Non-invasive Auricular Vagus Nerve Stimulation in Fibromyalgia: Impacts on Autonomic Function, Central Sensitization and Pain Catastrophizing

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 ± 7.3 years; mean disease duration 68 ± 24 months) underwent twice-daily 30-minute tVNS sessions using the Nurosym™ device for 28 consecutive days. Outcome measures included: COMPASS-31 (autonomic symptoms), 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 = 0.019), particularly within the orthostatic (p = 0.018), vasomotor (p = 0.049), and pupillomotor (p = 0.024) subdomains. FIQR scores decreased from 69.12 ± 17.58 to 62.24 ± 19.19 (p = 0.006), indicating a moderate reduction in overall symptom burden. PDQ and CSI-9 scores also improved significantly (p = 0.008 and p = 0.038, 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.