title: Stimulation of the greater occipital nerve: anatomical considerations and clinical implications.
abstract: BACKGROUND
  Stimulation of the greater occipital nerve has been employed for various intractable headache conditions for more than a decade. Still, prospective studies that correlate stimulation of the greater occipital nerve with outcome of patients with respect to alleviation of headache are sparsely found in literature.
  
  
  OBJECTIVE
  To identify anatomical landmarks for a reproducible stimulation of the greater occipital nerve. For the clinical implication, the individual response to therapy of patients with refractory chronic cluster headache undergoing occipital nerve stimulation was correlated with the postoperative localization of the electrodes and with the distribution of the stimulation field.
  
  
  METHODS
  Prospective observational study, approved by the local research ethics board (09-4143).
  
  
  METHODS
  University hospital, departments of neurosurgery and neurology, institute of anatomy and radiology.
  
  
  METHODS
  Ten formaldehyde fixed human cadavers were dissected to identify the passage of the greater occipital nerve through the trapezius muscle. The distance to the external occipital protuberance was triangulated measuring the distance of the nerve from the nuchal midline and the protuberance. Between December 2008 and December 2011, 21 consecutive patients suffering from chronic cluster headache underwent surgery in terms of bilateral occipital nerve stimulation, with electrodes placed horizontally at the level of C1. The postoperative x-rays were compared with the acquired landmarks from the anatomical study. The distribution of the stimulation field was correlated to the individual response of each patient to the therapy and prospectively analyzed with regard to reduction of daily cluster attacks and relief of pain intensity at 3 months and at last follow-up.
  
  
  RESULTS
  The greater occipital nerve crosses the trapezius muscle at a mean distance of 31 mm below the occipital external protuberance and 14 mm lateral to the midline as found in the anatomical subjects. The electrodes were targeted at this level in all of our patients and stimulated the greater occipital nerve in all patients. Eighteen of the patients (85.7%) reported a significant reduction of the frequency of their cluster attacks and/or declined intensity of pain during the attacks. Yet, 3 of 21 patients (14.3%) did not benefit from the stimulation despite an adequate spread of the stimulation over the occiput. The spread of the stimulation-induced paraesthesias over the occiput was not correlated to a reduction of cluster attacks, to the intensity of attacks, or to the response to treatment at all.
  
  
  CONCLUSIONS
  Single center non-randomized non-blinded study.
  
  
  CONCLUSIONS
  From our study we conclude that a reproducible stimulation of the greater occipital nerve can be achieved by placing the electrodes parallel to the atlas, at about 30 mm distance to the external occipital protuberance. The response to the stimulation is not correlated to the field width of the paraesthesia. We, therefore, consider stimulation of the main trunk of the greater occipital nerve to be more important than a large field of stimulation on the occiput. Still, an individual response to the occipital nerve stimulation cannot be predicted even by optimal electrode placement.
authors.affiliation: University Hospital Essen, Essen, Germany. oliver.mueller@uk-essen.de
authors.forename: Oliver
authors.initials: O
authors.lastname: Mueller
authors.forename: Vincent
authors.initials: V
authors.lastname: Hagel
authors.forename: Karsten
authors.initials: K
authors.lastname: Wrede
authors.forename: Marc
authors.initials: M
authors.lastname: Schlamann
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Hohn
authors.forename: Ulrich
authors.initials: U
authors.lastname: Sure
authors.forename: Charly
authors.initials: C
authors.lastname: Gaul
mesh_terms: D001703:Biophysics; D002102:Cadaver; D003027:Cluster Headache / Q000628:therapy*; D004599:Electric Stimulation Therapy / Q000379:methods*; D004566:Electrodes; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D019370:Observation; D009777:Occipital Bone / Q000033:anatomy & histology*; D010147:Pain Measurement; D011446:Prospective Studies; D012189:Retrospective Studies; D013127:Spinal Nerves / Q000033:anatomy & histology / Q000502:physiology*; D013997:Time Factors