Abstract
Excitability of the motor cortex can be suppressed during muscle pain. Yet the mechanisms
are largely unknown. Short interval intracortical inhibition (SICI) and intracortical
facilitation (ICF) were examined as possible candidate mechanisms to underpin this
change. SICI and ICF were investigated in 11 healthy individuals before, during and
after infusion of hypertonic saline into right first dorsal interosseous (FDI). Using
paired-pulse transcranial magnetic stimulation (TMS), interstimulus intervals of 2,
3, and 13 ms were investigated. Pain intensity and quality were recorded using a 10-cm
visual analogue scale and the McGill Pain Questionnaire. Resting motor threshold and
motor-evoked potentials (MEPs) to single TMS stimuli were recorded before and after
pain. Electromyographic recordings were made from right FDI and abductor digiti minimi.
Participants reported an average pain intensity of 5.8 (1.6) cm. MEP amplitudes decreased
in both muscles. Compared with the pre-pain condition, SICI was increased following
pain, but not during. ICF was decreased both during and after pain when compared with
the pre-pain condition. These findings suggest that muscle pain differentially modulates
SICI and ICF. Although the functional relevance is unknown, we hypothesize decreased
facilitation and increased inhibition may contribute to the restriction of movement
of a painful body part.
Perspective
This article provides evidence for decreased intracortical facilitation and increased
short interval intracortical inhibition in response to muscle pain. This finding is
relevant to clinicians as a mechanism which may underlie restricted movement in acute
and chronic pain.
Key words
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Article info
Publication history
Published online: January 09, 2012
Accepted:
October 28,
2011
Received in revised form:
October 23,
2011
Received:
May 4,
2011
Footnotes
Supported by a Clinical Research Fellowship (S.M.S.) and by a Senior Principal Research Fellowship (P.W.H.), both from the National Health and Medical Research Council of Australia.
There are no conflicts of interest associated with this work.
Identification
Copyright
© 2012 Published by Elsevier Inc. All rights reserved.
