Cortical Lewy body disease.

C ortical Lewy body disease is a pathological observation rather than a distinct clinicopathological entity. Cortical Lewy bodies (CLB) are typically found in Parkinson’s disease and dementia with Lewy bodies (DLB), although they may also occur in other neurological disorders. Unlike their brain stem counterparts, CLB are less distinctive and are poorly visualised using conventional histochemical methods. The protein a-synuclein is the main component of Lewy bodies and the related dystrophic Lewy neurites; immunohistochemistry using antibodies raised against this protein has greater sensitivity in demonstrating Lewy pathology within the cerebral cortex than histochemical methods and antiubiquitin immunohistochemistry. Dementia is a common occurrence in Parkinson’s disease, with a prevalence of 20–40% in cross sectional studies, 3 but a cumulative incidence approaching 80%. The clinical phenotype of this dementia shares many features with DLB. In neither condition, however, has the relation between the presence of CLB and the dementing process been clearly defined. The situation is complex in that there are several possible pathophysiological mechanisms that may underpin cognitive impairment in both Parkinson’s disease and DLB (table 1). This therefore leads to various fundamental questions regarding the role of the CLB and the contribution of this inclusion to dementia in DLB and Parkinson’s disease. Given the heterogeneous processes involved, the degree of interaction or synergism occurring between a-synuclein pathology and, for example, Alzheimer-type pathology that results in dementia also needs to be established.