Preservation Of Residual Hearing Research Articles

Hearing Preservation in Elderly Cochlear Implant Recipients.

Examine hearing preservation rates in cochlear implant recipients 72 years and older. Retrospective case series. Tertiary otology/neurotology practice. Cochlear implant recipients 72 years and older who are candidates for hearing preservation and were implanted between April 2017 and June 2018 INTERVENTION:: Surgical/rehabilitative. Hearing was measured preoperatively and 6 months after cochlear implantation. Between April 2017 and June 2018, 125 cochlear implant operations were performed by the senior author (A.J.). Of these patients, 62 were over age 72 and comprehensive pre- and postoperative residual hearing data were available on 24 patients. Although several methods for calculating hearing preservation are evaluated, our practice has found that hearing preservation techniques should be used in all patients having even a single frequency ≤85 dB HL between 125 and 2000 Hz before surgery. Using this method, 60% of recipients had at least one postoperative threshold ≤85 dB HL, and more importantly, over 80% of these patients subsequently used an electroacoustic MAP. Despite concerns about cochlear fragility in elderly patients, preservation of residual hearing is feasible in cochlear implant recipients 72 years and older. This suggests that the vast majority of patients, including an elderly cohort, can benefit from soft surgery techniques.

Comparison of the Pediatric Cochlear Implantation Using Round Window and Cochleostomy.

Introduction:Cochlear implantation (CI) is now regarded as a standard treatment for children with severe to profound sensor neural hearing loss. This study aimed to compare the efficacy of the round window approach (RWA) and standard cochleostomy approach (SCA) in the preservation of residual hearing after CI in pediatric patients.Materials and Methods:This double-blind randomized controlled trial was conducted on 97 pediatric patients receiving CI with 12-month follow-up. The study population was divided into two groups according to the surgical approaches they received, including RWA and SCA. Consequently, the patients were evaluated based on the Categories of Auditory Performance scale (CAP) and Speech Intelligibility Rating (SIR) test 45-60 days and 3, 6, 9, and 12 months post-surgery.Results:The CAP and SIR mean scores increased in both groups during the 12-month follow-up. This upward trend was significant in both groups (P<0.001). There was no significant difference between the two treatment groups in any of the follow-up stages regarding the CAP mean score. The mean SIR score (P=1.14±0.40) was significantly higher in the RWA group 3(P=0.001), 6(P=0.008), and 9(P=0.006) months after the surgery. However, there was no significant difference between the RWA and SCA groups, regarding 1-year SIR (P=0.258).Conclusion:The CI with either RWA or SCA could improve hearing and speech performance in pediatric patients. Although mid-term speech intelligibility was better for RWA, there was no significant difference in the 1-year outcome between these two methods.

Hearing Preservation Outcomes Using a Precurved Electrode Array Inserted With an External Sheath.

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. Retrospective review. Tertiary otologic center. Twenty-four adult patients who underwent hearing preservation CI with precurved electrode array. 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 ((Equation is included in full-text article.)), angular insertion depth). Twenty-four adults with less than 80 dB 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 (Equation is included in full-text article.)across all electrodes was 0.36 mm. Multivariate regression revealed a significant correlation between CNC scores at 6 months and angular insertion depth (p = 0.0122; r = 0.45, adjusted r = 0.35). Change in LFPTA was not significantly associated with angular insertion depth or (Equation is included in full-text article.). A low rate of translocation allows a precurved electrode array inserted using an external sheath to maintain hearing preservation rates comparable to straight electrode arrays. With scala tympani insertion, angular insertion depth is a positive marker of improved speech performance postoperatively but may be a confounder variable based on individual cochlear size.

Characterizing Insertion Pressure Profiles During Cochlear Implantation: Simultaneous Fluoroscopy and Intracochlear Pressure Measurements.

Combined electrical-acoustical stimulation (EAS) has gained popularity as patients with residual hearing are increasingly undergoing cochlear implantation. Preservation of residual hearing correlates with hearing outcomes, but loss of hearing occurs in a subset of these patients. Several mechanisms have been proposed as causing this hearing loss; we have previously described high amplitude pressure transients, equivalent to high-level noise exposures, in the inner ear during electrode insertion. The source of these transients has not been identified. Cadaveric human heads were prepared with an extended facial recess. Fiber-optic pressure sensors were inserted into the scala vestibuli and scala tympani to measure intracochlear pressures. Two cochlear implant (CI) electrode styles (straight and perimodiolar) were inserted during time-synced intracochlear pressures and video fluoroscopy measurements. CI electrode insertions produced pressure transients in the cochlea up to 160 to 170 dB pSPL equivalent for both styles, consistent with previous results. However, the position of the electrode within the cochlea when transients were generated differed (particularly contact with the medial or lateral walls). These results begin to elucidate the insertion pressure profiles of CI electrodes, which can be used to improve CI electrode designs and facilitate "silent-insertions" to improve chances of hearing preservation.

Preservation of residual hearing after cochlear implant surgery with slim modiolar electrode

PurposeTo evaluate the insertion results and hearing preservation of a novel slim modiolar electrode (SME) in patients with residual hearing.MethodsWe retrospectively collected the data from the medical files of 17 patients (18 ears) implanted with a SME. All patients had functional low frequency hearing (PTA (0.125–0.5 kHz) ≤ 80 dB HL). The insertion results were re-examined from the postoperative cone-beam computed tomography scans. Postoperative thresholds were obtained at the time of switch-on of the sound processors (mean 43 days) and at latest follow-up (mean 582 days). The speech recognition in noise was measured with the Finnish matrix sentence test preoperatively and at follow-up.ResultsThe mean insertion depth angle (IDA) was 395°. Neither scala dislocations nor tip fold over were detected. There were no total hearing losses. Functional low-frequency hearing was preserved in 15/18 (83%) ears at switch-on and in 14/17 (82%) ears at follow-up. According to HEARRING classification, 55% (10/18) had complete HP at switch-on and 41% (7/17) still at follow-up. Thirteen patients (14 ears) were initially fitted with electric–acoustic stimulation and seven patients (8 ears) continued to use it after follow-up.ConclusionsThe preliminary hearing preservation results with the SME were more favorable than reported for other perimodiolar electrodes. The results show that the array may also be feasible for electro-acoustic stimulation; it is beneficial in that it provides adequate cochlear coverage for pure electrical stimulation in the event of postoperative or progressive hearing loss.

Short and long term preservation of hearing thresholds corrected for natural hearing loss in cochlear implant recipients using a straight electrode

Objectives: The aim of this study is to investigate short and long term residual hearing preservation (HP), corrected for the natural progress of hearing loss, in cochlear implant (CI) patients receiving a straight electrode array using a round window (RW) approach.Methods: A retrospective and cross-sectional analysis on patients who received a CI with a straight electrode using a RW approach (n = 60) was performed. Audiometric data were obtained at three time points, preoperatively, at first fitting, and one year or more postoperatively. The HP outcome was calculated according to the HP definition as reported by Skarzynski with a PTA of 250, 500, and 1000 Hz (PTA3) and a PTA of 250, 500, 1000, and 2000 Hz (PTA4).Results: The HP outcome at first fitting and at long term follow up fell into the partial HP category, 63.5% (PTA3) and 40.5% (PTA4), respectively according to the Skarzynski definition. A decline in pure-tone average (PTA) was found in the CI ear and in the contralateral ear over time (p < 0.05). Interaural differences remained relatively stable at all frequencies on the long term, except for the frequency 250 Hz (p < 0.05).Discussion: After the initial loss of residual hearing, the hearing thresholds of the CI ear remain relatively stable at long term follow up when corrected for the natural course of hearing loss, except at 250 Hz.Conclusion: CI candidates should be counseled on the risk of long term deterioration of the residual hearing in both the CI ear and the contralateral ear.

Feasibility of early activation after cochlear implantation

The purpose of the study is to investigate feasibility of early activation after cochlear implantation by evaluating long-term impedance change and speech perception. Case-control study SETTING: Between July 2015 and December 2016, we prospectively enrolled 20 subjects for early activation (within 24hours after cochlear implantation). On the other hand, from November 2013 to July 2015, 20 age- and sex-matched control subjects from the database of cochlear implantees treated with conventional activation schedule (4weeks after surgery) were retrospectively enrolled. Forty patients who underwent cochlear implantation surgeries. The series impedance and speech perception score of both groups were compared. No statistical difference in long-term follow-up between the two groups was found using GEEs and multivariate analysis. In the early activation group, impedance reached a steady level by the 2nd postoperative week, and the hearing perception ability significantly improved by the 4th postoperative week. This comparative study illustrated sequential impedance data during early activation (24hours) and conventional activation (4weeks) after CI surgery. There were no major complications in either group, and the safety of early activation with respect to impedance changes, postoperative residual hearing preservation and speech perception scores were non-inferior to that of the conventional group. Therefore, in this study, we established the feasibility of early activation 24hours after cochlear implantation.

Sustained-Release Triamcinolone Acetonide Hydrogels Reduce Hearing Threshold Shifts in a Model for Cochlear Implantation with Hearing Preservation

Introduction: In recent years, the preservation of residual hearing has become a major factor in patients undergoing cochlear implantation (CI). In studies attempting to pharmaceutically improve hearing preservation rates, glucocorticoids (GCs) applied perioperatively in many institutions have emerged as a promising treatment regimen. Although dexamethasone is most commonly used and has been applied successfully by various research groups, recently pharmacological properties have been reported to be relatively unsuitable for topical delivery to the inner ear. Consequently other glucocorticoids merit further evaluation. The aim of this study was therefore to evaluate the otoprotective effects of the topical application of a sustained-release triamcinolone acetonide (TAAC) hydrogel in CI with hearing preservation. Methods: Normal-hearing pigmented guinea pigs were randomized into a group receiving a single dose of a 6% TAAC poloxamer 407 hydrogel, a group receiving a 30% TAAC hydrogel and a control group. All hydrogel applications were performed 1 day prior to CI. After a cochleostomy was drilled, a specifically designed silicone electrode was inserted into the scala tympani for 5 mm. Frequency-specific compound action potentials of the auditory nerve (0.5–32 kHz) were measured pre- and directly postoperatively as well as on days 3, 7, 14, 21, and 28. Finally, temporal bones were harvested for histological evaluation. Results: Application of the TAAC hydrogels resulted in significantly reduced hearing threshold shifts in low, middle and high frequencies and improved spiral ganglion cell survival in the second turn of the cochlea. Outer hair cell numbers in the basal and second turn of the cochlea were slightly reduced after TAAC application. Conclusion: In summary, we were able to demonstrate functional benefits of a single preoperative application of a TAAC hydrogel in a guinea pig model for CI, which persisted until the end of the observational period, that is, 28 days after surgery.

Biomarkers in Vestibular Schwannoma-Associated Hearing Loss.

Vestibular schwannomas (VSs) are benign tumors composed of differentiated neoplastic Schwann cells. They can be classified into two groups: sporadic VS and those associated with neurofibromatosis type 2 (NF2). VSs usually grow slowly, initially causing unilateral sensorineural hearing loss (HL) and tinnitus. These tumors cause HL both due to compression of the auditory nerve or the labyrinthine artery and due to the secretion of different substances potentially toxic to the inner ear or the cochlear nerve. As more and more patients are diagnosed and need to be managed, we are more than ever in need of searching for biomarkers associated with these tumors. Owing to an unknown toxic substance generated by the tumor, HL in VS may be linked to a high protein amount of perilymph. Previous studies have identified perilymph proteins correlated with tumor-associated HL, including μ-Crystallin (CRYM), low density lipoprotein receptor-related protein 2 (LRP2), immunoglobulin (Ig) γ-4 chain C region, Ig κ-chain C region, complement C3, and immunoglobulin heavy constant γ 3. Besides, the presence of specific subtypes of heat shock protein 70 has been suggested to be associated with preservation of residual hearing. It has been recently demonstrated that chemokine receptor-4 (CXCR4) is overexpressed in sporadic VS as well as in NF2 tumors and that hearing disability and CXCR4 expression may be correlated. Further, the genetic profile of VS and its relationship with poor hearing has also been studied, including DNA methylation, deregulated genes, growth factors, and NF2 gene mutations. The knowledge of biomarkers associated with VS would be of significant value to maximize outcomes of hearing preservation in these patients.

Preservation of Vestibular Function and Residual Hearing After Round Window Cochlear Implantation.

To examine the possible correlation between the loss of short-term residual hearing and vestibular function after cochlear implantation (CI). Retrospective patient review. Academic tertiary referral center. One hundred twenty patients with normal vestibular function (VF) in the caloric testing and residual hearing (RH) at the frequencies 250, 500, and 1000 Hz on the surgery side between 2008 and 2016 were included in the study. Primary CI on the first side via round window with a conventional full-length electrode. Changes of RH and VF 7 weeks after surgery were analyzed. Preservation of RH was defined as measurable postoperative thresholds at the frequencies 250, 500, and 1000 Hz in the pure-tone audiogram. Preservation of the VF after CI was assessed both by an absolute and relative threshold in the caloric testing. Seven weeks after implantation, the preservation of RH was achieved in 52 (43.3 %) patients and the preservation of VF in 95 (79.2 %) patients on the operated side. There was no significant statistical correlation between these two parameters. The loss of RH was more than twice as frequent as the loss of VF. However, no statistical correlation between the failure of the two inner ear functions was found. The exact causes are still unknown, but our data could give an indication that there may be different underlying pathomechanisms.

Intracochlear Pressure Changes After Cochlea Implant Electrode Pullback-Reduction of Intracochlear Trauma.

ObjectiveDifferent aspects should be considered to achieve an atraumatic insertion of cochlear implant electrode arrays as an important surgical goal. Intracochlear pressure changes are known to influence the preservation of residual hearing. By using the intraoperative “pullback technique,” an electrode position closer to the modiolus can be achieved than without the pullback. The aim of the present study was therefore to investigate to what extent the pullback technique can influence intracochlear pressure changes.MethodsInsertions of cochlear implant electrodes were performed in an artificial cochlear model with two different perimodiolar arrays. Intracochlear pressure changes were recorded with a micro‐optical pressure sensor positioned in the apical part of the cochlear. After complete insertion of the electrode array, a so‐called pullback of the electrode was performed.ResultsStatistically significant pressure differences were measured if the electrode array was wet (ie, moisturized) during the pullback. Relative pressure changes in electrodes with smaller total volume are lower than pressure changes in larger electrodes.ConclusionThe preservation of residual hearing and, thus, the resulting postoperative audiological outcome has a major impact on the quality of life of the patients and has become of utmost importance. Intracochlear pressure changes during the pullback manoeuver are small in absolute terms, but can even be still reduced statistically significantly by a moistening the electrode before insertion. Using the pullback technique in cases with residual hearing does not affect the probability of preservation of residual hearing but could lead to a better audiological outcome.Level of EvidenceNA

Assessment of cochlear trauma and telemetry measures after cochlear implantation: A comparative study between Nucleus® CI512 and CI532 electrode arrays.

The aim of this study was to compare the new Cochlear™ Nucleus® Profile with Slim Modiolar Electrode (CI532, Cochlear Ltd., Sidney, Australia) with the previous Contour Advance® (CI512) implant through postoperative residual hearing (RH) threshold shift and telemetry measurements as indirect measures of cochlear trauma. We compared 21 patients implanted with the CI532 and 20 patients implanted with the CI512, matching the 2 groups for age and for hearing loss etiology. All subjects received audiological pure tone average (PTA) calculation pre- and postimplant. Electrode impedance was measured, followed by AutoNRT® to measure and evaluate the Neural Response Telemetry (NRT®) thresholds. Telemetry recordings were made intraoperatively, one month after surgery and one month after activation. The NRT-Ratio was calculated to evaluate full scala tympani (ST) insertion. The results showed a higher number of patients with preserved measurable hearing with the CI532 (10/15; P>0.05) compared to the CI512 (5/14; P<0.05). A significant difference in post-operative low frequency PTA was observed between the two groups. There were no significant differences for telemetry measurements and NRTRatio evaluation of full ST insertion (CI512: 81%; CI532: 95%). A significantly higher number of patients who preserved measurable hearing with the CI532, and a significantly higher post-operative low frequency PTA threshold compared with the CI512 confirmed better RH preservation and lower apical cochlear damage with the CI532. There was a high number of full ST insertions for both electrode arrays. Future studies should investigate the audiological effect of implantation in patients with higher levels of RH, correlating the results with the scalar position, to assess any lesser trauma of the CI532.

Round Window Insertion in Veria Technique of Cochlear Implantation: An Essential Modification.

Cochlear implants have been done using various surgical approaches. The classical posterior tympanotomy approach has been practiced by majority of surgeons worldwide. An alternative approach is the transcanal Veria approach. This is non mastoidectomy approach where the electrode is threaded via a transcanal tunnel into the cochleostomy site. Majority of "Veria" surgeons are inserting the cochlear electrodes via a cochleostomy. This article focuses on round window insertion of cochlear electrode which has been proven to be a "softer "technique of electrode insertions and finds its role in preservation of residual hearing. Out of 115 cochlear implants done at AIIMS Patna between May 2014-May 2018, using the Veria approach, 52 patients have now been done using the round window insertion. Veria approach is a non-mastoidectomy technique where a special perforator is used to drill a trans canal tunnel which lodges the cochlear electrodes. All kind of implants were used and round window insertion was possible with different kind of electrodes. Out of 52 implants, 24 were MEDEL Sonata with straight electrode and flex soft electrode, 21 were Advanced Bionics Precurved 1J electrode, 2 were (CI 24 REST) Cochlear devices standard straight array and 5 were Neurelec standard straight array devices. Insertion was uneventful in all the cases and intra op telemetry results were satisfactory post insertion. Round window insertion has now become routine for cochlear implants especially in cases where we have to preserve residual hearing. Veria approach earlier was considered to be only a "cochleostomy" approach but our successful insertion via the round window using the Veria technique is a landmark modification and alleviates any such limitation which was associated with this technique before.

Intraoperative Intracochlear Electrocochleography and Residual Hearing Preservation Outcomes When Using Two Types of Slim Electrode Arrays in Cochlear Implantation.

To report residual hearing preservation outcomes in patients with low frequency hearing, after cochlear implant (CI) electrode insertion with two types of electrode arrays: one straight and other perimodiolar, when using intraoperative intracochlear electrocochleography (ECochG) during (CI) electrode insertion. Prospective, randomized study. Tertiary referral otology center. Fifteen patients ranging from 33 to 54 years old (mean 51.19). They had been diagnosed with a bilateral, profound sensorineural hearing loss and treated with a unilateral cochlear implant: eight of them with the CI532 and seven of them with the CI522 (Cochlear Ltd, Sydney, Australia). Pure-tone audiometry was performed preoperatively and at 1 and 6 months postoperatively. Interoperatively, intracochlear ECochG was performed using the apical-most electrode. The amplitude of the first harmonic was plotted and monitored in real time by the audiologist-surgeon team during their CI electrode insertion. The different ECoch patterns of the insertion track were recorded and analyzed. In 12 cases ECochG responses were successfully recorded. In three cases no ECochG responses could be recorded with no residual hearing observed postoperatively in two of them. With respect to the first harmonic amplitude changes, we found: four cases with an overall increase in amplitude measured from the beginning of insertion until completion, all of them showed residual hearing (<15 dB HL) at 6 months postoperation. Three cases with an increasing amplitude at the beginning of insertion, with a decrease in amplitude as insertion progressed to completion, in two cases dropping of residual hearing (15-30 dB HL) were observed after 6 months postoperation and, in one case, complete residual hearing was observed at 6 months postoperatively. And finally five cases presented amplitudes at the start of insertion with modifications of amplitude during the insertion dynamic, with increasing and descending in amplitude range during the whole insertion, two of them showed residual hearing at 6 months postoperation and three cases a drop of residual hearing (15-30 dB HL) was observed after 6 months postoperation. No statistical differences between CI532 and CI522 electrodes were found. Data of the ECochG responses are also presented (p value ≥ 0.05). ECochG is a useful tool to evaluate the residual hearing in CI patients with straight and perimodiolar cochlear implant. More studies are needed to fully understand the relationship between ECochG and the presence of residual hearing, cochlear trauma, and functional outcomes.

Exploration of factors influencing the preservation of residual hearing following cochlear implantation.

BackgroundIncreasing access to cochlear implants within the resource-constrained South African context calls for careful investigation of all factors that might influence benefit from this technological advancement.ObjectiveThe aim of this study was to investigate preservation of hearing following cochlear implant surgery and whether a relationship existed between the post-operative hearing findings and certain factors.MethodsWithin a quantitative paradigm, a retrospective data review design was adopted where a sample consisting of audiological records from 60 observations and surgical records from two cochlear implant units in South Africa was investigated. These records were selected using purposive sampling and consisted of records from participants ranging from 6 to 59 years. Comparative analysis of unaided audiological test results was pre- and post-operatively performed, where all paitents were implanted with cochlear devices. Factors documented to have a possible influence on post-operative outcomes were examined in an attempt to establish relationships that may exist. Findings were analysed by means of both inferential and descriptive statistics.ResultsThe findings indicated 92% success rate in preservation of residual hearing. There was a direct correlation between surgical techniques, as well as cochlear implant type and the successful hearing findings, in the absence of surgical complications. Other factors explored did not have any negative effect on the hearing findings.ConclusionThe study findings suggest improved surgical outcomes with enhanced surgical techniques and advanced technology, with a clear negative impact of intraoperative complications on the outcomes.

Preservation of Residual Hearing After Cochlear Implant Surgery With Deep Insertion Electrode Arrays.

To evaluate the hearing preservation (HP) in cochlear implant (CI) recipients who did not fulfill the criteria for electric acoustic stimulation (EAS). Prospective study SETTING:: Tertiary academic hospital. Adults undergoing CI with deep insertion electrode arrays who had measurable residual hearing (RH) before surgery. Demographic data, surgical technique, pure-tone average, and radiological findings were evaluated. Pre- and postoperative pure-tone audiometry. A preservation study was therefore performed for the whole range of frequencies (THP), and for low frequencies (LFHP). From the total 25 patients who underwent the surgical procedure, 6 of them (26.08%) did not retain any RH and 17 of them (73.91%) had some degree of HP. A clear association was observed between the use of the atraumatic technique (AT) and the percentage of some degree of HP. In patients who underwent the AT, LFHP was 72.79% and THP was 70.40%. In patients who did not undergo the technique, LFHP was 31.48% (p: 0.003) and THP was 23.50% (p: 0.002). LFHP was complete or partial (more than 25% of initial RH) in 92.3% of patients who underwent AT and in 50% of those who did not. Radiological findings showed that complete insertion is not associated with poorer HP. If the appropriate technique is used, preservation of RH is feasible after cochlear implant surgery with deep insertion electrode arrays.

Surgical Experience and Early Outcomes With a Slim Perimodiolar Electrode.

In 2016 the Cochlear CI532 received FDA approval and has since been the primary full-length electrode from this manufacturer implanted at our center. Our experience to date including surgical technique and early patient outcomes are reviewed here. Since 2016, this array was used as our standard full length Cochlear array, including children with normal anatomy, with 237 total implantations. Surgical experience and clinical outcomes including low frequency hearing preservation and speech perception on CNC words were analyzed in those with at least 6 months follow-up implanted through June 2017 (n = 94). Speech perception scores are improving over clinical follow-up in accord with other electrode arrays. Hearing preservation is possible with a number of patients utilizing acoustic low frequency hearing in conjunction with electric stimulation from their CI. Tip fold overs were infrequent (4.6%) and always identified on intraoperative x-ray. No patients left the operating room with a tip fold over. Speech perception outcomes with the CI532 slim periomodiolar array are similar to other full length arrays with the added potential for at least short term preservation of residual acoustic hearing. There is a learning curve to its use and intraoperative x-rays are valuable to ensure optimal placement.

Considerations and Rationale for Cochlear Implant Electrode Design - Past, Present and Future.

The electrode array of a cochlear implant forms a permanent, often lifelong interface between the implanted electronics and neural structures of the cochlea. A cochlear implant is primarily prescribed to restore hearing via electrical stimulation of the auditory nerve. As with any neural stimulator intended to either deliver electrical stimulus or record a neural response, the aim is to place the electrodes in close proximity to the target neural structures. The broadening of indications and the concept of preservation of low-frequency residual hearing over the last two decades has resulted in an increased understanding of the mechanisms and implications of intracochlear trauma for both the hearing preservation surgery and electrical stimulation outcomes with cochlear implantation, as well as the influence of many biographic and audiological patient factors correlated with achieving better hearing outcomes. These two goals, the proximity to the cochlear nerve for electrical stimulation and the preservation of cochlear structures, have typically been viewed as mutually exclusive, with perimodiolar electrode arrays being preferred for the former, and lateral wall electrode arrays for the latter. The design evolution of both the lateral wall and perimodiolar electrodes is presented, considering the cochlea anatomy and continued understanding of the mechanics and dynamics of electrode insertion, along with the influence of the ongoing changes to the intracochlear environment to provide a rationale for the electrode design with the intent to provide the greatest patient benefit over their implanted lifetime.

Monitoring of the Inner Ear Function During and After Cochlear Implant Insertion Using Electrocochleography.

To preserve residual hearing during cochlear implant (CI) surgery, it is desirable to use intraoperative monitoring of inner ear function (cochlear monitoring), especially during electrode insertion. A promising method is electrocochleography (ECochG). Within this project, the relations between ongoing responses (ORs), recorded extra- and intracochlearly (EC and IC), and preservation of residual hearing were investigated. Before, during, and after insertion of hearing preservation electrodes, intraoperative ECochG recordings were performed EC using a cotton wick electrode and after insertion also IC using the CI electrode (MED-EL) and a research software tool. The stimulation was delivered acoustically using low frequency tone bursts. The recordings were conducted in 10 adult CI recipients. The amplitudes of IC ORs were detected to be larger than EC ORs. Intraoperative EC thresholds correlated highly to preoperative audiometric thresholds at 1000 Hz, IC thresholds highly at 250 Hz and 500 Hz. The correlations of both intraoperative ECochG recordings to postoperative pure tone thresholds were low. When measured postoperatively at the same appointments, IC OR thresholds correlated highly to audiometric pure tone thresholds. For all patients, it was possible to record ORs during or directly after electrode insertion. Consequently, we conclude that we did not observe any cases with severe IC trauma. Delayed hearing loss could not be predicted with our method. Nevertheless, intraoperative ECochG recordings are a promising tool to gain further insight into mechanisms impacting residual hearing. Postoperatively recorded IC OR thresholds seem to be a reliable tool for frequency specific hearing threshold estimation.

The Effects of Gusher-Related Intracochlear Pressure Changes on Hearing Preservation in Cochlear Implantation: A Comparative Series

Aim: To investigate and compare residual hearing preservation between patients based on the presence of intraoperative gusher. Methodology: We retrospectively compared 2 cohorts of cochlear implant recipients significantly distinguished by whether or not they experienced gusher intraoperatively. Patients underwent cochlear implantation using 24-mm lateral wall electrode arrays as well pharmacologic steroid protection. All patients were assessed by a hearing implant MDT. Hearing preservation rates and speech perception outcomes were assessed at 1, 6, 12, 24, 36, 48, and 60 months. Results: The patients with no gusher demonstrated complete hearing preservation. The patients with gusher demonstrated significant postoperative reduction of hearing thresholds, which declined at a significantly higher pace during follow-up. All patients demonstrated significantly better speech performance after cochlear implantation. Conclusion: The present study suggests that intraoperative gusher is associated with a significant drop in residual hearing, both immediately and over time, which may be related to the large change in intracochlear pressure intraoperatively.