Quantitative electroencephalography in Alzheimer's disease: comparison with a control group, population norms and mental status

Given that quantitative electroencephalography (EEG) has repeatedly shown excessive slow wave activity in dementia of the Alzheimer type (DAT) that increases with disease progression, we assessed the clinical utility of this tool by comparing various approaches used to assess slowing. Cross-sectional study comparing quantitative EEG data from patients with DAT with normative data from an elderly control group and from EEG norms derived from a large population. 35 subjects diagnosed with probable DAT and 30 elderly controls. EEG recorded from 21 scalp sites of each patient and elderly control during vigilance-controlled, eyes-closed, resting conditions was spectrally analyzed to yield measures of absolute and relative power in delta, theta, alpha and beta bands and indices of mean alpha band and total band frequency. Group comparisons of raw or age-regressed z-score population normative values yielded different profiles with respect to direction of frequency band changes, regional topography and clinical rating correlations, but both procedures evidenced overall patterns of EEG slowing in DAT. However, both methodologies yielded only modest (75%) classification rates. Quantitative EEG remains a valuable research tool but, as yet, an unproven diagnostic tool, for DAT.