Purpose: To combine two unbiased (ie, without any a priori hypothesis) magnetic resonance (MR) imaging processing approaches, tract-based spatial statistics and voxel-based morphometry, to investigate the relationship between white matter and gray matter damage and computer-based measures of balance impairment assessed at static posturography in patients with multiple sclerosis (MS).
Materials and methods: Institutional review board approval and written informed consent were obtained. Forty-five ambulatory patients with MS (34 women, 11 men) and 25 sex- and age-matched healthy control subjects were assessed by using a force platform to compute the displacement (in millimeters) of the body center of pressure in 30 seconds. In a separate session, patients underwent MR imaging at 3 T, including a dual-echo fast spin-echo sequence, a T1-weighted volume sequence, and a diffusion-tensor imaging sequence. T2 lesion volumes were assessed by using a semiautomated technique. Tract-based spatial statistics and voxel-based morphometry were used for the white and gray matter analyses, respectively, to correlate force platform measures with diffusion-tensor imaging parameters and regional gray matter volumes, adjusting for the patients' sex, age, disease duration, and lesion volume.
Results: Patients with MS had worse postural stability, widespread alterations in most white matter bundles, and gray matter atrophy in several brain regions compared with control subjects. In patients with MS, balance impairment was correlated with worse diffusion-tensor imaging parameters along the cerebellar connections and supratentorial associative white matter bundles (P < .05, threshold-free cluster enhancement corrected). Gray matter atrophy of the superior lobules of the cerebellum (IV, V, VI), and lobules VIII also correlated with worse posturometric values (P < .05, family-wise error corrected).
Conclusion: Imbalance due to MS appears to be related to the disconnection between the spinal cord, cerebellum, and cerebral cortex, which in turn produces atrophy of the sensory motor cerebellar regions that are functionally connected with specific cortical areas.