Potential of Vagus Nerve Stimulation to Modulate Fibromyalgia's Network Physiology: A Systematic Review.

Background

Chronic pain conditions such as fibromyalgia syndrome (FMS) reflect maladaptive network physiology across perceptual-autonomic-immune axes, yet most treatments remain symptomatic and incompletely effective.

Methods

We conducted a comprehensive systematic review to evaluate vagus nerve stimulation (VNS) and FMS within a network physiology framework. PubMed, Embase, and Cochrane CENTRAL were searched on October 24, 2025. Risk of bias was assessed using the ROB-2 tool. An iterative thematic synthesis was performed to develop an integrative conceptual framework and to identify knowledge gaps and future research directions.

Results

We first summarize physiological evidence showing autonomic imbalance (e.g., decreased heart rate variability), neuroinflammatory activation, and aberrant cortical network connectivity in FMS, supporting a network-dysregulation model. We then included 6 studies (4 clinical studies and 2 protocols) on VNS effects, highlighting improvements in pain, fatigue, sleep disturbance and autonomic regulation, along with emerging mechanistic insights. Key methodological heterogeneity-such as stimulation parameters, outcome metrics, type of control arm, sham definition, and small samples-limits current interpretability. Finally, we outline a research agenda centered on network-based biomarkers, immunophenotyping, adaptive trial designs and stratification of responders, with the aim of validating taVNS as a scalable neuromodulatory intervention for FMS.

Conclusions

By reframing FMS from a symptom-centric pharmacologic model to a network-centric neuromodulation approach, taVNS is a promising tool for mechanism-based therapeutics in central sensitization syndromes and chronic pain.