Impact of electrode design and surgical approach on scalar location and cochlear implant outcomes.
OBJECTIVE
Three surgical approaches: cochleostomy (C), round window (RW), and extended round window (ERW); and two electrodes types: lateral wall (LW) and perimodiolar (PM), account for the vast majority of cochlear implantations. The goal of this study was to analyze the relationship between surgical approach and electrode type with final intracochlear position of the electrode array and subsequent hearing outcomes.


METHODS
Comparative longitudinal study.


METHODS
One hundred postlingually implanted adult patients were enrolled in the study. From the postoperative scan, intracochlear electrode location was determined and using rigid registration, transformed back to the preoperative computed tomography which had intracochlear anatomy (scala tympani and scala vestibuli) specified using a statistical shape model based on 10 microCT scans of human cadaveric cochleae. Likelihood ratio chi-square statistics were used to evaluate for differences in electrode placement with respect to surgical approach (C, RW, ERW) and type of electrode (LW, PM).


RESULTS
Electrode placement completely within the scala tympani (ST) was more common for LW than were PM designs (89% vs. 58%; P < 0.001). RW and ERW approaches were associated with lower rates of electrode placement outside the ST than was the cochleostomy approach (9%, 16%, and 63%, respectively; P < 0.001). This pattern held true regardless of whether the implant was LW or PM. When examining electrode placement and hearing outcome, those with electrode residing completely within the ST had better consonant-nucleus-consonant word scores than did patients with any number of electrodes located outside the ST (P = 0.045).


CONCLUSIONS
These data suggest that RW and ERW approaches and LW electrodes are associated with an increased likelihood of successful ST placement. Furthermore, electrode position entirely within the ST confers superior audiological outcomes.


METHODS
2b.
Department of Otolaryngology-Head and Neck Surgery, Vanderbilt University, Nashville, Tennessee, U.S.A.
George B
GB
Wanna
Jack H
JH
Noble
Matthew L
ML
Carlson
René H
RH
Gifford
Mary S
MS
Dietrich
David S
DS
Haynes
Benoit M
BM
Dawant
Robert F
RF
Labadie
D000328:Adult; D003051:Cochlea / Q000601:surgery; D019929:Cochlear Implantation / Q000379:methods*; D003054:Cochlear Implants; D004567:Electrodes, Implanted; D005260:Female; D006319:Hearing Loss, Sensorineural / Q000601:surgery*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D012533:Scala Tympani / Q000601:surgery*; D016896:Treatment Outcome
Cochlear implant; cochleostomy; electrode; round window; sensorineural hearing loss