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

Abstract

Purpose: To evaluate the influence of the size of lateral ventricles on diffusion parameters of the normal cingulate bundle.

Methods: Eighty normal subjects (17-55 years) underwent MRI at 3 T including diffusion tensor imaging. Superior (SC) and inferior (IC) cingulum were analyzed separately. Mean diffusivity (MD_0.30) and fractional anisotropy (FA_0.30) were measured by tractography at FA threshold 0.30; further diffusion parameters were analyzed by tractography-based core analysis in volumes of 3.0 cm³/1.5 cm³. 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.

Results: FA_0.30 values did not correlate with ventricular size, but there was a weak negative correlation (r = - 0.225) between MD_0.30 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.

Conclusion: 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.

Keywords: Cingulum; Diffusion tensor imaging; Diffusion tensor tractography; White matter.