title: Safety and efficacy of vagus nerve stimulation in fibromyalgia: a phase I/II proof of concept trial.
abstract: OBJECTIVE
  We performed an open-label Phase I/II trial to evaluate the safety and tolerability of vagus nerve stimulation (VNS) in patients with treatment-resistant fibromyalgia (FM) as well as to determine preliminary measures of efficacy in these patients.
  
  
  METHODS
  Of 14 patients implanted with the VNS stimulator, 12 patients completed the initial 3-month study of VNS; 11 patients returned for follow-up visits 5, 8, and 11 months after start of stimulation. Therapeutic efficacy was assessed with a composite measure requiring improvement in pain, overall wellness, and physical function. Loss of both pain and tenderness criteria for the diagnosis of FM was added as a secondary outcome measure because of results found at the end of 3 months of stimulation.
  
  
  RESULTS
  Side effects were similar to those reported in patients treated with VNS for epilepsy or depression and, in addition, dry mouth and fatigue were reported. Two patients did not tolerate stimulation. At 3 months, five patients had attained efficacy criteria; of these, two patients no longer met widespread pain or tenderness criteria for the diagnosis of FM. The therapeutic effect seemed to increase over time in that additional participants attained both criteria at 11 months.
  
  
  CONCLUSIONS
  Side effects and tolerability were similar to those found in disorders currently treated with VNS. Preliminary outcome measures suggested that VNS may be a useful adjunct treatment for FM patients resistant to conventional therapeutic management, but further research is required to better understand its actual role in the treatment of FM.
authors.affiliation: Department of Radiology, UMDNJ-New Jersey Medical School, Newark, New Jersey, USA.
authors.forename: Gudrun
authors.initials: G
authors.lastname: Lange
authors.forename: Malvin N
authors.initials: MN
authors.lastname: Janal
authors.forename: Allen
authors.initials: A
authors.lastname: Maniker
authors.forename: Jennifer
authors.initials: J
authors.lastname: Fitzgibbons
authors.forename: Malusha
authors.initials: M
authors.lastname: Fobler
authors.forename: Dane
authors.initials: D
authors.lastname: Cook
authors.forename: Benjamin H
authors.initials: BH
authors.lastname: Natelson
mesh_terms: D000328:Adult; D000698:Analgesia / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D005260:Female; D005356:Fibromyalgia / Q000503:physiopathology / Q000628:therapy*; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D010865:Pilot Projects; D011183:Postoperative Complications / Q000453:epidemiology / Q000503:physiopathology; D055536:Vagus Nerve Stimulation / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*