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Neurophysiological correlates of fatigue in people with multiple sclerosis
Author(s): ,
P. Ellison
Affiliations:
Department of Sport, Exercise & Rehabilitation, Northumbria University, Newcastle Upon Tyne, United Kingdom
,
S. Goodall
Affiliations:
Department of Sport, Exercise & Rehabilitation, Northumbria University, Newcastle Upon Tyne, United Kingdom
,
N. Kennedy
Affiliations:
School of Psychology, Ulster University, Co.Londonderry, Ireland
,
G. Howatson
Affiliations:
Department of Sport, Exercise & Rehabilitation, Northumbria University, Newcastle Upon Tyne, United Kingdom
,
H. Dawes
Affiliations:
Physiotherapy and Rehabilitation, Oxford Brookes University, Oxford
,
V. Pomeroy
Affiliations:
School of Health Sciences
,
A. Clark
Affiliations:
Norwich Medical School, University of East Anglia, Norwich, United Kingdom
J. Saxton
Affiliations:
Department of Sport, Exercise & Rehabilitation, Northumbria University, Newcastle Upon Tyne, United Kingdom
ECTRIMS Online Library. Ellison P. Oct 12, 2018; 228853
Paula Ellison
Paula Ellison
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Abstract: P1011

Type: Poster Sessions

Abstract Category: Clinical aspects of MS - MS symptoms

Background: Symptoms of fatigue are debilitating for many people with multiple sclerosis (PwMS). An improved understanding of the neurophysiological basis of MS fatigue could underpin the development of new therapeutic approaches for fatigue management.
Aims: To compare measures of neurophysiological function between people experiencing high and low levels of MS fatigue and healthy controls.
Methods: 40 patients with relapsing remitting MS (20 highly fatigued (MS-F); 20 less-fatigued (MS-LF) according to the Fatigue Severity Scale (≥5) and 20 healthy age and gender-matched controls (HC) were recruited. Maximal voluntary contraction (MVC), and twitch responses to electrical and transcranial magnetic stimulation (TMS) during isometric knee extensor muscle actions and at rest were measured to assess central (voluntary activation, VA) and peripheral (potentiated twitch force, Qtw) mechanisms of fatigue at baseline and following a submaximal intermittent motor task. Responses to single- and paired-pulse TMS were used to assess corticospinal excitability (motor evoked potential [MEP] and central motor conduction time [CMCT]), short-interval intracortical inhibition (SICI) and silent period (SP).
Results: MS-F had a higher level of subjective fatigue versus HC and MS-LF (P = 0.001). A submaximal intermittent motor task elicited group differences in MVC force decline (P = 0.003) but no differences in Qtw force between groups (P = 0.52), despite differences in time to task failure. VA differed between groups at rest (P = 0.023) with greater deficits in MS-F (P = 0.03), but with similar immediately post-task VA between the groups (P = 0.09). Corticospinal excitability was similar between MS-F and MS-LF but differed in PwMS compared to HC. SICI (P = 0.03) was reduced and SP was increased (P = 0.022) in MS-F compared to MS-LF and HC at rest and immediately post-fatigue task.
Conclusions: The findings that MS-F exhibited impaired activation of the quadriceps may be a result of compromised ability to fully drive the motor unit pool, indicative of impaired voluntary descending drive. Abnormal connectivity within motor cortical function, evidenced by deficits in SICI and SP in MS-F, may be a consequence of altered interactions between GABAergic intracortical circuits mediating SICI and SP projections in motor cortex networks. These differences in corticospinal output at rest and during motor tasks may contribute to subjective perceptions of fatigue experienced by PwMS.
Disclosure: JS (Principal Investigator), PE, NK, AC, VP and HD (supported by Elizabeth Casson Trust and Oxford BRC) acknowledge the support of the UK Multiple Sclerosis Society, which provided funding to support this research. There are no conflicts of interests
"Paula Ellison: nothing to disclose"
"Stuart Goodall: nothing to disclose"
"Niamh Kennedy: nothing to disclose"
"Glyn Howatson: nothing to disclose"
"Helen Dawes: nothing to disclose"
"Valerie Pomeroy: nothing to disclose"
"Allan Clark: nothing to disclose"
"John Saxton: nothing to disclose"

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