Fibromyalgia is a chronic condition characterized by widespread musculoskeletal pain, fatigue, sleep disturbances, and sensitivity to touch. Current treatments often provide only partial relief. This study evaluates a non-invasive technique called transcutaneous auricular vagus nerve stimulation (TaVNS), which delivers gentle electrical impulses to a part of the ear connected to the vagus nerve. The vagus nerve plays an important role in regulating pain, stress, and autonomic body functions such as sleep.

In this randomized controlled pilot trial, participants with fibromyalgia are assigned to receive either active TaVNS or sham (placebo) stimulation for 30 minutes per day, five days per week, over a four-week period. Participants are followed for a total of 8 weeks. The investigators will assess outcomes including pain intensity, sleep quality, central sensitization, and fear of movement (kinesiophobia).

Fibromyalgia (FM) is a chronic pain syndrome associated with widespread musculoskeletal pain, fatigue, sleep disturbances, and autonomic dysregulation. Current treatments provide only partial relief, highlighting the need for novel therapeutic approaches.

Rationale:

The vagus nerve is a key regulator of autonomic and inflammatory processes. Transcutaneous auricular vagus nerve stimulation (TaVNS) is a non-invasive technique that can modulate vagal activity through electrodes placed on the external ear, offering a potential alternative to surgically implanted vagus nerve stimulators.

Study Design:

This is a randomized, sham-controlled pilot trial conducted at Istanbul Medipol University. Thirty participants with fibromyalgia are randomized in a 1:1 ratio to receive either active TaVNS or sham stimulation.

Intervention:

Device: VagusStim® (Vagus Medical Technologies, Istanbul, Türkiye; CE-marked).

Electrode placement: left cymba concha (active group) vs. left earlobe (sham group).

Stimulation parameters: frequency 1-30 Hz, pulse width 50-250 μs, current intensity individually adjusted (0.1-36 mA) to each participant's sensory threshold.

Schedule: 30 minutes per day, 5 days per week, for 4 consecutive weeks (20 sessions total).

Supervision: All sessions are clinician-supervised.

Outcome Measures:

Primary outcomes:

Pittsburgh Sleep Quality Index (PSQI) - subjective sleep quality.

Fibromyalgia Impact Questionnaire (FIQ) - disease severity and functional impact.

Central Sensitization Inventory (CSI) - symptoms related to central sensitization.

Secondary outcomes:

Visual Analog Scale (VAS) - pain intensity.

Tampa Scale for Kinesiophobia (TSK) - fear of movement.

Symptom Severity Scale (SSS).

Widespread Pain Index (WPI).

Assessment timepoints: baseline, week 2, week 4, and week 8.

Inclusion Criteria:

Age between 18 and 65 years

Diagnosis of fibromyalgia according to the 2016 revised ACR criteria

Receiving stable pharmacological and/or non-pharmacological treatment for at least 3 months

Ability to understand study procedures and provide informed consent

Exclusion Criteria:

Pregnancy

History of epilepsy or cardiac arrhythmia

Acute or chronic infection

Heart failure (NYHA class II-IV)

Renal failure stage II or higher

Active malignancy

Psychotic disorders or current psychiatric treatment

Diagnosis of immune-mediated rheumatic disease

This study is a small, single-center pilot trial. Due to the limited sample size and ethical/privacy considerations, individual participant data will not be shared in a public repository. De-identified data may be made available from the corresponding author upon reasonable request.

Participants and outcome assessors were blinded to group allocation. The treating clinician who applied stimulation was aware of assignment but did not participate in outcome assessment