The Lewy body variant of Alzheimer's disease: clinical, pathophysiological and conceptual issues.

In 1923, Friedrich H. Lewy described dementia with Lewy bodies in a large proportion of his patients with paralysis agitans which had co-incident plaques and neurofibrillary tangles. The potential contribution of Lewy bodies to a dementia syndrome with fluctuating course, visual hallucinations, Parkinsonian features and neuroleptic hypersensitivity was rediscovered many decades later. The comorbidity of Alzheimer's and Parkinson's disease is not uncommon as both diseases show an exponential increase with advancing age and their coincidence is of great clinical importance. The combination of a cholinergic deficit--which is particularly severe due to the double pathology targeting the basal nucleus of Meynert--and a dopaminergic deficit requires cholinergic and cautious dopaminergic treatment. Excessive dopamine (L-dopa), antidopaminergic (neuroleptic) or anticholinergic treatment (anti-Parkinson or neuroleptic medication) may further complicate the condition, worsen extrapyramidal, psychotic or cognitive disturbances and even lead to a neuroleptic malignant syndrome.