title: Auditory brainstem activity and development evoked by apical versus basal cochlear implant electrode stimulation in children.
abstract: OBJECTIVE
  The role of apical versus basal cochlear implant electrode stimulation on central auditory development was examined. We hypothesized that, in children with early onset deafness, auditory development evoked by basal electrode stimulation would differ from that evoked more apically.
  
  
  METHODS
  Responses of the auditory nerve and brainstem, evoked by an apical and a basal implant electrode, were measured over the first year of cochlear implant use in 50 children with early onset severe to profound deafness who used hearing aids prior to implantation.
  
  
  RESULTS
  Responses at initial stimulation were of larger amplitude and shorter latency when evoked by the apical electrode. No significant effects of residual hearing or age were found on initial response amplitudes or latencies. With implant use, responses evoked by both electrodes showed decreases in wave and interwave latencies reflecting decreased neural conduction time through the brainstem. Apical versus basal differences persisted with implant experience with one exception; eIII-eV interlatency differences decreased with implant use.
  
  
  CONCLUSIONS
  Acute stimulation shows prolongation of basally versus apically evoked auditory nerve and brainstem responses in children with severe to profound deafness. Interwave latencies reflecting neural conduction along the caudal and rostral portions of the brainstem decreased over the first year of implant use. Differences in neural conduction times evoked by apical versus basal electrode stimulation persisted in the caudal but not rostral brainstem.
  
  
  CONCLUSIONS
  Activity-dependent changes of the auditory brainstem occur in response to both apical and basal cochlear implant electrode stimulation.
authors.affiliation: Cochlear Implant Laboratory, the Hospital for Sick Children, and Department of Otolaryngology-Head and Neck Surgery, University of Toronto, Ontario, Canada. karen.gordon@utoronto.ca
authors.forename: K A
authors.initials: KA
authors.lastname: Gordon
authors.forename: B C
authors.initials: BC
authors.lastname: Papsin
authors.forename: R V
authors.initials: RV
authors.lastname: Harrison
mesh_terms: D000200:Action Potentials; D001933:Brain Stem / Q000503:physiopathology; D002648:Child; D002675:Child, Preschool; D003054:Cochlear Implants; D003056:Cochlear Nerve / Q000503:physiopathology*; D003638:Deafness / Q000503:physiopathology* / Q000628:therapy*; D004558:Electric Stimulation / Q000379:methods*; D004566:Electrodes; D016057:Evoked Potentials, Auditory, Brain Stem; D005260:Female; D006801:Humans; D008297:Male; D009431:Neural Conduction; D011930:Reaction Time; D012720:Severity of Illness Index