Cortical diffusion-tensor imaging abnormalities in multiple sclerosis: a 3-year longitudinal study.

Abstract

To evaluate whether diffusion-tensor imaging can be combined with double inversion recovery to improve the detection of structural changes occurring in the cortex of patients with multiple sclerosis (MS). Once local ethics committee approval and informed consent were obtained, 168 patients with relapsing-remitting MS and 45 sex- and age-matched control subjects were included in a 3-year longitudinal study. Expanded Disability Status Scale (EDSS) and magnetic resonance (MR) imaging examinations were performed at study entry and after 3 years. Number and volume of cortical lesions, T2 white matter lesion volume (WMLV), and fractional anisotropy (FA) and mean diffusivity (MD) of normal-appearing gray matter (NAGM) and cortical lesions were analyzed. Between-group differences in terms of NAGM-FA and NAGM-MD were assessed with analysis of variance followed by Tukey test correction. At baseline, NAGM-FA was higher in patients (mean ± standard deviation, 0.149 ± 0.011) than in control subjects (0.125 ± 0.008; P < .001) and higher in patients with cortical lesions (0.154 ± 0.011) than in those without (0.138 ± 0.010; P < .001). Moreover, FA was higher in cortical lesions than in NAGM (P < .001). After 3 years, NAGM-FA was unchanged in control subjects and increased in patients (0.154 ± 0.012; P < .001), especially in patients with worsened EDSS score (0.170 ± 0.011; P < .001). The same behavior was observed for NAGM-MD. At baseline, NAGM-FA significantly correlated with EDSS score (r = 0.75; P < .001) and cortical lesion volume (r = 0.850; P < .001). Multivariate analysis identified NAGM-FA (B = 0.654; P < .001) and T2 WMLV (B = 0.310; P < .001) as independent predictors of EDSS score, while NAGM-FA change (B = 0.523; P < .001) and disease duration (B = 0.342; P < .001) were independent predictors of EDSS change. Compared with control subjects, patients with RRMS had an increase in FA of NAGM that strongly correlated with cortical lesion volume and clinical disability.