EEG spectral profile to stage Alzheimer's disease.

Objective: The present study was undertaken to investigate whether a synoptic parameter of quantitative EEG (qEEG), such as the power spectral profile, may be used as a simple marker to stage Alzheimer's disease (AD) in the clinical setting.
Methods: To this purpose, the qEEG spectral profile was examined in 48 patients (mean age: 73 years) with probable (NINCDS-ADRDA criteria) AD, who were divided into 4 groups, according to the Global Deterioration Scale (GDS; score: 3-6). The spectral profile of each patient was expressed by the relative power of seven frequency bands (2-3.5, 4-5.5, 6-7.5, 8-9.5, 10-11.5, 12-13.5, 14-22.5 Hz). Mean values in each of the four GDS groups as well as in a control group of 18 healthy elderly subjects underwent multivariate analysis of variance.
Results: A normally shaped but shifted-to-the left spectral profile was found in GDS 3 group, whereas a reduced background rhythm with various increase in slow activity power characterized both GDS 4 and 5 groups. Finally, an 'exponential asymptotic' profile with the highest power in the lowest frequencies was the hallmark of GDS 6 group. Overall, the 4-5.5 Hz and the 10-11.5 Hz band powers showed the highest statistical significance in differentiating the patient groups between one another and from controls (P < 0.0001).
Conclusions: These data show that spectral profile is a very simple parameter which can be used to stage the disease on a pathophysiological basis.