Is the walk ratio a window to the cerebellum in multiple sclerosis? A structural magnetic resonance imaging study

Background and purpose: Existing research studies have demonstrated a relationship between magnetic resonance imaging (MRI) neuroimaging measures and walking speed in people with multiple sclerosis (PwMS). However, to date there are no data as to the brain structures involved in gait coordination and control in PwMS. Therefore, the aim of our study was to investigate the association between walk ratio, an indicator of gait coordination, and related brain structures in PwMS. Methods: A brain MRI was performed by a 3.0-T MR scanner in conjunction with a volumetric analysis based on three-dimensional T1-weighted images. Regions of interest were volumes of the hippocampus, amygdala, putamen, caudate, pallidum, thalamus, cerebellum and the corpus callosum regions. Walking speed and walk ratio, defined as step length divided by step rate, was measured whilst walking on an electronic walkway. Results: In all, 343 PwMS (41.1 ± 13.4 years, 69.1% female, median Expanded Disability Status Scale 2.5) were included in the study. A significant association was found between the left cerebellum volume and walk ratio after controlling for age, gender, total cranial volume and disability; R² = 0.379, P = 0.002. A similar association was found between the right cerebellum volume and walk ratio, R² = 0.364, P = 0.002. No correlations were observed between walk ratio and the thalamus, basal ganglia, hippocampus, amygdala and the corpus callosum volumes. No association was found between walking speed and all brain measures. Conclusions: The walk ratio should be considered when evaluating and assessing PwMS presenting with ataxia. Furthermore, it is also hypothesized that a low walk ratio indicates a lower cerebellum volume in the MS population.