Differential associations of contralesional and ipsilesional brain functional connectivity with lower-limb impairment after stroke

Stroke may induce distinct plastic structural changes within the ipsilesional and contralesional hemispheres of the brain, leading to interhemispheric imbalances in cortical connectivity. Maximum joint range of motion (ROM max ) impairments may also occur in the paretic limb, contributing to increased interlimb asymmetry and impaired gait. This study examined the influence of ipsilesional and contralesional brain functional connectivity on hip flexion ROM max interlimb asymmetry and walking performance in stroke survivors. Eighteen individuals with chronic stroke (57.5 ± 14.8 years; 26.7 ± 22.2 months post-stroke) were assessed for functional connectivity of the ipsilesional and contralesional general hemispheres and specific primary motor cortex (M1) areas of the brain with resting-state electroencephalography (EEG). Participants were also assessed for hip flexion active ROM max of the paretic and non-paretic limbs and 10-m walk test, and ROM max interlimb asymmetry was further calculated. Relationships between changes in these variables were examined by Pearson product–moment (r) and regression analyses. Hip flexion ROM max interlimb asymmetry was significantly associated with contralesional functional connectivity in both general (r = 0.53) and M1-specific (r = 0.48) regions of the brain (P < 0.05). Walking performance was only associated with contralesional M1 connectivity (r = 0.51; P < 0.05). Contralesional hemisphere connectivity explained 28% of the variance in ROM max asymmetry, while contralesional M1 connectivity explained 26% of the variance in walking time. No significant relationships were found for brain connectivity within the ipsilesional hemisphere. Greater brain functional connectivity in contralesional cortical regions is associated with increased hip ROM max asymmetry and impaired walking performance in stroke survivors, highlighting the role of contralesional networks in post-stroke motor impairment.