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Impaired central drive to plantarflexors and minimal ankle proprioceptive deficit in people with multiple sclerosis.

Abstract：

BACKGROUND:A common and disruptive symptom of multiple sclerosis is difficulty in walking. Deficits in ankle proprioception and in plantarflexor muscle function may contribute to these mobility issues. In this study, ankle proprioceptive ability and plantarflexor performance of people with multiple sclerosis (PwMS) were compared to healthy controls to determine whether multiple sclerosis causes impairments in these systems. METHODS:PwMS (n = 30, median EDSS 4.0, IQR 2) were compared to age- and sex-matched healthy controls (n = 30) across tests of ankle proprioception and plantarflexor muscle performance. Proprioceptive tests: detection of passive movement, reaction time and ankle joint position sense. Plantarflexor performance: strength, fatigue, recovery and voluntary activation (level of neural drive) of the plantarflexor muscles, assessed through brief and sustained fatiguing (2 min) isometric maximal voluntary contractions with nerve stimulation to evoke superimposed and resting muscle twitches. RESULTS:PwMS had unimpaired movement detection and joint position sense but had a slower reaction time to respond with plantarflexion to an imposed ankle movement (between group difference = 0.11 [95% CI; 0.05 to 0.17] s). During brief, maximal contractions PwMS produced lower torque (difference = -25.1 [-42.0 to -8.2] Nm) with reduced voluntary activation (difference = -14.6 [-25.1 to -4.1]%) but no impairment of the muscle itself (resting twitch torque difference = 0.3 [-2.8 to 2.2] Nm). At the end of the fatiguing contraction, neural drive decreased for PwMS (-19.5 [-27.1 to -11.9]%, p <0.0001) but not for controls (-2.5 [-6.9 to 1.8]%, p = 0.242). Fatigue did not affect the resting twitch size for controls (-1.3 [-2.7 to -0.03] Nm, p = 0.134) or PwMS (-0.1 [-1.1 to 1.0] Nm, p = 0.90). CONCLUSIONS:PwMS showed no deficit in their ability to sense ankle position or imposed movements but were slow when a motor response was required. Their plantarflexor muscles produced similar torque with electrical stimulation but voluntary strength was impaired. Both groups experienced overall fatigue following the 2-minute maximal voluntary contraction but PwMS also had significantly reduced neural drive indicating central fatigue. PwMS showed mainly central deficits in motor output at the ankle with little impairment of proprioceptive acuity.

journal_name

Mult Scler Relat Disord

journal_title

Multiple sclerosis and related disorders

authors

Djajadikarta ZJ,Dongés SC,Brooks J,Kennedy DS,Gandevia SC,Taylor JL

doi

10.1016/j.msard.2020.102584

subject

Has Abstract

pub_date

2020-11-01 00:00:00

pages

102584

eissn

2211-0348

issn

2211-0356

pii

S2211-0348(20)30658-1

journal_volume

pub_type

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Impaired central drive to plantarflexors and minimal ankle proprioceptive deficit in people with multiple sclerosis.