title: Occipital nerve stimulation for chronic migraine--a systematic review and meta-analysis.
abstract: BACKGROUND
  Chronic migraine is a debilitating headache disorder that has significant impact on quality of life. Stimulation of peripheral nerves is increasingly being used to treat chronic refractory pain including headache disorders. This systematic review examines the effectiveness and adverse effects of occipital nerve stimulation (ONS) for chronic migraine.
  
  
  METHODS
  Databases, including the Cochrane Library, MEDLINE, EMBASE, CINAHL and clinical trial registers were searched to September 2014. Randomized controlled trials (RCTs), other controlled and uncontrolled observational studies and case series (n≥ 10) were eligible. RCTs were assessed using the Cochrane risk of bias tool. Meta-analysis was carried out using a random-effects model. Findings are presented in summary tables and forest plots.
  
  
  RESULTS
  Five RCTs (total n=402) and seven case series (total n=115) met the inclusion criteria. Pooled results from three multicenter RCTs show that ONS was associated with a mean reduction of 2.59 days (95% CI 0.91 to 4.27, I2=0%) of prolonged, moderate to severe headache per month at 3 months compared with a sham control. Results for other outcomes generally favour ONS over sham controls but quantitative analysis was hampered by incomplete publication and reporting of trial data. Lead migration and infections are common and often require revision surgery. Open-label follow-up of RCTs and case series suggest long-term effectiveness can be maintained in some patients but evidence is limited.
  
  
  CONCLUSIONS
  While the effectiveness of ONS compared to sham control has been shown in multiple RCTs, the average effect size is modest and may be exaggerated by bias as achieving effective blinding remains a methodological challenge. Further measures to reduce the risk of adverse events and revision surgery are needed.
  
  
  BACKGROUND
  this systematic review is an update and expanded work of part of a broader review registered with PROSPERO. Registration No. CRD42012002633.
authors: School of Health and Population Sciences, University of Birmingham, Birmingham, United Kingdom; Division of Health Sciences, University of Warwick, Coventry, United Kingdom.
authors: Yen-Fu
authors: YF
authors: Chen
authors: School of Health and Population Sciences, University of Birmingham, Birmingham, United Kingdom.
authors: George
authors: G
authors: Bramley
authors: School of Health and Population Sciences, University of Birmingham, Birmingham, United Kingdom; School of Psychology, University of Birmingham, Birmingham, United Kingdom.
authors: Gemma
authors: G
authors: Unwin
authors: University Hospitals Birmingham NHS Foundation Trust, Birmingham, United Kingdom.
authors: Dalvina
authors: D
authors: Hanu-Cernat
authors: School of Health and Population Sciences, University of Birmingham, Birmingham, United Kingdom.
authors: Janine
authors: J
authors: Dretzke
authors: School of Health and Population Sciences, University of Birmingham, Birmingham, United Kingdom.
authors: David
authors: D
authors: Moore
authors: School of Health and Population Sciences, University of Birmingham, Birmingham, United Kingdom.
authors: Sue
authors: S
authors: Bayliss
authors: School of Health and Population Sciences, University of Birmingham, Birmingham, United Kingdom.
authors: Carole
authors: C
authors: Cummins
authors: School of Health and Population Sciences, University of Birmingham, Birmingham, United Kingdom; Division of Health Sciences, University of Warwick, Coventry, United Kingdom.
authors: Richard
authors: R
authors: Lilford
mesh_terms: D002908:Chronic Disease; D004599:Electric Stimulation Therapy / Q000009:adverse effects; D006801:Humans; D008881:Migraine Disorders / Q000628:therapy*; D009778:Occipital Lobe / Q000503:physiopathology*; D017594:Publication Bias; D016032:Randomized Controlled Trials as Topic; D012307:Risk Factors; D016896:Treatment Outcome