BRAIN ATROPHY IN NORMAL AGING AND ALZHEIMERS-DISEASE - VOLUMETRIC DISCRIMINATION AND CLINICAL CORRELATIONS

Background. We examined the differences in volume of the ventricular a nd extracerebral cerebrospinal fluid spaces in normal ageing and in pr obable Alzheimer's disease (AD) and we tried to investigate the effect s of the severity of illness on the morphometric differentiation of AD and ageing, the principal components underlying brain atrophy in both conditions, and the correlations of these measurements with clinical findings. Method. Forty patients with probable AD were matched with 40 non-demented elderly controls. Both groups underwent standardised cli nical tests and unenhanced cranial computed tomography for post hoc vo lumetric analysis. Results. The lateral and third ventricles and the a nterior and lateral fissures were significantly larger in AD than in n ormal ageing. The volumes of the lateral ventricle and lateral fissure permitted a highly efficient differentiation between normal ageing an d AD even at the mild stage of dementia, and this differentiation was improved further in the more severe stages of illness. We identified o ne principal component underlying brain atrophy in normal ageing and t wo components in AD: a 'grey matter' component accounting for sulcal a nd third ventricular enlargement, and a 'white matter' component for l ateral Ventricular enlargement. In AD, most of the volumetric measurem ents were significantly correlated with cognitive impairment. but in t he group of non-demented elderly controls they were correlated with ag e. Conclusion. Volumetric indices of brain atrophy permit a highly eff icient differentiation between normal ageing and AD even in the mild s tages of illness and this demonstrates that substantial structural bra in changes have developed in the preclinical phase of illness. We sugg est that there is an uncoupling between lateral ventricular enlargemen t and cortical brain atrophy in AD.