The influence of posterior visual pathway damage on visual information processing speed in multiple sclerosis

Background: The injury of visual pathway and abnormalities of visual processing speed (VPS) are frequent in MS, but their association remains unexplored. Objective: To evaluate the impact of posterior visual pathway structural and functional integrity on VPS of MS patients. Methods: Cross-sectional study of 30 MS patients and 28 controls, evaluating the association of a VPS tests composite (Salthouse Perceptual Comparison test, Trail Making Test A and Symbol Digit Modalities Test) with 3T MRI visual cortex thickness, optic radiations (OR) diffusion tensor imaging indexes, and medial visual component (MVC) functional connectivity (FC) (MVC-MVC FC (iFC) and MVC-brain FC (eFC)) by linear regression, removing the effect of premorbid IQ, fatigue, and depression. Results: V2 atrophy, lower OR fractional anisotropy (FA) and MVC FC significantly influenced VPS in MS (at none or lesser extent in controls), even after removing the effect of Expanded Disability Status Scale and previous optic neuritis (V2 (r² = 0.210): β = +0.366, p = 0.046; OR FA (r² = 0.243): β = +0.378, p = 0.034; MVC iFC, for example, left cuneus (r² = 0.450): β = −0.613, p < 0.001; MVC eFC, for example, right precuneus-postcentral gyrus (r² = 0.368): β = −0.466, p = 0.002). Conclusion: Posterior visual pathway integrity, structural (V2 thickness and OR FA) and functional (MVC FC), may explain respectively up to 24% and 45% of VPS variability in MS.