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Repetitive transcranial magnetic stimulation over primary motor vs non-motor cortical targets; effects on experimental hyperalgesia in healthy subjects

Sacco, P and Prior, M and Poole, H and Nurmikko, T (2014) Repetitive transcranial magnetic stimulation over primary motor vs non-motor cortical targets; effects on experimental hyperalgesia in healthy subjects. BMC NEUROLOGY, 14 (166). ISSN 1471-2377

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Abstract

Background: High frequency repetitive transcranial magnetic stimulation (rTMS) targetted to different cortical
regions (primary motor/sensory, prefrontal) are known to alter somatosensory responses. The mechanism(s) for
these effects are unclear. We compared the analgesic effects of rTMS at different cortical sites on hyperalgesia
induced using topical capsaicin cream.
Methods: Fourteen healthy subjects had capsaicin cream applied to a 16 cm2 area of the medial aspect of the
right wrist (60 min) on 4 separate occasions over 6 weeks. rTMS (10Hz for 10s/min = 2000 stimuli @ 90% resting
motor threshold of first dorsal interosseus muscle) was applied to the optimum site for right hand (M1), left
dorsolateral prefrontal (DLFPC) and occipital midline (OCC) in a pseudo-randomised order. Thermal and mechanical
perception and pain thresholds were determined using standardised quantitative sensory testing (QST) methods
at the capsaicin site. Subjective responses to thermal stimuli (pain score on a numerical rating scale) from −2.5°C
to +2.5°C of the individualised heat pain threshold (HPT) resulted in a hyperalgesia curve. Sensory testing took
place prior to capsaicin application (PRE-CAP), after 30 min of capsaicin (POST-CAP) and following rTMS
(30 min = POST-TMS).
Results: Capsaicin application resulted in substantial changes in thermal (but not mechanical) sensitivity to
both heat and cold (eg. HPT PRE-CAP = 43.6°C to POST-CAP = 36.7°C (p < 0.001)) with no differences between
groups pre-rTMS. POST-TMS HPT showed no changes for any of the treatment groups, however the pain scores
for the hyperalgesia curve were significantly lower for M1 vs OCC (−24.7%, p < 0.001) and for M1 vs DLFPC
(−18.3%, p < 0.02).
Conclusion: rTMS over the primary motor cortex results in a significant analgesic effect compared to other
cortical areas.

Item Type: Article
Uncontrolled Keywords: 1109 Neurosciences, 1702 Cognitive Science
Subjects: B Philosophy. Psychology. Religion > BF Psychology
R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry
Divisions: Natural Sciences and Psychology
Publisher: BIOMED CENTRAL LTD
Related URLs:
Date Deposited: 15 Jun 2016 10:09
Last Modified: 15 Jun 2016 10:09
DOI or Identification number: 10.1186/s12883-014-0166-3
URI: http://researchonline.ljmu.ac.uk/id/eprint/3783

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