Special Considerations for the Assessment of Cerebral Function in Geriatric Patients

Abstract

Basic EEG activity changes during physiological aging processes. After age 50 there is a shift towards higher frequencies, which may be seen as a compensatory mechanism against diminishing cerebral vitality. Subsequently, a decrease of the dominant frequency by 1–2 Hz is usually seen. In old age, waning intellectual abilities correlate to irregular or slow EEG patterns, which are thought to be caused by metabolic disturbances and compromised cerebral perfusion. Geriatric patients thus give either normal findings with a slightly decreased dominant frequency of around 8 Hz, or else a markedly altered EEG pattern which, under anesthesia, shows abnormal and unpredictable changes on the EEG.