Unilateral and Bilateral taVNS in Fibromyalgia

Overview

This randomized controlled trial aimed to compare the effects of unilateral (left-sided) and bilateral transcutaneous auricular vagus nerve stimulation (taVNS) combined with a home exercise program on clinical outcomes, autonomic nervous system function, and exercise performance in individuals with fibromyalgia syndrome (FMS). Participants diagnosed with fibromyalgia were randomly assigned to one of three groups: unilateral taVNS, bilateral taVNS, or a home exercise program. The intervention period lasted two weeks and included ten treatment sessions. Clinical outcomes were assessed using validated scales including the Fibromyalgia Impact Questionnaire (FIQ), Beck Anxiety Inventory (BAI), Beck Depression Inventory (BDI), and Pittsburgh Sleep Quality Index (PSQI). Autonomic function was evaluated using heart rate variability (HRV) parameters, and exercise performance was assessed based on repetition capacity. The study aimed to determine whether bilateral stimulation provides additional benefits compared to unilateral stimulation and exercise alone. The findings may contribute to understanding the role of neuromodulation strategies in improving autonomic regulation, symptom severity, and functional performance in individuals with fibromyalgia.

Fibromyalgia syndrome (FMS) is a chronic condition characterized by widespread pain, fatigue, sleep disturbances, and psychological symptoms, often associated with autonomic nervous system dysfunction. Reduced heart rate variability (HRV) and increased sympathetic activity are commonly observed in individuals with FMS, contributing to impaired exercise tolerance and reduced quality of life. Transcutaneous auricular vagus nerve stimulation (taVNS) is a non-invasive neuromodulation technique that targets the auricular branch of the vagus nerve and has been shown to influence autonomic regulation and central pain processing. However, evidence regarding its effects on exercise performance and the comparative efficacy of unilateral versus bilateral stimulation remains limited. This study was designed as a randomized controlled trial including individuals diagnosed with fibromyalgia. Participants were allocated into three groups: unilateral taVNS, bilateral taVNS, and a home exercise program. The interventions were applied over a two-week period consisting of ten sessions. The taVNS intervention was administered via auricular stimulation targeting vagal afferents, while the exercise group followed a structured home-based program. Outcome measures included clinical symptom scales (FIQ, BAI, BDI, PSQI), autonomic nervous system parameters derived from HRV analysis (including RMSSD, pNN50, LF, HF, and LF/HF ratio), and exercise performance assessed through repetition capacity. Assessments were conducted before and after the intervention period. The primary objective was to compare the effects of unilateral and bilateral taVNS on autonomic function and exercise performance, and to evaluate whether combining neuromodulation with exercise provides additional clinical benefits in individuals with fibromyalgia. The results of this study may help inform rehabilitation strategies integrating neuromodulation and exercise-based interventions.