Regional Cervical Cord Atrophy and Disability in Multiple Sclerosis: A Voxel-based Analysis

To (a) apply an active surface method to map the regional distribution of cord atrophy across levels and sectors in a relatively large group of patients with multiple sclerosis (MS), (b) compare the anatomic location of cord atrophy between patients with relapsing-remitting (RR) MS and those with secondary progressive (SP) MS, and (c) assess correlations between atrophy and disability.This study was approved by the local ethical committee, and written informed consent was obtained from each participant. High-spatial-resolution magnetic resonance (MR) images of the cervical cord were acquired from 45 patients with RR MS, 26 patients with SP MS, and 67 age-matched healthy control subjects. The active surface method segmented the cord surface from C1 to C7 and created output images reformatted in planes perpendicular to the estimated cord center line. These unfolded cervical cord images were coregistered into a common standard space, and smoothed cord binary masks were used as input images for spatial statistics. Voxel-wise between-group comparisons and the correlation between regional cord atrophy versus clinical and conventional MR imaging variables were assessed with software.Compared with control subjects, patients with RR MS showed localized clusters of atrophy in the posterior cord. Conversely, patients with SP MS showed a widespread pattern of cord atrophy, predominantly in the posterior and lateral cord columns. In patients with MS, cervical cord atrophy was correlated with clinical disability, disease duration, and, to a lesser extent, conventional MR imaging measures of brain injury. No correlation was found between cord atrophy and the presence of focal cord lesions.Voxel-wise assessment of the regional distribution of damage in the cervical cord is feasible and might improve our understanding of the mechanisms related to the development of irreversible clinical disability in MS.