The Effect of Vagus Nerve Stimulation on Pain Severity Scores in Patients With Chronic Musculoskeletal Pain Syndrome: A Meta-Analysis.

This meta-analysis aimed to systematically evaluate and synthesize existing evidence on the efficacy of transcutaneous vagus nerve stimulation (tVNS) in reducing pain severity, as measured by numerical pain scales, among adults with chronic musculoskeletal (MSK) pain. A comprehensive PubMed literature search was conducted through March 2025. Inclusion criteria comprised randomized controlled trials or clinical trials involving adults with chronic MSK pain (e.g., fibromyalgia, lupus, and osteoarthritis) that evaluated tVNS using pre- and post-treatment Visual Analog Scale (VAS) or Numeric Rating Scale (NRS) pain scores. Six eligible studies were included. Data extraction encompassed study design, participant demographics, intervention parameters, and VAS/NRS outcomes. Statistical analyses were performed using both common-effects and random-effects models (REM), with heterogeneity assessed using I² and Tau² statistics. The findings support tVNS as a promising adjunctive treatment for individuals with chronic MSK pain. Across included studies, the pooled effect size demonstrated a significant mean improvement in pain severity from pre-treatment to post-treatment of 2.32 points (95% CI, 1.90-2.73) using the common-effects model and 2.23 points (95% CI, 0.31-4.15) using the REM. However, these findings are limited by the small number of included studies, small sample sizes, substantial heterogeneity related to variability in intervention parameters, and short follow-up durations. Accordingly, the results should be interpreted with caution. While tVNS appears to be a promising adjunctive therapy for chronic MSK pain, larger, well-controlled randomized trials are needed to establish its independent efficacy, optimal stimulation parameters, and safety.