Dementia in Parkinson's disease: cause and treatment

Dementia in Parkinson's disease is increasingly being recognized. A number of studies have recently appeared on the epidemiology, clinical features, pathological correlations and treatment of dementia in Parkinson's disease. The purpose of this article is to provide an overview of recent findings on dementia associated with Parkinson's disease, from February 2003 to the present.

The cumulative prevalence of dementia in Parkinson's disease can be as high as 78%; dementia is especially prevalent in older patients. The profile of dementia seems to be different from that of Alzheimer's disease and similar to that of dementia with Lewy bodies. Clinicopathological correlation studies have suggested that dementia correlates best with Lewy bodies in certain limbic and cortical areas, but not all patients with sufficient Lewy bodies for a pathological diagnosis of dementia with Lewy bodies are demented. Cholinergic deficits in the cerebral cortex can be shown with in-vivo imaging studies, and seem to be more severe than in Alzheimer's disease. Several small studies with three different cholinesterase inhibitors suggest that these drugs can be effective in the treatment of PD dementia.

Dementia is highly prevalent in Parkinson's disease. The prototype of dementia in Parkinson's disease is a dysexecutive syndrome with impaired attention, executive functions and secondarily impaired memory. Neurochemically the most significant deficit seems to be cholinergic; dementia seems to correlate best with cortical and limbic Lewy bodies. Preliminary evidence suggests that cholinesterase inhibitors may be effective in Parkinson's disease dementia, and the results of large-scale, randomized and controlled studies are awaited to confirm these findings.