Electrode Location and Angular Insertion Depth Are Predictors of Audiologic Outcomes in Cochlear Implantation

Abstract

Objectives-1) Investigate the impact of electrode type and surgical approach on scalar electrode location in a large patient cohort; and 2) examine the relation between electrode location and postoperative audiologic performance. Setting-Tertiary academic hospital. Patients-220 post-lingually deafened adults undergoing cochlear implant (CI).Main Outcome Measures-Primary outcome measures of interest were scalar electrode location and postoperative audiologic performance.Results-In 68% of implants, electrodes were observed to be located solely in the scala tympani (ST). Multivariate analysis demonstrated perimodiolar(PM) and Mid-scala(MS) electrodes were p<0.001) times more likely to have at least one electrode in the scala vestibuli (SV) compared to lateral wall(LW) electrodes, respectively. Compared to cochleostomy(C), round window(RW) and extended round window(ERW) approaches demonstrated 70% reduction in SV insertion (OR 0.28,95%CI:0.1-0.8, p=0.01; ERW (OR O.28,95%CI:0.1-0.7, p=0.005). Examining postoperative audiometric performance, CNC score increased 0.6% with every 10° increase in angular insertion depth beyond the group minimum of 208° (Coefficient 0.0006,95%CI:0.0001-0.001, p=0.03). SV insertion was associated with a 12% decrease in CNC score (Coefficient -0.12,95%CI:-0.22--0.02, p=0.02). CNC score decreased 0.3% for every 1 year increase in age (Coefficient -0.003,95%CI:-0.006--0.0006), p=0.02). HHS Public Access Author Manuscript Author ManuscriptAuthor Manuscript Author ManuscriptConclusions-Electrode design and surgical approach were predictors of scalar electrode location. Specifically, LW electrodes showed higher rates of ST insertion compared to PM or MS. RW and ERW approaches showed higher rates of ST insertion when compared to C. In regards to performance, ST insertion, younger age, and greater angular insertion depth were predictors of improved CNC scores.

Automatic Cochlear Duct Length Estimation for Selection of Cochlear Implant Electrode Arrays

“…Second, we recognize that multiple factors are considered in determining the appropriate electrode for each patient including residual hearing, etiology of hearing loss, and duration of hearing loss to name but a few. Volume and cross-sectional area of the scala tympani are other factors that might be important for electrode selection, although recent studies have not found volume to be significantly associated with scalar translocations 23 . In this study, those variables were ignored as our aim was to evaluate variability due to choice of CDL measurement technique alone.…”

“…Several studies have documented a correlation between the angular depth of insertion and speech performance outcomes following cochlear implantation 13–16 . The angular depth of insertion is dependent on CDL and length of the electrode array 12–17 .…”

“…Such contacts are sometimes deactivated during cochlear implant (CI) programming but often are left at default values due to adequate volume perception potentially leading to sub-optimal hearing outcomes by interfering with other electrodes. On the other hand, a larger CDL warrants a longer electrode to ensure the tip of the array can reach apical stimulation sites which has also been shown to be important in maximizing audiological outcomes 16 . Given that there has been little evidence on what electrode depth is best for optimal hearing outcomes, the specific threshold value of A ( thresh-A ) used to decide between Array 1 and Array 2 is a matter of surgeon preference.…”

“…Several studies have demonstrated that greater angular insertion depths result in improved speech perception performance 13–16 . Since the angular depth of insertion is dependent upon CDL and the length of the implanted electrode, the variability in CDL and electrode options can influence speech perception performance.…”

Does the intracochlear position of an electrode array impact performance?

“…One study was a prospective nonrandomized control trial (Gordin et al; level 2). One study retrospectively reviewed a prospectively acquired database (O'Connell et al; level 3). Three studies consisted of retrospective cohorts (Jeong, Matterson, Wanna; level 4).…”