A new electrode for residual hearing preservation in cochlear implantation: first clinical results

Using the Implant Electrode Array to Conduct Real-time Intraoperative Hearing Monitoring During Pediatric Cochlear Implantation: Preliminary Experiences

OBJECTIVES

To present the preliminary experiences and findings from a pilot study evaluating a novel technique for monitoring cochlear electrophysiological function during electrode insertion in cochlear implantation surgery.

STUDY DESIGN

Prospective pilot cohort study.

SETTING

Tertiary academic neuro-otology center.

PATIENTS

Pediatric patients with residual hearing undergoing hearing preservation cochlear implant surgery.

INTERVENTION

Monitoring of intraoperative cochlear microphonics during cochlear implant surgery.

MAIN OUTCOME MEASURE

Intraoperative intracochlear microphonic measurement, preservation of these responses postoperatively and preservation of hearing as measured by audiometry.

RESULTS

Intracochlear microphonics could be identified in both patients presented and were preserved during the surgical procedure and postoperatively. The preservation of intracochlear microphonics correlates with preservation of hearing.

CONCLUSION

The novel approach using the electrode array to detect and measure intracochlear microphonics during cochlear implantation surgery shows promise as an instrument to alert the operating surgeon to hair cell damage during electrode insertion. Further refinement of the technique is required to better understand the measurements and correlate these with pre- and postoperative hearing and risk of hearing loss from surgery. Improvements in the software algorithm will reduce the time required for each measurement, leading to the development a more real-time monitoring technique.

Hearing and Patient Satisfaction Among 19 Patients Who Received Implants Intended for Hybrid Hearing: A Two-Year Follow-Up

Objectives:

To measure patient satisfaction and correlate to hearing results in partially deaf patients, after hearing preservation cochlear implant surgery with hybrid hearing strategy, and to evaluate the stability of residual low-frequency hearing (LFH) over time.

Design:

A patient satisfaction survey and a retrospective, 2-year follow-up journal study. Nineteen partially deaf patients intended for hybrid hearing responded to a questionnaire when they had used their cochlear implants for at least a year. The questionnaire consisted of the International Outcome Inventory for Hearing Aids, EuroQol Group visual analogue scale and nine questions about hybrid hearing. Pure-tone audiometry, monosyllables, and hearing in noise test results from the patients’ medical records were evaluated and compared with the results from the patient satisfaction survey.

Results:

All of the patients were satisfied with their CIs. The mean International Outcome Inventory for Hearing Aids score was 29. The CIs provided a major contribution to the speech comprehension of these partially deaf patients. Two years after surgery, the patients’ mean binaural score on tests of monosyllables was 58%, and the mean signal to noise ratio was 4.6 dB. We observed ongoing deteriorations in the residual hearing of the operated ears that surpassed the deteriorations observed in the contralateral ears. One month after surgery, the LFH loss (125–500 Hz) was 17 dB, and after 2 years, this loss was 24 dB compared with 5 dB in the nonoperated ear. There were no significant correlations between preserved LFH and patient satisfaction or speech perception results.

Conclusions:

Electric stimulation provided a major contribution to speech comprehension of partially deaf patients. The gain reached in speech understanding widely exceeded the downside in losing some residual hearing. All the patients showed a high degree of satisfaction with their CIs regardless of varying hearing preservation.

Electric stimulation contributes to speech perception in partially deaf patients. Here patient satisfaction after cochlear implantation with hybrid hearing strategy is compared to preserved hearing and also to monosyllables and hearing in noise test results. There is an ongoing deterioration of residual hearing, but the gain reached in speech discrimination while the patients receive cochlear implants widely exceeds the downside in losing some residual hearing. All the patients were very satisfied with their implants.

Supplemental Digital Content is available in the text.

Preoperative steroids for hearing preservation cochlear implantation: A review

Preoperative steroids have been shown to be beneficial in reducing the hearing loss associated with cochlear implantation. This review article discusses the mechanism of action, effects of differing routes of administration, and side effects of steroids administered to the inner ear. Studies on the role of preoperative steroids in animal and human studies are also examined and future directions for research in this area are discussed.

Hearing Preservation Outcomes With a Mid-Scala Electrode in Cochlear Implantation

OBJECTIVE

To evaluate hearing preservation (HP) outcomes in adult cochlear implant recipients with a mid-scala electrode.

SETTING

Tertiary academic center.

PATIENTS

Adult patients implanted with a mid-scala electrode between May 2013 and July 2015.

INTERVENTIONS

Cochlear implantation.

MAIN OUTCOME MEASURE(S)

Age, sex, surgical approach, residual hearing changes post cochlear implantation, HP rates using different published classifications, and speech perception scores.

RESULTS

Fifty ears for 47 patients (mean age, 58.2 yr; range, 23-86) were implanted with the electrode. Recognizing that not all patients were true HP candidates and/or underwent generally accepted HP surgical techniques, 39 ears had preoperative low-frequency hearing (audiometric threshold ≤ 85dB HL at 250Hz), 24 preserved acoustic hearing postoperatively (75.0%). Patients who had preserved acoustic hearing were implanted via round window (N = 18), extended round window (N = 4), or via cochleostomy (N = 2) approaches. Mean threshold elevation for low-frequency pure-tone average (125, 250, and 500  Hz) was 20.2  dB after surgery. 43.8% of patients had aidable low-frequency hearing at activation, 30.0% at 6-months postoperatively, and 30.8% 1-year postopera tively. Using a formula outlined by Skarzynski and colleagues, at 6-months postoperatively, 15.0% of patients had complete HP, whereas 40.0% had partial HP. At 1-year, these percentages decreased to 0% and 38.5%, respectively. Age, type of approach, and perioperative steroid use were not correlated with HP outcomes at activation and 6-months postoperatively (p > 0.05).

CONCLUSION

The mid-scala electrode evaluated allows preservation of low-frequency hearing in patients undergoing cochlear implantation at rates and degrees of preservation close to other reports in the cochlear implant literature.

Delayed loss of hearing after hearing preservation cochlear implantation: Human temporal bone pathology and implications for etiology

After initially successful preservation of residual hearing with cochlear implantation, some patients experience subsequent delayed hearing loss. The etiology of such delayed hearing loss is unknown. Human temporal bone pathology is critically important in investigating the etiology, and directing future efforts to maximize long term hearing preservation in cochlear implant patients. Here we present the temporal bone pathology from a patient implanted during life with an Iowa/Nucleus Hybrid S8 implant, with initially preserved residual hearing and subsequent hearing loss. Both temporal bones were removed for histologic processing and evaluated. Complete clinical and audiologic records were available. He had bilateral symmetric high frequency severe to profound hearing loss prior to implantation. Since he was implanted unilaterally, the unimplanted ear was presumed to be representative of the pre-implantation pathology related to his hearing loss. The implanted and contralateral unimplanted temporal bones both showed complete degeneration of inner hair cells and outer hair cells in the basal half of the cochleae, and only mild patchy loss of inner hair cells and outer hair cells in the apical half. The total spiral ganglion neuron counts were similar in both ears: 15,138 (56% of normal for age) in the unimplanted right ear and 13,722 (51% of normal for age) in the implanted left ear. In the basal turn of the implanted left cochlea, loose fibrous tissue and new bone formation filled the scala tympani, and part of the scala vestibuli. Delayed loss of initially preserved hearing after cochlear implantation was not explained by additional post-implantation degeneration of hair cells or spiral ganglion neurons in this patient. Decreased compliance at the round window and increased damping in the scala tympani due to intracochlear fibrosis and new bone formation might explain part of the post-implantation hearing loss. Reduction of the inflammatory and immune response to cochlear implantation may lead to better long term hearing preservation post-implantation.

A Retrospective Analysis of the Contribution of Reported Factors in Cochlear Implantation on Hearing Preservation Outcomes

INTRODUCTION

Preservation of residual hearing is essential to perceive acoustic stimulation from hybrid cochlear implants (CI). Preservation is a good marker of atraumatic surgery and residual hearing may be exploited further or enhanced in future therapies, making complete hearing preservation a desirable goal for all current CI surgeries. There is large variability in the amount of hearing preserved and the timeframe over which it is lost after CI. The increase in numbers of patients with high levels of residual hearing at implantation means that understanding the variables affecting its preservation is more important than ever.

DATA SOURCES

An English search term with generic and specific items concerning hearing preservation and cochlear implantation was searched on the Web of Science service. The search timeframe was limited to 2000 to 2014, with no language limitations on results.

STUDY SELECTION

Hearing preservation, retrospective CI outcome studies which reported pre- and post-surgical pure-tone audiometry (PTA) were identified and selected.

DATA EXTRACTION

PTA thresholds were extracted from audiograms or tables and converted into a low-frequency hearing preservation (LFHP) score. Data for 21 factors associated with hearing preservation were collected from studies.

DATA SYNTHESIS

Factors were included in a hearing preservation model if they had both a significant bivariate correlation with LFHP and a significant Kruskal-Wallis H test result (for ordinal data) or a significant multiple regression analysis result (for scale data).

CONCLUSIONS

Seven factors were found to have a significant effect on hearing preservation: insertion site, progressive versus stable hearing loss, insertion angle of electrode, use of intraoperative topical steroids, use of steroids (via any route/timing), hearing etiology, and electrode array type. The best hearing preservation options are given.

Changes in Gene Expression and Hearing Thresholds After Cochlear Implantation

HYPOTHESIS

Gene expression changes occur in conjunction with hearing threshold changes after cochlear implantation.

BACKGROUND

Between 30 and 50% of individuals who receive electro-acoustic stimulation (EAS) cochlear implants lose residual hearing after cochlear implantation, reducing the benefits of EAS. The mechanism underlying this hearing loss is unknown; potential pathways include mechanical damage, inflammation, or tissue remodeling changes.

METHODS

Guinea pigs were implanted in one ear with cochlear implant electrode arrays, with non-implanted ears serving as controls, and allowed to recover for 1, 3, 7, or 14 days. Hearing threshold changes were measured over time. Cochlear ribonucleic acid was analyzed using real-time quantitative reverse transcription-polymerase chain reaction from the following gene families: cytokines, tight junction claudins, ion and water (aquaporin) transport channels, gap junction connexins, and tissue remodeling genes.

RESULTS

Significant increases in expression were observed for cochlear inflammatory genes (Cxcl1, IL-1β, TNF-α, and Tnfrsf1a/b) and ion homeostasis genes (Scnn1γ, Aqp3, and Gjb3). Upregulation of tissue remodeling genes (TGF-β, MMP2, MMP9) as well as a paracrine gene (CTGF) was also observed. Hearing loss occurred rapidly, peaking at 3 days with some recovery at 7 and 14 days after implantation. MM9 exhibited extreme upregulation of expression and was qualitatively associated with changes in hearing thresholds.

CONCLUSION

Cochlear implantation induces similar changes as middle ear inflammation for genes involved in inflammation and ion and water transport function, whereas tissue remodeling changes differ markedly. The upregulation of MMP9 with hearing loss is consistent with previous findings linking stria vascularis vessel changes with cochlear implant-induced hearing loss.

Morphological correlates of hearing loss after cochlear implantation and electro-acoustic stimulation in a hearing-impaired Guinea pig model

Hybrid or electro-acoustic stimulation (EAS) cochlear implants (CIs) are designed to provide high-frequency electric hearing together with residual low-frequency acoustic hearing. However, 30-50% of EAS CI recipients lose residual hearing after implantation. The objective of this study was to determine the mechanisms of EAS-induced hearing loss in an animal model with high-frequency hearing loss. Guinea pigs were exposed to 24 h of noise (12-24 kHz at 116 dB) to induce a high-frequency hearing loss. After recovery, two groups of animals were implanted (n = 6 per group), with one group receiving chronic acoustic and electric stimulation for 10 weeks, and the other group receiving no stimulation during this time frame. A third group (n = 6) was not implanted, but received chronic acoustic stimulation. Auditory brainstem responses were recorded biweekly to monitor changes in hearing. The organ of Corti was immunolabeled with phalloidin, anti-CtBP2, and anti-GluR2 to quantify hair cells, ribbons and post-synaptic receptors. The lateral wall was immunolabeled with phalloidin and lectin to quantify stria vascularis capillary diameters. Bimodal or trimodal diameter distributions were observed; the number and location of peaks were objectively determined using the Aikake Information Criterion and Expectation Maximization algorithm. Noise exposure led to immediate hearing loss at 16-32 kHz for all groups. Cochlear implantation led to additional hearing loss at 4-8 kHz; this hearing loss was negatively and positively correlated with minimum and maximum peaks of the bimodal or trimodal distributions of stria vascularis capillary diameters, respectively. After chronic stimulation, no significant group changes in thresholds were seen; however, elevated thresholds at 1 kHz in implanted, stimulated animals were significantly correlated with decreased presynaptic ribbon and postsynaptic receptor counts. Inner and outer hair cell counts did not differ between groups and were not correlated with threshold shifts at any frequency. As in the previous study in a normal-hearing model, stria vascularis capillary changes were associated with immediate hearing loss after implantation, while little to no hair cell loss was observed even in cochlear regions with threshold shifts as large as 40-50 dB. These findings again support a role of lateral wall blood flow changes, rather than hair cell loss, in hearing loss after surgical trauma, and implicate the endocochlear potential as a factor in implantation-induced hearing loss. Further, the analysis of the hair cell ribbons and post-synaptic receptors suggest that delayed hearing loss may be linked to synapse or peripheral nerve loss due to stimulation excitotoxicity or inflammation. Further research is needed to separate these potential mechanisms of delayed hearing loss.

Hearing preservation and cochlear implants according to inner ear approach: multicentric evaluation

Introduction

Electroacoustic stimulation is an excellent option for people with residual hearing in the low frequencies, who obtain insufficient benefit with hearing aids. To be effective, the subject's residual hearing should be preserved during cochlear implant surgery.

Objectives

To evaluate the hearing preservation in patients that underwent implant placement and to compare the results in accordance with the approach to the inner ear.

Methods

19 subjects underwent a soft surgical technique, and the electrode MED-EL FLEX™ EAS, designed to be atraumatic, was used. We evaluated pre- and postoperative tonal audiometric tests with an average of 18.4 months after implantation, to measure the rate of hearing preservation.

Results

17 patients had total or partial preservation of residual hearing; 5 had total hearing preservation and two individuals had no preservation of hearing. The insertion of the electrode occurred through a cochleostomy in 3 patients, and in 2 of these there was no hearing preservation; the other 16 patients experienced electrode insertion through a round window approach. All patients benefited from the cochlear implant, even those who are only using electrical stimulation.

Conclusion

The hearing preservation occurred in 89.4% of cases. There was no significant difference between the forms of inner ear approach.

The advantages of sound localization and speech perception of bilateral electric acoustic stimulation

CONCLUSION

Bilateral electric acoustic stimulation (EAS) effectively improved speech perception in noise and sound localization in patients with high-frequency hearing loss.

OBJECTIVE

To evaluate bilateral EAS efficacy of sound localization detection and speech perception in noise in two cases of high-frequency hearing loss.

METHODS

Two female patients, aged 38 and 45 years, respectively, received bilateral EAS sequentially. Pure-tone audiometry was performed preoperatively and postoperatively to evaluate the hearing preservation in the lower frequencies. Speech perception outcomes in quiet and noise and sound localization were assessed with unilateral and bilateral EAS.

RESULTS

Residual hearing in the lower frequencies was well preserved after insertion of a FLEX(24) electrode (24 mm) using the round window approach. After bilateral EAS, speech perception improved in quiet and even more so in noise. In addition, the sound localization ability of both cases with bilateral EAS improved remarkably.

Pediatric Cochlear Implantation in Residual Hearing Candidates

Objectives:

To propose categories for the various types of residual hearing in children and to review the outcomes of cochlear implantation (CI) in children with these different hearing conditions.

Methods:

We identified 53 children with residual hearing who had received a cochlear implant. Five groups were arbitrarily defined based on auditory features: G1, characterized by low-frequency residual hearing (n = 5); G2, characterized by severe sensorineural hearing loss (SNHL) and low speech discrimination (n = 12); G3, characterized by asymmetric SNHL (n = 9); G4, characterized by progressive SNHL (n = 15); and G5, characterized by fluctuating SNHL (n = 12). The main audiometric features and outcomes of the groups were analyzed.

Results:

The mean age at implantation was 10.15 years (range, 2.5-21 years). The mean preoperative score for the discrimination of open-set words was 48%; this score increased to 74% at 12 months and 81% at 24 months after the CI procedure (G1 to G5, respectively: 79/62/77%, 50/81/88%, 59/75/86%, 35/74/67%, and 39/69/80%). Children who were implanted after 10 years of age did not improve as much as those who were implanted at a younger age (open-set word list speech perception [OSW] score at 12 months: 62% vs 83%; P = .0009). Shorter delays before surgery were predictive of better performance ( P = .003). Inner ear malformation and SLC26A4 mutations were not predictive of the outcome.

Conclusions:

CIs provide better results compared with hearing aids in children with residual hearing. Factors that may impact the benefits of CIs in patients with residual hearing are age, delay in performing the CI procedure, which ear is implanted, and initial underestimation of the patient’s hearing difficulties.

Hearing preservation outcomes with different cochlear implant electrodes: Nucleus® Hybrid™-L24 and Nucleus Freedom™ CI422

OBJECTIVES

In recent years, it has been possible to preserve hearing after cochlear implantation in patients with significant amounts of low-frequency residual hearing. Due to the dimensions and characteristics of the cochlear implants (CIs) Nucleus® Hybrid™-L24 and Nucleus Freedom™ CI422, both can be used to preserve residual hearing. The aim was to investigate the degree and progression of hearing preservation over a longitudinal postoperative period in a large consecutive cohort of implanted patients with preoperative residual hearing who received either the Nucleus Hybrid-L24 or the Nucleus Freedom CI422 implant. The intention was to examine potential characteristics and triggers of resulting postoperative hearing loss which may support a differentiation of CI candidacy criteria for a certain implant type.

METHODS

A retrospective data analysis of patient files on consecutively implanted subjects presenting with a severe-to-profound sensorineural hearing loss at frequencies>1,500 Hz and substantial residual hearing at frequencies≤1,500 Hz, implanted with a Nucleus Hybrid-L24 (n=97) or a CI422 implant (n=100), was undertaken. A single-subject repeated-measure design comparing the mean threshold shift for pure-tone thresholds under headphones up to 24 months after implantation was used.

RESULTS

Hearing preservation is observed in the majority of subjects with either implant (250-1,500 Hz frequency range). Hybrid-L24 patients exhibited a median hearing loss of 10 dB at initial fitting (n=97) and of 15 dB after 24 months (n=51). A 14.4-dB decrease in median hearing loss at initial fitting (n=100) and a 30-dB decrease after 24 months (n=28) was observed with the CI422 electrode. At initial fitting, 54.6% of the Hybrid-L24 (n=97) and 49.0% of the CI422 (n=100) subjects showed a mean threshold shift<15 dB. After 24 months, 58.8% (Hybrid-L24, n=51) and 28.6% (CI422, n=28) of the patients showed a mean threshold shift<15 dB.

CONCLUSIONS

The results indicate that residual hearing was preserved for the majority of implanted patients with the Hybrid-L24 and the CI422 implant. Patients implanted with the Hybrid-L24 implant demonstrate greater stability and less median hearing loss over time than those with the CI422 implant. Assessments of onset and stability of hearing loss prior to implantation are important factors to consider during candidacy evaluation for electrode selection to potentially maximize the performance outcome for each patient.

Factors associated with hearing loss in a normal-hearing guinea pig model of Hybrid cochlear implants

The Hybrid cochlear implant (CI), also known as Electro-Acoustic Stimulation (EAS), is a new type of CI that preserves residual acoustic hearing and enables combined cochlear implant and hearing aid use in the same ear. However, 30-55% of patients experience acoustic hearing loss within days to months after activation, suggesting that both surgical trauma and electrical stimulation may cause hearing loss. The goals of this study were to: 1) determine the contributions of both implantation surgery and EAS to hearing loss in a normal-hearing guinea pig model; 2) determine which cochlear structural changes are associated with hearing loss after surgery and EAS. Two groups of animals were implanted (n = 6 per group), with one group receiving chronic acoustic and electric stimulation for 10 weeks, and the other group receiving no direct acoustic or electric stimulation during this time frame. A third group (n = 6) was not implanted, but received chronic acoustic stimulation. Auditory brainstem response thresholds were followed over time at 1, 2, 6, and 16 kHz. At the end of the study, the following cochlear measures were quantified: hair cells, spiral ganglion neuron density, fibrous tissue density, and stria vascularis blood vessel density; the presence or absence of ossification around the electrode entry was also noted. After surgery, implanted animals experienced a range of 0-55 dB of threshold shifts in the vicinity of the electrode at 6 and 16 kHz. The degree of hearing loss was significantly correlated with reduced stria vascularis vessel density and with the presence of ossification, but not with hair cell counts, spiral ganglion neuron density, or fibrosis area. After 10 weeks of stimulation, 67% of implanted, stimulated animals had more than 10 dB of additional threshold shift at 1 kHz, compared to 17% of implanted, non-stimulated animals and 0% of non-implanted animals. This 1-kHz hearing loss was not associated with changes in any of the cochlear measures quantified in this study. The variation in hearing loss after surgery and electrical stimulation in this animal model is consistent with the variation in human patients. Further, these findings illustrate an advantage of a normal-hearing animal model for quantification of hearing loss and damage to cochlear structures without the confounding effects of chemical- or noise-induced hearing loss. Finally, this study is the first to suggest a role of the stria vascularis and damage to the lateral wall in implantation-induced hearing loss. Further work is needed to determine the mechanisms of implantation- and electrical-stimulation-induced hearing loss.

Hearing preservation and clinical outcome of 32 consecutive electric acoustic stimulation (EAS) surgeries

Conclusions

Our results indicated that electric acoustic stimulation (EAS) is beneficial for Japanese-speaking patients, including those with less residual hearing at lower frequencies. Comparable outcomes for the patients with less residual hearing indicated that current audiological criteria for EAS could be expanded. Successful hearing preservation results, together with the progressive nature of loss of residual hearing in these patients, mean that minimally invasive full insertion of medium/long electrodes in cochlear implantation (CI) surgery is a desirable solution. The minimally invasive concepts that have been obtained through EAS surgery are, in fact, crucial for all CI patients.

Objectives

This study was conducted to evaluate hearing preservation results and speech discrimination outcomes of hearing preservation surgeries using medium/long electrodes.

Methods

A total of 32 consecutive minimally invasive hearing preservation CIs (using a round window approach with deep insertion of a flexible electrode) were performed in 30 Japanese patients (two were bilateral cases), including patients with less residual hearing. Hearing preservation rates as well as speech discrimination/perception scores were investigated on a multicenter basis.

Results

Postoperative evaluation after full insertion of the flexible electrodes (24 mm, 31.5 mm) showed that residual hearing was well preserved in all 32 ears. In all patients, speech discrimination and perception scores were improved postoperatively.

Cochlear implantation with hearing preservation yields significant benefit for speech recognition in complex listening environments

OBJECTIVE

The aim of this study was to assess the benefit of having preserved acoustic hearing in the implanted ear for speech recognition in complex listening environments.

DESIGN

The present study included a within-subjects, repeated-measures design including 21 English-speaking and 17 Polish-speaking cochlear implant (CI) recipients with preserved acoustic hearing in the implanted ear. The patients were implanted with electrodes that varied in insertion depth from 10 to 31 mm. Mean preoperative low-frequency thresholds (average of 125, 250, and 500 Hz) in the implanted ear were 39.3 and 23.4 dB HL for the English- and Polish-speaking participants, respectively. In one condition, speech perception was assessed in an eight-loudspeaker environment in which the speech signals were presented from one loudspeaker and restaurant noise was presented from all loudspeakers. In another condition, the signals were presented in a simulation of a reverberant environment with a reverberation time of 0.6 sec. The response measures included speech reception thresholds (SRTs) and percent correct sentence understanding for two test conditions: CI plus low-frequency hearing in the contralateral ear (bimodal condition) and CI plus low-frequency hearing in both ears (best-aided condition). A subset of six English-speaking listeners were also assessed on measures of interaural time difference thresholds for a 250-Hz signal.

RESULTS

Small, but significant, improvements in performance (1.7-2.1 dB and 6-10 percentage points) were found for the best-aided condition versus the bimodal condition. Postoperative thresholds in the implanted ear were correlated with the degree of electric and acoustic stimulation (EAS) benefit for speech recognition in diffuse noise. There was no reliable relationship among measures of audiometric threshold in the implanted ear nor elevation in threshold after surgery and improvement in speech understanding in reverberation. There was a significant correlation between interaural time difference threshold at 250 Hz and EAS-related benefit for the adaptive speech reception threshold.

CONCLUSIONS

The findings of this study suggest that (1) preserved low-frequency hearing improves speech understanding for CI recipients, (2) testing in complex listening environments, in which binaural timing cues differ for signal and noise, may best demonstrate the value of having two ears with low-frequency acoustic hearing, and (3) preservation of binaural timing cues, although poorer than observed for individuals with normal hearing, is possible after unilateral cochlear implantation with hearing preservation and is associated with EAS benefit. The results of this study demonstrate significant communicative benefit for hearing preservation in the implanted ear and provide support for the expansion of CI criteria to include individuals with low-frequency thresholds in even the normal to near-normal range.

Towards a consensus on a hearing preservation classification system

CONCLUSION

The comprehensive Hearing Preservation classification system presented in this paper is suitable for use for all cochlear implant users with measurable pre-operative residual hearing. If adopted as a universal reporting standard, as it was designed to be, it should prove highly beneficial by enabling future studies to quickly and easily compare the results of previous studies and meta-analyze their data.

OBJECTIVES

To develop a comprehensive Hearing Preservation classification system suitable for use for all cochlear implant users with measurable pre-operative residual hearing.

METHODS

The HEARRING group discussed and reviewed a number of different propositions of a HP classification systems and reviewed critical appraisals to develop a qualitative system in accordance with the prerequisites.

RESULTS

The Hearing Preservation Classification System proposed herein fulfills the following necessary criteria: 1) classification is independent from users' initial hearing, 2) it is appropriate for all cochlear implant users with measurable pre-operative residual hearing, 3) it covers the whole range of pure tone average from 0 to 120 dB; 4) it is easy to use and easy to understand.

A systematic review of electric-acoustic stimulation: device fitting ranges, outcomes, and clinical fitting practices

Cochlear implant systems that combine electric and acoustic stimulation in the same ear are now commercially available and the number of patients using these devices is steadily increasing. In particular, electric-acoustic stimulation is an option for patients with severe, high frequency sensorineural hearing impairment. There have been a range of approaches to combining electric stimulation and acoustic hearing in the same ear. To develop a better understanding of fitting practices for devices that combine electric and acoustic stimulation, we conducted a systematic review addressing three clinical questions: what is the range of acoustic hearing in the implanted ear that can be effectively preserved for an electric-acoustic fitting?; what benefits are provided by combining acoustic stimulation with electric stimulation?; and what clinical fitting practices have been developed for devices that combine electric and acoustic stimulation? A search of the literature was conducted and 27 articles that met the strict evaluation criteria adopted for the review were identified for detailed analysis. The range of auditory thresholds in the implanted ear that can be successfully used for an electric-acoustic application is quite broad. The effectiveness of combined electric and acoustic stimulation as compared with electric stimulation alone was consistently demonstrated, highlighting the potential value of preservation and utilization of low frequency hearing in the implanted ear. However, clinical procedures for best fitting of electric-acoustic devices were varied. This clearly identified a need for further investigation of fitting procedures aimed at maximizing outcomes for recipients of electric-acoustic devices.

Hearing Preservation after Cochlear Implantation: UNICAMP Outcomes

Background. Electric-acoustic stimulation (EAS) is an excellent choice for people with residual hearing in low frequencies but not high frequencies and who derive insufficient benefit from hearing aids. For EAS to be effective, subjects' residual hearing must be preserved during cochlear implant (CI) surgery. Methods. We implanted 6 subjects with a CI. We used a special surgical technique and an electrode designed to be atraumatic. Subjects' rates of residual hearing preservation were measured 3 times postoperatively, lastly after at least a year of implant experience. Subjects' aided speech perception was tested pre- and postoperatively with a sentence test in quiet. Subjects' subjective responses assessed after a year of EAS or CI experience. Results. 4 subjects had total or partial residual hearing preservation; 2 subjects had total residual hearing loss. All subjects' hearing and speech perception benefited from cochlear implantation. CI diminished or eliminated tinnitus in all 4 subjects who had it preoperatively. 5 subjects reported great satisfaction with their new device. Conclusions. When we have more experience with our surgical technique we are confident we will be able to report increased rates of residual hearing preservation. Hopefully, our study will raise the profile of EAS in Brazil and Latin/South America.

The use of Nucleus CI422 in a ski-slope high-frequency hearing loss and chronic external ear pathology: a case study

OBJECTIVE AND IMPORTANCE

This case report illustrates the ongoing extending criteria for cochlear implantation (CI). It reinforces the statement that patients who do not fulfill the standard criteria for CI should be carefully considered on an individual basis.

CLINICAL PRESENTATION

The patient on this report presented with a ski-slope high-frequency hearing loss and chronic external ear canal infections. The latter precluded the consistent use of hearing aids with moulds. His speech discrimination in quiet and in noise was poor and his hearing loss was interfering with his ability to work.

INTERVENTION

After years of frustration, this patient decided to risk losing his low-frequency residual hearing and was implanted with the new Nucleus CI422 (Cochlear Ltd).

CONCLUSION

Hearing preservation was achieved and he gained a remarkable improvement in his hearing performance. It is thought that his outcomes are the result of the combination of hearing presentation surgery, electrode design, and intensive auditory training.

Comparison of Cochlear Implant Performance after Round Window Electrode Insertion Compared with Traditional Cochleostomy

Objective

To compare speech perception after undergoing round window (RW) electrode insertion with those who underwent traditional cochleostomy (C) cochlear implant (CI) surgery.

Study Design

Case series with chart review.

Setting

Academic cochlear implant center.

Subjects

Patients who met CI criteria with favorable intraoperative RW anatomy who underwent RW CI electrode insertion. Patients who underwent traditional C surgery were matched for age, duration of deafness, and preoperative hearing.

Methods

Postoperative speech performance using the consonant-nucleus-consonant (CNC) test, Northwestern University Children’s Perception of Speech (NUCHIPS), and Hearing in Noise Test (HINT) between 3 and 48 months after CI.

Results

A total of 84 patients underwent RW insertion between 2004 and 2011. Of these, 55 had pre- and postoperative speech perception data for analysis. Average age of implantation ranged from 2.4 to 87.3 years (mean ± SD, 42.1 ± 24.2 years) for RW patients. Average age of implantation for matched traditional C patients ranged from 2.3 to 85.6 years (mean ± SD, 43.3 ± 25.0 years). No significant differences in postoperative CI speech perception scores were noted between the RW and C groups at 12 months post-CI (RW group, 55.28% ± 23.26% vs C group, 53.19% ± 24.14%; P = .70).

Conclusion

Our study found that patients with favorable RW anatomy who underwent RW CI electrode insertion demonstrated comparable speech perception compared with the traditional cochleostomy insertion group.

Evolution of electrode array diameter for hearing preservation in cochlear implantation

CONCLUSION

Residual hearing could be preserved with various arrays ranging from 16 to 18 mm in insertion length and 0.25 to 0.5 mm tip diameter. Whether array insertion is performed through a cochleostomy or a round window, tip diameter is an essential criterion for the array design to improve hearing preservation results.

OBJECTIVES

The goal of this study was to report the outcome of patients implanted with electric acoustic cochlear implants with various surgical techniques and array designs.

METHODS

Thirty-two implanted ears (30 patients) were included in this retrospective study. Three array models were inserted: Contour Advance implant (n = 16), Nucleus Hybrid-L (n = 12), and Med-El Flex EAS (n = 4). Postoperative pure tone audiometry was performed at 3 and 12 months after implantation.

RESULTS

Three months postoperatively, hearing preservation within 30 dB was achieved in 50%, 50%, and 84% cases of patients implanted with a Contour Advance, Flex-EAS, and Hybrid-L, respectively. Two patients (Hybrid-L group) had a delayed sudden hearing loss (> 30 dB) 3 months postoperatively and three patients (Contour Advance group) had total hearing loss at 1 year. Best results were achieved using arrays with small tip diameters. Cochleostomy or round window insertion did not affect hearing preservation results.

Observations on hearing preservation in patients with hybrid-L electrode implanted at Poznan University of Medical Sciences in Poland

The objective of the paper is to evaluate the hearing preservation rate in patients with high frequency hearing loss, treated with Cochlear Nucleus Freedom Hybrid-L implant in the Otolaryngology Department, Poznan University of Medical Sciences in Poland. Study was designed as the retrospective analysis. Twenty-one patients were operated and implanted with Nucleus Freedom Hybrid-L implant. Pure tone thresholds were recorded prior to the surgery and at the time of speech processor switch-on. Patients were subdivided into two groups with respect to their PTA thresholds: group A—classic indications and group B—extended indications. Average PTA for three frequencies (250, 500, 1,000 Hz) were calculated for each patient pre- and postoperatively. In the group of 21 implanted patients in 17 cases we have observed preservation of hearing (12 patients from group A, 5 patients from group B) with a mean value of 13.1 dB. In 4 out of 21 patients deafness on the implanted ear was noted. Our results clearly indicate that with standard procedure hearing preservation can be obtained in majority of patients. Hearing preservation was not achieved in 19 %, but owing to design of the electrode of the Cochlear Nucleus Hybrid-L that enables to work as CI platform alone, in patients who lost their hearing after surgery re-implantations were not required. This proves that EAS is a safe and reliable method to help patients with specific type of hearing loss.

The cochlear implant: historical aspects and future prospects

The cochlear implant (CI) is the first effective treatment for deafness and severe losses in hearing. As such, the CI is now widely regarded as one of the great advances in modern medicine. This article reviews the key events and discoveries that led up to the current CI systems, and we review and present some among the many possibilities for further improvements in device design and performance. The past achievements include: (1) development of reliable devices that can be used over the lifetime of a patient; (2) development of arrays of implanted electrodes that can stimulate more than one site in the cochlea; and (3) progressive and large improvements in sound processing strategies for CIs. In addition, cooperation between research organizations and companies greatly accelerated the widespread availability and use of safe and effective devices. Possibilities for the future include: (1) use of otoprotective drugs; (2) further improvements in electrode designs and placements; (3) further improvements in sound processing strategies; (4) use of stem cells to replace lost sensory hair cells and neural structures in the cochlea; (5) gene therapy; (6) further reductions in the trauma caused by insertions of electrodes and other manipulations during implant surgeries; and (7) optical rather electrical stimulation of the auditory nerve. Each of these possibilities is the subject of active research. Although great progress has been made to date in the development of the CI, including the first substantial restoration of a human sense, much more progress seems likely and certainly would not be a surprise.

Cochlear implantation and hearing preservation: Results in 21 consecutively operated patients using the round window approach

CONCLUSION

Prevalent hearing conservation may be achieved after round window (RW) cochlear implantation using soft and flexible electrode arrays if variations of RW anatomy, topography, and facial nerve position are considered. The most favorable electrode insertion depth remains to be established.

OBJECTIVES

We assessed the incidence of cochlear function after cochlear implant (CI) electrode insertion through the RW in our first 21 consecutively operated patients aimed at hearing conservation.

METHODS

Eleven patients had a preoperative low frequency hearing suitable for electro-acoustic stimulation. Hearing was preserved in an additional nine patients at their request with the intention to use full frequency CI stimulation. Anatomic variations of the RW were carefully considered using our temporal bone collection of micro-dissected ears. Electrode extension was assessed on X-ray by measuring the insertion angle of the first electrode and intra-cochlear length and correlated with audiometric data.

RESULTS

There was no incidence of total loss of residual hearing in any of the patients. A slight deterioration of low frequency thresholds occurred in some patients. Mean hearing loss at 125-500 Hz was 14.4 dB at 1 month following surgery and 15.6 dB after 1 year. Insertion angle (300-540°) and depth (17.5-28.5 mm) were not statistically correlated to hearing loss.

Intraoperative monitoring using cochlear microphonics in cochlear implant patients with residual hearing

OBJECTIVES

To describe a technique for the intraoperative monitoring of residual hearing during a cochlear implant (CI) procedure and, thus, to identify the time of occurrence and surgical steps leading to hearing loss.

STUDY DESIGN

Prospective audiologic analysis in a patient series.

SETTING

Tertiary referral center.

SUBJECTS

Patients with residual hearing subjected to cochlear implantation.

INTERVENTIONS

During cochlear implantation, cochlear microphonics (CMs) in response to frequency-specific stimuli were recorded in patients with residual hearing. Thresholds were determined before and after opening of the cochlea, with a limited portion of the electrode array inserted, and after full insertion.

RESULTS

Monitoring of the hearing state using CMs was quick, reliable, and capable of detecting an intracochlear trauma. In a first series of patients, thresholds were preserved in all patients after opening of the cochlea. Thresholds were preserved in 5 of 6 patients after limited insertion and half of the patients after full insertion of the electrode array. Despite threshold preservation until the end of surgery, the residual hearing was lost in patients with deep insertions 1 week postoperative.

CONCLUSION

Intraoperative monitoring of CM thresholds may be valuable for identifying the exact point of time at which residual hearing is affected in CI patients. Opening of the cochlea itself seems to be unrelated to hearing loss. A significant proportion of patients may have hearing loss caused by secondary effects rather than a direct trauma.

Beneficial acoustic speech cues for cochlear implant users with residual acoustic hearing

This study investigated which acoustic cues within the speech signal are responsible for bimodal speech perception benefit. Seven cochlear implant (CI) users with usable residual hearing at low frequencies in the non-implanted ear participated. Sentence tests were performed in near-quiet (some noise on the CI side to reduce scores from ceiling) and in a modulated noise background, with the implant alone and with the addition, in the hearing ear, of one of four types of acoustic signals derived from the same sentences: (1) a complex tone modulated by the fundamental frequency (F0) and amplitude envelope contours; (2) a pure tone modulated by the F0 and amplitude contours; (3) a noise-vocoded signal; (4) unprocessed speech. The modulated tones provided F0 information without spectral shape information, whilst the vocoded signal presented spectral shape information without F0 information. For the group as a whole, only the unprocessed speech condition provided significant benefit over implant-alone scores, in both near-quiet and noise. This suggests that, on average, F0 or spectral cues in isolation provided limited benefit for these subjects in the tested listening conditions, and that the significant benefit observed in the full-signal condition was derived from implantees' use of a combination of these cues.

Cochlear implantation: current and future device options

Today most cochlear implant users achieve above 80% on standard speech recognition in quiet testing, and enjoy excellent device reliability. Despite such success, conventional designs often fail to provide the frequency resolution required for complex listening tasks. Furthermore, performance variability remains a vexing problem, with a select group of patients performing poorly despite using the most recent technologies and processing strategies. This article provides a brief history of the development of cochlear implant technologies, reviews current implant systems from all 3 major manufacturers, examines recently devised strategies aimed at improving device performance, and discusses potential future developments.

Electro acoustic stimulation of the auditory system: UNICAMP's surgical approach

A new era has arrived in auditory rehabilitation with the introduction of new technologies such as electroacoustic stimulation (EAS). EAS is indicated for patients with residual hearing at low frequencies and severe or profound hearing loss at high frequencies. These patients have no indication for conventional cochlear implant and have difficulties in adapting to individual sound amplification devices. Preservation of hearing is vital in this process; the surgical technique must be based on this concept.

Objectives

To present the cochlear implant surgical technique with MED-EL Mand FlexEAS to preserve hearing in patients with hearing loss at high frequencies and to maintain low frequency hearing. We are the first institution to carry out this treatment in Brazil.

Methods

A case report of the surgical technique carried out in four patients; the procedure was carried out by the cochlear implant group of a specialized clinical hospital.

Results

The procedures were successful and uneventful.

Conclusion

We described the technique used at our institution for implants using EAS; the surgical technique is complex and includes steps for preservation of hearing.

Evaluation of an electrode prototype for atraumatic cochlear implantation in hearing preservation candidates: preliminary results from a temporal bone study

OBJECTIVES

This study aimed to evaluate an atraumatic prototype electrode carrier for cochlear implantation, the FLEX electrode. This electrode is designed to preserve hearing and to achieve a 360-degree insertion.

STUDY DESIGN

A cross-sectional human temporal bone study was conducted.

SETTING

Preliminarily, the prototype electrode was inserted in a scala tympani model to measure the insertion force. Thirteen human temporal bones were acquired postmortem and implanted with the new device using the round window approach. Three of them were implanted under radiologic control to demonstrate the insertion path. After embedding, the remaining 10 temporal bones were sectioned undecalcified and examined macroscopically and histologically.

MAIN OUTCOME MEASURES

The insertion force was measured to determine intracochlear resistance peaks. The insertion angle was measured, and the degree of intracochlear trauma was determined.

RESULTS

The round window approach caused cochlear trauma in 1 of 10 specimens. An exact 360-degree insertion was achieved in 7 of 10 specimens (mean overall insertion angle, 360 degrees). Radiologic examination and insertion force measurements revealed the smooth and atraumatic insertion.

CONCLUSION

The new prototype electrode carrier is suitable for clinical application. It can be handled easily and allows atraumatic 360-degree insertion of all electrode contacts. Therefore, this electrode concept allows good coverage of the cochlea for electrical and additional acoustic stimulation.