Diagnosing dementia and normal aging: clinical relevance of brain ratios and cognitive performance in a Brazilian sample

The main objective of the present study was to evaluate the diagnostic Valu e (clinical application) of brain measures and cognitive function. Alzheime r and multiinfarct patients (N = 30) and normal subjects over the age of 50 (N = 30) were submitted to a medical, neurological and cognitive investiga tion, The cognitive tests applied were Mini-Mental, word span, digit span, logical memory, spatial recognition span, Boston naming test, praxis, and c alculation tests. The brain ratios calculated were the ventricle-brain, bif rontal, bicaudate, third ventricle, and suprasellar cistern measures. These data were obtained from a brain computer tomography scan, and the cutoff v alues from receiver operating characteristic curves. We analyzed the diagno stic parameters provided by these ratios and compared them to those obtaine d by cognitive evaluation. The sensitivity and specificity of cognitive tes ts were higher than brain measures, although dementia patients presented hi gher ratios, showing poorer cognitive performances than normal individuals. Normal controls over the age of 70 presented higher measures than younger groups, but similar cognitive performance. We found diffuse losses of tissu e from the central nervous system related to distribution of cerebrospinal fluid in dementia patients. The likelihood of case identification by functi onal impairment was higher than when changes of the structure of the centra l nervous system were used. Cognitive evaluation still seems to be the best method to screen individuals from the community, especially for developing countries, where the cost of brain imaging precludes its use for screening and initial assessment of dementia.