• Y Tamura, M Hoshiyama, K Inui, H Nakata, Y Qiu, Y Ugawa, K Inoue, and R Kakigi.
• Department of Integrative Physiology, National Institute for Physiological Sciences, Okazaki, Japan. ytamura@nips.ac.jp
• Neurology. 2004 Jun 22;62(12):2176-81.

BackgroundRepetitive transcranial magnetic stimulation (rTMS) of the motor cortex modulates acute and chronic pain perception. The authors previously showed that rTMS over the primary motor cortex (M1) inhibited capsaicin-induced acute pain ascending through C-fibers.ObjectiveTo investigate the effects of 1-Hz rTMS over M1 on acute experimentally induced pain mediated by Adelta-fibers (i.e., another type of acute pain).MethodsThe authors examined whether rTMS over M1 affected laser evoked potentials (LEPs) in 13 normal subjects using thulium: yttrium-aluminum-garnet laser stimulation. Subjective pain-rating scores and LEPs obtained under three different conditions--rTMS, realistic sham stimulation, and a control condition with no stimulation--were compared.ResultsThe authors found that 1-Hz rTMS over M1 significantly aggravated the subjective pain and enhanced the N2-P2 amplitudes compared with the sham or control sessions. Because the pain-rating scores and the N2-P2 amplitudes correlated positively, the N2-P2 amplitudes in the present study can be regarded as the cortical correlate of subjective pain.ConclusionsTogether with the authors' previous study on C-fiber pain, this facilitatory effect of repetitive transcranial magnetic stimulation on Adelta-fiber-mediated further strengthens the notion of a relationship between repetitive transcranial magnetic stimulation over M1 and pain perception.

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