Non-invasive auricular vagus nerve stimulation in fibromyalgia: Impacts on autonomic function, central sensitization and pain catastrophizing

Abstract

Introduction: Fibromyalgia is a complex chronic pain disorder frequently associated with autonomic dysregulation, central sensitization, and cognitive-emotional disturbances. Transcutaneous vagus nerve stimulation (tVNS) has recently emerged as a non-invasive neuromodulatory approach with potential to modulate autonomic function, pain perception, and affective processing. We aim to evaluate the short-term effects of a 28-day tVNS protocol on autonomic function, symptom severity, central sensitization, neuropathic-like pain features, and pain catastrophizing in patients with fibromyalgia.

Methods: Twenty-five female patients with fibromyalgia (mean age 48.6±7.3years; mean disease duration 68±24 months) underwent twice-daily 30-minute tVNS sessions using the Nurosym™ device for 28 consecutive days. Outcome measures included: Composite Autonimic Symptom Score 31 (COMPASS-31), Revised Fibromyalgia Impact Questionnaire (FIQR), PainDETECT Questionnaire (PDQ), Central Sensitization Inventory (CSI-9), and Pain Catastrophizing Scale (PCS). Pre- and post-treatment scores were compared using paired statistical analyses.

Results: Significant improvements were observed in total COMPASS-31 scores (P<0.05), particularly within the orthostatic (P<0.05), vasomotor (P<0.05), and pupillomotor (P<0.05) subdomains. FIQR scores decreased from 69.12±17.58 to 62.24±19.19 (P<0.01), indicating a moderate reduction in overall symptom burden. PDQ and CSI-9 scores also improved significantly (P<0.01 and P<0.05, respectively), suggesting a reduction in neuropathic-like symptoms and central sensitization. Although PCS scores showed a downward trend, the change was not statistically significant (P=0.070).

Conclusions: This pilot study suggests that tVNS may be a safe, well-tolerated, and effective intervention for modulating autonomic and central mechanisms in fibromyalgia. The results support further controlled trials to define optimal protocols and assess long-term outcomes.

Keywords: Autonomic dysfunction; Central sensitization; Fibromyalgia; Neuromodulation; Neuropathic pain; Non-pharmacological therapies; Pain catastrophizing; Vagus nerve stimulation.