AGE-RELATED-CHANGES IN INTRACRANIAL COMPARTMENT VOLUMES IN NORMAL ADULTS ASSESSED BY MAGNETIC-RESONANCE-IMAGING

Magnetic resonance (MR) image-based computerized segmentation was used to measure various intracranial compartments in 49 normal volunteers ranging in age from 24 to 80 yeats to determine age-related changes in brain, ventricular, and extraventricular cerebrospinal fluid (CSF) vo lumes. The total intracranial volume (sum of brain, ventricular, and e xtraventricular CSF) averaged 1469 +/- 102 cm(3) in men and 1289 +/- 1 11 cm(3) in women. The difference was attributable primarily to brain volume, which accounted for 88.6% of the respective intracranial volum es in both sexes, but was significantly larger in men (1302 +/- 112 cm (3)) than in women (1143 +/- 105 cm(3)). In both, the cranial CSF volu me averaged 11.4%. Total intracranial volume did not change with age, although the normalized brain volume of both men and women began to de crease after the age of 40 years. This decrease was best reflected by expansion of the extraventricular CSF volume which, after the age of 5 0 years, was more marked in men than in women. The volume of the crani al CSF, as determined by MR image-based computerized segmentation, is considerably larger than traditionally accepted and resides mostly ext raventricularly. Expansion of CSF volume with age provides a good inde x of brain shrinkage although evolving changes and growth of the head with age tend to confound the results.