title: Electrophysiologic effects of placing cochlear implant electrodes in a perimodiolar position in young children.
abstract: OBJECTIVE
  The purpose of this study was to intraoperatively record the electrically evoked auditory brainstem response (EABR) before and after placement of the electrode positioning system (EPS) (CII Bionic Ear with HiFocus I cochlear implant electrode array) as well as before and after stylet removal (Nucleus Contour cochlear implant electrode array). It was hypothesized that physiologic changes would occur after perimodiolar positioning of the electrode array and these changes would be evident from the EABR recordings.
  
  
  METHODS
  Consecutive young (11-36 month old) pediatric cochlear implant recipients (n = 17) had intraoperative EABRs recorded from three intracochlear electrodes that represented apical, medial, and basal locations. Wave V amplitudes and thresholds were studied relative to electrode location and pre- versus postperimodiolar positioning. These evoked potential measures were analyzed for statistical significance.
  
  
  METHODS
  Tertiary referral children's hospital/medical college.
  
  
  RESULTS
  Wave V thresholds of the EABR were lower, and amplitudes were larger after perimodiolar positioning, although the changes were dependent on electrode location and implant design. Statistically significant decreases in EABR wave V threshold and increases in suprathreshold wave V amplitude were found for the basal electrode for the CII Bionic Ear HiFocus I and for the apical electrode for the Nucleus Contour.
  
  
  CONCLUSIONS
  Placement of either the CII Bionic Ear HiFocus I or Nucleus Contour cochlear implant electrode array in the perimodiolar position in young children resulted in less electrical current necessary to stimulate the auditory system. Changes in electrophysiologic thresholds and amplitudes, measured with EABR, indicate that the electrode array is placed closer to the modiolus with both electrode designs.
authors.affiliation: Department of Otolaryngology and Communication Sciences, Medical College of Wisconsin/Children's Hospital of Wisconsin, Milwaukee 53226, USA. wackym@mcw.edu
authors.forename: Phillip A
authors.initials: PA
authors.lastname: Wackym
authors.forename: Jill B
authors.initials: JB
authors.lastname: Firszt
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Gaggl
authors.forename: Christina L
authors.initials: CL
authors.lastname: Runge-Samuelson
authors.forename: Ruth M
authors.initials: RM
authors.lastname: Reeder
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Raulie
mesh_terms: D002675:Child, Preschool; D019929:Cochlear Implantation; D003054:Cochlear Implants; D003638:Deafness / Q000628:therapy*; D004567:Electrodes, Implanted; D004594:Electrophysiology; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D006801:Humans; D007223:Infant; D007432:Intraoperative Period; D011474:Prosthesis Design