EEG alterations in subjects at high familial risk for Alzheimer's disease.

Twenty first-order relatives of patients with early-onset Alzheimer's disease (AD; mean age 43.7 +/- 1.3 years), 20 patients with early-onset AD (mean age 65.7 +/- 0.9 years) and age-matched normal controls for the relatives and the patients underwent quantitative EEG (qEEG) examinations. In AD patients, delta and theta relative power values were increased and alpha relative power was decreased compared with normal controls. The AD patients' relatives had normal resting EEG parameters. Under hyperventilation in the AD relatives, synchronous high-voltage delta and theta activity and sharp waves were revealed, theta and delta relative powers were increased and alpha relative power was decreased compared with the resting EEG in the same persons. Moreover, under hyperventilation, the theta and delta relative powers in the EEG of the relatives were higher, and the alpha relative power was lower compared with the EEG of normal controls under the same conditions. It is suggested that the excitotoxic processes and oxidative stress underlie the EEG alterations in the AD patients' relatives and that these alterations may be related to the further AD development.