A prospective sample of 69 healthy adults, age range 18-80 years, was studied with magnetic resonance imaging scans (T2 weighted, 5 mm thick) of the entire cranium. Volumes were obtained by a segmentation algorithm that uses proton density and T2 pixel values to correct field inhomogeneities ("shading"). Average (-SD) brain volume, excluding cerebellum, was 1090.91 ml (±# 114.30; range, 822.19-1363.66), and cerebrospinal fluid (CSF) volume was 127.91 ml (±57.62; range, 34.00-297.02). Brain volume was higher (by 5 ml) in the right hemisphere (P < 0.0001). Men (n = 34) had 91 ml higher brain and 20 ml higher CSF volume than women (n = 35). Age was negatively correlated with brain volume [r(67) =-0.32, P < 0.01] and positively correlated with CSF volume (r = 0.74, P < 0.0001). The slope of the regression line with age for CSF was steeper for men than women (P = 0.03). This difference in slopes was significant for sulcal (P < 0.0001), but not ventricular, CSF. The greatest amount of atrophy in elderly men was in the left hemisphere, whereas in women age effects were symmetric. The findings may point to neuroanatomic substrates of hemispheric specialization and gender differences in age-related changes in brain function. They suggest that women are less vulnerable to age-related changes in mental abilities, whereas men are particularly susceptible to aging effects on left hemispheric functions.The study of brain regulation of human behavior requires measurement of structural variables, and this has been done primarily by postmortem studies (e.g., refs. 1-6). Atrophy was inferred from reduced brain weight or volume or increased differences between brain volume and cranial capacity-i.e., cerebrospinal fluid (CSF) volume. Several studies found aging associated with atrophy (7-9). Others did not find age effects until senescence (usually defined as age >55 or 60; refs. 4, 10, and 11). Women have lower brain volume, related to body and cranial size (e.g., refs. 4, 6, and 9).In vivo measurement of brain volume became feasible with computed tomography, and more recently with magnetic resonance imaging (MRI), which is more sensitive than computed tomography for determining sulcal changes and has better tissue contrast, multiplanar imaging capabilities, absence of bone artifact, and no ionizing radiation. In addition to elucidating structural substrates of brain function, anatomic volume measures are important for interpreting metabolic data (12). Thus, decline in cerebral blood flow and metabolism with age (e.g., refs. 13-15), and higher cerebral blood flow in women (16), could be explained by structural effects (17).Several computed tomography studies investigated ageassociated changes. Takeda and Matsuzawa (18) subjects aged 21-81 studied with a 2-T magnet and a spinlattice relaxation time (T1)-weighted sequence. However, in contrast to the other studies, which yielded brain volume estimates averaging 1100-1200 ml, their estimates were >2000 ml for men and >1800 ml for women. Jernigan et al. (23) found a linear re...

A computerized system was developed to process standard spin-echo magnetic resonance (MR) imaging data for estimation of brain parenchyma and cerebrospinal fluid (CSF) volumes. In phantom experiments, the estimated volumes corresponded closely to the true volumes (r = .998), with a mean error less than 1.0 cm3 (for phantom volumes ranging from 5 to 35 cm3), with excellent intra- and interobserver reliability. In a clinical validation study with actual brain images of 10 human subjects, the average coefficient of variation between observers for the measurement of absolute brain and CSF volumes was 1.2% and 6.4%, respectively. The intraclass correlations for three expert operators is greater than .99 in the measurement of brain and ventricular volumes and greater than .94 for total CSF volume. Therefore, the authors believe that their technique to analyze MR images of the brain performed with acceptable levels of accuracy and reliability and that it can be used to measure brain and CSF volumes for clinical research. This technique could be helpful in the correlation of neuroanatomic measurements to behavioral and physiologic parameters in neuropsychiatric disorders.

A new, computerized segmentation technique, in which magnetic resonance (MR) imaging produces accurate volumetric measurements of brain and cerebrospinal fluid (CSF) without the limitations of computed tomography, was used in a retrospective analysis of digitized T2-weighted MR images of 16 healthy elderly control subjects and 16 patients with Alzheimer dementia. Ventricular and extraventricular CSF was quantified, and the effects of aging were studied; in both groups, the atrophy measurement was used to correct metabolic values obtained with positron emission tomography. Patients with Alzheimer dementia had higher total CSF; extraventricular, total ventricular, and third ventricular CSF volumes (49%, 37%, 99%, and 74%, respectively); and 7% lower brain volumes than the control group. The patients also showed a more marked decline in brain volumes and a greater increase in CSF volumes with advancing age than the control group. They had a 25.0% increase in corrected whole-brain metabolic rates; the control group had only a 15.8% increase. The use of this technique may provide a basis for further studies of aging and dementia, including regional volume analysis.

Distal intersection tenosynovitis may be related to the biomechanical pulley effect exerted by Lister's tubercle on the EPL tendon as it leaves the third compartment and crosses over the extensor carpi radialis tendons, as well as the constraining effect of the extensor retinaculum. These anatomical features determine the presence of characteristic MR imaging findings.

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