Role of left motor cortex in post-stroke fatigue: a corticospinal excitability study

Abstract

BackgroundThe neural mechanisms that underlie post-stroke fatigue are poorly understood. Previous work show an inverse relationship between motor cortex excitability and post-stroke fatigue, however, it is unclear if the side of lesion influences this relationship. The left hemisphere plays a dominant role in motor control, therefore we hypothesised that left hemisphere strokes are more likely to show a significant inverse relationship between corticospinal excitability and fatigue.MethodsResting motor threshold (measure of corticospinal excitability) using transcranial magnetic stimulation was measured in the affected hemisphere of 98 stroke survivors. Fatigue was measured using the fatigue severity scale. The effect of fatigue and hemisphere affected on corticospinal excitability was analysed using a multiple linear regression.ResultsA multiple linear regression with trait fatigue as the outcome variable (F(4,93)=12.04, p < 0.001, adj R2 = 0.313) revealed that RMT was not a significant predictor of FSS-7 (β = −0.063, p = 0.706, CI[-0.394, 0.268]), while the interaction between lesioned hemisphere and RMT was a significant predictor of FSS-7 (β = 0.339, p = 0.039, CI[0.018, 0.659]). The additional explanatory variables of HADSDepression and sex were also significant predictors of FSS-7 (β = 903, p < 0.001, CI[0.584, 1.223] and β = 1.127, p = 0.002, CI[0.425, 1.830] respectively).ConclusionLower corticospinal excitability of the left hemisphere may indicate altered perception of effort and reduced sensory attenuation. This provides evidence to support the sensory attenuation model of fatigue.

Mechanisms of Post-Stroke Fatigue: A Follow-Up From the Third Stroke Recovery and Rehabilitation Roundtable

“…Sensory processing is also reliant on inter-hemispheric interactions, and the normal left hemispheric dominance in such interactions shifts to a right hemispheric dominance 57 in people with PSF. Attention to visual and auditory sensory streams also appear to be poorly attenuated, specifically in relation to processing of distractors both in auditory 58 and visual processing 59 in PSF. This series of results support the sensory attenuation model of fatigue, however, functional connectivity studies beyond the somatosensory-motor networks do not fully support the hypothesis, 60 but indicate network level dysfunction does underpin PSF.…”