Neurophysiological Effects of Dry Needling: A Systematic Review and Meta-analysis.

Abstract

To evaluate the neurophysiological effects associated with dry needling. This review evaluates the influence of dry needling on pain-related biomarkers, conditioned pain modulation, and temporal summation to clarify the potential mechanisms underlying its therapeutic effects. A literature search across the Physiotherapy Evidence Database, Web of Science, PubMed, Cochrane Library, and Scopus databases until October 2024 was conducted. Studies were included if they assessed the neurophysiological effects of dry needling in animal or human models. Fourteen results were included in the qualitative synthesis (n=4 in animals, n=10 in humans) and 4 in the quantitative analysis. Selection was performed independently by 2 reviewers. Data were extracted independently by 2 reviewers using a standardized form. Neurophysiological outcomes included levels of biomarkers (eg, substance P [SP], cortisol, interleukins, calcitonin gene-related peptide , serotonin, and tumor necrosis factor-α) as well as measures of conditioned pain modulation and temporal summation. The methodological quality was assessed using the Physiotherapy Evidence Database, Cochrane Risk of Bias-2, and Risk of Bias in Nonrandomized Studies of Interventions scales. Dry needling showed increases in microRNA-939, microRNA-25, β-endorphin, interleukin-2 (IL-2), tumor necrosis factor-α, inducible isoform of nitric oxide synthases, hypoxia-inducible factor-1α, cyclooxygenase-2, vascular endothelial growth factor, inflammatory cells, IL-6, and acetylcholinesterase, whereas decreases were observed in Myozenin 2, SP, calcitonin gene-related peptide, acetylcholine, and acetylcholine receptor. The effects on neurophysiological variables related to pain processing are limited, leading to small improvements in conditioned pain modulation (standardized mean differences, 0.36; 95% CI, 0.05-0.67) and no apparent changes in temporal summation (standardized mean difference, -0.08; 95% CI, -0.44 to 0.27). The application of dry needling can induce significant changes in pain-related biomarker levels in animal and human studies, providing insights into its underlying mechanisms of action and potential clinical effects.