Diffusion Changes in the Aging Human Brain

Abstract

BACKGROUND AND PURPOSE: Quantifying changes in the human brain that occur as part of normal aging may help in the diagnosis of diseases that affect the elderly and that cause structural changes in the brain. We sought to assess diffusion changes that are inherently related to brain structure during aging.

METHODS: MR scans were obtained from 11 healthy volunteers and 27 patients (ages 26 to 86 years [53.4 ± 17.0 years]). Images acquired from the patients either showed no abnormalities, contained minimal periventricular white matter changes, or revealed focal lesions. Maps of the average diffusion constant (D_av) were calculated for each subject. Changes in D_av were determined with distribution analysis (histogram) for the entire brain and compared with region-of-interest measurements from the periventricular white matter and thalamus.

RESULTS: Mean D_av of the entire brain (0.74 ± 0.02 × 10⁻⁵ cm²/s) showed weaker age dependency compared with the periventricular white matter D_av(0.76 ± 0.04 × 10⁻⁵ cm²/s). The D_av of the thalamus D_av (0.75 ± 0.03 × 10⁻⁵ cm²/s) had no age dependency. The age-dependent changes of entire brain D_av may be significant for subjects older than 60 years compared with younger subjects.

CONCLUSION: In this study, we observed minimal changes in the D_av of the entire brain with aging. The mean D_av of the human brain is nearly constant throughout most of adulthood.