Vagus Nerve Stimulation in Fibromyalgia

In the current study, the investigators will investigate the effects of transcutaneous cervical vagus stimulation (t-VNS) on 90 Female patients above 18 years, with a clinical diagnosis of fibromyalgia according to 2016 American College of Rheumatology (ACR) fibromyalgia diagnostic criteria.

The ninety patients will be divided into 3 groups:

Group A: will receive cervical transcutaneous vagus nerve stimulation that will be carried out with a transcutaneous electrical nerve stimulation (TENS) device, using a small self-adhesive surface electrodes (1 cm diameter). The electrodes will be positioned on the surface of the neck that corresponds to the position of the left cervical branch of the vagus nerve, using a biphasic, asymmetrical waveform with a pulse duration that is less than 250 microseconds and a frequency of 20 hertz. Intensity is adjusted according to the sensory threshold level of each patient, each session lasts for 30 minutes. All patients will receive 3 sessions per week for a total of 12 sessions, The sessions will be carried on at Department of Rheumatology and Rehabilitation, Cairo University Hospital.

Group B will receive cervical t-VNS in the same protocol like group A, in addition to medical treatment in the form of: Gabapentin 300 mg capsule once at night, and Duloxetine 30 mg cap once daily for 30 days.

Group C will receive medical treatment in the form of: Gabapentin 300 mg capsule once at night, and Duloxetine 30 mg cap once daily for 30 days.

All the patients in the 3 groups will be advised to stop any medication one week before intervention, and to report if any kind of medications is taken during the study period. They will be assessed before starting intervention (at baseline), just after completion of intervention (at one month), and one month after stoppage of intervention (at 2 months).

Inclusion criteria

• Female patients above 18 years, with a clinical diagnosis of fibromyalgia according to 2016 ACR fibromyalgia diagnostic criteria, will be included in this study.

Exclusion criteria

• - Pregnant, and postmenopausal women.
• Patients with any medical disorder including: cardiovascular, pulmonary, renal, hepatic, endocrine, blood, gastrointestinal, diabetes, neuropathic disorders, psychiatric disorders (for example; post traumatic stress disorder (PTSD), mania, psychosis, suicidality, bipolar/schizophrenia/autism spectrum disorders) and/or neurodegenerative disorders (e.g., Parkinson's, Alzheimer's, Huntington's disease).
• Cancer diagnosis within the preceding 5 years.
• Planned surgery.
• Use of other medical devices electrically active for example a cardiac pacemaker, or TENS for chronic pain.
• Electrocardiogram (ECG) abnormalities.
• History of Electroconvulsive therapy (ECT).
• Symptomatic orthostatic hypotension, or history of recurrent vagal syncope.
• History of vagotomy.
• Uncontrolled hypertension or hypotension.
• Documented sleep apnea.
• Other rheumatic diseases like (Rheumatoid Arthritis, Systemic lupus erythematosus, Seronegative spondyloarthropathies).