Pathophysiology of Facial Nerve Stimulation and Its Implications for Electrical Stimulation in Cochlear Implants.

OBJECTIVES: A small number of cochlear implant (CI) users experience facial nerve stimulation (FNS), which can manifest as facial twitching. In some patients, this can be resolved by adjusting the electrical stimulation parameters. However, for others, facial stimulation can significantly impair CI outcomes or even prevent its use. The exact mechanisms underlying FNS are unclear and may vary among patients. DESIGN: Transimpedance measurements were used to assess lateral and longitudinal spread of current within 15 cochlea of nucleus CI recipients with FNS (13 unilateral recipients and 1 bilateral recipient). We compared the transimpedance measurements with programming parameters from clinical visits and pre- and postoperative temporal bone computed tomography (CT) scans to identify factors that may contribute to FNS in each CI ear. RESULTS: In nine ears, transimpedance curves showed inflection, which suggests a localized current sink within the cochlea. This indicates a low-impedance pathway through which current exits the cochlea and stimulates the labyrinthine segment of the facial nerve canal. Electrodes near this current sink were disabled or underfit to minimize facial stimulation. In the other seven ears, current flow peaked toward the basal end of the cochlea, suggesting that current exits through the round window or other structures near the basal end of the cochlea, stimulating the tympanic segment of the facial nerve. CONCLUSIONS: Objective transimpedance measurements can be used to elucidate the mechanisms of FNS and to develop strategies for optimizing electrical stimulation parameters and speech coding to minimize or eliminate FNS in a small subset of CI users.

Risk of Monopolar Electrosurgery in Cochlear Implant Recipients is Nominal: Evidence to Guide Clinical Practice.

OBJECTIVE: Comprehensively assess the prevalence of monopolar electrosurgery-related device complications among cochlear implant (CI) recipients. STUDY DESIGN: Multifaceted retrospective review and survey. SETTING: Tertiary medical center. METHODS: Multifaceted approach including: (i) review of the current literature; (ii) historical review of institutional data from an academic, tertiary CI center; (iii) review of industry data provided by 3 Food and Drug Administration-approved CI manufacturers; and (iv) survey of high-volume CI centers. RESULTS: Literature review identified 9 human studies, detailing 84 devices with 199 episodes of device-cautery exposure. From studies reporting on patients records, no implant showed evidence of damage after exposure. One cadaveric study using dental cautery reported 1 episode of device damage. Review of institutional records did not identify any CI damage in 84 instances of exposure. Data from the 3 major implant manufacturers showed a single report of damage that could be reasonably linked to monopolar electrosurgery, out of a possible 689,426 CIs. Last, a survey of 8 high-volume CI centers did not identify any adverse events associated with monopolar cautery. CONCLUSION: These data estimate the risk of adverse device-related events or tissue injury to be extraordinarily low. Short of operating in immediate proximity to the CI (ie, the ipsilateral temporoparietal scalp), these data indicate that monopolar electrosurgery can be used in the body and the head-and-neck of CI recipients with nominal risk. These findings may guide decision-making in cases that are optimally or preferably performed with monopolar electrocautery and can be used to counsel CI patients following inadvertent exposures.

Comparing Speech Recognition Outcomes Between Cochlear Implants and Auditory Brainstem Implants in Patients With NF2-Related Schwannomatosis.

OBJECTIVE: To compare cochlear implant (CI) and auditory brainstem implant (ABI) performance in patients with NF2-related schwannomatosis (NF2). STUDY DESIGN: Historical cohort. SETTING: Tertiary academic center. PATIENTS: A total of 58 devices among 48 patients were studied, including 27 ABIs implanted from 1997 to 2022 and 31 CIs implanted from 2003 to 2022. Three patients had bilateral ABIs, three had bilateral CIs, three had an ABI on one side and a CI on the other, one had a CI that was later replaced with an ipsilateral ABI, and one had an ABI and CI concurrently on the same side. INTERVENTIONS: CI or ABI ipsilateral to vestibular schwannoma. MAIN OUTCOME MEASURES: Open-set speech perception, consonant-nucleus-consonant word scores, and AzBio sentence in quiet scores. RESULTS: Among all patients, 27 (47%) achieved open-set speech perception, with 35 (61%) daily users at a median of 24 months (interquartile range [IQR], 12-87 mo) after implantation. Comparing outcomes, CIs significantly outperformed ABIs; 24 (77%) CIs achieved open-set speech perception compared with 3 (12%) ABIs, with median consonant-nucleus-consonant and AzBio scores of 31% (IQR, 0-52%) and 57% (IQR, 5-83%), respectively, for CIs, compared with 0% (IQR, 0-0%) and 0% (IQR, 0-0%), respectively, for ABIs. Patients with ABIs were younger at diagnosis and at implantation, had larger tumors, and were more likely to have postoperative facial paresis. CONCLUSION: Many patients with NF2-associated vestibular schwannoma achieved auditory benefit with either a CI or an ABI; however, outcomes were significantly better in those patients who were able to receive a CI. When disease and anatomy permit, hearing rehabilitation with a CI should be considered over an ABI in these patients. Tumor management strategies that increase the ability to successfully use CIs should be strongly considered given the high risk of losing bilateral functional acoustic hearing in this population.

Initial Experiences with the Envoy Acclaim® Fully Implanted Cochlear Implant.

Introduction: Cochlear implantation has become the standard of care for the treatment of moderate-to-profound bilateral sensorineural hearing loss. However, current technologies, all of which rely on an external sound processor, have intrinsic limitations that prevent certain activities and diagnostics, thus hampering full integration into a patient's lifestyle. The Envoy Medical (White Bear Lake, MN, USA) Acclaim® fully implanted cochlear implant is a new device currently undergoing testing that has been designed to alleviate many of the current constraints by housing all components within the patient, thus allowing for near-constant use in many environments that are not conducive to a traditional cochlear implant. Methods: As part of an Early Feasibility Study, three adult implant candidates were implanted with the Acclaim® cochlear implant. Surgical video and photography were taken, and initial observations were recorded. Implantation with the Acclaim® device is largely similar to a traditional cochlear implant, with modifications to allow room for the implanted sensor as well as the implantation of a battery in the subcutaneous tissues of the chest. Results: This study demonstrates a step-by-step overview of implanting the Acclaim® and discusses initial insight and experiences with the first three implantations with this new device. Conclusions: All three surgeries proceeded without complication, and at activation, all three patients were hearing through their devices. Surgery is more technically challenging compared to a standard cochlear implant, but the skills needed can all be mastered by a dedicated otologic surgeon.

Multi-Frequency Electrocochleography and Electrode Scan to Identify Electrode Insertion Trauma during Cochlear Implantation.

Intraoperative electrocochleography (ECOG) is performed using a single low-frequency acoustic stimulus (e.g., 500 Hz) to monitor cochlear microphonics (CM) during cochlear implant (CI) electrode insertion. A decrease in CM amplitude is commonly associated with cochlear trauma and is used to guide electrode placement. However, advancement of the recording electrode beyond the sites of CM generation can also lead to a decrease in CM amplitude and is sometimes interpreted as cochlear trauma, resulting in unnecessary electrode manipulation and increased risk of cochlear trauma during CI electrode placement. In the present study, multi-frequency ECOG was used to monitor CM during CI electrode placement. The intraoperative CM tracings were compared with electrode scan measurements, where CM was measured for each of the intracochlear electrodes. Comparison between the peak CM amplitude measured during electrode placement and electrode scan measurements was used to differentiate between different mechanisms for decrease in CM amplitude during CI electrode insertion. Analysis of the data shows that both multi-frequency electrocochleography and electrode scan could potentially be used to differentiate between different mechanisms for decreasing CM amplitude and providing appropriate feedback to the surgeon during CI electrode placement.

Development and validation of a new disease-specific quality of life instrument for sporadic vestibular schwannoma: the Mayo Clinic Vestibular Schwannoma Quality of Life Index.

OBJECTIVE: Facial nerve function, hearing preservation, and tumor control have been the primary benchmarks used to assess vestibular schwannoma (VS) outcomes. Acknowledging the frequent discrepancy between what physicians prioritize and what patients value, there has been increasing prioritization of patient-reported outcome measures when evaluating the impact of VS diagnosis and its treatment. Motivated by reported limitations of prior instruments used to assess quality of life (QOL) in patients with VS, the authors describe the development and validation of a new disease-specific QOL measure: the Vestibular Schwannoma Quality of Life (VSQOL) Index. METHODS: The content development phase comprised identification of clinically important domains and prioritization of feelings or concerns individuals with VS may have. The validation phase encompassed determining how items were grouped into domains and eliminating redundant items. Both phases leveraged data from cross-sectional and longitudinal surveys, expertise from a multidisciplinary working group, and patients with a broad range of experiences with VS (n = 42 during content development and n = 263 during validation). Domain scores from the new instrument were assessed for reliability and correlation with other measures of similar constructs. RESULTS: The VSQOL Index consists of 40 items that evaluate the impact of VS diagnosis and its management on QOL, treatment satisfaction, and employment and is estimated to take 8-10 minutes to complete. Domain scores range from 0 (worst) to 100 (best) and demonstrate excellent psychometric properties, including content, construct, and convergent validity and both internal consistency (Cronbach's alphas 0.83 to 0.91) and test-retest reliability (reliability coefficients 0.86 to 0.96). CONCLUSIONS: The VSQOL Index is a valid and reliable measure that overcomes several limitations of prior instruments, including omission or underrepresentation of domains that frequently impact well-being, such as pain, cognition, satisfaction or regret surrounding treatment decisions, and occupational limitations, to comprehensively evaluate the impact of VS diagnosis or its treatment on QOL.

Co-Registration of pre- and post-Operative images after cochlear Implantation: A proposed technique to Improve cochlear visualization and localization of cochlear electrodes.

BACKGROUND AND PURPOSE: After cochlear implantation, metallic artifact can obscure nearby structures on CT images, which is problematic in patients with facial nerve stimulation (FNS). This study evaluated the usefulness of co-registered pre- and post-operative examinations to evaluate the cochlear implant and adjacent structures. MATERIALS AND METHODS: A retrospective review was completed of consecutive patients that underwent CT imaging of the temporal bone before and after placement of a cochlear implant. Two blinded neuroradiologists independently reviewed all available examinations. All examinations were assessed for the presence or absence of dehiscence of the osseous ridge between the cochlea and facial nerve canal (FNC). Pre-operative and fused pre- and post-operative examinations were compared in their ability to visualize the osseous ridge using a 5-point Likert scale (ranging from 1 = unfused images were substantially superior to 5 = fused images were substantially superior). The electrode closest to the FNC were noted. RESULTS: Of 34 included patients, 13 (38.2%) were female and 21 (61.8%) were male; average age was 72.2. Seven patients (20.6%) had frank dehiscence between the cochlea and FNC. Fused images were superior to the post-operative study alone for assessing the integrity of the osseous partition between the cochlea and FNC and for reducing artifact from the electrode array (average Likert scores for both reviewers were 4.4 and 4.7). There was good agreement between reviewers in noting electrode closest to the FNC (concordance correlation coefficient=0.82). CONCLUSIONS: Following cochlear implantation, co-registered pre- and post-operative CT images are superior to conventional images in assessing the anatomic relationship between the cochlea and FNC.

Relationship Between Intraoperative Electrocochleography Responses and Immediate Postoperative Bone Conduction Thresholds in Cochlear Implantation.

OBJECTIVE: To determine the relationship between intraoperative electrocochleography (ECochG) measurements and residual hearing preservation after cochlear implant (CI) surgery by comparing differences between preoperative and immediate postoperative bone conduction thresholds. STUDY DESIGN: Prospective cohort study. SETTING: Tertiary academic referral center. PATIENTS: Sixteen patients with preoperative residual hearing and measurable (no-vibrotactile) bone conduction thresholds at 250 and/or 500 Hz who underwent cochlear implantation. MAIN OUTCOME MEASURE: Intraoperative ECochG and air and bone conduction thresholds. RESULTS: Nine patients showed no significant drop (<30%) in ECochG amplitude during CI surgery with an average preoperative and immediate postoperative BC threshold of 46 and 39 dB HL, respectively, at 500 Hz. Seven patients with a decrease in ECochG amplitude of 30% or greater showed an average preoperative 500 Hz BC threshold of 32 dB HL and immediate postoperative threshold of 55 dB HL. Air and bone conduction thresholds measured approximately 1 month after CI surgery show delayed-onset of hearing loss across our study patients. CONCLUSIONS: A small decrease (<30%) in difference response or cochlear microphonics amplitude correlates with no significant changes in immediate postoperative residual hearing, whereas patients who show larger changes (≥30%) in difference response or cochlear microphonics amplitude during intraoperative ECochG measurements show significant deterioration in BC thresholds. This study reveals the necessity of prompt postoperative bone conduction measurement to isolate the intraoperative cochlear trauma that may be detected during intraoperative ECochG measurements. Although delayed postoperative audiometrics represent longer-term functional hearing, it includes the sum of all postoperative changes during the recovery period, including subacute changes after implantation that may occur days or weeks later. Measuring air and bone conduction thresholds immediately postoperatively will better isolate factors influencing intraoperative, early postoperative, and delayed postoperative hearing loss. This will ultimately help refine surgical technique, device design, and highlight the use of intraoperative ECochG in monitoring cochlear trauma during CI surgery.

Implementation Strategy for Highly-Coordinated Cochlear Implant Care With Remote Programming: The Complete Cochlear Implant Care Model.

OBJECTIVE: To introduce and discuss implementation strategy for the Complete Cochlear Implant Care (CCIC) model, a highly-coordinated cochlear implant (CI) care delivery model requiring a single on-site visit for preoperative workup, surgery, and postoperative programming. STUDY DESIGN: Prospective, nonrandomized, two-arm clinical trial. SETTING: Tertiary referral CI center. PATIENTS: Adults who meet audiologic criteria for cochlear implantation. INTERVENTIONS: Cochlear implantation, coordinated care delivery, including remote programming. MAIN OUTCOME MEASURES: Care delivery model feasibility and process implementation. RESULTS: Patients determined to be likely CI candidates based on routine audiometry are eligible for enrollment. The CCIC model uses telemedicine and electronic educational materials to prepare patients for same-day on-site consultation with CI surgery, same or next-day activation, and postoperative remote programming for 12 months. Implementation challenges include overcoming inertia related to the implementation of a new clinical workflow, whereas scalability of the CCIC model is limited by current hardware requirements for remote programming technology. A dedicated CCIC process coordinator is critical for overcoming obstacles in implementation and process improvement through feedback and iterative changes. Team and patient-facing materials are included and should be tailored to fit each unique CI program looking to implement CCIC. CONCLUSION: The CCIC model has the potential to dramatically streamline hearing healthcare delivery. Implementation requires an adaptive approach, as obstacles may vary according to institutional infrastructure and policies.

Preoperative Imaging of Temporoparietal Scalp Thickness Predicts Off-the-Ear Sound Processor Retention in Cochlear Implants With Diametric Magnets.

OBJECTIVE: To determine if temporoparietal scalp thickness assessed via preoperative imaging predicts retention events in patients who have cochlear implants with diametric magnets and various sound processor types. STUDY DESIGN: Retrospective chart and radiological review. SETTING: Tertiary referral center. PATIENTS: One hundred forty-three adult patients who have cochlear implants with diametric magnets. MAIN OUTCOME MEASURES: Skin flap thickness, retention events, body mass index (BMI), and magnet strength. RESULTS: Of 42 patients with the most recent generation off-the-ear sound processor (OTE2), 13 (31.0%) had retention events. Of patients with a temporoparietal scalp thickness less than 8 mm, all patients could ultimately retain the device, though one of 26 was noted to have tenuous retention. Of patients with 8 to 10 mm skin flaps, 3 of 6 (50%) could not retain the device, and with more than 10 mm skin flaps, 7 of 10 (70%) could not retain the device. In the more than 10 mm group, two additional patients could not either retain the device at initial activation or were noted to have tenuous retention. Of 124 patients with behind-the-ear (BTE) sound processors, only 2 (1.6%) could not retain the device at initial activation, and 3 (2.4%) exhibited tenuous retention after 3 months of device use. Results from the first generation off-the-ear sound processor (OTE1) are also reported. CONCLUSIONS: Temporoparietal scalp thickness measured by preoperative imaging is associated with processor retention for patients with the OTE2 sound processor and diametric magnets. All patients with less than 8 mm scalp thickness could retain the OTE2, while 50% of patients with 8 to 10 mm scalp thickness and 70% with more than 10 mm scalp thickness could not retain the device. Patients should be counseled regarding their sound processor choice and/or considered candidates for skin flap reduction or other intervention as indicated. Retention events with BTE processors are rare.

Intraoperative Use of Electrical Stapedius Reflex Testing for Cochlear Nerve Monitoring During Simultaneous Translabyrinthine Resection of Vestibular Schwannoma and Cochlear Implantation.

OBJECTIVE: To report the novel use of intraoperative electrically evoked stapedial reflex (eSR) for cochlear nerve monitoring during simultaneous translabyrinthine resection of vestibular schwannoma (VS) and cochlear implantation. STUDY DESIGN: Clinical capsule report with video demonstration. SETTING: Tertiary academic referral center. PATIENT: A 58-year-old female presented with a small right intracanalicular VS with associated asymmetrical right moderate to severe sensorineural hearing loss, poor word recognition, tinnitus, and disequilibrium. Based on patient symptomatology and goals, simultaneous CI with translabyrinthine resection of the VS was performed. INTERVENTION: Cochlear implantation before the tumor was resected facilitated intraoperative eSRs by delivering repeated single-electrode stimulations through the cochlear implant (CI) electrode during tumor resection. A pulse duration of 50-us and a current amplitude of 200-CL or 648-us was used to elicit eSRs visible through the facial recess. Intraoperative eSR was monitored in conjunction with electrically evoked compound action potentials via neural response telemetry and electrical auditory brainstem response. RESULTS: Despite the transient evoked compound action potentials amplitude and electrical auditory brainstem response latency changes, the visually observed eSR was preserved and remained robust throughout tumor dissection, indicating an intact cochlear nerve. Four weeks postoperatively, the patient exhibited open-set speech capacity (14% CNC and 36% AzBio in quiet). CONCLUSION: The current study demonstrates the feasibility of using intraoperative eSR via a CI electrode to monitor cochlear nerve integrity during VS resection, which may indicate successful CI outcomes. These preliminary findings require further substantiation in a larger study.

Catchment Profile of Large Cochlear Implant Centers in the United States.

OBJECTIVE: To characterize the catchment area and patient profile of large cochlear implant (CI) centers in the United States. STUDY DESIGN: Multi-institutional retrospective case series. SETTING: Tertiary referral CI centers. METHODS: Patients who underwent CI surgery at 7 participating CI centers between 2015 and 2020 were identified. Patients' residential zip codes were used to approximate travel distances and urban vs rural residential areas. RESULTS: Over the 6-year study period (2015-2020), 6313 unique CI surgical procedures occurred (4529 adult, 1784 pediatric). Between 2015 and 2019, CI procedures increased by 43%. Patients traveled a median 52 miles (interquartile range, 21-110) each way; patients treated at rural CI centers traveled greater distances vs those treated at urban centers (72 vs 46 miles, P < .001). Rural residents represented 61% of the patient population and traveled farther than urban residents (73 vs 24 miles, P < .001). Overall, 91% of patients lived within a 200-mile radius of the institution, while 71% lived within a 100-mile radius. In adults, multiple regression analysis redemonstrated an association between greater travel distances and (1) older age at the time of CI and (2) residential rural setting (both P < .001, r2 = 0.2). CONCLUSIONS: While large CI centers serve geographically dispersed populations, most patients reside within a 200-mile radius. Strategies to expand CI utilization may leverage remote programming, telemedicine, and strategic placement of new centers and satellite clinics to ameliorate travel burden.

Does early activation within hours after cochlear implant surgery influence electrode impedances?

OBJECTIVE: This study aims to determine if early device activation can influence cochlear implant electrode impedances by providing electrical stimulation within hours after cochlear implant surgery. DESIGN: Electrode impedances were measured intraoperatively, at device activation, and one-month after device activation in three groups: users whose devices were activated (1) on the same day (Same Day), (2) the next day (Next Day), and (3) 10-14 days (Standard), after cochlear implant surgery. STUDY SAMPLE: Electrode impedances are reported in fifty-one patients implanted with a Cochlear™ Nucleus® Cochlear Implant. RESULTS: Compared to intraoperative levels, impedances dropped within hours for the Same Day activation group (p < 0.001) and continued dropping on the next day after surgery (p < 0.001). Similarly, electrode impedances were significantly (p < 0.001) lower at device activation for the Next Day group as compared to their intraoperative measurements. For Standard activation, impedances increased significantly from intraoperative levels, prior to device activation (p < 0.001). One-month after initial activation, impedances were not statistically different between the Same Day, Next Day, and Standard activation groups. CONCLUSIONS: Early device activation does not influence long-term impedances in a clinically meaningful manner.

Impact of Duration of Deafness on Speech Perception in Single-Sided Deafness Cochlear Implantation in Adults.

OBJECTIVE: To evaluate the impact of prolonged auditory deprivation on speech perception outcomes in adult acquired single-sided deafness (SSD) cochlear implant (CI) recipients. STUDY DESIGN: Retrospective case series. SETTING: Tertiary care academic center. PATIENTS: Acquired SSD in adults with and without prolonged duration of deafness (defined as >10 yr) who underwent CI between 2014 and 2019. INTERVENTIONS: CI. MAIN OUTCOME MEASURES: Consonant-nucleus-consonant (CNC) and AzBio in quiet scores within first year of follow-up. RESULTS: A total of 35 adult patients with SSD were evaluated, with a median overall duration of deafness of 2.4 years (interquartile range [IQR] 1.2-6.0 yr): seven patients with prolonged auditory deprivation (median 18 yr, IQR 15-28) were compared with 28 SSD patients with duration of deafness less than 10 years (median 1.7 yr, IQR 1.1-3.2). At last follow-up, the median CNC scores were 39% (IQR 31-64) and 54% (IQR 46-64) for the prolonged and shorter duration of deafness cohorts, respectively (p = 0.3). The median AzBio scores were 66% (IQR 65-68) and 72% (IQR 60-82) for the prolonged and shorter duration of deafness cohorts, respectively (p = 0.6). In a separate analysis evaluating duration of deafness as a continuous variable across all 35 patients, Spearman correlation coefficients for associations of duration of deafness with most recent CNC and AzBio scores were -0.02 (p = 0.9) and 0.02 (p = 0.9), respectively. CONCLUSIONS: Adult CI recipients with acquired SSD, with and without prolonged auditory deprivation, demonstrated comparable speech perception scores. Prolonged duration of deafness alone should not preclude a motivated SSD patient from undergoing cochlear implantation.

Speech Perception Performance Growth and Benchmark Score Achievement After Cochlear Implantation for Single-Sided Deafness.

OBJECTIVES: Compare speech perception performance growth and benchmark score achievement among adult cochlear implant (CI) recipients with single-sided deafness (SSD) versus bilateral moderate to profound hearing loss. STUDY DESIGN: Retrospective matched cohort analysis. SETTING: Tertiary referral center. PATIENTS: Adults with SSD or bilateral moderate to profound hearing sensorineural hearing loss who underwent cochlear implantation from 2014 to 2019. INTERVENTIONS: Cochlear implantation. MAIN OUTCOME MEASURES: Time-to-benchmark speech perception score (CNC, AzBio in quiet) and speech performance within first postoperative year. RESULTS: Thirty-three SSD patients were matched to 66 bilateral hearing loss patients (referent cohort) for duration of deafness and preoperative ipsilateral CNC scores. Although SSD patients were more likely to achieve benchmark CNC scores more quickly compared with matched referents, this difference did not reach statistical significance (HR 1.72; 95% CI 0.78-3.82; p = 0.18). AzBio scores showed similar trends (HR 1.40; 95% CI 0.66-2.98; p = 0.38). At last follow-up, the SSD cohort had lower CNC (median 54% vs. 62%; p = 0.019) and AzBio scores (median 72% vs. 84%; p = 0.029) compared to the referent cohort. CONCLUSIONS: No significant difference in speech perception performance growth (i.e., time-to-benchmark speech perception score) was identified between SSD and bilateral hearing loss CI recipients, although patients with bilateral hearing loss achieved higher scores in the implanted ear within the first year of follow-up.

Analysis of electrode impedance and its subcomponents for lateral wall, mid-scala, and perimodiolar electrodes in cochlear implants.

OBJECTIVE: Electrode impedances play an important role in cochlear implant patient management. During clinical visits, electrode impedances are calculated from a single point voltage waveform. In the present study, multipoint electrode impedance analysis was performed to study electrode impedance and its subcomponents in patients with three different types of cochlear implant electrode arrays. DESIGN: Voltage waveforms were measured at six different time points during the cathodic phase of a biphasic pulse in forty-seven cochlear implant patients with perimodiolar, mid-scala, or lateral wall electrode arrays. Multipoint electrode impedances were used to determine access resistance and polarization impedance. RESULTS: Access resistance of approximately 5 kΩ was calculated across the three different electrode arrays. Mid-scala electrodes showed a smaller increase in impedances as a function of pulse duration compared to the other electrodes. Patients with lower impedances showed higher capacitance and lower resistance, suggesting that differences in electrochemical reaction at the electrodes' surface can influence impedances in cochlear implants. CONCLUSIONS: Analysis of cochlear implant electrode impedances and their subcomponents provides valuable information about resistance to the flow of current between stimulating and return electrodes, and build an understanding of the contribution of electrochemical processes used to deliver electrical stimulation to the auditory nerve.

Subcutaneous Air Around Receiver-Stimulator Causing Open-Circuit Failures: An Uncommon But Readily Treatable Condition Related to CPAP Use After Cochlear Implant Surgery.

OBJECTIVE: To raise awareness of a unique complication associated with continuous positive airway pressure (CPAP) use after cochlear implantation to improve early detection, prevent unnecessary testing, and facilitate treatment. STUDY DESIGN: Case series. SETTING: Tertiary referral center. SUBJECTS: Patients who developed subcutaneous air around the receiver-stimulator device and the associated ground electrode in the setting of CPAP usage, which resulted in open-circuit electrode failures. MAIN OUTCOME MEASURES: Clinical course and intervention. RESULTS: Two patients were identified that fit this criterion. Both patients were noted to have poor implant performance secondary to high or open impedances and concomitant emphysema surrounding the cochlear implant receiver-stimulator. Manual massage offered transient improvement, but programming changes ultimately led to improved sound quality and resolution of impedance anomalies in both cases. CONCLUSIONS: Subcutaneous air collection surrounding the cochlear implant receiver-stimulator in the setting of CPAP use is an uncommon but clinically relevant complication that can be recognized by characteristic physical examination findings and impedance changes. Early and accurate recognition of this event can prevent unnecessary testing and facilitate early effective treatment.

Effect of Number of Electrodes Used to Elicit Electrical Stapedius Reflex Thresholds in Cochlear Implants.

INTRODUCTION: When mapping cochlear implant (CI) patients with limited reporting abilities, the lowest electrical stimulus level that produces a stapedial reflex (i.e., the electrical stapedius reflex threshold [eSRT]) can be measured to estimate the upper bound of stimulation on individual or a subset of CI electrodes. However, eSRTs measured for individual electrodes or a subset of electrodes cannot be used to predict the global adjustment of electrical stimulation levels needed to achieve comfortable loudness sensations that can be readily used in a speech coding strategy. In the present study, eSRTs were measured for 1-, 4-, and 15-electrode stimulation to (1) determine changes in eSRT levels as a function of the electrode stimulation mode and (2) determine which stimulation mode eSRT levels best approximate comfortable loudness levels from patients' clinical maps. METHODS: eSRTs were measured with the 3 different electrical stimulation configurations in 9 CI patients and compared with behaviorally measured, comfortable loudness levels or M-levels from patients' clinical maps. RESULTS: A linear, mixed-effects, repeated-measures analysis revealed significant differences (p < 0.01) between eSRTs measured as a function of the stimulation mode. No significant differences (p = 0.059) were measured between 15-electrode eSRTs and M-levels from patients' clinical maps. The eSRTs measured for 1- and 4-electrode stimulation differed significantly (p < 0.05) from the M-levels on the corresponding electrodes from the patients' clinical map. CONCLUSION: eSRT profiles based on 1- or 4-electrode stimulation can be used to determine comfortable loudness level on either individual or a subset of electrodes, and 15-electrode eSRT profiles can be used to determine the upper bound of electrical stimulation that can be used in a speech coding strategy.

Clinical Utility of Intraoperative Electrocochleography (ECochG) During Cochlear Implantation: A Systematic Review and Quantitative Analysis.

OBJECTIVE: To evaluate the utility of intraoperative electrocochleography (ECochG) as a predictive tool for preservation of residual acoustic hearing after cochlear implantation. DATA SOURCES: A systematic review employing a multi-database search strategy (Ovid MEDLINE, Embase, EBM Cochrane, and Scopus) was conducted from inception to August 1, 2019. English language studies in humans were included. STUDY SELECTION: All articles were independently reviewed by two authors according to Preferred Reporting Items of Systematic Reviews and Meta-analysis (PRISMA) guidelines. Studies without intraoperative ECochG obtained during cochlear implantation were excluded. DATA EXTRACTION: Extracted variables included number of patients, ECochG recording technique, success rate of obtaining ECochG potentials, intraoperative changes in ECochG signal, and postoperative hearing preservation outcomes. DATA SYNTHESIS: Among 537 eligible articles, 22 met inclusion criteria encompassing 498 unique patients. Ten studies featured extracochlear measurements, eight featured intracochlear measurements, and four featured both. Extracochlear ECochG had an average (SD) recording success rate of 94.9% (12.7%) while intracochlear ECochG had an average (SD) recording success rate of 91.8% (9.8%). One hundred forty five unique patients from six studies had complete intraoperative ECochG data with postoperative behavioral audiometry. After accounting for study-specific definitions of ECochG signal disturbance, worsening changes in intraoperative ECochG signal predicted postoperative hearing loss with limited sensitivity and specificity and notable heterogeneity across studies. CONCLUSIONS: Intraoperative ECochG recordings can be obtained in over 90% of patients, but accuracy in predicting postoperative hearing loss remains limited. Standardization of intraoperative ECochG monitoring technique and data interpretation are necessary to more robustly investigate outcomes and refine technique.