[Quantified EEG in the diagnosis of Alzheimer's type dementia].

79 subjects (mean age 70.2 ans, 31 males, 48 females) selected as probable dementia of the Alzheimer type, at the early stage of the disease and 17 normal aged people (mean age: 72.2, 5 males, 12 females) were recorded with a 16 channel computerized-EEG (C-EEG) with topographical analysis of the observed changes and with classical visual analysis of the EEG. Quite simple C-EEG parameters as mean dominant frequency (MF) and alpha to theta ratio are able to discriminate patients from normal with a greater accuracy than visual analysis. The values of 8.6 for the MF and 1.3 for the alpha/theta ratio are proposed as cut off values between normal and DAT patients. The topographical analysis appear to be of no additional usefulness in the discrimination of the two groups.