Reduction of intractable deafferentation pain by navigation-guided repetitive transcranial magnetic stimulation of the primary motor cortex

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Abstract
The precentral gyrus (M1) is a representative target for electrical stimulation therapy of pain. To date, few researchers have investigated whether pain relief is possible by stimulation of cortical areas other than M1. According to recent reports, repetitive transcranial magnetic stimulation (rTMS) can provide an effect similar to that of electrical stimulation. With this in mind, we therefore examined several cortical areas as stimulation targets using a navigation-guided rTMS and compared the effects of the different targets on pain. Twenty patients with intractable deafferentation pain received rTMS of M1, the postcentral gyrus (S1), premotor area (preM), and supplementary motor area (SMA). Each target was stimulated with ten trains of 10-s 5-Hz TMS pulses, with 50-s intervals in between trains. Intensities were adjusted to 90% of resting motor thresholds. Thus, a total of 500 stimuli were applied. Sham stimulations were undertaken at random. The effect of rTMS on pain was rated by patients using a visual analogue scale (VAS) and the short form of the McGill Pain Questionnaire (SF-MPQ). Ten of the 20 patients (50%) indicated that stimulation of M1, but not other areas, provided significant and beneficial pain relief (p<0.01). Results indicated a statistically significant effect lasting for 3 hours after the stimulation of M1 (p<0.05). Stimulation of other targets was not effective. The M1 was the sole target for treating intractable pain with rTMS, in spite of the fact that M1, S1, preM, and SMA are located adjacently.

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