Distinctive neuropsychological patterns in frontotemporal dementia, semantic dementia, and Alzheimer disease

To assess the ability of a brief neuropsychological bedside screening battery to discriminate between Alzheimer disease, frontotemporal dementia, and semantic dementia.

Subjects were 21 patients with frontotemporal dementia, 14 patients with semantic dementia, and 30 patients with Alzheimer disease comparable in terms of Mini Mental Status Examination score, age, and education. Frontotemporal dementia and semantic dementia diagnoses were made clinically using the consensus criteria of Neary et al. 1 Subjects were administered a brief neuropsychological screening assessing episodic memory, working memory, executive function, naming, spatial ability, abstract reasoning, and calculations.

Both the Alzheimer disease and semantic dementia groups were significantly impaired relative to the frontotemporal dementia group on verbal memory, whereas only the Alzheimer disease group was impaired on visual memory. Frontotemporal dementia patients performed significantly worse on backward digit span and made significantly more executive errors than Alzheimer disease and semantic dementia patients. Semantic dementia patients were more impaired than Alzheimer disease and frontotemporal dementia patients on confrontation naming. Discriminant function analyses identified the 5 most discriminating variables that correctly classified 89.2% of cases.

Frontotemporal dementia, semantic dementia, and Alzheimer disease are associated with distinct neuropsychological profiles that classify these dementia syndromes with considerable success. The neuropsychological profiles highlight the distinctiveness between the 3 syndromes, are consistent with the known loci of neuropathology in these conditions, and can potentially serve as an adjunct to the current clinical criteria.