Effects of 10 Hz Repetitive Transcranial Magnetic Stimulationin Acute Human Muscle Pain Model

ABSTRACT

OBJECTIVE: To investigate the analgesic effect of high frequency repetitive transcranial magnetic stimulation (rTMS) on the experimental human muscle pain and its underlying mechanism. METHOD: Twenty healthy Korean volunteers participated in this study. The acute muscle pain was induced by infusion of hypertonic saline (5%) into the left extensor carpi radialis longus (ECRL) muscle. During the hypertonic saline injection, 10 Hz rTMS were applied on the hot spot of left ECRL. The changes of visual analogue scale (VAS) of muscle pain and motor evoked potential (MEP) were measured from the start of saline injection to 70 minutes after the start of stimulation. At 90 minutes after the first stimulation, the subjects completed the Korean version of the McGill Pain Questionnaire (MPQ). The sham stimulation was applied with the same method as rTMS experiment. RESULTS: In rTMS, the VAS of muscle pain was significantly decreased from 2.5 minutes and continued until 3 minutes after the last rTMS. While the amplitude of MEP was significantly increased, the latency of MEP was significantly decreased after the start of rTMS and the effect on MEP continued until 5 minutes after the last rTMS. The quality of pain experiment by rTMS and sham stimulation showed no difference in MPQ. CONCLUSION: The present results suggested that 10 Hz rTMS over primary motor cortex decreased the perception of muscle pain and increased the excitability of corticospinal pathway.