• Incidence of adverse events [ Time Frame: Measured at Week 16, which is the acute study exit ] [ Designated as safety issue: Yes ]
  

• FM 20 multidimensional response index (FM 20) [ Time Frame: Measured at Week 16, which is the acute study exit ] [ Designated as safety issue: No ]
  
• Assessment of pain intensity [ Time Frame: Measured at Week 16, which is the acute study exit ] [ Designated as safety issue: No ]
  
• Assessment of function [ Time Frame: Measured at Week 16, which is the acute study exit ] [ Designated as safety issue: No ]
  
• Assessment of patient global perception [ Time Frame: Measured at Week 16, which is the acute study exit ] [ Designated as safety issue: No ]
  

FMS affects about 5% of the general population and occurs most often in women between the ages of 20 and 50 years old. Overall, more than 80% of FMS patients report that pain is the primary symptom that limits their ability to work, about 30% of patients are disabled, and about 45% collect Social Security Disability insurance. Conventional treatments, which include pharmacological and behavioral interventions, fail to provide adequate pain relief in more than half of FMS patients, strongly suggesting the need for improved treatment options.

One such option is a treatment called vagus nerve stimulation (VNS), in which short bursts of electrical energy are directed into the brain by way of the vagus nerve. The vagus nerve is a cranial nerve that originates in the brainstem, travels through the neck, and then continues down through the thorax and abdomen. The nerve acts as both a sensory and motor nerve, and it can regulate several brain areas involved in pain and emotional processing. With VNS, a small battery device is surgically implanted under the skin, usually under the chest, and provides the necessary electrical energy for stimulation. Although VNS has been FDA approved for some forms of epilepsy and depression, it has yet to receive FDA approval for FMS. Also, it is unknown whether the safety and tolerability profile of an FMS patient receiving VNS is the same as that of a patient with epilepsy or depression who is receiving VNS. The purpose of this study is to determine the safety, tolerability, and effectiveness of VNS as a treatment option for adults with refractory FMS.

Participants will be in this study for about 25 months. An initial screening period that may last up to 6 weeks will include a medical history review, various examinations, and the use of a wrist-mounted device called an Actiwatch to record pain severity and mood over seven consecutive days. Eligible participants will then undergo surgical implantation of the VNS system. This will be followed by a 2-week recovery period, then a 2-week period of gradually increasing the electrical output of the VNS system, and finally a 12-week VNS treatment period during which the electrical output level will remain constant, unless a participant develops intolerable side effects. Study visits will occur weekly for the first month after implantation and then every 2 weeks during the treatment period. During most study visits, participants will undergo a clinical assessment, including evaluation of any side effects, and they will complete written assessments on pain, mood, fatigue, and quality of life and sleep. The VNS system will also be checked for safety and programmed appropriately. During the Week 16 visit, some of the screening evaluations will be repeated. Also at Week 16, which will mark the end of the treatment period, participants will have the option to continue receiving treatment. All participants will have follow-up evaluations at Months 6, 9, 12, and 24. Participants who wish to retain the VNS implantation beyond the length of the study will be referred to a qualified neurologist for follow-up care. For the other participants, the VNS system will be turned off and surgically explanted.