Amnestic MCI, in which memory impairment predominates, is often a precursor of clinical Alzheimer's disease. Nonamnestic forms of MCI are characterized by various cognitive impairments, the most common of which is probably impaired executive function. A substantial number of patients with MCI may be judged to have normal cognition on follow-up visits. The pathophysiology of MCI is multifactorial. Most cases of amnestic MCI result from pathologic changes of Alzheimer's disease that have not yet become severe enough to cause clinical dementia. Nonamnestic MCI may be associated with cerebrovascular disease, frontotemporal dementia (as a precursor), or no specific pathology.
Some cognitive patterns may help to differentiate vascular dementia clinically from Alzheimer's disease. Patients with vascular dementia tend to show greater deficits on measures of frontal executive functioning than patients with Alzheimer's disease, whereas patients with Alzheimer's disease show greater long-term memory deficits than patients with vascular dementia.
The following clinical features help to distinguish Lewy body dementia from Alzheimer's disease:
Fluctuations in cognitive function, with varying levels of alertness and attention (eg, excessive daytime drowsiness despite adequate nighttime sleep or daytime sleep > 2 hours, staring into space for long periods, episodes of disorganized speech)
Parkinsonian motor features
Relatively early extrapyramidal features (vs may occur late in Alzheimer's disease)
Anterograde memory loss: May be less prominent (vs prominent early sign in Alzheimer's disease)
More prominent executive function deficits and visuospatial impairment (eg, Stroop, digit span backward)
In patients with frontotemporal dementia, memory is usually preserved for orientation; however, information retrieval may be difficult. Short-term memory deficits may be present in some patients but are less characteristic and early than those associated with Alzheimer's disease.
This Fast Five Quiz was excerpted and adapted from the Medscape Drugs & Diseases articles Mild Cognitive Impairment, Alzheimer Disease, Parkinson Disease, Vascular Dementia, Frontotemporal Dementia and Frontotemporal Lobar Degeneration, and Lewy Body Dementia.
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Any views expressed above are the author's own and do not necessarily reflect the views of WebMD or Medscape.
Cite this: Helmi L. Lutsep. Fast Five Quiz: Memory Loss and Cognitive Impairment - Medscape - Apr 28, 2021.