Diffusion tensor imaging of acute inflammatory lesion evolution in multiple sclerosis

Abstract

The initiating events in multiple sclerosis (MS) plaque formation are poorly understood. Retrospective analysis of serial imaging data can improve the understanding of tissue changes characterising acute MS lesion evolution. This study aimed to assess lesion evolution using diffusion tensor imaging data from serially acquired scans from 22 patients with MS. Mean diffusivity (MD) and fractional anisotropy (FA) were measured from 13 suitable plaques from five patients and carefully matched regions of contralateral normal-appearing white matter. Measurement times were on average: 5months and 1month prior to, during, and 1month and 2months post gadolinium-enhancement. A significant increase in MD (7.25%) but no change in FA was observed in white matter areas that exhibited enhancement 5months later. The pre-lesional MD increase was significantly correlated with the MD increase 2months subsequent to enhancement (R=0.73, p=0.04) but not to the MD increase during enhancement (R=0.11). These results suggest that MD is sensitive to tissue changes that precede blood–brain barrier (BBB) breakdown by at least 5months and that MD assessments may predict injury following BBB restoration.