The assessment of changes in brain volume using combined linear measurements. A CT-scan study.

All linear measurements employed for evaluation of brain atrophy, were performed on 148 computed tomograms of patients aged 28 to 84 without evidence of any nervous system disorder. These included size of lateral, third and fourth ventricles, width of the Sylvian and frontal interhemispheric fissures and cortical sulci and size of the pre-pontine cistern. Various parameters indicated decrease in brain mass with age. Since the atrophic process is a diffuse phenomenon, integration of several measurements evaluating separate brain regions was made. The bicaudate ratio and the Sylvian fissure ratio (representing both central and cortical atrophy) were combined arithmetically, resulting in a correlation of 0.6390 with age (P less than 0.0005). With a computed canonical correlation analysis; a formula was obtained which combined measurements of the lateral and third ventricles, the Sylvian fissure and the pre-pontine cistern. This formula yielded a correlation of 0.67795 (P less than 0.0005). These linear measurements will allow simple and reliable assessement of reduction in brain volume during the normal aging process and in disorders accompanied by brain atrophy.