The association between cognition and motor performance is beyond structural damage in relapsing-remitting multiple sclerosis

Background: Previous studies demonstrated an association between motor and cognitive performance in multiple sclerosis (MS). However, disease-related brain damage might represent a common substrate to both phenomena, which was not considered before. Objective: Aim of this study is to investigate whether the association between cognition and motor function is beyond structural damage in patients with MS. Methods: Eighty-one healthy controls and 106 relapsing-remitting (RR) MS patients underwent a 3.0 T MRI with quantification of T2-lesion volumes, T1-lesion volumes and normalized brain volumes. A functional examination [Nine-Hole Peg Test (9-HPT), Timed 25-Foot Walk test (T25FW) and Expanded Disability Status Scale] and a neuropsychological evaluation (Brief Repeatable Battery of Neuropsychological Tests) were also administered. Association between demographic, clinical, cognitive, MRI and functional measures were analysed with univariate analyses and hierarchical linear regression. Results: In RRMS patients, Spatial Recall Test and Symbol Digit Modalities Test were positively correlated with 9-HPT (p < 0.001) and T25FW (p ≤ 0.035); Paced Auditory Serial Addition Test (PASAT) correlated with 9-HPT (p ≤ 0.009). 9-HPT and T25FW were significantly associated with normalized brain volumes (p ≤ 0.016), T2- and T1-lesion volumes (p ≤ 0.009). Hierarchical regression models selected age and normalized deep gray matter volume as predictors of T25FW (adjusted-R2 = 0.109). Younger age, female sex, higher normalized gray matter volume and higher PASAT 2″ scores predicted higher 9-HPT scores (adjusted-R2 = 0.337). Conclusions: In RRMS patients, deficit in information processing speed and executive function may contribute to hand motor dysfunction beyond the effect of structural disease-related burden, supporting the integration of motor and cognitive assessment in clinical settings.