Thalamo-cortical dysfunction contributes to fatigability in multiple sclerosis patients: A neurophysiological study

Abstract

BackgroundFatigue and fatigability are common symptoms reported by patients affected by Multiple Sclerosis (MS). The pathogenic mechanisms of such symptoms are currently unknown, but increasing evidence suggests that thalamus could play a key-role. High-frequency oscillations (HFOs) are a neurophysiological measure reflecting the activity of thalamo-cortical network. In particular, the early component is generated from thalamic axons while the late part results from neurons located in somatosensory cortex. ObjectiveTo investigate the effect of a fatigue-inducing exercise on HFOs and on strength performances in MS patients and healthy controls (HCs). MethodsFifteen patients and fifteen HCs participated in this study. We recorded HFOs from median nerve somatosensory evoked potentials and assessed strength performances, before and after a fatigue-inducing exercise of hand muscles. ResultsCompared to HCs, after repeated fatiguing tasks, patients showed a significant reduction of early component of HFOs area and a significant increase of late component of HFOs duration. Strength performance declined both in patients and in HCs but remained lower in patients at all time-points. ConclusionsHFOs, a neurophysiological marker of thalamo-cortical pathway, are significantly modified by fatiguing tasks in MS patients, in particular the early component that refers to the functionality of thalamic axons.