time of evaluation (72.9 +/- 8.1 vs. 63.6 +/- 11.9), and also at the onset of the disease (61.1 +/- 10.6 vs. 54.4 +/- 12.1) than nondemented patients. Their parkinsonism, as judged on the base of the Activity of Daily Living Scale, was more pronounced (57.4 +/- 13.7 vs. 73.3 +/- 15.6) and they developed psychotic side-effects of L-DOPA treatment (53% vs. 9%) more often. A weak negative correlation between age and intellectual quotient (IQ) was found, and a much stronger positive correlation between education and IQ. 25 patients of those diagnosed previously as non-demented were reassessed for dementia after another 5 years of disease. Only two of them were found demented. Both died and an immunohistochemical study of their brains was performed. In the 2 cases we found neuropathological features of both PD (Lewy bodies) and Alzheimer's disease (AD)--neurofibrillary tangles (NFT) and senile plaques (SP). This finding may support the hypothesis that, at least in some cases, dementia in PD could be due to an accompanying AD.