EEG analysis in patients with senile dementia and Alzheimer's disease.

An EEG frequency analysis using the wave-form recognition method was performed in different stages of senile dementia (SD), evaluated according to the Hasegawa Dementia Rating Scale (HDS), and the differences in EEG changes between patients with Alzheimer's disease (AD) and patients with SD were studied. We found that the EEG changes in the SD patients correlated with HDS, and that an increase in slow theta (4-5.8 Hz) and a decrease in fast theta (7-7.8 Hz) waves were early changes in the SD patients. Furthermore, delta and slow theta waves increased mainly in the anterior frontal and temporal areas in the severe SD patients. The AD patients showed more severe EEG abnormalities than the SD patients and showed severe focal abnormalities in the temporal area.