Clinical efficacy of auricular vagus nerve stimulation in the treatment of chronic and acute pain A systematic review

Background: Current guidelines recommend a personalized, multimodal, and interdisciplinary approach for the treatment of chronic pain. Already in the acute treatment of postoperative pain, it can be useful to minimize risk factors for chronification. Auricular vagus nerve stimulation (aVNS) could be an effective non-drug therapy for the treatment of chronic and acute pain.Aim of the work: The aim of this systematic review is to evaluate the clinical efficacy of aVNS in chronic and acute pain as well as its effect on medication intake.Materials and methods: A systematic literature search was carried out on the application of auricular electrical stimulation in chronic and acute pain. Studies were classified according to their level of evidence and evaluated via the Jadad scale as well as their scientific validity, and then analyzed in terms of indication, method, stimulation parameters, duration of treatment, efficacy, and safety.Results: Twenty studies on chronic pain indications, ten studies on acute postoperative pain, as well as seven studies on experimental acute pain were identified and analyzed. The search revealed a total of n = 1105 aVNS-treated patients. The best evidence on the efficacy of aVNS is available for the indications chronic low back pain, chronic cervical syndrome, chronic abdominal pain, and chronic migraine as well as acute postoperative pain in oocyte aspiration, laparoscopic nephrectomy, and open colorectal surgery. Additionally a significant reduction in analgesic or opiate intake was evident in most studies. In three randomized controlled trials in chronic pain patients, a sustainable pain reduction over a period of up to 12 months was shown. Overall, aVNS was very well tolerated.Conclusion: This review indicates that aVNS can be a complementary and effective non-drug treatment for patients with chronic and acute postoperative pain. Future studies in these indications should focus on standardizing and optimizing treatment parameters, inclusion of quality-of-life outcome parameters, and longer follow-up periods to better understand the sustainable therapeutic effect of aVNS.