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Clinical Efficacy of Auricular Vagus Nerve Stimulation in the Treatment of Chronic and Acute Pain: A Systematic Review and Meta-analysis
Pain Ther
2024 Oct 9;13(6):1407–1427. doi: 10.1007/s40122-024-00657-8
Author
Irina T Duff , Rudolf Likar , Christophe Perruchoud , Stefan Kampusch , Markus Köstenberger , Sabine Sator , Caroline Stremnitzer , Andreas Wolf , Stefan Neuwersch-Sommeregger , Alaa Abd-Elsayed
Author Information
1Neurosurgery Department, Johns Hopkins University, Baltimore, MD USA
2Department for Anesthesia and Critical Care, Klinikum Klagenfurt am Wörthersee, Klagenfurt, Austria
3Sigmund Freud University, Vienna, Austria
4Clinique de la Douleur, Hopital de La Tour, Geneva, Switzerland
5AURIMOD GmbH, Vienna, Austria
6Medical University of Graz, Graz, Austria
7Department for Anesthesia, Critical Care and Pain Medicine, Medical University of Vienna, Vienna, Austria
8Department of Anesthesia, Krankenhaus St. Vinzenz, Zams, Austria
9Department for Anesthesiology and Intensive Care, Krankenhaus der Barmherzigen Brüder, St. Veit/Glan, Austria
10Department of Anesthesiology, University of Wisconsin, Madison, WI USA
✉Corresponding author.
Article notes
Received 2024 Jun 11; Accepted 2024 Aug 29; Issue date 2024 Dec.
Copyright and License information
© The Author(s) 2024
Open Access This article is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, which permits any non-commercial use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc/4.0/.
PMC Copyright notice
PMCID: PMC11543973 PMID: 39382792
Abstract
Introduction
Current guidelines for pain treatment recommend a personalized, multimodal and interdisciplinary approach as well as the use of a combination of drug and non-drug therapies. Risk factors for chronification should already be reduced in patients with acute pain, e.g., after surgery or trauma. Auricular vagus nerve stimulation (aVNS) could be an effective non-drug therapy in the multimodal treatment of chronic and acute pain. The aim of this systematic review and meta-analysis is to evaluate the clinical efficacy and safety of aVNS in treating chronic and acute pain conditions.
Methods
A systematic literature search was performed regarding the application of auricular electrical stimulation in chronic and acute pain. Studies were classified according to their level of evidence (Jadad scale), scientific validity and risk of bias (RoB 2 tool) and analyzed regarding indication, method, stimulation parameters, duration of treatment and efficacy and safety. A meta-analysis on (randomized) controlled trials (using different comparators) was performed for chronic and acute pain conditions, respectively, including subgroup analysis for percutaneous (pVNS—needle electrodes) and transcutaneous (tVNS—surface electrodes) aVNS. The visual analog pain scale (VAS) was defined as primary efficacy endpoint.
Results
A total of n = 1496 patients were treated with aVNS in 23 identified and analyzed studies in chronic pain, 12 studies in acute postoperative pain and 7 studies in experimental acute pain. Of these, seven studies for chronic pain and six studies for acute postoperative pain were included in the meta-analysis. In chronic pain conditions, including back pain, migraine and abdominal pain, a statistically significant reduction in VAS pain intensity for active compared to sham aVNS or control treatment with an effect size Hedges’ g/mean difference of − 1.95 (95% confidence interval [CI]: − 3.94 to 0.04, p = 0.008) could be shown and a more favorable effect in pVNS compared to tVNS (− 5.40 [− 8.94; − 1.85] vs. − 1.00 [− 1.55; − 0.44]; p = 0.015). In acute pain conditions, single studies showed significant improvements with aVNS, e.g., in kidney donor surgery or tonsillectomy but, overall, a non-statistically significant reduction in VAS pain intensity for active compared to sham aVNS or control with − 0.70 [− 2.34; 0.93] (p = 0.15) could be observed in the meta-analysis. In acute pain results vary greatly between studies depending especially on co-medication and timepoints of assessment after surgery. A significant reduction in analgesics or opiate intake was documented in most studies evaluating this effect in chronic and acute pain. In 3 of the 12 randomized controlled trials in patients with chronic pain, a sustainable pain reduction over a period of up to 12 months was shown. Overall, aVNS was very well tolerated.
Conclusion
This systematic review and meta-analysis indicate that aVNS can be an effective and safe non-drug treatment in patients with specific chronic and acute postoperative pain conditions. Further research is needed to identify the influence of simulation parameters and find optimal and standardized treatment protocols while considering quality-of-life outcome parameters and prolonged follow-up periods. A more standardized approach and harmonization in study designs would improve comparability and robustness of outcomes.
Supplementary Information
The online version contains supplementary material available at 10.1007/s40122-024-00657-8.
Keywords:
Neuromodulation, Auricular vagus nerve stimulation, Chronic pain, Acute pain, Postoperative pain