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DOI: 10.1055/s-0031-1272726
Exploring the CNS effects of acupuncture needling with TMS
Background: Acupuncture has been suggested to exert its controversial therapeutic effects by modulation of the peripheral and central nervous system. However, the central nervous effects of acupuncture are still a matter of debate, since few direct neurophysiological measures using proper placebo conditions have been reported.
Aim: Modulations of CNS excitability can be determined with transcranial magnetic stimulation (TMS) using the motor cortex as a model region. The aim of the present study was to explore the short term effects of manual acupuncture needling on motor system excitability with TMS, while controlling for non-specific effects of needle insertion by using a single-blind, non-penetrating sham condition („Streitberger Needle“).
Methods: Motor system excitability, as represented by resting motor threshold (rMT), active motor threshold (aMT), cortical silent period (CSP), short intra-cortical inhibition (SICI) and intra-cortical facilitation (ICF), was assessed before and after needling in healthy volunteers from the abductor digiti minimi of both hands. Both verum acupuncture and sham acupuncture using „Streitberger needles“ with retractable tips were performed for 200 seconds at the „Yang Ling Quan“ (GB 34) near the right knee.
Results: Verum compared to sham acupuncture needling was found to decrease motor system excitability for rMT and CSP. Both verum and sham needling decreased motor system excitability contralateral to the needling side in accord with the crossing of afferent fibers in the spinal pathways. No significant effect of needling and no laterality differences post acupuncture was found for active motor threshold, short intra-cortical inhibition, or intra-cortical facilitation.
Conclusion: These results suggest a significant inhibitory effect of deep manual acupuncture on the excitability of the motor system on a spinal or supraspinal level. The mechanisms underlying this effect might be relevant for the proposed therapeutic effect of acupuncture and therefore pose a promising target for further investigations.