title: Role of electrode placement as a contributor to variability in cochlear implant outcomes.
abstract: OBJECTIVE
  Suboptimal cochlear implant (CI) electrode array placement may reduce presentation of coded information to the central nervous system and, consequently, limit speech recognition.
  
  
  BACKGROUND
  Generally, mean speech reception scores for CI recipients are similar across different CI systems, yet large outcome variation is observed among recipients implanted with the same device. These observations suggest significant recipient-dependent factors influence speech reception performance. This study examines electrode array insertion depth and scalar placement as recipient-dependent factors affecting outcome.
  
  
  METHODS
  Scalar location and depth of insertion of intracochlear electrodes were measured in 14 patients implanted with Advanced Bionics electrode arrays and whose word recognition scores varied broadly. Electrode position was measured using computed tomographic images of the cochlea and correlated with stable monosyllabic word recognition scores.
  
  
  RESULTS
  Electrode placement, primarily in terms of depth of insertion and scala tympani versus scala vestibuli location, varies widely across subjects. Lower outcome scores are associated with greater insertion depth and greater number of contacts being located in scala vestibuli. Three patterns of scalar placement are observed suggesting variability in insertion dynamics arising from surgical technique.
  
  
  CONCLUSIONS
  A significant portion of variability in word recognition scores across a broad range of performance levels of CI subjects is explained by variability in scalar location and insertion depth of the electrode array. We suggest that this variability in electrode placement can be reduced and average speech reception improved by better selection of cochleostomy sites, revised insertion approaches, and control of insertion depth during surgical placement of the array.
authors.affiliation: Departments of Otolaryngology-Head and Neck Surgery and Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA. ccf@med.unc.edu
authors.forename: Charles C
authors.initials: CC
authors.lastname: Finley
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Holden
authors.forename: Laura K
authors.initials: LK
authors.lastname: Holden
authors.forename: Bruce R
authors.initials: BR
authors.lastname: Whiting
authors.forename: Richard A
authors.initials: RA
authors.lastname: Chole
authors.forename: Gail J
authors.initials: GJ
authors.lastname: Neely
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Hullar
authors.forename: Margaret W
authors.initials: MW
authors.lastname: Skinner
mesh_terms: D000328:Adult; D017668:Age of Onset; D000368:Aged; D002470:Cell Survival; D003051:Cochlea / Q000601:surgery; D019929:Cochlear Implantation / Q000009:adverse effects / Q000379:methods*; D003638:Deafness / Q000601:surgery; D004566:Electrodes; D004867:Equipment Design; D006801:Humans; D008144:Loudness Perception; D008875:Middle Aged; D010898:Pitch Perception; D012533:Scala Tympani / Q000601:surgery; D013063:Speech Discrimination Tests; D013065:Speech Intelligibility; D013067:Speech Perception / Q000502:physiology*; D013136:Spiral Ganglion / Q000166:cytology / Q000473:pathology; D016896:Treatment Outcome