Motor reorganization in multiple sclerosis

Objective: To assess intra-hemispheric and interhemispheric reorganization of motor activation in multiple sclerosis ( MS). Motor reorganization may contribute to minimizing motor deficits after demyelination in MS. Methods: We used surface-based analysis to study functional organization for motor function in ten healthy controls and in 15 MS subjects. Results and discussion: In MS subjects, activation in the right hemisphere ( ipsilateral to the hand moved) was significantly increased compared with control subjects. We interpreted this increase as interhemispheric reorganization of motor activation. The increases in right hemisphere activation were the greatest in the pre-motor cortex ( Brodmann area 6) and the cognitive areas. Within the left hemisphere, contralateral to the right hand, total motor activation was not increased and the centroid of activation was not displaced when MS subjects were compared with controls. However, we found that MS subjects with high MS plaque loads showed an anterior shift of the focus of motor activation with right hand movement when compared with the low MS plaque load subjects ( p < 0.05). Furthermore, there was more activation in pre-motor cortex ( Brodmann area 6) in the high plaque load group and less activation in sensory areas ( Brodmann areas 1, 2 and 3). Conclusion: Functional magnetic resonance imaging ( fMRI) provides evidence that both interhemispheric and intra-hemispheric motor reorganization occur in MS.