Clinical Aspects of Non-Alzheimer Disease Dementias

Abstract

There are a relatively small number of disorders that account for the majority of dementia in the elderly that is not Alzheimer disease (AD): cerebrovascular disease, Lewy body disease (α-synucleinopathies), and the frontotemporal lobar degenerations. Cerebrovascular disease and Lewy body disease account for most non-AD dementia among persons in the eighth decade of life and beyond. These two frequently co-occur with AD but can occur in their pure forms rarely (in the case of dementia associated with cerebrovascular disease) or more commonly (in the case of Lewy body disease). There is no one cognitive or behavioral syndrome associated with cerebrovascular disease; however, attempts to isolate a common theme suggest that cognitive slowing is typical of cerebrovascular contributions to cognitive impairment. Cerebrovascular pathology relevant to cognitive impairment accumulates subclinically more commonly than it causes acute, strokelike declines in cognition. Dementia with Lewy bodies is a multidimensional disorder that includes a nonamnestic dementia, Parkinson disease or at least some parkinsonian features, a disorder of sleep and wakefulness, autonomic disturbances, and depression. The disorders of sleep prominently include rapid eye movement sleep behavior disorder, excessive daytime sleepiness, visual hallucinations, and marked fluctuations in level of alertness. The frontotemporal lobar degenerations are nearly as common as causes of dementia in persons under age 65 as is AD. The group of disorders includes two cognitive syndromes (primary progressive aphasia and behavior variant frontotemporal dementia) and two neuropathologic subtypes (tauopathy and TDP43 proteinopathy) and is associated with three major autosomal dominant genetic mutations (in MAPT, GRN, and C9ORF72). Key words: dementia with Lewy bodies, frontotemporal lobar degenerations, vascular cognitive impairment