Summary

There have been a number of reports detailing the occurrence of pathology sufficient for the diagnosis of Alzheimer's disease and Lewy body dementia in the same patient, leading to the term ‘Lewy body variant of Alzheimer's disease’ (LBV). The data available emphasize the difficulty in differentiating patients with pure Alzheimer's disease from those with the Lewy body variant but clinical features such as extrapyramidal signs or psychotic phenomena may be helpful. Patients with LBV can present with progressive memory loss and so, at least in the early stages of the disease, they are indistinguishable from patients with pure Alzheimer's disease and it is likely that such patients will be found in groups of patients with Alzheimer's disease. Generally, neuropsychological tests are disappointing in differentiating the two groups although there is a suggestion that frontal lobe dysfunction (as evidenced by atrophy on Computed Tomography scanning and neuropsychological tests) is more common in patients with Lewy bodies than those without. It is traditional to view such a clinical dilemma in terms of a spectrum disorder. One would postulate that the presence of Lewy bodies along with Alzheimer's disease pathology edges patients towards a presentation more clearly associated with diffuse Lewy body disease (confusional states, psychotic features, extrapyramidal signs). This is confirmed by clinical observations and supported by biological marker studies (such as apolipoprotein e4) in which patients with Lewy bodies take up an intermediate position between pure Lewy body disease and pure Alzheimer's disease. The exact contribution of Lewy bodies to the clinical syndrome of dementia needs to be more fully evaluated.