Objective To describe the incidence, clinical presentation, and performance of cochlear implant (CI) recipients with tip fold-over. Study design Retrospective case series. Setting Tertiary referral center. Patients CI recipients who underwent postoperative CT scanning. Intervention(s) Tip fold-over was identified tomographically using previously-validated software that identifies the electrode array. Electrophysiologic testing including spread of excitation (SOE) or electric field imaging (EFI) was measured on those with fold-over. Main outcome measure(s) Location of the fold-over; audiological performance pre and post selective deactivation of fold-over electrodes. Results 303 ears of 235 CI recipients had postoperative CTs available for review. Six (1.98%) had tip fold-over with 5/6 right-sided ears. Tip fold-over occurred predominantly at 270° and was associated with pre-curved electrodes (5/6). Patients did not report audiological complaints during initial activation. In one patient, the electrode array remained within the scala tympani with preserved residual hearing despite the fold-over. SOE supported tip fold-over, but the predictive value was not clear. EFI predicted location of the fold-over with clear predictive value in one patient. At an average follow-up of 11 months, three subjects underwent deactivation of the overlapping electrodes with two of them showing marked audiological improvement. Conclusions In a large academic center with experienced surgeons, tip fold-over occurred at a rate of 1.98% but was not immediately identifiable clinically. CT imaging definitively showed tip fold-over. Deactivating involved electrodes may improve performance possibly avoiding revision surgery. EFI may be highly predictive of tip fold-over and can be run intraoperatively, potentially obviating the need for intra-op fluoroscopy.
Introduction: The objectives of the current study were to (1) determine the relationship between electrocochleography (ECochG), measured from the cochlear implant (CI) electrode array during and after implantation, and postoperative audiometric thresholds, (2) determine the relationship between ECochG amplitude and electrode scalar location determined by computerized tomography (CT); and (3) determine whether changes in cochlear microphonic (CM) amplitude during electrode insertion were associated with postoperative hearing.Materials and Methods: Eighteen subjects undergoing CI with an Advanced Bionics Mid-Scala device were prospectively studied. ECochG responses were recorded using the implant coupled to a custom signal recording unit. ECochG amplitude collected intraoperatively concurrent with CI insertion and at activation was compared with audiometric thresholds postoperatively. Sixteen patients also underwent postoperative CT to determine scalar location and the relationship to ECochG measures and residual hearing.Results: Mean low-frequency pure tone average (LFPTA) increased following surgery by an average of 28 dB (range 8–50). Threshold elevation was significantly greater for electrodes with scalar dislocation. No correlation was found between intraoperative ECochG and postoperative behavioral thresholds collapsed across frequency; however, mean differences in thresholds measured by intraoperative ECochG and postoperative audiometry were significantly smaller for electrodes inserted completely within scala tympani (ST) vs. those translocating from ST to scala vestibuli. A significant correlation was observed between postoperative ECochG thresholds and behavioral thresholds obtained at activation.Discussion: Postoperative audiometry currently serves as a marker for intracochlear trauma though thresholds are not obtained until device activation or later. When measured at the same time-point postoperatively, low-frequency ECochG thresholds correlated with behavioral thresholds. Intraoperative ECochG thresholds, however, did not correlate significantly with postoperative behavioral thresholds suggesting that changes in cochlear physiology occur between electrode insertion and activation. ECochG may hold clinical utility providing surgeons with feedback regarding insertion trauma due to scalar translocation, which may be predictive of postoperative hearing preservation.Conclusion: CI insertion trauma is generally not evident until postoperative audiometry when loss of residual hearing is confirmed. ECochG has potential to provide estimates of trauma during insertion as well as reliable information regarding degree of hearing preservation.
The purpose of this study was to investigate horizontal plane localization and interaural time difference (ITD) thresholds for 14 adult cochlear implant recipients with hearing preservation in the implanted ear. Localization to broadband noise was assessed in an anechoic chamber with a 33-loudspeaker array extending from −90 to +90°. Three listening conditions were tested including bilateral hearing aids, bimodal (implant + contralateral hearing aid) and best aided (implant + bilateral hearing aids). ITD thresholds were assessed, under headphones, for low-frequency stimuli including a 250-Hz tone and bandpass noise (100–900 Hz). Localization, in overall rms error, was significantly poorer in the bimodal condition (mean: 60.2°) as compared to both bilateral hearing aids (mean: 46.1°) and the best-aided condition (mean: 43.4°). ITD thresholds were assessed for the same 14 adult implant recipients as well as 5 normal-hearing adults. ITD thresholds were highly variable across the implant recipients ranging from the range of normal to ITDs not present in real-world listening environments (range: 43 to over 1600 μs). ITD thresholds were significantly correlated with localization, the degree of interaural asymmetry in low-frequency hearing, and the degree of hearing preservation related benefit in the speech reception threshold (SRT). These data suggest that implant recipients with hearing preservation in the implanted ear have access to binaural cues and that the sensitivity to ITDs is significantly correlated with localization and degree of preserved hearing in the implanted ear.
Intracochlear ECochG may provide information about CI electrode location and hearing preservation.
Objectives: Describe audiologic outcomes in hearing preservation cochlear implantation (CI) using a precurved electrode array inserted using an external sheath and evaluate association of electrode positioning and preservation of residual hearing. Study Design: Retrospective review.Setting: Tertiary otologic center.Patients: Twenty-four adult patients who underwent hearing preservation CI with precurved electrode array. Interventions: CI, intraoperative computed tomography (CT)Outcome measures: Audiologic measures [Consonant-nucleus-consonant (CNC) words, AzBio sentences, low-frequency pure tone averages (LFPTA)] and electrode location (scalar location, electrode-to-modiolus distance (M -), angular insertion depth).Results: Twenty-four adults with <80dB LFPTA with a precurved electrode array inserted using an external sheath; 16 underwent intraoperative CT. LFPTA was 58.5 dB HL preoperatively, with a 17.3 dB threshold shift at CI activation (p=0.005). CNC word scores improved from 6% preoperatively to 64% at 6 months postoperatively (p<0.0001). There was one scalar translocation and no tip fold-overs. The average angular insertion depth was 388.2 degrees, and the average M across all electrodes was 0.36 mm. Multivariate regression revealed a significant correlation
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