[Volumetric brain changes and quantitative EEG in normal aging and Alzheimer's dementia]

We studied (1) the differences of volumetric estimates of brain atrophy in normal ageing and Alzheimer's disease (AD); (2) the correlation of these estimates with age and cognitive performance; (3) the differences between absolute EEG power between ageing and AD; (4) the correlation between EEG power and age or cognitive performance; and (5) the correlation between volumetric and EEG data. 84 patients with a clinical diagnosis of AD and 45 age-approximated non-demented controls between 48 and 91 years of age were examined. For statistical comparisons the volumetric estimates of intracranial cerebrospinal fluid (csf) spaces were converted into percentages of total intracranial volume. The EEG was recorded from 17 locations at resting conditions, eyes closed, according to the 10/20 system. Logtransformed absolute band powers were compared between the AD and control groups and correlated with clinical and volumetric findings. The total intracranial csf-space, both lateral ventricles, the third ventricle, anterior, lateral and posterior fissures were significantly larger in AD than in non-demented controls. In normal ageing the csf-volumes were significantly correlated with age, whereas age and cognitive performance were differentially correlated with these variables in AD. In AD, the absolute delta or theta power was significantly higher in all locations, whereas alpha power was lower than in normal controls. These differences were significantly correlated with cognitive performance. There were no significant correlations between the csf-volumes and EEG-power in AD and the control group with one exception: we found a significant inverse correlation between the volumes of the anterior and posterior fissure and the alpha-1 and alpha-2 power independent of electrode location in AD. We conclude that the morphological and EEG-changes in AD are largely independent and suggest that the functional relationship between alpha-power and anterior or posterior fissure volume needs further examination.