Functional and structural balances of homologous sensorimotor regions in multiple sclerosis fatigue

Objective Fatigue in Multiple Sclerosis (MS) is a highly disabling symptom affecting social relationships and daily cognitive and physical activities of patients, being complained by up to 90% of MS sufferers. Among the central mechanisms behind it, an involvement of sensorimotor networks is evident from structural and functional studies. We aimed at assessing whether functional/structural balances of homologous sensorimotor regions – known to be crucial for sensorimotor networks effectiveness – decrease with MS fatigue increase. Methods Functional connectivity measures at rest and during a simple motor task (weak handgrip of either the right or left hand) were derived from primary sensorimotor areas EEG recordings in twenty-seven mildly disabled MS patients. Structural MRI-derived inter-hemispheric asymmetries included the cortical thickness of Rolandic regions and the volume of thalami. Results Fatigue symptoms increased together with the functional inter-hemispheric imbalance of sensorimotor homologous areas activities at rest and during movement, in absence of any appreciable parenchymal asymmetries. Conclusion People with MS suffering of chronic fatigue have higher left (dominant) than right hemispheric primary sensorimotor activity power in the resting state, without structural asymmetries. Key message This finding supports the development of compensative interventions that may revert these neuronal activity imbalances to relieve fatigue in MS.