Robotic-Assisted Electrode Array Insertion Improves Rates of Hearing Preservation

Robotic-assisted electrode array (EA) insertion is a promising technique that may enhance preservation of residual acoustic hearing after cochlear implant (CI) surgery. The purpose of this study is to evaluate the impact of robotic-assisted EA insertion on rates of delayed-onset hearing loss (DOHL). Sixty (Advanced Bionics [AB]: 30, MED-EL: 30) adult patients underwent CI surgery with manual EA insertion and 29 (AB: 13, MED-EL: 16) with robotic-assisted insertion using the iotaSOFT system. The primary outcome variable was longitudinal change in low frequency pure-tone average (LFPTA). DOHL was defined as a decrease in LFPTA of > 10 dB compared to previous best postoperative LFPTA. Twenty-two (37%) out of the 60 subjects in the manual cohort and two (7%) out of the 29 subjects in the robotic-assisted cohort had DOHL over the entire length of available follow-up (p = 0.002, Fisher's exact test, two-tailed). When evaluating DOHL results for subjects who had LFPTA data at 12 months (±4 weeks) post initial activation, 11 (29%) out of the 38 (AB: 15, MED-EL: 23) subjects in the manual cohort and zero (0%) out of the 18 (AB: 8, MED-EL: 10) subjects in the robotic-assisted cohort had DOHL (p = 0.011, Fisher's exact test, two-tailed). The number needed to treat was 4. Robotic-assisted EA insertion is associated with a clinically meaningful reduction in rates of DOHL. Preservation of residual acoustic hearing is a critical goal in CI surgery, and robotic-assisted EA insertion contributes towards achieving this goal.

Background: As an advanced surgical technique to reduce trauma to the inner ear, robot-assisted electrode array (EA) insertion has been applied in adult cochlear implantation (CI) and was approved as a safe surgical procedure that could result in better outcomes. As the mastoid and temporal bones are generally smaller in children, which would increase the difficulty for robot-assisted manipulation, the clinical application of these systems for CI in children has not been reported. Given that the pediatric candidate is the main population, we aim to investigate the safety and reliability of robot-assisted techniques in pediatric cochlear implantation.Methods: Retrospective cohort study at a referral center in Shanghai including all patients of simultaneous bilateral CI with robotic assistance on one side (RobOtol® system, Collin ORL, Bagneux, France), and manual insertion on the other (same brand of EA and CI in both side), from December 2019 to June 2020. The surgical outcomes, radiological measurements (EA positioning, EA insertion depth, mastoidectomy size), and audiological outcomes (Behavior pure-tone audiometry) were evaluated.Results: Five infants (17.8 ± 13.5 months, ranging from 10 to 42 months) and an adult (39 years old) were enrolled in this study. Both perimodiolar and lateral wall EAs were included. The robot-assisted EA insertion was successfully performed in all cases, although the surgical zone in infants was about half the size in adults, and no difference was observed in mastoidectomy size between robot-assisted and manual insertion sides (p = 0.219). The insertion depths of EA with two techniques were similar (P = 0.583). The robot-assisted technique showed no scalar deviation, but scalar deviation occurred for one manually inserted pre-curved EA (16%). Early auditory performance was similar to both techniques.Conclusion: Robot-assisted technique for EA insertion is approved to be used safely and reliably in children, which is possible and potential for better scalar positioning and might improve long-term auditory outcome. Standard mastoidectomy size was enough for robot-assisted technique. This first study marks the arrival of the era of robotic CI for all ages.

The objective was to evaluate the effect of cochlear implant (CI) insertion technique on electrode insertion forces and intracochlear trauma. We hypothesize that robotics-assisted insertions will reduce insertion forces and intracochlear trauma compared with manual insertions. Variability in CI outcomes exists across patients, implant centers, surgeons, and electrode types. While surgical techniques that reduce electrode insertion trauma are well established, insertion trauma remains one contributing factor to variability in CI outcomes. Previous work demonstrates that micromechanically controlled insertion tools reduce both maximum insertion forces and insertion variability compared with manual insertions. CI electrode insertions were performed either by hand (n = 12) or utilizing a robotics-assisted tool (n = 12) in fresh frozen, human cadaveric cochleae using electrodes from four different CI manufacturers. Electrodes array insertion forces were additionally evaluated in benchtop cochlea models. Following cadaveric insertions, samples were imaged via high resolution x-ray microscopy to evaluate electrode position and intracochlear trauma events based on a modified Eshraghi scale. Electrode array insertions performed by robotics-assisted system showed significantly lower insertion forces and variability. Manual electrode array insertions had a significantly higher overall trauma score of 3.1 ± 2.0 compared with 0.9 ± 1.0 for robotics-assisted insertions. Robotics-assisted insertions had higher rate of basilar membrane elevations while manual insertions showed higher rates of severe trauma events. The robotic-assisted insertion system reduced trauma events associated with CI electrode insertions in cadaveric cochleae compared with manual insertions. Surgical devices which help to precisely and more consistently insert electrodes may improve CI outcomes and hearing preservation.

A cochlear implant (CI) is a hearing device introduced in the 1980s for profoundly deaf subjects who gained little or no benefit from powerful hearing aids. This device comprises an electrode array inserted in the cochlea, connected to an internal receiver, and an externally worn speech processor. The CI transforms acoustic signals into electrical currents which directly stimulate the auditory nerve. Since the early 1990s, cochlear implantation in children has been developing rapidly. Although it is still difficult to predict how a child will perform with a cochlear implant, the success of cochlear implantation can no longer be denied. In this paper, some recent papers and reports, and the results of the various Nijmegen cochlear implant studies, are reviewed. Issues about selection, examinations, surgery and the outcome are discussed. Overall, our results were comparable with those of other authors. It can be concluded that cochlear implantation is an effective treatment for postlingually deaf as well as prelingually (congenital or acquired) deaf children with profound bilateral sensorineural deafness.

Objective: To investigate the effect of insertion technique and electrode array type on the insertion force of electrode array, and to provide a basis for further optimizing electrode design and facilitating mini-invasive electrode insertion. Methods: Three types of electrode array from Nurotron (Standard Electrode, Slim-medium Electrode, Slim-long Electrode) were studied. from July 2019 to December 2019. These electrode arrays were inserted into the phantom models of the cochlea, manually or robot-assisted(medium speed and low speed). The real-time force during electrode array insertion was recorded by ATI Nano 17 Ti sensors and was analyzed by accessory software. Origin 2020b software was used for statistical processing. Results: The insertion force of all electrode arrays progressively increased with the insertion depth. With the manual technique, the peak force of slim-medium electrode insertion was significantly smaller than that of the standard electrode insertion((71.0±16.6) mN vs (140.9±52.7) mN, Z=3.683, P<0.01), and the peak force of the slim-long electrode insertion was between the peak force of standard electrode and slim-medium electrode(P>0.05). No difference was found in the force variation of insertion among the three electrodes(P>0.05). With medium-speed and low-speed robotic assistance, the peak force characteristics of three electrodes were similar to those with the manual technique, but the force variation of standard electrode insertion ((83.9±9.7) mN/s) at medium speed was significantly larger than that of the slim-long electrode insertion ((69.2±4.0)mN/s), and the force variation of the standard electrode insertion at low speed was significantly greater than the other two electrodes. For the same electrode, robot-assisted insertion presented significantly lower peak force and force variation than manual insertion for each type of electrode array. But there was no difference in the peak force and force variation between two-speed levels of robot assistance (P>0.05). Conclusions: The insertion force of the electrode array will be lower when a slim electrode array or robot technique is applied. Long electrode array might make manual insertion difficult or less precise. Robot assistance has advantage on force control during electrode array insertion.

Intracochlear electrocochleography (ECochG) in cochlear implant (CI) recipients is a potential tool for monitoring cochlear function during and after electrode array (EA) insertion. However, mechanisms underlying ECochG amplitude variations along the cochlear duct, and their significance for hearing preservation (HP), remain unclear. Therefore, a longitudinal study was conducted to monitor maximum ECochG amplitude and its tonotopic location from EA insertion to 1 yr postimplantation. It was hypothesized that changes in maximum amplitude (>30%) and/or shifts in its location (>1 octave) across timepoints reflect intracochlear alterations associated with residual hearing changes. ECochG recordings were obtained in 80 adult CI recipients with measurable residual hearing. For Contour Advance (CI612) and Slim Straight (CI622) arrays (Cochlear Ltd.), recordings were taken from every second intracochlear electrode. For HiFocus SlimJ and MidScala arrays (Advanced Bionics LLC), recordings were obtained from all electrodes. Measurements were conducted at four timepoints: (1) intraoperatively, during EA insertion (Intraop1), (2) intraoperatively, immediately after full insertion (Intraop2), (3) approximately 7 wk after surgery (Postop1), and (4) approximately 1 yr after surgery (Postop2). 500 Hz tone bursts were used for acoustic stimulation and the magnitude of the difference between responses to alternating-polarity stimuli was analyzed. Tonotopic electrode locations were determined from postoperative cone beam computed tomography scans. Pure-tone audiograms were obtained preoperatively and at approximately 7 wk and 1 yr postoperatively. HP was determined using the HEARRING group formula. Maximum ECochG amplitudes remained largely stable intraoperatively, with no significant difference between Intraop1 and Intraop2 in complete-case analysis (n = 44). In contrast, a significant decrease in maximum amplitude was observed between Intraop2 and Postop1 (p < 0.001). Participants with >30% amplitude reduction between the 2 intraoperative recordings (Intraop1 versus Intraop2) did not differ significantly in HP from those with stable amplitudes. However, those showing a >30% reduction in the early postoperative period (Intraop2 versus Postop1) showed significantly lower HP (p = 0.028). Nonapical peak location during Intraop1 occurred in 41% of the cases, although tonotopic location of the maximum peak during insertion monitoring (Intraop1) did not show a relationship with HP. Tonotopic location shifts of the maximum amplitude (>1 octave) were observed in a small subset of cases between consecutive recordings up to Postop2. However, peak location changes (apical, basal, stable) were not associated with significant differences in HP. Our results suggest that nonapical peak patterns are not necessarily markers of insertion trauma and may instead reflect variability in cochlear integrity (e.g., dead regions). Peak location during insertion monitoring was not associated with postoperative HP, and both maximum amplitude and tonotopic peak location remained stable intraoperatively. In contrast, early postoperative reductions in ECochG amplitude were common and associated with HP, highlighting the need to investigate strategies to minimize early intracochlear reactions. Overall, the study demonstrates the value of ECochG for monitoring intracochlear processes over time.

Introduction: Recent investigations focused on the optimization of atraumatic cochlear implant surgery have highlighted the relevance of the electrode array (EA) insertion trajectory. This is particularly studied in the context of minimally-invasive “keyhole” and robotic-assisted approaches, e.g. to avoid injuring structures inside and outside the cochlea. However, little is known about the natural, manual movements and trajectory followed during the insertion process. The present work illustrates the orientation changes within the trajectory a surgeon follows during insertions of EAs into a human cadaveric cochlea. Methods: An EA insertion tool equipped with a gyroscope was developed in our laboratory. During the insertion trials, the gyroscope captures the tool’s spatial orientation. A human head specimen and a single EA were used to perform insertions into a cochlea. A cochlear implant surgeon performed all insertion trials. The recorded orientations were compared to the initial orientation upon cochlea entry to assess the surgeon’s range of motion by calculating the angle between orientation vectors. Results: Fifteen EA insertions were performed with a median maximal deviation from the initial orientation of 7.2° (5.3 -11.1°) across trials. The largest orientation changes were seen towards the last half of each insertion trial. A negative relationship between degree of axis change and number of insertion trial was observed (r = -0.5). Conclusion: Manual EA insertions into a cadaveric cochlea revealed an insertion trajectory with maximum orientation changes of approximately &lt; 10° degrees. The observed trend on decreasing range of motion with increasing number of insertion trials may be attributed to surgeon’s familiarization with the insertion trajectory for this specific specimen but other contributing factors (e.g. EA softening) need to be further elucidated with several EAs. Future evaluations can help determine if this orientation change is influenced by surgeon expertise.

Despite successful preservation of low-frequency hearing in patients undergoing cochlear implantation (CI) with shorter electrode lengths, there is still controversy regarding which electrodes maximize hearing preservation (HP). The thin straight electrode array (TSEA) has been suggested as a full cochlear coverage option for HP. However, very little is known regarding its HP potential. A retrospective review was performed at two tertiary academic medical centers, reviewing the electronic records for 52 patients (mean, 58.2 yr; range, 11-85 yr) implanted with the Cochlear Nucleus CI422 Slim Straight (Centennial, CO, USA) electrode array, referred to herein as the thin straight electrode array or TSEA. All patients had a preoperative low-frequency pure-tone average (LFPTA) of 85 dB HL or less. Hearing thresholds were measured at initial activation (t1) and 6 months after activation (t2). HP was assessed by evaluating functional HP using a cutoff level of 85 dB HL PTA. At t1, 54% of the subjects had functional hearing; 33% of these subjects had an LFPTA between 71 and 85 dB HL, and 17% had an LFPTA between 56 and 70 dB HL. At t2, 47% of the patients had functional hearing, with 31% having an LFPTA between 71 and 85 dB HL. Preliminary research suggests that the TSEA has the potential to preserve functional hearing in 54% of patients at t1. However, 22% (n = 6) of the patients who had functional hearing at t1 (n = 28) lost their hearing between t1 and t2. Further studies are needed to evaluate factors that influence HP with the TSEA electrode and determine the speech perception benefits using electric and acoustic hearing over electric alone.

To analyze the relationship of electrode array (EA) type and position on hearing preservation longevity following cochlear implantation. Retrospective chart review. Tertiary referral center. Adult cochlear implant recipients between 2013 and 2019 with hearing preserved postoperatively and postoperative CT scans. CT scan analysis of EA position. Stepwise regression to determine influence of EA position, EA type, and patient demographics on postoperative low frequency hearing. Low frequency pure tone average (LFPTA), LFPTA shift, angular insertion depth, base insertion depth, scalar position, mean perimodiolar distance. Of 792 cochlear implant recipients, 121 had preoperative LFPTA <80 dB HL with 60 of the 121 (49.6%) implanted with straight, 32 (26.4%) with precurved, styletted, and 29 (24.0%) implanted precurved, nonstyletted EA. Mean follow up was 28.6 months (range 1-103). There was no statistically significant difference in activation, 6- and 12-month, and last follow-up LFPTA (125, 250, and 500 Hz) shift based on EA type (straight p = 0.302, precurved, styletted p = 0.52, precurved, nonstyletted p = 0.77). Preoperative LFPTA and age of implantation were significant predictors of LFPTA shift at activation, accounting for 30.8% of variance ( F [2, 113] = 26.603, p < 0.0001). LFPTA shift at activation, scalar position, and base insertion depth were significant predictors of variability and accounted for 39.1% of variance in LFPTA shift at 6 months ( F [3, 87] = 20.269, p < 0.0001). Only LFPTA shift at 12 months was found to be a significant predictor of LFPTA shift at last follow up, accounting for 41.0% of variance ( F [1, 48] = 32.653, p < 0.0001). Patients had excellent long-term residual hearing regardless of EA type. Age, preoperative acoustic hearing, and base insertion depth may predict short term preservation, while 12-month outcomes significantly predicted long-term hearing preservation.

It is unknown how electrode array position in the cochlea influences long-term hearing preservation for cochlear implant (CI) recipients with preserved low-frequency hearing after surgery. The aim of this study was to evaluate the influence of electrode insertion depth relative to regions of post-operative acoustic hearing and hearing preservation ≥ 1 year after CI activation. A retrospective review of adult CI recipients of a straight electrode array from 2017 to 2022 with functional acoustic hearing preservation (≤ 80 dB HL at 250 Hz) at device activation was performed. Proximity was quantified as the angular insertion depth (AID) of the most apical contact relative to the region of preserved functional acoustic hearing. Positive values indicate placement within the functional acoustic region; negative values indicate placement basal to the functional acoustic region. Low-frequency pure tone average (LFPTA) was queried from the preoperative, device activation, and annual post-activation visits. Stepwise regression analyzed whether proximity, AID, age, biological sex, and pre-operative LFPTA were significant predictors for change in unaided hearing thresholds. One hundred and six CI recipients met inclusion criteria. AID ranged from 330° to 717° (mean 513°, SD 79°). Proximity values ranged from -183° to 442° (mean 35°, SD 110°). None of the reviewed independent variables, including proximity, significantly predicted unaided hearing threshold shifts at the 1-year or the ≥ 3-year visits (p ≥ 0.128). Deeper insertion depths and electrode array placement within the functional acoustic hearing region did not predispose CI recipients to delayed loss of residual hearing.

Cochlear implants (CI) have revolutionized the treatment of patients with severe to profound sensory hearing loss by providing a method of bypassing normal hearing to directly stimulate the auditory nerve. A further advance in the field has been the introduction of "hearing preservation" surgery, whereby the CI electrode array (EA) is carefully inserted to spare damage to the delicate anatomy and function of the cochlea. Preserving residual function of the inner ear allows patients to receive maximal benefit from the CI and to combine CI electric stimulation with acoustic hearing, offering improved postoperative speech, hearing, and quality of life outcomes. However, under the current paradigm of implant surgery, where EAs are inserted by hand, the cochlea cannot be reliably spared from damage. Robotics-assisted EA insertion is an emerging technology that may overcome fundamental human kinetic limitations that prevent consistency in achieving steady and slow EA insertion. This review begins by describing the relationship between EA insertion speed and generation of intracochlear forces and pressures. The various mechanisms by which these intracochlear forces can damage the cochlea and lead to worsened postoperative outcomes are discussed. The constraints of manual insertion technique are compared to robotics-assisted methods, followed by an overview of the current and future state of robotics-assisted EA insertion.

To describe the first cochlear array insertions using a robot-assisted technique, with different types of straight or precurved electrode arrays, compared with arrays manually inserted into the cochlea. Retrospective review. Tertiary otologic center. Twenty cochlear implantations in the robot-assisted group and 40 in the manually inserted group. Cochlear implantations using a robot-assisted technique (RobOtol) with straight (eight Cochlear CI522/622, and eight Advanced Bionics Hifocus Slim J) or precurved (four Advanced Bionics Hifocus Mid-Scala) matched to manual cochlear implantations. Three-dimensional reconstruction images of the basilar membrane and the electrode array were obtained from pre- and postimplantation computed tomography. Rate and localization of scalar translocations. For straight electrode arrays, scalar translocations occurred in 19% (3/16) of the robot-assisted group and 31% (10/32) of the manually inserted group. Considering the number of translocated electrodes, this was lower in the robot-assisted group (7%) than in the manually inserted group (16%) (p < 0.0001, χ2 test). For precurved electrode arrays, scalar translocations occurred in 50% (2/4) of the robot-assisted group and 38% (3/8) of the manually inserted group. This study showed a safe and reliable insertion of different electrode array types with a robot-assisted technique, with a less traumatic robotic insertion of straight electrode arrays when compared with manual insertion.

Goals of cochlear implantation have shifted from complete insertion of the cochlear electrode array towards low traumatic insertion with minimally invasive techniques. The aim of this study was first to evaluate, in a guinea pig model of cochlear implantation, the effect of a motorized insertion technique on hearing preservation. The second goal was to study a new gel formulation containing dexamethasone phosphate loaded in liposomes (DEX-P). Guinea pigs had a unilateral cochlear implantation with either a manual technique (n=12), or a motorized technique (n=15), with a 0.4mm diameter and 4mm long array trough a cochleostomy. At the end of the procedure, hyaluronic acid gel containing drug-free liposomes, or liposomes loaded with DEX-P, was injected into the bulla. Auditory brainstem responses thresholds were recorded before surgery and day 2 and 7 after surgery. All the animals had increased auditory brainstem responses thresholds after the cochlear implantation. Implanted animals with the motorized insertion tool experienced a partial hearing recovery at day 7 but not in those implanted with the manual insertion procedure (p<0.001). In the manually implanted animals, a partial recovery was observed when DEX-P contained in liposomal gel was locally administrated (p<0.0001). Finally, no additive effect with the motorized insertion was noticed. The deleterious effect of manual insertion, during cochlear implantation, can be prevented with local DEX-P administration in the bulla at day 7. The use of a motorized tool performed more atraumatic electrode array insertion for postoperative hearing.

The prevalence of hearing loss (presbycusis) is 35–50% in those aged 65 years or older; consequently, hearing assistant devices become more and more important [1]. Cochlear implantation (CI) is believed to be one of the most important technologic achievements to have occurred in the 20th century for the treatment of profound hearing loss, continually improved since its approval by the International Consensus Conference in 1995 [2]. Recent advances in biology and medicine have introduced new concepts in the study of CI and its related science. Many changes have taken place including improvements in hardware technique, expansion of candidacy, and clinical outcome. The cornucopia of all novel technologies and approaches serves as important blessings for hearing-impaired people. This special issue is to exhibit the diversity and advances in recent progress that contributes to the different subspecialties of CI and its related science. It has motivated intense investigation on developing stem cell therapy as a new therapeutic strategy, for example, through the transplantation of stem cells into the inner ear for hearing restoration [3]. H.-C. Chen et al. investigated the long-term effect of hypoxia on stemness and the bioenergetic status of cochlear stem/progenitor cells cultured at different low oxygen tensions. Recent advances in hearing preservation studies have introduced new concepts and technologies to be applied in CI [4, 5]. To develop skills sufficient for hearing preservation CI surgery, surgeons need to perform several electrode insertion trials in ex vivo temporal bones, thereby consuming relatively expensive electrode carriers. J.-P. Kobler et al. design low-cost dummy electrodes that are cheap alternatives for surgical training and for in vitro, ex vivo, and in vivo research purposes. P. T. Bhatti et al. also present an effective method for tailoring the flexibility of a commercial thin-film polymer electrode array for intracochlear electrical stimulation. The benefits of residual hearing preservation in cochlear implant recipients have promoted the development of atraumatic surgeries. The surgeons prefer round window approach to preserve low frequency hearing [6]. The incidence and severity of intracochlear trauma were not influenced by electrode array insertion through the anterosuperior or anteroinferior quadrant of the round window membrane. A bone-anchored hearing aid (BAHA) or bone-anchored hearing device is a type of hearing aid based on bone conduction [7, 8]. They are more expensive than conventional hearing aids, and their placement involves invasive surgery which carries a risk of complications [8]. The use of a wide fixture implant and the nonskin thinning surgical technique indicates that the combination is a safe procedure with good stability and no abutment losses in M. Hultcrantz's research. The diagnostic value of high resolution computed tomography (HRCT) and magnetic resonance imaging (MRI) before CI is very high [9]. M. Busi et al. suggest that CI is a safe and effective procedure even for patients with brain and inner ear abnormalities at neuroimaging investigations with HRCT and MRI. Nonetheless, common cavity and stenosis of the internal auditory canal (less than 2 mm) are negative prognostic factors even if brain lesions are absent. Limiting the assessment of CI performance strictly to speech perception improvement does not properly evaluate the characteristics of the prosthesis-neural interface. Electrophysiological testing should provide a more accurate proxy of the interaction between the electrodes of the CI and the auditory neurons. F. Venail et al. modeled the activation of auditory neurons in CI recipients. Distribution of Neural Responses Telemetry residues could provide a proxy of auditory neurons functioning in implanted cochleas. The outcome of CI varies over a wide range among pediatric patients [10]. M. Park et al. assess the correlation between performance intelligence and postoperative CI outcome. Performance intelligence, especially social cognition, was strongly related to the postoperative CI outcome. Therefore, auditory rehabilitation, including social rehabilitation, should maximize the postoperative CI outcomes. According to H.-S. Hsieh et al., implanted children tend to write stories that are shorter, worse organized, and without a plot, while formulating morphosyntactically correct sentences. Special attention is required on their auditory and language performances, which could be the underlying causes of the written language problems. In this special issue, we collected both basic and clinical original research articles stimulating the continuing efforts to understand the cochlear implant technology, the development of strategies to treat deafness, and the evaluation of outcomes. It is our wish to increase interest in CI and its related science research with this special issue and further accelerate the development of novel therapies for hearing impairment.

To examine the results of hearing preservation in cochlear implantation surgery to identify surgical technical factors, electrode array design factors, and steroid usage, which predicts greater low-frequency hearing preservation. A thorough search of Medline and Pubmed of English studies from January 1, 1995, to January 1, 2013, was performed using the key words "electric and acoustic hearing" or "hybrid cochlear implant" or "EAS cochlear implant" or "partial deafness cochlear implant" or "bimodal hearing cochlear implant" or "hearing preservation cochlear implant." The meta-analysis was conducted according to the PRISMA statement. Only articles in English were included. Studies were included if hearing preservation was the primary end point. A final number of 24 studies met the inclusion criteria. Patient populations were analyzed as intention to treat. Data were extracted from raw audiograms where possible. Data were excluded if not all explanatory variables were present or if variable values were ambiguous. The weighted least-squares regression method was used to determine the predictive power of each explanatory variable across all studies. In this meta-analysis, the following are associated with better hearing preservation: cochleostomy over the round window approach, posterior tympanotomy over the suprameatal approach, a slow electrode array insertion technique over insertion of less than 30 seconds, a soft tissue cochleostomy seal over a fibrin glue only seal and the use of postoperative systemic steroids. Longer electrode arrays, topical steroid use, and lubricant use for electrode array insertion did not give an advantage.