title: Image-guided placement of eye muscle electrodes for intraoperative cranial nerve monitoring.
abstract: OBJECTIVE
  Monitoring of the oculomotor system during cranial base or brainstem surgery requires extraocular intraorbital insertion of electromyography electrodes. We investigated the use of image-guidance technology for anatomically correct intraorbital electrode placement.
  
  
  METHODS
  For neuronavigation, an optical tracking system was used in a standard fashion. Needle electrodes were inserted percutaneously into the lateral rectus, inferior rectus, and superior oblique muscle along the axis of a hand-held pointer or by means of an electrode applicator to allow direct tracking with the navigation system. Electromyographic monitoring was performed by multichannel recordings of free running or evoked activity from the selected muscles.
  
  
  RESULTS
  We have used this method in 10 patients; 5 had cranial base tumors and 5 underwent operations for brainstem lesions. No additional instruments or resources were required compared with the routine setup, and no intraorbital structures were injured. Successful monitoring of oculomotor, trochlear, or abducent nerve function was possible in each case.
  
  
  CONCLUSIONS
  This method may have the potential to increase the safety and success rate of intraoperative electro-ophthalmography during microsurgery focused on preservation of neurological function.
authors.affiliation: Department of Neurosurgery, Phillipps-University Marburg, Germany. albertio@mailer.uni-marburg.de
authors.forename: O
authors.initials: O
authors.lastname: Alberti
authors.forename: U
authors.initials: U
authors.lastname: Sure
authors.forename: T
authors.initials: T
authors.lastname: Riegel
authors.forename: H
authors.initials: H
authors.lastname: Bertalanffy
mesh_terms: D000010:Abducens Nerve / Q000502:physiology; D003391:Cranial Nerves / Q000502:physiology*; D004567:Electrodes, Implanted; D004576:Electromyography / Q000379:methods; D004867:Equipment Design; D006801:Humans; D008866:Microsurgery / Q000379:methods; D016343:Monitoring, Intraoperative; D009801:Oculomotor Muscles / Q000502:physiology*; D009802:Oculomotor Nerve / Q000502:physiology; D019291:Skull Base / Q000294:innervation* / Q000601:surgery*; D025321:Surgery, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D014321:Trochlear Nerve / Q000502:physiology