Abstract
ObjectivesReduced corticospinal excitability at rest is associated with post-stroke fatigue (PSF). However, it is not known if corticospinal excitability prior to a movement is also altered in fatigue which may then influence subsequent behaviour. We hypothesized that the levels of PSF can be explained by differences in modulation of corticospinal excitability during movement preparation. Methods73 stroke survivors performed an auditory reaction time task. Corticospinal excitability was measured using transcranial magnetic stimulation. Fatigue was quantified using the fatigue severity scale. The effect of time and fatigue on corticospinal excitability and reaction time was analysed using a mixed effects model. ResultsThose with greater levels of PSF showed reduced suppression of corticospinal excitability during movement preparation and increased facilitation immediately prior to movement onset (β = −0.0066, t = −2.22, p = 0.0263). Greater the fatigue, slower the reaction times the closer the stimulation time to movement onset (β = 0.0024, t = 2.47, p = 0.0159). ConclusionsLack of pre-movement modulation of corticospinal excitability in high fatigue may indicate poor sensory processing supporting the sensory attenuation model of fatigue. SignificanceWe take a systems-based approach and investigate the motor system and its role in pathological fatigue allowing us to move towards gaining a mechanistic understanding of chronic pathological fatigue.
Highlights
Post-stroke fatigue (PSF) is one of the most commonly selfreported symptoms after stroke that has significant implicationsAbbreviations: PSF, post-stroke fatigue; TMS, transcranial magnetic stimulation; M1, primary motor cortex; EMG, electromyography; RT, reaction time; Hospital Anxiety and Depression Scale (HADS), hospital anxiety and depression scale; nine hole peg test (NHPT), nine-hole peg test; FDI, first dorsal interosseous; Resting motor threshold (RMT), resting motor threshold; WS, warning stimulus; IS, imperative stimulus; WP, warning period; RT30, 30% Reaction time; RT50, 50% Reaction time; RT70, 70% Reaction Time; FSS-7, fatigue severity scale; SDMT, symbol digit modalities test.⇑ Corresponding author at: Box 146, 33 Queen Square, London WC1N 3BG, UK.for morbidity, disability, quality of life and mortality (Barbour and Mead 2012)
We have previously shown that self-selected ballistic movement speeds are slower and resting corticospinal excitability assessed using transcranial magnetic stimulation (TMS) is reduced in the affected hemisphere of stroke survivors who report high levels of PSF (Kuppuswamy et al 2015a, 2015b)
A non-linear mixed effects model with time (WS, WP, IS, RT30, RT50 and RT70) and FSS-7 as fixed effects and participant nested in time as random effects best described the rate of change of corticospinal excitability during movement preparation
Summary
Post-stroke fatigue (PSF) is one of the most commonly selfreported symptoms after stroke that has significant implications⇑ Corresponding author at: Box 146, 33 Queen Square, London WC1N 3BG, UK.for morbidity, disability, quality of life and mortality (Barbour and Mead 2012). Post-stroke fatigue (PSF) is one of the most commonly selfreported symptoms after stroke that has significant implications. The majority of stroke survivors report fatigue in the first few weeks after stroke. This is linked to high levels of inflammation immediately following an injury and such fatigue is part of sickness behaviour (Dantzer and Kelley 2007). The more debilitating symptom is fatigue that fails to resolve and persists for months or even years after the stroke.
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