Efficacy of vagus nerve stimulation in gastrointestinal disorders: a systematic review.

Dysfunction of the vagus nerve has been suggested as a contributing factor in various gastrointestinal disorders, prompting interest in vagus nerve stimulation (VNS) as a non-pharmacological therapy. We performed a systematic review to determine the efficacy of invasive and non-invasive VNS in gastrointestinal disorders, including inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), functional dyspepsia (FD), functional constipation, gastroesophageal reflux disease, and gastroparesis. We applied a systematic search of the literature in the PubMed, Embase, Web of Science, and Cochrane Library databases in order to identify studies comparing VNS with an adequate control condition (sham stimulation) in patients with gastrointestinal disorders. The primary outcome was adequate symptom relief. Methodological quality was evaluated using the revised Cochrane risk-of-bias tool. Meta-analyses were not performed due to study heterogeneity. Seven randomized controlled trials investigating non-invasive VNS were included, with a total of 644 patients: FD (=426), IBD (=22), IBS (=92), and abdominal pain-related functional gastrointestinal disorder (=104), with a mean age ranging from 15 to 65 years. Non-invasive VNS significantly improved symptoms across all subsets of patients, as measured differently according to disease type, compared with sham stimulation. Adverse events, if reported, were low, with no serious complications. Putative mechanisms of action were assumed to be related to anti-inflammatory and anti-nociceptive effects. Non-invasive VNS holds promise as a safe therapy for diverse gastrointestinal disorders. However, these findings are derived from studies with small sample sizes and provide preliminary insights. Further research is warranted to define its exact position within the therapeutic arsenal.