Clinicopathological aspects of Parkinson's disease.

Clinicopathological studies have shown that the accuracy of a clinical diagnosis of Parkinson's disease (PD) is less than 80%. More selected diagnostic criteria can increase the proportion of true PD cases identified to more than 90%. However, by using these criteria almost a third of pathologically confirmed cases may be rejected. Awareness of the high misdiagnosis rate and refinements in the clinical diagnostic criteria for other conditions that may present with parkinsonism seem to have led to an improvement in the accuracy of diagnosis to 84%. Cortical Lewy bodies, often in small numbers, are seen in almost all patients with PD. This has prompted intense efforts to clarify both the clinical and pathological criteria for diffuse Lewy body disease. The nomenclature of conditions with plentiful numbers of Lewy bodies in the neocortex and the relevance of associated pathology has become confusing and the subject of intense nosological debate. A recent consensus paper has suggested clinical and pathological diagnostic criteria for what has been termed 'dementia with Lewy bodies'. This new term awaits general acceptance while the proposed diagnostic criteria remain to be validated. The neuropathological substrate of dementia in PD continues to receive a lot of attention with suggestions that additive deficits from pathology in both cortical and subcortical structures probably explain most of the dementia seen in PD.