This study evaluates the efficacy and safety of ultrasound-guided stellate ganglion block (SGB) as an adjunctive treatment for patients with treatment-resistant fibromyalgia. Patients who continue to experience significant symptoms despite stable duloxetine therapy (60 mg/day) were randomized to receive either ultrasound-guided SGB or a sham control procedure. The study aims to determine if SGB can provide clinically meaningful improvements in fibromyalgia impact and pain intensity compared to a sham injection.

This is a single-center, randomized, single-blind, sham-controlled trial conducted at Sanliurfa Education and Research Hospital.

Participants: Adults aged 18-65 years diagnosed with fibromyalgia (2016 ACR criteria) who have been receiving a stable dose of duloxetine 60 mg/day for at least 4 weeks but remain symptomatic.

Procedures: Participants were randomized 1:1 to either the SGB group or the sham control group.

SGB Group: Received ultrasound-guided stellate ganglion block at the C7 level using a mixture of 8 mg dexamethasone and 2 mL of 2% lidocaine (diluted to 7 mL with saline).

Sham Group: Received an intramuscular injection of 2 mL normal saline into the sternocleidomastoid muscle under ultrasound guidance.

Both groups received two procedures, performed one week apart. All patients continued their fixed-dose duloxetine throughout the study.

Assessments: The primary outcome is the change in the FIQR total score from baseline to 1 week. Secondary outcomes include FIQR changes at 1 month, pain intensity (NRS), and responder rates. This is a single-blind study where only the participants were blinded to the intervention.

Inclusion Criteria:

• Diagnosis of Fibromyalgia Syndrome (FMS) according to the 2016 American College of Rheumatology criteria.
• Followed for at least 1 year with insufficient benefit from previous pharmacological and/or non-pharmacological treatments.
• Receiving a stable dose of duloxetine 60 mg once daily for at least 4 weeks prior to inclusion.
• Willingness to continue the fixed dose of duloxetine throughout the study.
• Aged between 18 and 65 years.

Exclusion Criteria:

• Non-pharmacological treatments within the previous 6 months (e.g., acupuncture, ozone therapy, cognitive behavioral therapy).
• Local infection at the injection site.
• Pregnancy or suspected pregnancy.
• Known allergy to local anesthetics.
• History of malignancy.
• Bleeding or coagulation disorders or use of oral anticoagulants.
• Uncontrolled hypertension, diabetes mellitus, asthma, chronic obstructive pulmonary disease, or heart failure.
• Psychiatric or cognitive disorders that could interfere with treatment compliance (e.g., severe psychiatric illness, dementia).
• Refusal of interventional treatment.

Individual participant data will not be publicly shared to protect participant privacy. De-identified data may be made available from the corresponding author upon reasonable request and with appropriate institutional approvals.

"Single-blind. Participants were blinded to treatment assignment. The investigator performing the procedures and the outcome assessors were aware of the group allocation."