Mohammed T. Abou-Saleh

40 PRINCIPLES AND PRACTICE OF GERIATRIC PSYCHIATRYFigure 7.1 Typical coronal MRI images (TR=500 ms, TE=25 ms) illustrating anatomic landmarks and computer-assisted measurement of regionalbrain areas (A) Coronal section at level of optic chiasm, illustrating measurement of the right frontal lobe, the lateral ventricles and the left temporal lobe.(B) Coronal section at the level of the interpeduncular cistern, illustrating measurement of the left temporal lobe, the third ventricle and the rightamygdala–hippocampal complexan experienced research team that is blind to the subject’s age andgroup status (i.e. normal control vs. patient).These studies are ongoing, and several important findings haveemerged 41,99–104 . First, our quantitative imaging and measurementtechniques provide highly accurate and reliable assessments ofbrain size. For example, intraclass correlation coefficients forinterrater reliability range from 0.88 to 0.99, depending upon theparticular brain region under study. The intraclass correlationcoefficients for intrarater reliability range from 0.93 to 0.99.Second, regional brain volume clearly changes with age, with apredilection for the frontal lobes. We have observed a rate ofdecline of about 0.23%/year for cerebral hemisphere volume. Yetthe rate of decrease we have observed for the frontal lobes is twiceas great (0.55%/year). Our data also indicate that age relatedchanges in regional cerebral volume is greater for ventricularregions than for parenchymal regions (3%/year vs. 0.23–0.55%/year). Thus, ventricular enlargement may prove to be a moresensitive index of brain aging than cortical atrophy. Third, formalassessments of cortical atrophy and ventricular enlargementsuggest that the statistically significant age-related changes inbrain volume may not be clinically significant. That is to say,anything more than mild cortical atrophy or mild ventricularenlargement appears to be distinctly uncommon in a medicallyhealthy sample of elderly community volunteers. Fourth, theincidence of subcortical hyperintensity increases with age, butagain it is uncommon for such changes to be severe 39,96 . Fifth, therelationship between aging and changes in brain size is not asimple one, in that it may be affected by a number of covariates(e.g. sex, height, years of education) that can modify the maineffects of aging 38 . For instance, we recently found that age-relatedchanges in brain size were significantly greater in men than womenfor peripheral (sulcal) CSF volume, the lateral (Sylvian) fissureCSF volume, and the parieto-occipital region area 103 . In additionwe have observed significant effects of years of formal educationon peripheral CSF volume, a marker of cortical atrophy 104 .Inasample of healthy elderly volunteers living independently in thecommunity and Mini Mental State Examination (MMSE) scoresof at least 24, each year of education was associated with anincrease in peripheral CSF volume of 1.77 ml. These findings areconsistent with the ‘reserve hypothesis’, which posits thateducation (or factors for which it is a surrogate) provides aprotective buffer against the injurious effects of age-related brainchanges.SUMMARYAdvanced brain imaging techniques produce highly accurateanatomic information and provide exciting opportunities toexamine in vivo the effects of aging on the human brain. Ourreview of the existing literature indicates that normal aging isassociated with cortical and subcortical atrophy, enlargement ofthe lateral and third ventricles, and an increase in subcorticalhyperintensities. The extent of these anatomic changes can now be