Hearing Preservation in Cochlear Implant Surgery: A Meta-Analysis

Hearing Preservation Techniques in Pediatric Cochlear Implantation: A Systematic Review and Meta-Analysis

OBJECTIVE

Preserving residual hearing following cochlear implantation (CI) improves outcomes and allows patients to use electrical and acoustic stimulation. Hearing preservation and minimizing intracochlear trauma during implantation have become key areas of research and device development in recent years. This meta-analysis evaluated whether patient characteristics or surgical methodology impact hearing preservation postpediatric CI.

DATA SOURCES

A systematic search was performed in PubMed, Web of Science, Cochrane Library, PsycINFO, and Cumulative Index to Nursing and Allied Health Literature.

REVIEW METHODS

Per Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, the databases were searched for English studies published before August 2024. Search terms were "hearing preservation," "cochlear implant," "audiometry," and "pediatric" and their synonyms. The main outcome was the percentage of ears with hearing preservation after CI. Patient, audiological, device, and surgical technique characteristics were extracted. The impact of these factors on hearing preservation was evaluated.

RESULTS

Twenty-four studies were included, with a total of 567 patients. Males comprised 50% of patients (95% confidence interval [CI]: 45%-55%). Mean patient age was 9.68 years (95% CI: 8.27-11.09 years). Mean pure tone averages (PTAs) before and after CI were 60.48 dB (95% CI: 48.81-72.14 dB) and 70.95 dB (95% CI: 56.75-85.15 dB), respectively. Hearing preservation was reported in 78% of ears (95% CI: 71%-85%), with high heterogeneity between studies (I2 = 79.96%). Gender, surgical approach, electrode array, topical corticosteroids, and initial PTA were not significantly associated with hearing preservation.

CONCLUSIONS

Hearing preservation following pediatric CI occurred in 78% of ears. In this meta-analysis, no patient characteristic or surgical technique was significantly associated with hearing preservation.

Outcomes of attempted hearing preservation after cochlear implantation (HPCI): a prognostic factor (PF) systematic review of the literature

OBJECTIVE

There's a need to highlight prognostic factors (PFs) determining hearing preservation in cochlear implantation (HPCI), as currently there is large variability in outcomes. Given the potential benefits of HPCI, it is important to understand the factors influencing this variation. We apply a novel methodology to outline and assess the accuracy of prognostic factors reporting for HPCI.

DATA SOURCES

A preferred reporting item for systematic reviews and meta-analyses compliant systematic review, searches applied to Medline, EMBASE, and Cochrane.

STUDY SELECTION

The CHARMS-PF tool assessed the strength of PF study designs.

DATA EXTRACTION

The QUIPS tool assessed for risk of bias.

DATA SYNTHESIS AND RESULTS

Ninety-two papers were suitable for data extraction. The domain's preoperative hearing loss, size of the round window opening, round window accessibility, surgical insertion speed and route (Round window or cochleostomy), electrode length and type were identifiable exploratory PFs for HPCI. Overall, the study's heterogeneity and risk of bias precluded reporting by forest plots and meta-analysis.

CONCLUSIONS

Most exploratory PF studies for HPCI are hindered by the risk of bias. This systematic review identifies potential independent PFs which should be measured, and adjusted for, in future confirmatory studies using a multivariate analysis. This would determine the independent prognostic effects associated with HPCI while facilitating prognostic model development and the predict individual HPCI.

Hearing preservation in paediatric cochlear implantation with the Nucleus Slim Straight Electrode - our experience

OBJECTIVE

to evaluate the levels of successful hearing preservation and preservation of functional hearing following cochlear implantation (HPCI) in children using the Cochlear Nucleus® Slim Straight Electrode (SSE).

DESIGN

retrospective case note review of paediatric HPCI cases in our CI centre from 2013 to 2023. Inclusion criteria were attempted hearing preservation surgery, SSE used for implantation, pre-operative hearing thresholds ≤80dBHL at 250 Hz, CI before 18 years of age. Patients were excluded if no postoperative unaided PTA was obtained (poor attendance). Primairy outcome was hearing preservation using the HEARRING group formula; secondary outcome was residual functional hearing (≤80dBHL at 250 Hz/<90dB LFPTA).

STUDY SAMPLE

56 patients with 94 CI's were included for review.

RESULTS

Hearing preservation was achieved in 94.7% (89/94) of ears and complete preservation in 72% (68/94)). Average functional hearing was preserved in 89% using both criteria for preservation. Long-term follow up data was available for 36 ears (average 35.2 months), demonstrating 88.9% (32/36) complete preservation.

CONCLUSION

We have reliably achieved and maintained a high success rate of HPCI using the SSE in our paediatric population. The field of HPCI would benefit from unification of outcome reporting in order to optimise the evidence available to professionals, patients and their carers.

The Effect of Cochlear Implant Electrode Array Type on Hearing Preservation

ObjectiveTo compare hearing preservation outcomes between lateral wall and perimodiolar electrode arrays for cochlear implant patients.Study DesignRetrospective cohort study.SettingA large Western Australian cochlear implant clinicMethodsA total of 311 adult cochlear implant recipients (321 ears) implanted between 2017 and 2022 were included. Of these, 174 presented with postlingual hearing loss and preoperative functional low-frequency hearing. The change in low-frequency pure-tone average was assessed as the difference between preoperative to 3-, 6-, and 12-months postoperative measurements. Data were analyzed through linear mixed-effects modeling and one-way ANOVA.ResultsPreoperative low-frequency, pure-tone average was higher for those implanted with perimodiolar compared with lateral wall electrodes (P < .05). The linear mixed-effects model revealed that change in low-frequency pure-tone average at all postoperative timepoints was similar between lateral wall and perimodiolar electrodes (P > .05).ConclusionThere were similar changes in residual postoperative hearing between all electrode types when controlling for preoperative low-frequency hearing and age implanted. These data suggest that newer, thinner perimodiolar and lateral wall electrodes could be considered for individuals with greater levels of preoperative low-frequency hearing.

Hearing preservation in pediatric cochlear implantation

PURPOSE OF REVIEW

Pediatric cochlear implantation has evolved considerably over the past three decades to include more patients at earlier ages with greater degrees of residual hearing. As an extension, a significant focus of research over the past decade has surrounded preservation of existing acoustic hearing.

RECENT FINDINGS

Multiple studies published within the last 5 years demonstrate aidable acoustic hearing preservation in 60-90% of pediatric patients, with 40-60% experiencing complete hearing preservation following cochlear implantation. Durability of preserved hearing varies among patients, with some patients losing residual hearing within 1 year of surgery whereas others maintain acoustic hearing through at least 5 years of follow-up. Speech outcomes appear superior among patients with preserved acoustic hearing, particularly in the presence of background noise. Several recent studies suggest a music appreciation advantage in children with preserved acoustic hearing following cochlear implantation.

SUMMARY

Hearing preservation rates during cochlear implantation in children matches, if not often exceeds, hearing preservation rates observed among adults. Preservation of acoustic hearing during cochlear implantation confers multiple advantages for the pediatric population. Beyond improved speech understanding and music appreciation, minimizing intracochlear trauma and resultant scarring facilitates potential future regenerative treatments or revision surgery.

Cochlear Implantation in a Patient with Intractable Tinnitus: A Case Report of an Endoscope-Assisted Approach

Preservation of residual hearing and vestibular function is a crucial factor in cochlear implantation (CI), especially in patients with residual low-frequency hearing thresholds. We report a case of a patient who underwent unilateral endoscope-assisted CI with a challenging surgical view following rigorous posterior tympanotomy. A 53-year-old male presented with left-sided intractable tinnitus due to sudden sensorineural hearing loss that had occurred 10 years prior. Due to the abnormal location of the round window (RW), which was far more posterior and inferior than usual and impeded insertion of the electrode using the conventional RW approach, endoscope-assisted CI was performed. Pure-tone audiometry at 3 months after CI revealed satisfactory hearing thresholds. Furthermore, there was alleviation of the left-sided tinnitus, which was indicated by a marked decrease in both the subjective visual analog scale loudness and Tinnitus Handicap Inventory scores. With proper indications, we strongly recommend applying the RW approach with endoscopic assistance over conventional bony cochleostomy for the preservation of low-frequency hearing thresholds in cases where RW visualization is insufficient following posterior tympanotomy.

Molded Round Window Niche Implant as a Dexamethasone Delivery System in a Cochlear Implant-Trauma Animal Model

BACKGROUND

Preserving residual hearing after cochlear implant (CI) surgery remains a crucial challenge. The application of dexamethasone (DEX) has been proven to positively affect residual hearing. To deliver DEX in a localized and controlled way, a round window niche implant (RNI), allowing drug diffusion via the round window membrane into the cochlea, may be used. To prove this concept, an RNI for guinea pigs as a CI-trauma model was manufactured by molding and tested for its drug release in vitro and biological effects in vivo.

METHODS

The RNIs were molded using silicone containing 10% DEX. Release was analyzed over time using high-performance liquid chromatography (HPLC). Fourteen adult guinea pigs were randomly assigned to two groups (CI or CI + RNI group). All animals received a unilateral CI electrode insertion trauma followed by CI insertion. The CI + RNI group was additionally implanted with an RNI containing 10% DEX. Animals were followed up for 4 weeks. Acoustically evoked auditory brainstem response and impedance measurement, micro-computed tomography (µCT) imaging, and histology were performed for evaluation.

RESULTS

DEX was released for more than 250 days in vitro, with an initial burst followed by a slower release over time. Comparing the hearing threshold shift (from day 0 to day 28) of the CI and CI + RNI groups, significant differences were observed at 32 and 40 kHz. The impedance shift at basal contacts was lower in the CI + RNI group than in the CI group. Moreover, the fibrosis in the lower basal turn was reduced in the CI + RNI group in contrast to the CI group.

CONCLUSIONS

The RNI containing 10% DEX has anti-inflammatory potential concerning fibrosis inhibition and has beneficial effects on hearing preservation at high frequencies.

Evaluating Wideband Tympanometry Absorbance Changes in Cochlear Implant Recipients: Mechanical Insights and Influencing Parameters

Background: Cochlear implant (CI) electrode insertion can change the mechanical state of the ear whereby wideband tympanometry absorbance (WBTA) may serve as a sensitive tool to monitor these mechanical changes of the peripheral auditory pathway after CI surgery. In WBTA, the amount of acoustic energy reflected by the tympanic membrane is assessed over a wide frequency range from 226 Hz to 8000 Hz. The objective of this study was to monitor changes in WBTA in CI recipients before and after surgery. Methods: Following otoscopy, WBTA measurements were conducted twice in both ears of 38 standard CI recipients before and in the range of 4 to 15 weeks after CI implantation. Changes from pre- to postoperative absorbance patterns were compared for the implanted as well as the contralateral control ear for six different frequencies (500 Hz, 750 Hz, 1000 Hz, 2000 Hz, 3000 Hz, 4000 Hz). Furthermore, the influence of the time point of the measurement, surgical access, electrode type, sex and side of the implantation were assessed for the implanted and the control ear in a linear mixed model. Results: A significant decrease in WBTA could be observed in the implanted ear when compared with the contralateral control ear for 750 Hz (p < 0.01) and 1000 Hz (p < 0.05). The typical two-peak pattern of WBTA measurements was seen in both ears preoperatively but changed to a one-peak pattern in the newly implanted ear. The linear mixed model showed that not only the cochlear implantation in general but also the insertion through the round window compared to the cochleostomy leads to a decreased absorbance at 750 and 1000 Hz. Conclusions: With WBTA, we were able to detect mechanical changes of the acoustical pathway after CI surgery. The implantation of a CI led to decreased absorbance in the lower frequencies and the two-peak pattern was shifted to a one-peak pattern. The result of the linear mixed model indicates that WBTA can detect mechanical changes due to cochlear implantation not only in the middle ear but also in the inner ear.

Impedance and Functional Outcomes in Robotic-Assisted or Manual Cochlear Implantation: A Comparative Study

INTRODUCTION

Preservation of residual hearing, mainly the low frequencies, is the current main objective of cochlear implantation. New electrode arrays and the development of minimally invasive surgery have allowed electroacoustic stimulation. Over the past several years, robotic-assisted cochlear implant surgery aimed to improve the insertion process while respecting inner ear structures. However, the introduction of a foreign body inside the cochlea can lead to the development of fibrous tissue around the electrode array, or even induce osteogenesis. These histological changes disrupt the parameters of the cochlear implant, resulting in elevated impedance. In addition, long-term auditory performance can be affected, with a deterioration in word comprehension. We evaluated the potential impact of RobOtol® on impedance changes over time, leading to potentially positive functional outcomes.

METHODS

Cochlear implant surgery with a round window approach was performed under general anesthesia. Fifteen Med-El Flex24 electrode arrays were inserted manually and 24 using RobOtol®. All subjects underwent pure-tone audiometry tests before the surgery and at regular intervals up to 1 year after the surgery. Based on the pure-tone average at the low frequencies from 250 to 1,000 Hz, we divided the patients according to the degree of auditory preservation (full preservation ≤15 dB, partial preservation 15 dB-30 dB, significant loss >30 dB). These different groups were compared in terms of impedance changes and auditory performance, specifically word recognition score.

RESULTS

We found proportionally fewer patients who experienced significant low-frequency hearing loss after robotic insertion (53.33% in the manual group compared to 41.67% in the robot-assisted insertion group). Impedance changes at the apex of the electrode array, especially at the first electrode (p = 0.04), after robotic surgery, with less overall variability, a continuous decreasing trend without secondary elevation, and lower values in cases of complete residual hearing preservation (for the three first electrodes: p = 0.017, p = 0.04, p = 0.045). The speech intelligibility amelioration over time showed favorable evolution in patients with complete residual hearing preservation regardless of the insertion method. However, in the absence of auditory preservation, the positive evolution continued more than 6 months after robotic surgery but stagnated after manual insertion (difference at 1 year, p = 0.038; median auditory capacity index 83% vs. 57%).

CONCLUSION

Atraumatic electrode array insertion with consistent, slow speed and the assistance of RobOtol® minimizes disturbances in the delicate neurosensory structures of the inner ear and leads to better auditory performance.

Vestibular function and hearing preservation in children following a minimally invasive cochlear implantation

PURPOSE

This retrospective cohort study aimed to investigate the effect of minimally invasive cochlear implantation (CI) on the vestibular function (VF) and residual hearing (RH) as well as their relationship in pediatric recipients before and after surgery.

METHODS

Twenty-four pediatric patients with preoperative low frequency residual hearing (LFRH) (250 or 500 Hz ≤ 80 dB HL) who underwent minimally invasive CI were enrolled. Pure-tone thresholds, the cervical/ocular vestibular-evoked myogenic potential (cVEMP/oVEMP), and video head impulse test (vHIT) were all evaluated in the 24 pediatric patients with preoperative normal VF before and at 1 and 12 months after surgery. The relationship between changes in hearing and VF was analyzed preoperatively and at 1 and 12 months postoperatively.

RESULTS

There were no significant differences on VF preservation and hearing preservation (HP) at both 1 and 12 months post-CI (p > 0.05). At 1 month post-CI, the correlations of the variations in vestibulo-ocular reflex (VOR) gains of horizontal semicircular canal (HSC) and posterior semicircular canal (PSC) and the shift in 250 Hz threshold were negatively correlated (r = - 0.41, p = 0.04 and r = - 0.43, p = 0.04, respectively). At 12 months post-CI, the shift in 250 Hz threshold negatively correlated to the variations in VOR gain of superior semicircular canal (SSC) (r = - 0.43, p = 0.04); the HP positively correlated to the variation in oVEMP-amplitude ratio (AR) (r = 0.41, p = 0.04).

CONCLUSION

Our study confirmed that there were partial correlations between VF preservation and HP both in the short- and long-terms after atraumatic CI surgery, especially with the 250 Hz threshold. Regarding the variation of PSC function, the correlation with hearing status was variable with time after atraumatic CI surgery. Minimally invasive techniques for HP are successful and effective for the preservation of VF in pediatric patients both in the short- and long-terms.

The Benefits of Cochlear Implantation for Adults: A Systematic Umbrella Review

OBJECTIVES

The uptake of cochlear implants among adults who could benefit (based on pure-tone audiometry) in developed countries is estimated to be less than 10%. Concerns about potential surgical complications, fear of losing residual hearing, and limited awareness about the benefits of this intervention contribute to the low adoption rate. To enhance quality of life and improve the uptake of cochlear implants, it is essential to have a clear understanding of their benefits.

DESIGN

This umbrella review aims to summarize the major benefits of cochlear implant usage in adults, by synthesizing findings from published review articles. A comprehensive search of databases including MEDLINE, EMBASE, PsycINFO, and Google Scholar, was conducted. The search was limited to English-language review articles published between 1990 and 2022, focusing on cochlear implant outcomes in at least 5 adults (aged ≥18 years). Two independent reviewers screened titles, abstracts, and full-text articles, and conducted a quality assessment using the Joanna Briggs Checklist for Systematic Reviews and Research Syntheses.

RESULTS

Forty-two articles were included in this review. There were 15 systematic reviews with meta-analysis, 25 systematic reviews without meta-analysis, and 2 systematic scoping reviews. All 42 articles underwent quality assessment using the Joanna Briggs Institute Checklist for Systematic Reviews and Research Syntheses, of which 40% (n = 17) satisfied 9 out of 11 quality criteria. This umbrella review shows that cochlear implants are associated with improvements in speech perception and recognition as well as improved quality of life and cognition. These benefits are observed in a significant proportion of adults undergoing the procedure, highlighting its effectiveness as a viable intervention for individuals with severe to profound hearing loss.

CONCLUSIONS

The potential benefits of cochlear implantation appear to outweigh the risks and complications associated with the procedure. It is recommended that adults with severe to profound hearing loss in particular, engage in informed discussions with healthcare professionals to consider cochlear implantation as a viable treatment option.

Correlation of Scalar Cochlear Volume and Hearing Preservation in Cochlear Implant Recipients with Residual Hearing

OBJECTIVE

Preservation of residual hearing is one of the main goals in cochlear implantation. There are many factors that can influence hearing preservation after cochlear implantation. The purpose of the present study was to develop an algorithm for validated preoperative cochlear volume analysis and to elucidate the role of cochlear volume in preservation of residual hearing preservation after atraumatic cochlear implantation.

STUDY DESIGN

Retrospective analysis.

SETTING

Tertiary referral center.

PATIENTS

A total of 166 cochlear implant recipients were analyzed. All patients were implanted with either a MED-EL (Innsbruck, Austria) FLEXSOFT (n = 3), FLEX28 (n = 72), FLEX26 (n = 1), FLEX24 (n = 41), FLEX20 (n = 38), or FLEX16 (n = 11, custom made device) electrode array through a round window approach. Main outcome measures: Cochlear volume as assessed after manual segmentation of cochlear cross-sections in cone beam computed tomography, and preservation of residual hearing 6 months after implantation were analyzed. The association between residual hearing preservation and cochlear volume was then assessed statistically.

RESULTS

Rapid and valid cochlear volume analysis was possible using the individual cross-sections and a newly developed and validated algorithm. Cochlear volume had the tendency to be larger in patients with hearing preservation than in those with hearing loss. Significant correlations with hearing preservation could be observed for the basal width and length of the basal turn.

CONCLUSIONS

Preservation of residual hearing after cochlear implantation may depend on cochlear volume but appears to be influenced more strongly by other cochlear dimensions.

Intraoperative Measurement of Insertion Speed in Cochlear Implant Surgery: A Preliminary Experience with Cochlear SmartNav

OBJECTIVES

The objectives were to present the real-time estimated values of cochlear implant (CI) electrode insertion speed (IS) during intraoperative sessions using the Cochlear Nucleus SmartNav System to assess whether this measure affected CI outcomes and to determine whether real-time feedback assists expert surgeons in achieving slow insertion.

METHODS

The IS was measured in 52 consecutive patients (65 implanted ears) using the CI632 electrode. The IS values were analyzed in relation to procedure repetition over time, NRT ratio, and CI audiological outcomes.

RESULTS

The average IS was 0.64 mm/s (SD = 0.24); minimum and maximum values were 0.23 and 1.24 mm/s, respectively. The IS significantly decreased with each array insertion by the operator (p = 0.006), and the mean decreased by 24% between the first and last third of procedures; however, this reduction fell within the error range of SmartNav for IS (+/-0.48 mm/s). No correlation was found between IS and the NRT ratio (p = 0.51), pure-tone audiometry (PTA) at CI activation (p = 0.506), and PTA (p = 0.94) or word recognition score (p = 0.231) at last evaluation.

CONCLUSIONS

The estimated IS reported by SmartNav did not result in a clinically significant reduction in insertion speed or an improvement in CI hearing outcomes. Real-time feedback of IS could potentially be used for training, but its effectiveness requires confirmation through additional studies and more accurate tools. Implementation of IS assessment in clinical practice will enable comparisons between measurement techniques and between manual and robot-assisted insertions. This will help define the optimal IS range to achieve better cochlear implant (CI) outcomes.

Benefits and risks related to cochlear implantation for children with residual hearing: a systematic review

OBJECTIVE

This study aimed to synthesise information concerning the potential benefits and risks related to cochlear implants (CIs) versus hearing aids (HAs) in children with residual hearing.

DESIGN

A systematic review of articles published from January 2003 to January 2019 was conducted.

STUDY SAMPLE

Our review included studies that compared the benefits and risks of CIs versus HAs in children (≤18 years old) with residual hearing. A total of 3265 citations were identified; 8 studies met inclusion criteria.

RESULTS

Children with CIs showed significantly better speech perception scores post-CI than pre-CI. There was limited evidence related to improvement in everyday auditory performance, and the results showed non-significant improvement in speech intelligibility. One study on social-emotional functioning suggested benefits from CIs. In four studies, 37.2% (16/43) of children showed loss of residual hearing and 14.0% (8/57) had discontinued or limited use of their device.

CONCLUSIONS

Children with CIs showed improvement in speech perception outcomes compared to those with HAs. However, due to the limited number of studies and information to guide decision-making related to other areas of development, it will be important to conduct further research of both benefits and risks of CIs in this specific population to facilitate decision-making.

Human Histology after Structure Preservation Cochlear Implantation via Round Window Insertion

OBJECTIVES

Current surgical techniques aim to preserve intracochlear structures during cochlear implant (CI) insertion to maintain residual cochlear function. The optimal technique to minimize damage, however, is still under debate. The aim of this study is to histologically compare insertional trauma and intracochlear tissue formation in humans with a CI implanted via different insertion techniques.

METHODS

One recent temporal bone from a donor who underwent implantation of a full-length CI (576°) via round window (RW) insertion was compared with nine cases implanted via cochleostomy (CO) or extended round window (ERW) approach. Insertional trauma was assessed on H&E-stained histological sections. 3D reconstructions were generated and virtually re-sectioned to measure intracochlear volumes of fibrosis and neo-ossification.

RESULTS

The RW insertion case showed electrode translocation via the spiral ligament. 2/9 CO/ERW cases showed no insertional trauma. The total volume of the cochlea occupied by fibro-osseous tissue was 10.8% in the RW case compared with a mean of 30.6% (range 8.7%-44.8%, N = 9) in the CO/ERW cases. The difference in tissue formation in the basal 5 mm of scala tympani, however, was even more pronounced when the RW case (12.3%) was compared with the cases with a CO/ERW approach (mean of 93.8%, range 81% to 100%, N = 9).

CONCLUSIONS

Full-length CI insertions via the RW can be minimally traumatic at the cochlear base without inducing extensive fibro-osseous tissue formation locally. The current study further supports the hypothesis that drilling of the cochleostomy with damage to the endosteum incites a local tissue reaction.

LEVEL OF EVIDENCE

4: Case-control study Laryngoscope, 134:945-953, 2024.

The impact of the size and angle of the cochlear basal turn on translocation of a pre-curved mid-scala cochlear implant electrode

Scalar translocation is a severe form of intra-cochlear trauma during cochlear implant (CI) electrode insertion. This study explored the hypothesis that the dimensions of the cochlear basal turn and orientation of its inferior segment relative to surgically relevant anatomical structures influence the scalar translocation rates of a pre-curved CI electrode. In a cohort of 40 patients implanted with the Advanced Bionics Mid-Scala electrode array, the scalar translocation group (40%) had a significantly smaller mean distance A of the cochlear basal turn (p < 0.001) and wider horizontal angle between the inferior segment of the cochlear basal turn and the mastoid facial nerve (p = 0.040). A logistic regression model incorporating distance A (p = 0.003) and horizontal facial nerve angle (p = 0.017) explained 44.0-59.9% of the variance in scalar translocation and correctly classified 82.5% of cases. Every 1mm decrease in distance A was associated with a 99.2% increase in odds of translocation [95% confidence interval 80.3%, 100%], whilst every 1-degree increase in the horizontal facial nerve angle was associated with an 18.1% increase in odds of translocation [95% CI 3.0%, 35.5%]. The study findings provide an evidence-based argument for the development of a navigation system for optimal angulation of electrode insertion during CI surgery to reduce intra-cochlear trauma.

Comparative study of vestibular function preservation in manual versus robotic-assisted cochlear implantation

OBJECTIVE

To compare vestibular outcomes in cochlear implant (CI) surgery, between robotic-assisted insertion of the electrodes versus manual insertion.

METHODS

We performed a monocentric retrospective study. From March 2021, the robotic system RobOtol© was used for all CI cases. We compared this robotic-assisted insertion group with a manual insertion group of patients who received a CI between July 2020 and March 2021. Primary objective was vestibular outcome. We used objective vestibular function tests: caloric testing, Vestibular Evoked Myogenic Potential (VEMP), and Video Head Impulse Test (VHIT). Secondary objectives were postoperative complications including patient-reported postoperative vertigo.

RESULTS

We found no statistically significant difference between the two groups in terms of caloric testing, VEMP or VHIT outcomes. In patient-reported outcomes, there was significantly more vertigo in the manual insertion group compared with robotic-assisted insertion.

CONCLUSION

It is hypothesized that a non-traumatic insertion would cause less vestibular dysfunction postoperatively. Larger prospective studies are required to determine whether robotic-assisted CI insertion has a significant impact on vestibular outcomes in CI surgery.

Stable long-term outcomes after cochlear implantation in subjects with TMPRSS3 associated hearing loss: a retrospective multicentre study

BACKGROUND

The spiral ganglion hypothesis suggests that pathogenic variants in genes preferentially expressed in the spiral ganglion nerves (SGN), may lead to poor cochlear implant (CI) performance. It was long thought that TMPRSS3 was particularly expressed in the SGNs. However, this is not in line with recent reviews evaluating CI performance in subjects with TMPRSS3-associated sensorineural hearing loss (SNHL) reporting overall beneficial outcomes. These outcomes are, however, based on variable follow-up times of, in general, 1 year or less. Therefore, we aimed to 1. evaluate long-term outcomes after CI implantation of speech recognition in quiet in subjects with TMPRSS3-associated SNHL, and 2. test the spiral ganglion hypothesis using the TMPRSS3-group.

METHODS

This retrospective, multicentre study evaluated long-term CI performance in a Dutch population with TMPRSS3-associated SNHL. The phoneme scores at 70 dB with CI in the TMPRSS3-group were compared to a control group of fully genotyped cochlear implant users with post-lingual SNHL without genes affecting the SGN, or severe anatomical inner ear malformations. CI-recipients with a phoneme score ≤ 70% at least 1-year post-implantation were considered poor performers and were evaluated in more detail.

RESULTS

The TMPRSS3 group consisted of 29 subjects (N = 33 ears), and the control group of 62 subjects (N = 67 ears). For the TMPRSS3-group, we found an average phoneme score of 89% after 5 years, which remained stable up to 10 years post-implantation. At both 5 and 10-year follow-up, no difference was found in speech recognition in quiet between both groups (p = 0.830 and p = 0.987, respectively). Despite these overall adequate CI outcomes, six CI recipients had a phoneme score of ≤ 70% and were considered poor performers. The latter was observed in subjects with residual hearing post-implantation or older age at implantation.

CONCLUSION

Subjects with TMPRSS3-associated SNHL have adequate and stable long-term outcomes after cochlear implantation, equal to the performance of genotyped patient with affected genes not expressed in the SGN. These findings are not in line with the spiral ganglion hypothesis. However, more recent studies showed that TMPRSS3 is mainly expressed in the hair cells with only limited SGN expression. Therefore, we cannot confirm nor refute the spiral ganglion hypothesis.

Can an individual with low frequency hearing in the candidate ear benefit from a cochlear implant even if they have normal hearing in the other ear?

PURPOSE

To determine hearing preservation and subjective benefit after cochlear implant (CI) surgery in patients with low frequency hearing in the ear to be implanted (i.e., they have partial deafness, PD) and close to normal hearing in the other.

METHODS

There were two study groups. The test group was made up of 12 adult patients (mean age 43.4 years; SD 13.6) with normal hearing or mild hearing loss in one ear, and with PD in the ear to be implanted. The reference group consisted of 12 adult patients (mean age 44.5 years; SD 14.1) who had PD in both ears and who underwent unilateral implantation in their worse ear. Hearing preservation was assessed 1 and 14 months after CI surgery using the Skarzynski Hearing Preservation Classification System. The APHAB questionnaire was used to evaluate the benefit from the CI.

RESULTS

The differences in HP% between the groups were not significant: mean hearing preservation (HP%) in the test group was 82% one month after CI surgery and 75% some 14 months after implantation; corresponding results in the reference group were 71% and 69%. However, on the APHAB background noise subscale, the benefit in the test group was significantly larger than in the reference group.

CONCLUSION

To a large extent it was possible to preserve low-frequency hearing in the implanted ear. This means that individuals with low frequency hearing in the implanted ear (partial deafness) and with normal hearing in the other generally received more benefits from cochlear implantation than did patients with partial deafness in both ears. We conclude that residual low frequency hearing in the ear to be implanted should not be considered a contraindication for a CI in a patient with single-sided deafness.

A Five-Decade Text Mining Analysis of Cochlear Implant Research: Where We Started and Where We Are Heading

Background and Objectives: Since its invention in the 1970s, the cochlear implant (CI) has been substantially developed. We aimed to assess the trends in the published literature to characterize CI. Materials and Methods: We queried PubMed for all CI-related entries published during 1970-2022. The following data were extracted: year of publication, publishing journal, title, keywords, and abstract text. Search terms belonged to the patient's age group, etiology for hearing loss, indications for CI, and surgical methodological advancement. Annual trends of publications were plotted. The slopes of publication trends were calculated by fitting regression lines to the yearly number of publications. Results: Overall, 19,428 CIs articles were identified. Pediatric-related CI was the most dominant sub-population among the age groups, with the highest rate and slope during the years (slope 5.2 ± 0.3, p < 0.001), while elderly-related CIs had significantly fewer publications. Entries concerning hearing preservation showed the sharpest rise among the methods, from no entries in 1980 to 46 entries in 2021 (slope 1.7 ± 0.2, p < 0.001). Entries concerning robotic surgery emerged in 2000, with a sharp increase in recent years (slope 0.5 ± 0.1, p < 0.001). Drug-eluting electrodes and CI under local-anesthesia have been reported only in the past five years, with a gradual rise. Conclusions: Publications regarding CI among pediatrics outnumbered all other indications, supporting the rising, pivotal role of CI in the rehabilitation of children with sensorineural hearing loss. Hearing-preservation publications have recently rapidly risen, identified as the primary trend of the current era, followed by a sharp rise of robotic surgery that is evolving and could define the next revolution.

Min-Max Similarity: A Contrastive Semi-Supervised Deep Learning Network for Surgical Tools Segmentation

A common problem with segmentation of medical images using neural networks is the difficulty to obtain a significant number of pixel-level annotated data for training. To address this issue, we proposed a semi-supervised segmentation network based on contrastive learning. In contrast to the previous state-of-the-art, we introduce Min-Max Similarity (MMS), a contrastive learning form of dual-view training by employing classifiers and projectors to build all-negative, and positive and negative feature pairs, respectively, to formulate the learning as solving a MMS problem. The all-negative pairs are used to supervise the networks learning from different views and to capture general features, and the consistency of unlabeled predictions is measured by pixel-wise contrastive loss between positive and negative pairs. To quantitatively and qualitatively evaluate our proposed method, we test it on four public endoscopy surgical tool segmentation datasets and one cochlear implant surgery dataset, which we manually annotated. Results indicate that our proposed method consistently outperforms state-of-the-art semi-supervised and fully supervised segmentation algorithms. And our semi-supervised segmentation algorithm can successfully recognize unknown surgical tools and provide good predictions. Also, our MMS approach could achieve inference speeds of about 40 frames per second (fps) and is suitable to deal with the real-time video segmentation.

One-Year Hearing Preservation and Speech Outcomes Comparing Slim Modiolar and Lateral Wall Arrays

OBJECTIVE

Compare postoperative speech outcomes in hearing preservation (HP) cochlear implantation (CI) patients with a low-frequency pure-tone average (LFPTA) ≤ 60 dB using 2 electrode array designs.

STUDY DESIGN

Retrospective cohort study.

SETTING

Large academic cochlear implant referral center.

METHODS

We reviewed adult HP CI cases using either the slim modiolar electrode (SME) (CI 532/CI 632) or th slim lateral wall electrode (SLWE) (CI 624). One-year speech outcomes and HP status were the primary outcomes.

RESULTS

A total of 132 implanted ears were analyzed (mean age 73.1 years, standard deviation [SD] 12.6), with 72% (N = 95) with CI 532/632 and 28% (N = 37) with CI 624. The mean preoperative LFPTA was 44.8 dB, SD 11.8. One-year functional HP was 27.2% (mean LFPTA shift 46.1 dB, SD 22.1) and was as follows: SME 23.9% and SLWE 36.4%, p = .168. The mean age at implantation was significantly younger only in SLWE patients with preserved hearing (66.9 vs 80.3 years, p = .008). At 6 months, speech measures were significantly better in all outcomes in HP patients with an SLWE than nonpreserved SLWE patients; this effect abated at 1 year as performance among nonpreserved SLWE patients became equivalent to the remaining cohort. Speech outcomes in SME patients were similar regardless of HP status. Age at implantation and datalogging was correlated with speech outcomes.

CONCLUSION

In this cohort of HP patients, a 1-year functional HP rate of 23.9% (SME) and 36.4% (SLWE) was observed (p = 0.168). This was initially 57.1% (SME) and 70.3% (SLWE) at activation, p = .172. Datalogging and age at implantation were correlated with postoperative speech outcomes.

Electro-vibrational stimulation results in improved speech perception in noise for cochlear implant users with bilateral residual hearing

A cochlear implant is a neuroprosthetic device that can restore speech perception for people with severe to profound hearing loss. Because of recent evolutions, a growing number of people with a cochlear implant have useful residual acoustic hearing. While combined electro-acoustic stimulation has been shown to improve speech perception for this group of people, some studies report limited adoption rates. Here, we present electro-vibrational stimulation as an alternative combined stimulation strategy that similarly targets the full cochlear reserve. This novel strategy combines the electrical stimulation by the cochlear implant with low-frequency bone conduction stimulation. In a first evaluation of electro-vibrational stimulation, speech perception in noise was assessed in 9 subjects with a CI and symmetrical residual hearing. We demonstrate a statistically significant and clinically relevant improvement for speech perception in noise of 1.9 dB signal-to-noise ratio. This effect was observed with a first prototype that provides vibrational stimulation to both ears with limited transcranial attenuation. Future integration of electro-vibrational stimulation into one single implantable device could ultimately allow cochlear implant users to benefit from their low-frequency residual hearing without the need for an additional insert earphone.

The Influence of Activities and Functional Social Support on Adult Cochlear Implant Outcomes

Objective

The objective of this study is to assess whether patient participation in specific activities and perceived social support correlate with speech perception following cochlear implantation.

Setting

Tertiary referral hospital.

Methods

Adult cochlear implantation patients implanted in their poorer hearing ear between January 2019 and December 2020 completed the Functional Social Support Questionnaire (FSSQ) and a modified version of the Victoria Lifestyle Study-Activities Lifestyle Questionnaire (VLS-ALQ). Demographics, FSSQ score, and individual activities were correlated with implanted ear and binaural AzBio scores.

Results

Twenty-three patients completed the survey and had at least 6 months of follow-up with appropriate speech perception testing. The average age at survey completion was 71.7 (SD, 9.1). Average pure-tone average in the contralateral ear was 70.1 (SD: 20) dB. The majority (N = 21, 91.3%) wore a hearing aid in the contralateral ear following cochlear implantation. Mean AzBioQuiet score improvement was 60.6% (range: 20%-99%) in the implanted ear and 42.6% (range: -2% to 67%) binaurally. Work-related social support correlated positively with improvement in the implanted ear (Pearson's R = 0.473; 95% CI, 0.075-0.741; P = 0.023). Improvement in the implanted ear correlated positively with creative writing (R = 0.542; 95% CI, 0.167-0.780; P = 0.008), attending films (R = 0.448; 95% CI, 0.044-0.726; P = 0.032), going out with friends (R = 0.423; 95% CI, 0.013-0.711; P = 0.044) listening to audiobooks (R = 0.433; 95% CI, 0.025-0.717; P = 0.039), and public speaking (R = 0.468; 95% CI, 0.069-0.738; P = 0.024). Gains in binaural performance correlated positively with watching TV news (R = 0.819; 95% CI, 0.509-0.941; P < 0.001) and negatively with eating at restaurants (R = -0.532; 95% CI, -0.829 to -0.002; P = 0.05).

Conclusions

Activities that provide intellectual stimulation and engage auditory faculties correlate with greater speech perception testing improvements in adult cochlear implantation patients.

Cochlear implant electrode impedance subcomponents as biomarker for residual hearing

Introduction and objectives

Maintaining the structural integrity of the cochlea and preserving residual hearing is crucial for patients, especially for those for whom electric acoustic stimulation is intended. Impedances could reflect trauma due to electrode array insertion and therefore could serve as a biomarker for residual hearing. The aim of this study is to evaluate the association between residual hearing and estimated impedance subcomponents in a known collective from an exploratory study.

Methods

A total of 42 patients with lateral wall electrode arrays from the same manufacturer were included in the study. For each patient, we used data from audiological measurements to compute residual hearing, impedance telemetry recordings to estimate near and far-field impedances using an approximation model, and computed tomography scans to extract anatomical information about the cochlea. We assessed the association between residual hearing and impedance subcomponent data using linear mixed-effects models.

Results

The progression of impedance subcomponents showed that far-field impedance was stable over time compared to near-field impedance. Low-frequency residual hearing demonstrated the progressive nature of hearing loss, with 48% of patients showing full or partial hearing preservation after 6 months of follow-up. Analysis revealed a statistically significant negative effect of near-field impedance on residual hearing (-3.81 dB HL per kΩ; p < 0.001). No significant effect of far-field impedance was found.

Conclusion

Our findings suggest that near-field impedance offers higher specificity for residual hearing monitoring, while far-field impedance was not significantly associated with residual hearing. These results highlight the potential of impedance subcomponents as objective biomarkers for outcome monitoring in cochlear implantation.

'Real-life' benefit of hearing preservation cochlear implantation in the paediatric population: a single-site case-control study

INTRODUCTION

Cochlear implantation with hearing preservation (HPCI) has allowed a cochlear implant (CI) electrode to be implanted while trying to preserve residual acoustic low-frequency hearing. The concept arises from the importance of this low-frequency information and the limitations of a CI in several auditory domains. The combination of electrical hearing with either preserved acoustic hearing or amplified 'natural' hearing has the potential to address these issues and enable children with HPCI to closely follow normal auditory development.The aim of this study is to evaluate the 'real-life' benefit of preserved acoustic low-frequency hearing in children with a CI, understand the benefits of preserved natural hearing in complex listening situations and so enable parents and children to make an informed choice about implantation. Ultimately, helping to ensure the maximum number of children benefit from this life-changing intervention.

METHODS AND ANALYSIS

Nineteen ears in children and young people aged 6-17 years old with 'successful' HPCI will be subjected to a test battery consisting of: (1) spatial release from masking; (2) complex pitch direction discrimination; (3) melodic identification; (4) perception of prosodic features in speech and (5) threshold equalising noise test. Subjects will be tested in the electro-acoustic stimulation (EAS)/electro-natural stimulation (ENS) and the electric-only (ES) condition, thereby acting as their own control group. Standard demographic and hearing health information will be collected. In the absence of comparable published data to power the study, sample size was determined on pragmatic grounds. Tests are exploratory and for hypothesis-generating purposes. Therefore, the standard criterion of p<0.05 will be used.

ETHICS AND DISSEMINATION

This study has been approved by the Health Research Authority and NHS Research Ethics Committee (REC) within the UK (22/EM/0017). Industry funding was secured via a competitive researcher-led grant application process. Trial results will be subject to publication according to the definition of the outcome presented in this protocol.

A new paradigm of hearing loss and preservation with cochlear implants: Learnings from fundamental studies and clinical research

In 2010 Cochlear initiated a coordinated preclinical research program to identify the factors and underlying mechanisms of acoustic hearing loss following cochlear implantation and device use. At its inception the program was structured around several major hypotheses implicated in the loss of acoustic hearing. The understanding of causes evolved over the course of the program, leading to an increased appreciation of the role of the biological response in post-implant hearing loss. A systematic approach was developed which mapped the cochlear implant journey along a timeline that considers all events in an individual's hearing history. By evaluating the available data in this context, rather than by discrete hypothesis testing, causative and associated factors may be more readily detected. This approach presents opportunities for more effective research management and may aid in identifying new prospects for intervention. Many of the outcomes of the research program apply beyond preservation of acoustic hearing to factors important to overall cochlear health and considerations for future therapies.

Acute effects of cochleostomy and electrode-array insertion on compound action potentials in normal-hearing guinea pigs

Introduction

Electrocochleography (ECochG) is increasingly used in cochlear implant (CI) surgery, in order to monitor the effect of insertion of the electrode array aiming to preserve residual hearing. However, obtained results are often difficult to interpret. Here we aim to relate changes in ECochG responses to acute trauma induced by different stages of cochlear implantation by performing ECochG at multiple time points during the procedure in normal-hearing guinea pigs.

Materials and methods

Eleven normal-hearing guinea pigs received a gold-ball electrode that was fixed in the round-window niche. ECochG recordings were performed during the four steps of cochlear implantation using the gold-ball electrode: (1) Bullostomy to expose the round window, (2) hand-drilling of 0.5-0.6 mm cochleostomy in the basal turn near the round window, (3) insertion of a short flexible electrode array, and (4) withdrawal of electrode array. Acoustical stimuli were tones varying in frequency (0.25-16 kHz) and sound level. The ECochG signal was primarily analyzed in terms of threshold, amplitude, and latency of the compound action potential (CAP). Midmodiolar sections of the implanted cochleas were analyzed in terms of trauma to hair cells, modiolar wall, osseous spiral lamina (OSL) and lateral wall.

Results

Animals were assigned to cochlear trauma categories: minimal (n = 3), moderate (n = 5), or severe (n = 3). After cochleostomy and array insertion, CAP threshold shifts increased with trauma severity. At each stage a threshold shift at high frequencies (4-16 kHz) was accompanied with a threshold shift at low frequencies (0.25-2 kHz) that was 10-20 dB smaller. Withdrawal of the array led to a further worsening of responses, which probably indicates that insertion and removal trauma affected the responses rather than the mere presence of the array. In two instances, CAP threshold shifts were considerably larger than threshold shifts of cochlear microphonics, which could be explained by neural damage due to OSL fracture. A change in amplitudes at high sound levels was strongly correlated with threshold shifts, which is relevant for clinical ECochG performed at one sound level.

Conclusion

Basal trauma caused by cochleostomy and/or array insertion should be minimized in order to preserve the low-frequency residual hearing of CI recipients.

Three-dimensional quantification of fibrosis and ossification after cochlear implantation via virtual re-sectioning: Potential implications for residual hearing

Hearing preservation may be achieved initially in the majority of patients after cochlear implantation, however, a significant proportion of these patients experience delayed hearing loss months or years later. A prior histological report in a case of delayed hearing loss suggested a potential cochlear mechanical origin of this hearing loss due to tissue fibrosis, and older case series highlight the frequent findings of post-implantation fibrosis and neoosteogenesis though without a focus on the impact on residual hearing. Here we present the largest series (N = 20) of 3-dimensionally reconstructed cochleae based on digitally scanned histologic sections from patients who were implanted during their lifetime. All patients were implanted with multichannel electrodes via a cochleostomy or an extended round window insertion. A quantified analysis of intracochlear tissue formation was carried out via virtual re-sectioning orthogonal to the cochlear spiral. Intracochlear tissue formation was present in every case. On average 33% (SD 14%) of the total cochlear volume was occupied by new tissue formation, consisting of 26% (SD 12%) fibrous and 7% (SD 6%) bony tissue. The round window was completely covered by fibro-osseous tissue in 85% of cases and was associated with an obstruction of the cochlear aqueduct in 100%. The basal part of the basilar membrane was at least partially abutted by the electrode or new tissue formation in every case, while the apical region, corresponding with a characteristic frequency of < 500 Hz, appeared normal in 89%. This quantitative analysis shows that after cochlear implantation via extended round window or cochleostomy, intracochlear fibrosis and neoossification are present in all cases at anatomical locations that could impact normal inner ear mechanics.

Differential auditory cortical development in left and right cochlear implanted children

Unilateral aural stimulation has been shown to cause massive cortical reorganization in brain with congenital deafness, particularly during the sensitive period of brain development. However, it is unclear which side of stimulation provides most advantages for auditory development. The left hemisphere dominance of speech and linguistic processing in normal hearing adult brain has led to the assumption of functional and developmental advantages of right over left implantation, but existing evidence is controversial. To test this assumption and provide evidence for clinical choice, we examined 34 prelingually deaf children with unilateral cochlear implants using near-infrared spectroscopy. While controlling for age of implantation, residual hearing, and dominant hand, cortical processing of speech showed neither developmental progress nor influence of implantation side weeks to months after implant activation. In sharp contrast, for nonspeech (music signal vs. noise) processing, left implantation showed functional advantages over right implantation that were not yet discernable using clinical, questionnaire-based outcome measures. These findings support the notion that the right hemisphere develops earlier and is better preserved from adverse environmental influences than its left counterpart. This study thus provides, to our knowledge, the first evidence for differential influences of left and right auditory peripheral stimulation on early cortical development of the human brain.

Gene therapy with a synthetic adeno-associated viral vector improves audiovestibular phenotypes in Pjvk-mutant mice

Recessive PJVK mutations that cause a deficiency of pejvakin, a protein expressed in both sensory hair cells and first-order neurons of the inner ear, are an important cause of hereditary hearing impairment. Patients with PJVK mutations garner limited benefits from cochlear implantation; thus, alternative biological therapies may be required to address this clinical difficulty. The synthetic adeno-associated viral vector Anc80L65, with its wide tropism and high transduction efficiency in various inner ear cells, may provide a solution. We delivered the PJVK transgene to the inner ear of Pjvk mutant mice using the synthetic Anc80L65 vector. We observed robust exogenous pejvakin expression in the hair cells and neurons of the cochlea and vestibular organs. Subsequent morphologic and audiologic studies demonstrated significant restoration of spiral ganglion neuron density and hair cells in the cochlea, along with partial recovery of sensorineural hearing impairment. In addition, we observed a recovery of vestibular ganglion neurons and balance function to WT levels. Our study demonstrates the utility of Anc80L65-mediated gene delivery in Pjvk mutant mice and provides insights into the potential of gene therapy for PJVK-related inner ear deficits.

The effect of the surgical approach and cochlear implant electrode on the structural integrity of the cochlea in human temporal bones

Cochlear implants (CI) restore hearing of severely hearing-impaired patients. Although this auditory prosthesis is widely considered to be very successful, structural cochlear trauma during cochlear implantation is an important problem, reductions of which could help to improve hearing outcomes and to broaden selection criteria. The surgical approach in cochlear implantation, i.e. round window (RW) or cochleostomy (CO), and type of electrode-array, perimodiolar (PM) or lateral wall (LW), are variables that might influence the probability of severe trauma. We investigated the effect of these two variables on scalar translocation (STL), a specific type of severe trauma. Thirty-two fresh frozen human cadaveric ears were evenly distributed over four groups receiving either RW or CO approach, and either LW or PM array. Conventional radiological multiplanar reconstruction (MPR) was compared with a reconstruction method that uncoils the spiral shape of the cochlea (UCR). Histological analysis showed that RW with PM array had STL rate of 87% (7/8), CO approach with LW array 75% (6/8), RW approach with LW array 50% (4/8) and CO approach with PM array 29% (2/7). STL assessment using UCR showed a higher inter-observer and histological agreement (91 and 94% respectively), than that using MPR (69 and 74% respectively). In particular, LW array positions were difficult to assess with MPR. In conclusion, the interaction between surgical approach and type of array should be preoperatively considered in cochlear implant surgery. UCR technique is advised for radiological assessment of CI positions, and in general it might be useful for pathologies involving the inner ear or other complex shaped bony tubular structures.

Robotics and cochlear implant surgery: goals and developments

PURPOSE OF REVIEW

Cochlear implantation (CI) is a viable option for patients with severe sensorineural hearing loss. Advances in CI have focused on minimizing cochlear trauma to improve hearing preservation outcomes, and in doing so expanding candidacy to patients with useful cochlear reserve. Robotics holds promise as a potential tool to minimize intracochlear trauma with electrode insertion, improve surgical efficiency, and reduce surgical complications. The purpose of this review is to summarize efforts and advances in the field of robotic-assisted CI.

RECENT FINDINGS

Work on robotics and CI over the past few decades has explored distinct surgical aspects, including image-based surgical planning and intraoperative guidance, minimally invasive robotic-assisted approaches mainly through percutaneous keyhole direct cochlear access, robotic electrode insertion systems, robotic manipulators, and drilling feedback control through end effector sensors. Feasibility and safety have been established and many devices are undergoing clinical trials for clinical adoption, with some having already achieved approval of national licensing bodies.

SUMMARY

Significant work has been done over the past two decades that has shown robotic-assisted CI to be feasible and safe. Wider clinical adoption can potentially result in improved hearing preservation and quality of life outcomes to more CI candidates.

Minimally invasive surgical techniques in vestibular function preservation in patients with cochlear implants

Background

Cochlear implantation (CI) is an effective and successful method of treating individuals with severe-to-profound sensorineural hearing loss (SNHL). Coupled with it’s great clinical effectiveness, there is a risk of vestibular damage. With recent advances in surgical approach, modified electrode arrays and other surgical techniques, the potential of hearing preservation (HP) has emerged, in order to preserve the inner ear function. These techniques may also lead to less vestibular damage. However, a systematic study on this at different follow-ups after CI surgery has not been documented before.

Aims

To investigate changes of vestibular function systematically in recipients at short and long follow-ups after a minimally invasive CI surgery.

Methods

In this retrospective study, 72 patients (72 ears) with minimally invasive CI were recruited. All participants selected had bilateral SNHL and pre-operative residual hearing (RH) and underwent unilateral CI. They were treated to comprehensive care. All patients underwent vestibular function tests 5 days prior to CI. During the post-operative period, follow-up tests were performed at 1, 3, 6, 9, and 12 months. The contemporaneous results of caloric, cervical vestibular-evoked myogenic potential (cVEMP), ocular vestibular-evoked myogenic potential (oVEMP), and video head impulse (vHIT) tests were followed together longitudinally.

Results

On the implanted side, the percent fail rate of caloric test was significantly higher than that of vHIT at 1, 3, and 9 months post-operatively (p < 0.05); the percent fail rate of oVEMP was higher than vHIT of superior semicircular canal (SSC), posterior semicircular canal (PSC), or horizontal semicircular canal (HSC) at 1, 3, and 9 months (p < 0.05); at 3 and 9 months, the percent fail rate of cVEMP was higher than that of SSC and PSC (p < 0.05). There were no significant differences in the percent fail rates among all tests at 6 and 12 months post-CI (p > 0.05). The percent fail rates showed decreased trends in caloric (p = 0.319) and HSC tested by vHIT (p = 0.328) from 1–3 to 6–12 months post-operatively. There was no significant difference in cVEMP between 1–3 and 6–12 months (p = 0.597). No significant differences on percent fail rates of cVEMP and oVEMP between short- and long-terms post-CI were found in the same subjects (p > 0.05). Before surgery, the abnormal cVEMP and oVEMP response rates were both lower in patients with enlarged vestibular aqueduct (EVA) than patients with a normal cochlea (p = 0.001, 0.018, respectively).

Conclusion

The short- and long-term impacts on the vestibular function from minimally invasive CI surgery was explored. Most of the vestibular functions can be preserved with no damage discrepancy among the otolith and three semicircular canal functions at 12 months post-CI. Interestingly, a similar pattern of changes in vestibular function was found during the early and the later stages of recovery after surgery.

Current Concepts and Future Trends in Increasing the Benefits of Cochlear Implantation: A Narrative Review

Hearing loss is the most common neurosensory disorder, and with the constant increase in etiological factors, combined with early detection protocols, numbers will continue to rise. Cochlear implantation has become the gold standard for patients with severe hearing loss, and interest has shifted from implantation principles to the preservation of residual hearing following the procedure itself. As the audiological criteria for cochlear implant eligibility have expanded to include patients with good residual hearing, more attention is focused on complementary development of otoprotective agents, electrode design, and surgical approaches. The focus of this review is current aspects of preserving residual hearing through a summary of recent trends regarding surgical and pharmacological fundamentals. Subsequently, the assessment of new pharmacological options, novel bioactive molecules (neurotrophins, growth factors, etc.), nanoparticles, stem cells, and gene therapy are discussed.

Inner Ear Drug Delivery for Sensorineural Hearing Loss: Current Challenges and Opportunities

Most therapies for treating sensorineural hearing loss are challenged by the delivery across multiple tissue barriers to the hard-to-access anatomical location of the inner ear. In this review, we will provide a recent update on various pharmacotherapy, gene therapy, and cell therapy approaches used in clinical and preclinical studies for the treatment of sensorineural hearing loss and approaches taken to overcome the drug delivery barriers in the ear. Small-molecule drugs for pharmacotherapy can be delivered via systemic or local delivery, where the blood-labyrinth barrier hinders the former and tissue barriers including the tympanic membrane, the round window membrane, and/or the oval window hinder the latter. Meanwhile, gene and cell therapies often require targeted delivery to the cochlea, which is currently achieved via intra-cochlear or intra-labyrinthine injection. To improve the stability of the biomacromolecules during treatment, e.g., RNAs, DNAs, proteins, additional packing vehicles are often required. To address the diverse range of biological barriers involved in inner ear drug delivery, each class of therapy and the intended therapeutic cargoes will be discussed in this review, in the context of delivery routes commonly used, delivery vehicles if required (e.g., viral and non-viral nanocarriers), and other strategies to improve drug permeation and sustained release (e.g., hydrogel, nanocarriers, permeation enhancers, and microfluidic systems). Overall, this review aims to capture the important advancements and key steps in the development of inner ear therapies and delivery strategies over the past two decades for the treatment and prophylaxis of sensorineural hearing loss.

National study of hearing preservation rates and outcomes after cochlear implantation in Ireland

OBJECTIVE

To study the rate of hearing preservation and outcomes of hearing preservation candidates in a national cochlear implant centre. The HEARRING criteria was used.

METHODS

All cochlear implant candidates with preserved low frequency pure tone average (PTA) were included. All patients underwent cochlear implantation using a standard 'soft-surgery' technique. PTA was assessed at switch-on, 3, 6, 9 and 12 months postoperatively. The primary outcome was hearing preservation at 12 months.

RESULTS

Sixty six patients were included in the study between 2015 and 2020. Seventy one ears were implanted including 33 adults and 33 children with 5 bilateral implantations. Mean preoperative PTA was 74.8 dB (range 52.3-92 dB), mean postoperative PTA was 95.3 dB corresponding to a mean shift of 20.5 dB. In the adult population, HP rates were as follows: complete HP in 13%, partial HP in 39.1%, minimal HP in 30.4%, loss of hearing in 17.4%. In the paediatric population: complete HP in 20.7%, partial HP in 51.7%, minimal HP in 13.8% and loss of hearing in 13.8%. After the initial postoperative shift, there was no significant worsening of residual hearing during follow-up between 3 and 12 months. There were no significant prognostic factors for hearing preservation.

CONCLUSION

Hearing preservation rates using the HEARRING criteria are described. This study will help counselling and decision making in patients eligible for cochlear implantation with hearing preservation. Further studies are required to assess the performances and outcomes of electronatural and electroacoustic stimulation.

Measurement and Mitigation of Intracochlear Pressure Transients During Cochlear Implant Electrode Insertion

HYPOTHESIS

High intracochlear pressure transients associated with cochlear implant placement are reduced with smaller, non-styleted arrays, and longer insertion durations.

BACKGROUND

With increasing focus on hearing preservation during cochlear implant surgery, atraumatic technique is of the utmost importance. Previous studies revealed that high intensity pressure transients can be generated during the insertion of implant electrodes. Resulting acoustic trauma may be one contributing factor to postoperative loss of residual hearing.

METHODS

Thirty ears in cadaveric specimens were surgically prepared with placement of intracochlear pressure sensors. Sequential implant insertions were made over 10, 30, or 60 seconds using seven randomly ordered electrode styles. Pressures were also measured during common post-insertion electrode manipulations and removal. Measurements were compared between electrode styles and characteristics using analysis of variance (ANOVA) and Pearson correlation.

RESULTS

Implant insertion and post-insertion manipulations produced high-intensity pressure transients with all electrodes tested, with some measurements exceeding 170 dB peak SPL. Average peak pressures were significantly lower for straight, non-stylet electrodes (p << 0.001). The likelihood of generating transients was lowest with the slowest insertions (p << 0.001).

CONCLUSIONS

Cochlear implant insertion can generate transients in intralabyrinthine pressure levels equivalent to high intensity, impulsive acoustic stimuli known to cause hearing loss. Although transients were observed in all conditions, exposure may be mitigated by using non-styleted electrodes and slow insertion speeds. Additional surgical manipulations can also produce similar high-pressure events. Results from this investigation suggest that use of non-styleted electrodes, slow but steady insertion speeds, and avoidance of post-insertional manipulations are important to reduce cochlear trauma.

Increased Threshold and Reduced Firing Rate of Auditory Cortex Neurons after Cochlear Implant Insertion

The cochlear implant (CI) is the most successful neuroprosthesis allowing thousands of patients with profound hearing loss to recover speech understanding. Recently, cochlear implants have been proposed to subjects with residual hearing and, in these cases, shorter CIs were implanted. To be successful, it is crucial to preserve the patient’s remaining hearing abilities after the implantation. Here, we quantified the effects of CI insertion on the responses of auditory cortex neurons in anesthetized guinea pigs. The responses of auditory cortex neurons were determined before and after the insertion of a 300 µm diameter CI (six stimulating electrodes, length 6 mm). Immediately after CI insertion there was a 5 to 15 dB increase in the threshold for cortical neurons from the middle to the high frequencies, accompanied by a decrease in the evoked firing rate. Analyzing the characteristic frequency (CF) values revealed that in large number of cases, the CFs obtained after insertion were lower than before. These effects were not detected in the control animals. These results indicate that there is a small but immediate cortical hearing loss after CI insertion, even with short length CIs. Therefore, efforts should be made to minimize the damages during CI insertion to preserve the cortical responses to acoustic stimuli.

A Window of Opportunity: Perilymph Sampling from the Round Window Membrane Can Advance Inner Ear Diagnostics and Therapeutics

In the clinical setting, the pathophysiology of sensorineural hearing loss is poorly defined and there are currently no diagnostic tests available to differentiate between subtypes. This often leaves patients with generalized treatment options such as steroids, hearing aids, or cochlear implantation. The gold standard for localizing disease is direct biopsy or imaging of the affected tissue; however, the inaccessibility and fragility of the cochlea make these techniques difficult. Thus, the establishment of an indirect biopsy, a sampling of inner fluids, is needed to advance inner ear diagnostics and allow for the development of novel therapeutics for inner ear disease. A promising source is perilymph, an inner ear liquid that bathes multiple structures critical to sound transduction. Intraoperative perilymph sampling via the round window membrane of the cochlea has been successfully used to profile the proteome, metabolome, and transcriptome of the inner ear and is a potential source of biomarker discovery. Despite its potential to provide insight into inner ear pathologies, human perilymph sampling continues to be controversial and is currently performed only in conjunction with a planned procedure where the inner ear is opened. Here, we review the safety of procedures in which the inner ear is opened, highlight studies where perilymph analysis has advanced our knowledge of inner ear diseases, and finally propose that perilymph sampling could be done as a stand-alone procedure, thereby advancing our ability to accurately classify sensorineural hearing loss.

Is Characteristic Frequency Limiting Real-Time Electrocochleography During Cochlear Implantation?

Objectives

Electrocochleography (ECochG) recordings during cochlear implantation have shown promise in estimating the impact on residual hearing. The purpose of the study was (1) to determine whether a 250-Hz stimulus is superior to 500-Hz in detecting residual hearing decrement and if so; (2) to evaluate whether crossing the 500-Hz tonotopic, characteristic frequency (CF) place partly explains the problems experienced using 500-Hz.

Design

Multifrequency ECochG comprising an alternating, interleaved acoustic complex of 250- and 500-Hz stimuli was used to elicit cochlear microphonics (CMs) during insertion. The largest ECochG drops (≥30% reduction in CM) were identified. After insertion, ECochG responses were measured using the individual electrodes along the array for both 250- and 500-Hz stimuli. Univariate regression was used to predict whether 250- or 500-Hz CM drops explained low-frequency pure tone average (LFPTA; 125-, 250-, and 500-Hz) shift at 1-month post-activation. Postoperative CT scans were performed to evaluate cochlear size and angular insertion depth.

Results

For perimodiolar insertions (N = 34), there was a stronger linear correlation between the largest ECochG drop using 250-Hz stimulus and LFPTA shift (r = 0.58), compared to 500-Hz (r = 0.31). The 250- and 500-Hz CM insertion tracings showed an amplitude peak at two different locations, with the 500-Hz peak occurring earlier in most cases than the 250-Hz peak, consistent with tonotopicity. When using the entire array for recordings after insertion, a maximum 500-Hz response was observed 2-6 electrodes basal to the most-apical electrode in 20 cases (58.9%). For insertions where the apical insertion angle is >350 degrees and the cochlear diameter is <9.5 mm, the maximum 500-Hz ECochG response may occur at the non-apical most electrode. For lateral wall insertions (N = 14), the maximum 250- and 500-Hz CM response occurred at the most-apical electrode in all but one case.

Conclusion

Using 250-Hz stimulus for ECochG feedback during implantation is more predictive of hearing preservation than 500-Hz. This is due to the electrode passing the 500-Hz CF during insertion which may be misidentified as intracochlear trauma; this is particularly important in subjects with smaller cochlear diameters and deeper insertions. Multifrequency ECochG can be used to differentiate between trauma and advancement of the apical electrode beyond the CF.

Evaluating cochlear insertion trauma and hearing preservation after cochlear implantation (CIPRES): a study protocol for a randomized single-blind controlled trial

Background

In order to preserve residual hearing in patients with sensorineural hearing loss (SNHL) who receive a cochlear implant (CI), insertion trauma to the delicate structures of the cochlea needs to be minimized. The surgical approach comprises the conventional mastoidectomy-posterior tympanotomy (MPT) to arrive at the middle ear, followed by either a cochleostomy (CO) or the round window (RW) approach. Both techniques have their benefits and disadvantages. Another important aspect in structure preservation is the design of the electrode array. Two different designs are used: a “straight” lateral wall lying electrode array (LW) or a “pre-curved” perimodiolar lying electrode array (PM). Interestingly, until now, the best surgical approach and design of the implant is uncertain. Our hypothesis is that there is a difference in hearing preservation outcomes between the four possible treatment options.

Methods

We designed a monocenter, multi-arm, randomized controlled trial to compare insertion trauma between four groups of patients, with each group having a unique combination of an electrode array type (LW or PM) and surgical approach (RW or CO). In total, 48 patients will be randomized into one of these four intervention groups. Our primary objective is the comparison of postoperative hearing preservation between these four groups. Secondly, we aim to assess structure preservation (i.e., scalar translocation, with basilar membrane disruption or tip fold-over of array) for each group. Thirdly, we will compare objective outcomes of hearing and structure preservation by way of electrocochleography (ECochG).

Discussion

Cochlear implantation by way of a cochleostomy or round window approach, using different electrode array types, is the standard medical care for patients with severe to profound bilateral sensorineural hearing loss, as it is a relatively simple and low-risk procedure that greatly benefits patients. However, loss of residual hearing remains a problem. This trial is the first randomized controlled trial that evaluates the effect of cochlear insertion trauma of several CI treatment options on hearing preservation.

Trial registration

Netherlands Trial Register (NTR) NL8586. Registered on 4 May 2020. Retrospectively registered; 3/48 participants were included before registration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-021-05878-2.

Residual hearing preservation for cochlear implantation surgery

Cochlear implantation (CI) has developed for more than four decades. Initially, CI was used for profound bilateral hearing impairment. However, the indications for CI have expanded in recent years to include children with symptomatic partial deafness. Therefore, CI strategies to preserve residual hearing are important for both patients and otologists. The loss of residual low-frequency hearing is thought to be the result of many factors. All surgical methods have the same goal: protect the delicate intracochlear structures and preserve residual low-frequency hearing to improve speech perception abilities. Fully opening the round window membrane, a straight electrode array, slower insertion speed, and the use of corticosteroids result in a higher rate of hearing preservation. Several factors, like the way of surgical approaches, length of arrays and timing of activation, may not affect the residual hearing preservation. Therefore, the classic atraumatic technique, including the very slow and delicate insertion and administration of intraoperative corticosteroids, can improve hearing outcomes.

The resilience of the inner ear-vestibular and audiometric impact of transmastoid semicircular canal plugging

Background

Certain cases of superior semicircular canal dehiscence or benign paroxysmal positional vertigo can be treated by plugging of the affected semicircular canal. However, the extent of the impact on vestibular function and hearing during postoperative follow-up is not known.

Objective

To evaluate the evolution of vestibular function and hearing after plugging of a semicircular canal.

Methods

Six patients underwent testing before and 1 week, 2 months, and 6 months after plugging of the superior or posterior semicircular canal. Testing included caloric irrigation test, video Head Impulse Test (vHIT), cervical and ocular Vestibular Evoked Myogenic Potentials (VEMPs) and audiometry.

Results

Initially, ipsilateral caloric response decreased in all patients and vHIT vestibulo-ocular reflex (VOR) gain of each ipsilateral semicircular canal decreased in 4/6 patients. In 4/6 patients, postoperative caloric response recovered to > 60% of the preoperative value. In 5/6 patients, vHIT VOR gain was restored to > 85% of the preoperative value for both ipsilateral non-plugged semicircular canals. In the plugged semicircular canal, this gain decreased in 4/5 patients and recovered to > 50% of the preoperative value. Four patients preserved cervical and ocular VEMP responses. Bone conduction hearing deteriorated in 3/6 patients, but recovered within 6 months postoperatively, although one patient had a persistent loss of 15 dB at 8 kHz.

Conclusion

Plugging of a semicircular canal can affect both vestibular function and hearing. After initial deterioration, most patients show recovery during follow-up. However, a vestibular function loss or high-frequency hearing loss can persist. This stresses the importance of adequate counseling of patients considering plugging of a semicircular canal.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00415-021-10693-5.

Initial Experience With a Recently Developed Lateral Wall Electrode

OBJECTIVE

To review our hearing preservation rates and speech recognition outcomes in patients undergoing cochlear implantation with a recently developed lateral wall electrode.

STUDY DESIGN

Retrospective cohort study.

METHODS

Retrospective case series of all patients, both pediatric and adult, undergoing cochlear implantation with the Advanced Bionics Hifocus™ SlimJ electrode between December 2017 and January 2020. Main outcomes included hearing preservation rates using several definitions, speech recognition testing primarily through Arizona Biosciences (AzBio) and Consonant-Nucleus-Consonant (CNC) testing, intra- and postoperative complications.

RESULTS

Sixty-one ears underwent implantation with the new electrode. Hearing preservation rates were 13.0% to 36.0% depending on the definition used. Speech recognition testing showed significant increases from pre- to postoperative condition (Implant-only AzBio: 24.1 to 48.3, P = .004, binaural AzBio: 46.1 to 65.9, P = .002, Implant-only CNC: 9.7 to 35.1, P < .001, binaural CNC: 29.8 to 59.40, P < .001) with last speech recognition testing occurring an average of 8.8 months postoperatively. The elderly population had the worst hearing preservation rates across all definitions. Five explantations were required due to two infections and three device failures.

CONCLUSION

Hearing preservation rates varied significantly depending on the definition used, but users experienced a significant improvement in speech recognition testing after implantation. More work is needed in the community to standardize the definition of residual hearing and hearing preservation.

LEVEL OF EVIDENCE

4 Laryngoscope, 2021.

Feasibility of Cochlea High-frequency Ultrasound and Microcomputed Tomography Registration for Cochlear Computer-assisted Surgery: A Testbed

INTRODUCTION

There remains no standard imaging method that allows computer-assisted surgery of the cochlea in real time. However, recent evidence suggests that high-frequency ultrasound (HFUS) could permit real-time visualization of cochlear architecture. Registration with an imaging modality that suffers neither attenuation nor conical deformation could reveal useful anatomical landmarks to surgeons. Our study aimed to address the feasibility of an automated three-dimensional (3D) HFUS/microCT registration, and to evaluate the identification of cochlear structures using 2D/3D HFUS and microCT.

METHODS

MicroCT, and 2D/3D 40 MHz US in B-mode were performed on ex vivo guinea pig cochlea. An automatic rigid registration algorithm was applied to segmented 3D images. This automatic registration was then compared to a reference method using manual annotated landmarks placed by two senior otologists. Inter- and intrarater reliabilities were evaluated using intraclass correlation coefficient (ICC) and the mean registration error was calculated.

RESULTS

3D HFUS/microCT automatic registration was successful. Excellent levels of concordance were achieved with regards intra-rater reliability for both raters with micro-CT and US images (ICC ranging from 0.98 to 1, p < 0.001) and with regards inter-rater reliability (ICC ranging from 0.99 to 1, p < 0.001). The mean HFUS/microCT automated RE for both observers was 0.17 ± 0.03 mm [0.10-0.25]. Identification of the basilar membrane, modiolus, scala tympani, and scala vestibuli was possible with 2D/3D HFUS and micro-CT.

CONCLUSIONS

HFUS/microCT image registration is feasible. 2D/3D HFUS and microCT allow the visualization of cochlear structures. Many potential clinical applications are conceivable.