Diffusion parameters of the core of cingulum are associated with age-related ventricular enlargement: a diffusion tensor tractography study.

Abstract

To evaluate the influence of the size of lateral ventricles on diffusion parameters of the normal cingulate bundle. Eighty normal subjects (17-55years) underwent MRI at 3T including diffusion tensor imaging. Superior (SC) and inferior (IC) cingulum were analyzed separately. Mean diffusivity (MD0.30) and fractional anisotropy (FA0.30) were measured by tractography at FA threshold 0.30; further diffusion parameters were analyzed by tractography-based core analysis in volumes of 3.0cm3/1.5cm3. The diffusion parameters were correlated with corresponding cross-sectional coronal areas of lateral ventricles. The analysis was performed also separately for young (17-34) and middle-aged (35-55) subjects. FA0.30 values did not correlate with ventricular size, but there was a weak negative correlation (r = - 0.225) between MD0.30 of SC and ventricular size. In all controls and in the older age group, ventricular size correlated positively with core FA of SC (r = 0.262/r = 0.391) and negatively with mean diffusivity (r = - 0.324/r = - 0.303) and radial diffusivity (λ2: r = - 0.238/r = - 0.277; λ3: r = - 0.353/r = - 0.424) of the core of SC. In the younger age group, only the mean diffusivity of SC correlated with ventricular size (r = - 0.273). Ventricular size was not associated with axial diffusivity. The core parameters of IC did not correlate with ventricular size. Radial diffusivity of the core of cingulum decreases in age-dependent ventricular enlargement, which can be related to tissue compaction with stretching of axons and diminution of extracellular spaces. The phenomenon, which is reverse to the assumed effect of age-related myelin loss, can influence on DTI parameters in middle-aged subjects.