Neuropsychological function in Alzheimer's disease. Pattern of impairment and rates of progression.

Although patients with Alzheimer's disease (AD) generally have impairments in multiple areas of cognitive function, there are those patients who appear to have neuropsychological deficits more prominent in one domain than in other domains. We examined the neuropsychological status of 86 patients with probable AD and 92 elderly control subjects and identified the patterns of impairments in the patients with AD. Independent deficits of visuoconstructional and lexical/semantic abilities were identified in a subset of patients by a principal components analysis. Individual patients were identified who were predominantly impaired in one, but not the other, neuropsychological domain. There were no striking relationships between the demographic characteristics of the patients and their pattern of deficits at the initial evaluation. There were no significant differences in age at onset or rate of progression of dementia among patients with different patterns of cognitive dysfunction. A review of the results of this and other studies suggests that the language impairment in AD may be associated with two distinct neuropsychological abnormalities: a lexical/semantic impairment that is unrelated to onset or progression of symptoms, and a syntactic impairment that may be associated with earlier onset and more rapid progression of dementia.