Dementia with Lewy bodies is a progressive, degenerative dementia of unknown etiology. Because the sensitivity and specificity of clinical diagnosis are poor, reliable epidemiologic data on the incidence and prevalence of Lewy body dementia are sparse. It is generally recognized as a disease of late middle age and old age. It is believed to be slightly more common among men than women.
Lewy body dementia is a progressive, degenerative dementia. The following clinical features help to distinguish this condition from Alzheimer disease:
Fluctuations in cognitive function, with varying levels of alertness and attention; clues to the presence of fluctuations include excessive daytime drowsiness (if nighttime sleep is adequate) or daytime sleep longer than 2 hours, staring into space for long periods, and episodes of disorganized speech
Parkinsonian motor features
Although extrapyramidal features may occur late in the course of Alzheimer disease, they appear relatively early in Lewy body dementia. In addition, whereas patients with Alzheimer disease virtually always have anterograde memory loss as a prominent symptom and sign early in the course of the illness, anterograde memory loss may be less prominent in Lewy body dementia.
Patients with Lewy body dementia usually have impaired cognition consistent with dementia. Cognitive function, as measured by Mini-Mental State Examination scores, appears to be relatively preserved in Lewy body dementia compared with Alzheimer disease or Alzheimer disease and Lewy body dementia.
An important observation during mental status testing is that the patient has periods of being alert, coherent, and oriented that alternate with periods during which the patient is confused and unresponsive to questions (even though he or she is awake). This fluctuation is a relatively specific feature of Lewy body dementia. Retrieval from memory may be relatively worse than memory storage. Patients may do relatively well with confrontation naming tests and poorly on tests of visuospatial skills (eg, drawing a clock, copying figures).
No sensitive or specific blood or urine tests are currently available for Lewy body dementia. Laboratory studies should include those usually ordered in a dementia evaluation. CSF examination is not required in routine cases. However, CSF findings in Lewy body dementia include the following:
Patients with Alzheimer disease have higher levels of tau protein in their CSF than do patients with Lewy body dementia.
Patients with Lewy body variant of Alzheimer disease have intermediate values.
CSF levels of beta-amyloid are lower than normal in Lewy body dementia, Alzheimer disease, and Lewy body variant of Alzheimer disease; however, CSF beta-amyloid levels in Lewy body dementia, Lewy body variant of Alzheimer disease, and Alzheimer disease do not differ from each other.
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Cite this: Helmi L. Lutsep. Fast Five Quiz: Dementia Key Aspects - Medscape - May 21, 2020.