Diffusion changes in the aging human brain.

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 x 10(-5) cm2/s) showed weaker age dependency compared with the periventricular white matter D(av)(0.76 +/- 0.04 x 10(-5) cm2/s). The D(av) of the thalamus D(av) (0.75 +/- 0.03 x 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.