The effect of age and cerebral ischemia on diffusion-weighted proton MR spectroscopy of the human brain.

BACKGROUND AND PURPOSE DW-MRS is a promising tool for the noninvasive identification of the cellular response to cerebral ischemia. To date, the potential confounding effects of aging and the stage of ischemia are unknown. We, therefore, examined the cross-sectional effects of age and different stages of cerebral ischemia on the diffusion of brain metabolites. MATERIALS AND METHODS The ADCs of 3 major metabolites, including Cho, Cr, and NAA were measured by DW-MRS in healthy younger (n = 26, 24 ± 2.2 years of age) and older (n = 17, 63 ± 7.0 years of age) adults, as well as in patients with acute (n = 7, 57 ± 4.0 years of age) and subacute (n = 12, 62 ± 7.8 years of age) cerebral ischemia. RESULTS Compared with younger adults, healthy older adults presented with significantly reduced ADC values of NAA (P = .000052), Cr (P = .000018), and Cho (P = .00075). Meanwhile, the ADC values of NAA (F(2,36) = 6.057, P = .006), Cr (F(2,36) = 5.634, P = .008), and Cho (F(2,36) = 8.167, P = .001) were significantly different among the acute cerebral ischemia group, subacute cerebral ischemia group, and healthy older controls. These metabolites decreased in the acute stage of cerebral ischemia but increased in the subacute stage, compared with age-matched controls. CONCLUSIONS The effect of age should be considered when analyzing diffusion of cerebral metabolites with DW-MRS. Our observations also suggest that metabolite diffusion data may be used to reveal changes in the intracellular environment, depending on the pathologic status of ischemia.