Analgesic efficacy of radial extracorporeal shockwave therapy in myofascial pain syndrome: a fNIRS study

ABSTRACT

Background: Cervical myofascial pain syndrome (CMPS) commonly causes neck pain. Radial extracorporeal shock wave therapy(rESWT) is regarded as a beneficial option for alleviating pain in different musculoskeletal disorders. Further studies are necessary to explore the neurophysiological basis and pain-relief efficacy of rESWT in CMPS. Objective: To investigate the pain-relief effects and the brain activation patterns of rESWT by integration of clinical assessments and functional near-infrared spectroscopy(fNIRS) technique.
Methods: This randomized controlled study recruited 32 CMPS patients. The participants were divided into rESWT group and sham group. The rESWT group received three sessions of rESWT administered over a two-week period. The sham group received placebo-rESWT treatment. Consecutive treatment sessions were kept a rest interval of 3 to 5 days. All participants were evaluated by Visual Analogue Scale (VAS), Pressure Pain Threshold (PPT) measurement, Neck Disability Index (NDI) and fNIRS assessment at baseline and finial session of the treatment.
Results: Compared with pre-treatment outcomes, both the rESWT and placebo groups showed better results in VAS, PPT, and NDI (P<0.05). The post-treatment comparative analysis showed that the rESWT group had significantly better improvements in VAS, PPT, and NDI scores compared with the placebo group, highlighting its superior pain-relieving effects. Interestingly, the rESWT group showed greater activation in bilateral frontal polar areas (FPA) compared with placebo group. Moreover, rESWT greatly increased the resting-state functional connectivity within the cortical pain processing network, specifically reinforcing the connectivity between the left pre-motor supplementary motor cortex (PM-SMC) and the left dorsolateral prefrontal cortex (DLPFC) post-treatment.
Conclusion: The findings demonstrated that rESWT is a beneficial therapeutic option for CMPS. The PM-SMC, FPA, and DLPFC are critical in mediating therapeutic effects of rESWT by neural mechanisms.