Verbal fluency in dementia of frontal lobe type and dementia of Alzheimer type.

This study compares semantic (category) and letter-initial verbal fluency performance in dementia of frontal lobe type, dementia of Alzheimer type, and control subjects matched for age, sex, and level of education. As well as demographic characteristics, patients were matched for severity of dementia as estimated by the mini mental scale (23.2 (SD 4.9)). All patients with dementia of frontal lobe type had a frontal hypoperfusion on single photon emission computed tomography whereas patients with dementia of Alzheimer type showed mainly posterior deficits. Patients had significantly lower verbal fluency than controls but those with dementia of frontal lobe type did not differ from those with dementia of Alzheimer type in the number of words generated, intrusions, or preservations. Category fluency was more impaired than letter fluency in both dementias. No correlation between frontal index, frontal/parietal index, and fluency was found. Verbal fluency tests are sensitive tools for detecting dementia but do not seem useful in distinguishing between patients with dementia of Alzheimer type and those with dementia of frontal lobe type in early disease.