F138. The effect of velum and sham acupuncture on corticomotor excitability in healthy adults

Introduction Acupuncture is a therapeutic technique that is being used as an adjuvant to treatment in a variety of health-related disorders. However despite its increasing use in western countries, the underlying mechanisms are not fully understood. The aim of this study is to investigate the underlying neurophysiological mechanisms of acupuncture by examining the effect of real (verum) and sham acupuncture to the hand on the excitability of the motor cortex (M1) in healthy adults. A better understanding of the underlying mechanisms of acupuncture may improve the potential therapeutic application of acupuncture for neurological disorders in the future. Methods Healthy, right-handed, adults with no neurological or musckuloskeletal conditions participated in the study. Participants were randomised to receive verum or sham acupuncture to the Hegu acupoint of the hand on separate days, with a minimum 5 day washout. The intervention type was double-blinded, and the acupuncturist was not involved in data collection or analysis. Transcranial magnetic stimulation (TMS) was delivered to the left M1 and surface electromyography was used to record TMS-induced responses from the First Dorsal Interossues (FDI) and Adductor Digiti Minimi (ADM). Stimulus-response curves, short-intracortical inbhition (SICI-2 ms) and intracortical facilitaiton (ICF-15 ms) were measured before, during, immediately after needle removal, and 30 min after needle removal. Needling sensation questionnaires were administered after each session, and self-rated anxiety was assessed before, during and after needle removal. Results Relative to sham, verum acupuncture did not modulate corticomotor or intracortical excitability in either muscle across time (all P > 0.05). There were no differences in the severity of needling sensations between sessions (all P > 0.05), therefore sham park needle acupuncture was likely an adequate sham control. Conclusion There was little-to-no evidence that acupuncture to the Hegu acupoint of the hand modulated corticomotor or intracortical excitability to a hand muscle adjacent (FDI) and distant (ADM) to the acupoint. Previous research has reported neural changes after acupuncture using TMS, however these studies were of low-quality. The present study builds upon the previous literature by using an effective sham control, double-blinding, and records responses from the same limb being stimulated. The study findings suggest the putative effects of acupuncture are unlikely to be mediated by changes in motor cortex excitability.