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.

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.

Comparison of Pure-Tone Thresholds and Cochlear Microphonics Thresholds in Pediatric Cochlear Implant Patients.

OBJECTIVES: In adult cochlear implant patients, conventional audiometry is used to measure postoperative residual hearing which requires active listening and patient feedback. However, audiological measurements in pediatric cochlear implant patients are both challenging as well as time consuming. Intracochlear electrocochleography (ECOG) offers an objective and a time-efficient method to measure frequency-specific cochlear microphonic or difference thresholds (CM/DIF) thresholds that closely approximate auditory thresholds in adult cochlear implant patients. The correlation between CM/DIF and behavioral thresholds has not been established in pediatric cochlear implant patients. In the present study, CM/DIF thresholds were compared with audiometric thresholds in pediatric cochlear implant patients with postoperative residual hearing. DESIGN: Thirteen (11 unilateral and 2 bilateral) pediatric cochlear implant patients (mean age = 9.2 years ± 5.1) participated in this study. Audiometric thresholds were estimated using conventional, condition play, or visual reinforcement audiometry. A warble tone stimulus was used to measure audiometric thresholds at 125, 250, 500, 1000, and 2000 Hz. ECOG waveforms were elicited using 50-msec acoustic tone-bursts. The most apical intracochlear electrode was used as the recording electrode with an extra-cochlear ground electrode. The ECOG waveforms were analyzed to determine CM/DIF thresholds that were compared with pediatric cochlear implant patients' audiometric thresholds. RESULTS: The results show a significant correlation (r = 0.77, p < 0.01) between audiometric and CM/DIF thresholds over a frequency range of 125 to 2000 Hz in pediatric cochlear implant patients. Frequency-specific comparisons revealed a correlation of 0.82, 0.74, 0.69, 0.41, and 0.32 between the audiometric thresholds and CM/DIF thresholds measured at 125, 250, 500, 1000, and 2000 Hz, respectively. An average difference of 0.4 dB (±14 dB) was measured between the audiometric and CM/DIF thresholds. CONCLUSIONS: Intracochlear ECOG can be used to measure CM/DIF thresholds in pediatric cochlear implant patients with residual hearing in the implanted ear. The CM/DIF thresholds are similar to the audiometric thresholds at lower test frequencies and offer an objective method to monitor residual hearing in difficult-to-test pediatric cochlear implant patients.

Increase in cochlear implant electrode impedances with the use of electrical stimulation.

OBJECTIVE: Electrode impedances play a critical role in cochlear implant programming. It has been previously shown that impedances rise during periods of non-use, such as the post-operative recovery period. Then when the device is activated and use is initiated, impedances fall and are typically stable. In this study, we report a new pattern where electrode impedances increase with device use and decrease with device rest. DESIGN: Electrode impedances were measured three to four times every day over a span of 1-3 months for two cochlear implant patients. STUDY SAMPLE: Two patients with a Nucleus cochlear implant participated in this study. RESULTS: Both subjects in this study show wide fluctuations in electrode impedances. By taking serial electrode impedance measurements throughout a day of use, we observe that electrode impedances consistently increase with device use and decrease with device rest. CONCLUSION: In this study, we report two cases of electrode impedances increasing as a function of device use. Numerous management strategies were employed to reduce this effect but none prevailed; a clear pathophysiologic mechanism remains elusive. Further study into the cause of this electrode impedance pattern is warranted to establish a management strategy for these cochlear implant users.

Effect of Probe-Tone Frequency on Ipsilateral and Contralateral Electrical Stapedius Reflex Measurement in Children With Cochlear Implants.

OBJECTIVES: The upper loudness limit of electrical stimulation in cochlear implant patients is sometimes set using electrically elicited stapedius reflex thresholds (eSRTs), especially in children for whom reporting skills may be limited. In unilateral cochlear implant patients, eSRT levels are measured typically in the contralateral unimplanted ear because the ability to measure eSRTs in the implanted ear is likely to be limited due to the cochlear implant surgery and consequential changes in middle ear dynamics. This practice is particularly limiting in the case of fitting bilaterally implanted pediatric cases because there is no unimplanted ear option to choose for eSRT measurement. The goal of this study was to identify an improved measurement protocol to increase the success of eSRT measurement in ipsilateral or contralateral or both implanted ears of pediatric cochlear implant recipients. This work hypothesizes that use of a higher probe frequency (e.g., 1000 Hz compared with the 226 Hz standard), which is closer to the mechanical middle ear resonant frequency, may be more effective in measuring middle ear muscle contraction in either ear. DESIGN: In the present study, eSRTs were measured using multiple probe frequencies (226, 678, and 1000 Hz) in the ipsilateral and contralateral ears of 19 children with unilateral Advanced Bionics (AB) cochlear implants (mean age = 8.6 years, SD = 2.29). An integrated middle ear analyzer designed by AB was used to elicit and detect stapedius reflexes and assign eSRT levels. In the integrated middle ear analyzer system, an Interacoustics Titan middle ear analyzer was used to perform middle ear measurements in synchrony with research software running on an AB Neptune speech processor, which controlled the delivery of electrical pulse trains at varying levels to the test subject. Changes in middle ear acoustic admittance following an electrical pulse train stimulus indicated the occurrence of an electrically elicited stapedius reflex. RESULTS: Of the 19 ears tested, ipsilateral eSRTs were successfully measured in 3 (16%), 4 (21%), and 7 (37%) ears using probe tones of 226, 678, and 1000 Hz, respectively. Contralateral eSRT levels were measured in 11 (58%), 13 (68%), and 13 (68%) ears using the three different probe frequencies, respectively. A significant difference was found in the incidence of successful eSRT measurement as a function of probe frequency in the ipsilateral ears with the greatest pair-wise difference between the 226 and 1000 Hz probe. A significant increase in contralateral eSRT measurement success as a function of probe frequency was not found. These findings are consistent with the idea that changes in middle ear mechanics, secondary to cochlear implant surgery, may interfere with the detection of stapedius muscle contraction in the ipsilateral middle ear. The best logistic, mixed-effects model of the occurrence of successful eSRT measures included ear of measurement and probe frequency as significant fixed effects. No significant differences in average eSRT levels were observed across ipsilateral and contralateral measurements or as a function of probe frequency. CONCLUSION: Typically, measurement of stapedius reflexes is less successful in the implanted ears of cochlear implant recipients compared with measurements in the contralateral, unimplanted ear. The ability to measure eSRT levels ipsilaterally can be improved by using a higher probe frequency.

Pure-Tone Masking Patterns for Monopolar and Phantom Electrical Stimulation in Cochlear Implants.

OBJECTIVES: Monopolar stimulation of the most apical electrode produces the lowest pitch sensation in cochlear implants clinically. A phantom electrode that uses out-of-phase electrical stimulation between the most apical and the neighboring basal electrode can produce a lower pitch sensation than that associated with the most apical electrode. However, because of the absence of contacts beyond the apical tip of the array, the ability to assess the spread of electrical excitation associated with phantom stimulation is limited in the typical cochlear implant subject with no residual hearing. In the present study, the spread of electrical excitation associated with monopolar and phantom stimulation of the most apical electrode was assessed using electrical masking of acoustic thresholds in cochlear implant subjects with residual, low-frequency, acoustic hearing. DESIGN: Eight subjects with an Advanced Bionics cochlear implant and residual hearing in the implanted ear participated in this study (nine ears in total). Unmasked and masked thresholds for acoustic pure tones were measured at 125, 250, 500, 750, 1000, and 2000 Hz in the presence of monopolar and phantom electrode stimulation presented at the apical-most end of the array. The current compensation for phantom electrode stimulation was fixed at 50%. The two electrical maskers were loudness balanced. Differences between the unmasked and masked acoustic thresholds can be attributed to (1) the electrical stimulus-induced interference in the transduction/conduction of the acoustic signal through cochlear periphery and the auditory nerve and/or (2) masking at the level of the central auditory system. RESULTS: The results show a significant elevation in pure-tone thresholds in the presence of the monopolar and phantom electrical maskers. The unmasked thresholds were subtracted from the masked thresholds to derive masking patterns as a function of the acoustic probe frequency. The masking patterns show that phantom stimulation was able to produce more masking than that associated with the monopolar stimulation of the most apical electrode. CONCLUSION: These results suggest that for some cochlear implant subjects, phantom electrode stimulation can shift the neural stimulation pattern more apically in the cochlea, which is consistent with reports that phantom electrode stimulation produces lower pitch sensations than those associated with monopolar stimulation of the most apical electrode alone.

Electrocochleography in Cochlear Implant Recipients With Residual Hearing: Comparison With Audiometric Thresholds.

OBJECTIVES: To determine whether electrocochleography (ECoG) thresholds, especially cochlear microphonic and auditory nerve neurophonic thresholds, measured using an intracochlear electrode, can be used to predict pure-tone audiometric thresholds following cochlear implantation in ears with residual hearing. DESIGN: Pure-tone audiometric thresholds and ECoG waveforms were measured at test frequencies from 125 to 4000 Hz in 21 Advanced Bionics cochlear implant recipients with residual hearing in the implanted ear. The "difference" and "summation" responses were computed from the ECoG waveforms measured from two alternating phases of stimulation. The interpretation is that difference responses are largely from the cochlear microphonic while summating responses are largely from the auditory nerve neurophonic. The pure-tone audiometric thresholds were also measured with same equipment used for ECoG measurements. RESULTS: Difference responses were observed in all 21 implanted ears, whereas summation response waveforms were observed in only 18 ears. The ECoG thresholds strongly correlated (r = 0.87, n = 150 for difference response; r = 0.82, n = 72 for summation response) with audiometric thresholds. The mean difference between the difference response and audiometric thresholds was -3.2 (±9.0) dB, while the mean difference between summation response and audiometric thresholds was -14 (±11) dB. In four out of 37 measurements, difference responses were measured to frequencies where no behavioral thresholds were present. CONCLUSIONS: ECoG thresholds may provide a useful metric for the assessment of residual hearing in cochlear implant subjects for whom it is not possible to perform behavioral audiometric testing.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.