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

Objective: 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.

Data sources: A literature search across the Physiotherapy Evidence Database, Web of Science, PubMed, Cochrane Library, and Scopus databases until October 2024 was conducted.

Study selection: 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 extraction: 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.

Data synthesis: 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).

Conclusions: 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.