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

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.

Predictive Factors for Subjective Vertigo Following Cochlear Implantation: A Regional Multicenter Cohort Study of 395 Patients

INTRODUCTION

Cochlear implantation (CI) is generally accepted as having a low rate of postoperative complications, but between 9.3% and 13% of cases experience vertigo postoperatively. This study aimed to examine patient, surgical, and device factors contributing toward the risk of postoperative vertigo.

METHODOLOGY

A retrospective review was conducted of adult patients who underwent cochlear implant in a regional area of New South Wales from 2007 to 2018. A total of 395 cochlear implant cases were included in the final study.

RESULTS

The overall incidence of vertigo at 3 months of follow-up was 7.1% (n = 28/395). No difference was identified in this study between rates of postoperative vertigo between device factors, including implant make (Cochlear vs. Med-El), electrode shape (perimodiolar vs. straight), and electrode model. No significant difference was found also for surgical factors such as the number of electrode rings inserted, side of implantation, or surgical approach of tympanic ramp (round window insertion vs. cochleostomy).A higher percentage of patients with preoperative vertigo experienced vertigo postoperatively (18.4%, n = 7/38), compared with the population without preoperative vertigo (6.0%, n = 21/352) ( p = 0.005). Patients with previous mastoid surgery also reported a higher rate of postoperative vertigo (20%, n = 9/45) compared with those who had not had mastoid surgery (5.43%, n = 19/350) ( p = 0.006). The mean age of patients experiencing postoperative vertigo was higher than the population without postoperative symptoms (67 vs. 63).

CONCLUSION

This study of a large multicenter population outlines that patient factors are more critical than surgical or device factors when considering risk factors for vertigo post-cochlear implant.

Impedance development after implantation of hybrid-L24 cochlear implant electrodes

OBJECTIVE

Shorter and thinner electrodes were developed for preserving residual hearing after cochlear implantation by minimising trauma. As trauma is regarded as one of the causes of fibrous tissue formation after implantation, and increase in impedance is considered to be connected to fibrous tissue formation, the aim of the current study was to evaluate impedance development after implantation of Hybrid-L electrodes.

DESIGN

Impedance values were retrospectively collected from our clinical database and evaluated for all active contacts and basal, middle and apical contacts separately for up to 10 years.

STUDY SAMPLES

All 137 adult patients received a Hybrid-L electrode and had to be implanted for at least 1 year.

RESULTS

On average impedances increased to 13 kOhm before first fitting and dropped to 5-7 kOhm under electrical stimulation with lower values measured on apical contacts. Mean values remained stable over years, but variability increased. Values before first fitting were independent of age at implantation whereas lower values were found later in patients of higher age at implantation.

CONCLUSION

Despite smaller contacts, impedance values after start of electrical stimulation were comparable to published values of Contour electrodes. This might suggest less tissue growth with the Hybrid-L electrode array.

Evaluation of the Performance of OTOPLAN-Based Cochlear Implant Electrode Array Selection: A Retrospective Study

Otoplan is a surgical planning software designed to assist with cochlear implant surgery. One of its outputs is a recommendation of electrode array type based on imaging parameters. In this retrospective study, we evaluated the differences in auditory outcomes between patients who were implanted with arrays corresponding to those recommended by the Otoplan software versus those in which the array selection differed from the Otoplan recommendation. Pre-operative CT images from 114 patients were imported into the software, and array recommendations were generated. These were compared to the arrays which had actually been implanted during surgery, both in terms of array type and length. As recommended, 47% of patients received the same array, 34% received a shorter array, and 18% received a longer array. For reasons relating to structure and hearing preservation, 83% received the more flexible arrays. Those who received stiffer arrays had cochlear malformations or ossification. A negative, although non-statistically significant correlation was observed between the CNC scores at 12 months and the absolute value of the difference between recommended array and implanted array. In conclusion, clinicians may be slightly biased toward shorter electrode arrays due to their perceived greater ability to achieve full insertion. Using 3D imaging during the pre-operative planning may improve clinicians' confidence to implant longer electrode arrays, where appropriate, to achieve optimum hearing outcomes.

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.

Slim Modiolar Electrode Placement in Candidates for Electroacoustic Stimulation

OBJECTIVES

To determine rates of hearing preservation and performance in patients who met candidacy for electroacoustic stimulation (EAS) and were implanted with a slim modiolar electrode (CI532 or CI632).

DESIGN

Adult patients meeting Food and Drug Administration criteria for electroacoustic stimulation (preoperative low-frequency pure-tone average [LFPTA] less than 60 dB at 125, 250, and 500 Hz and monosyllabic word scores between 10% and 60% in the ear to be implanted), who received a slim modiolar electrode were included. Main outcome measures included rates of hearing preservation, defined as a LFPTA ≤80 dB at 125, 250, and 500 Hz, as well as postoperative low-frequency pure-tone threshold shifts, consonant-Nucleus-Consonant (CNC) word scores and AzBio sentences in noise scores.

RESULTS

Forty-six patients met inclusion criteria during a 4-year period. Mean (standard deviation) preoperative LFPTA was 34.5 (13.0) dB, and 71.7% had preserved hearing at initial activation. The mean LFPTA shift in patients who preserved hearing at initial activation was 19.7 (14.6) dB, compared with 62.6 (17.7) dB in patients who did not preserve hearing as per our definition. Perioperative steroid use was not different in patients with and without preserved hearing (X 2 (1, N = 46) = 0.19, p = .67, V = 0.06). One year after surgery, 57% of patients had a decline in LFPTA >80 dB and were no longer considered candidates for EAS, with 34.7% still retaining low-frequency thresholds ≤80 dB. CNC word scores at 1 year were 69.9% and 61.4% among individuals with and without preserved low-frequency hearing respectively, measured in their CI ear alone, in their regular listening condition of EAS or electric only ( t (32) = 1.13, p = 0.27, d = 0.39, 95% CI = -6.51, 22.86). Device use time did not differ between groups. Among adults with preserved residual hearing at 1 year (n = 16), 44% used EAS, although there was no significant difference in performance between EAS users and nonusers with preserved hearing. Loss of residual hearing over time did not result in a decline in speech perception performance.

CONCLUSION

The present study demonstrated favorable early rates of hearing preservation with a slim modiolar array. Performance was not significantly different in individuals with and without preserved low-frequency acoustic hearing, independent of EAS use. Compared with reports of short electrode use, the loss of residual hearing in patients implanted with this array did not impact speech perception performance.

Cochlear Implantation in Hearing-Impaired Elderly: Clinical Challenges and Opportunities to Optimize Outcome

Cochlear implant (CI) overall provides a very good outcome, but speech comprehension outcome in the elderly is more variable. Several clinical factors play an important role. The management of residual hearing, the presence of comorbidities, and especially the progression of cognitive decline seem to be the clinical parameters that strongly determine the outcome of cochlear implantation and need to be discussed prospectively in the consultation process with the elderly hearing impaired. In the context of this review article, strategies for dealing with these will be discussed. Timely cochlear implantation should already be considered by hearing aid acousticians or practicing otolaryngologists and communicated or initiated with the patient. This requires intensive cooperation between hearing aid acousticians and experts in the clinic. In addition, residual hearing and comorbidities in the elderly need to be considered to make realistic predictions about speech comprehension with CI. Long-term aftercare and its different implementations should be discussed preoperatively, so that the elderly person with hearing impairments feels well taken care of together with his or her relatives. Elderly patients with hearing impairments benefit most from a CI in terms of speech comprehension if there is a large cochlear coverage (electrical or acoustic electrical) and the therapy is not hampered by comorbidities, especially cognitive decline.

Cochlear implantation in an animal model documents cochlear damage at the tip of the implant

INTRODUCTION

Electrocochleography has recently emerged as a diagnostic tool in cochlear implant surgery, purposing hearing preservation and optimal electrode positioning.

OBJECTIVE

In this experimental study, extra-cochlear potentials were obtained during cochlear implant surgery in guinea pigs. The aim was to determine electrophysiological changes indicating cochlear trauma after cochleostomy and after electrode implantation in different insertion depths.

METHODS

Normal-hearing guinea pigs (n = 14) were implanted uni- or bilaterally with a multichannel electrode. The extra-cochlear cochlear nerve action potentials were obtained in response to acoustic stimuli at specific frequencies before and after cochleostomy, and after introduction of the electrode bundle. After the electrophysiological experiments, the guinea pigs were euthanized and microtomography was performed, in order to determine the position of the electrode and to calculate of the depth of insertion. Based on the changes of amplitude and thresholds in relation to the stimulus frequency, the electrophysiological data and the position obtained by the microtomography reconstruction were compared.

RESULTS

Cochleostomy promoted a small electrophysiological impact, while electrode insertion caused changes in the amplitude of extra-cochlear electrophysiological potentials over a wide range of frequencies, especially in the deepest insertions. There was, however, preservation of the electrical response to low frequency stimuli in most cases, indicating a limited auditory impact in the intraoperative evaluation. The mean insertion depth of the apical electrodes was 5339.56 μm (±306.45 - 6 inserted contacts) and 4447.75 μm (±290.23 - 5 inserted contacts).

CONCLUSIONS

The main electrophysiological changes observed during surgical procedures occurred during implantation of the electrode, especially the deepest insertions, whereas the cochleostomy disturbed the potentials to a lesser extent. While hearing loss was often observed apical to the cochlear implant, it was possible to preserve low frequencies after insertion.

Cochlear Implant Electrode Impedance as Potential Biomarker for Residual Hearing

Introduction and Objectives

Among cochlear implant candidates, an increasing number of patients are presenting with residual acoustic hearing. To monitor the postoperative course of structural and functional preservation of the cochlea, a reliable objective biomarker would be desirable. Recently, impedance telemetry has gained increasing attention in this field. The aim of this study was to investigate the postoperative course of the residual acoustic hearing and clinical impedance in patients with long electrode arrays and to explore the applicability of impedance telemetry for monitoring residual hearing.

Methods

We retrospectively analyzed records of 42 cochlear implant recipients with residual hearing covering a median postoperative follow-up of 25 months with repeated simultaneous pure tone audiometry and impedance telemetry. We used a linear mixed-effects model to estimate the relation between clinical electrode impedance and residual hearing. Besides the clinical impedance, the follow-up time, side of implantation, gender, and age at implantation were included as fixed effects. An interaction term between impedance and follow-up time, as well as subject-level random intercepts and slopes, were included.

Results

Loss of residual hearing occurred either during surgery or within the first 6 post-operative months. Electrode contacts inserted further apically (i.e., deeper) had higher impedances, independent of residual hearing. The highest impedances were measured 1 month postoperatively and gradually decreased over time. Basal electrodes were more likely to maintain higher impedance. Follow-up time was significantly associated with residual hearing. Regardless of the time, we found that a 1 kΩ increase in clinical impedance was associated with a 4.4 dB deterioration of residual hearing (p < 0.001).

Conclusion

Pure tone audiometry is the current gold standard for monitoring postoperative residual hearing. However, the association of clinical impedances with residual hearing thresholds found in our study could potentially be exploited for objective monitoring using impedance telemetry. Further analysis including near-field related impedance components could be performed for improved specificity to local immune responses.

Clinical experiences with intraoperative electrocochleography in cochlear implant recipients and its potential to reduce insertion trauma and improve postoperative hearing preservation

Access to low-frequency acoustic information in cochlear implant patients leads to better speech understanding in noise. Electrocochleography (ECochG) can provide real-time feedback about the health of the cochlea during the insertion process with the potential to reduce insertion trauma. We describe our experiences of using this technique. Data from 47 adult subjects with measurable residual hearing and an Advanced Bionics (Valencia, CA) SlimJ (46) or MidScala (1) electrode array were analyzed. ECochGs were recorded intraoperatively via the implant. The surgeon adjusted the course of the electrode insertion based on drops in the ECochG. The final array position was assessed using postoperative imaging and pure tone thresholds were measured before and after surgery. Three different patterns of ECochG response amplitude were observed: Growth, Fluctuating and Total Loss. Subjects in the growth group showed the smallest postoperative hearing loss. However, the group with fluctuating amplitudes showed no meaningful correlation between the ECochG responses and the postoperative hearing loss, indicating that amplitude alone is insufficient for detecting damage. Considering the phase of the signal additionally to the amplitude and reclassifying the data by both the phase and amplitude of the response into three groups Type I–Type III produced statistically significant correlations between postoperative hearing loss and the grouping based on amplitude and phase respectively. We showed significantly better hearing preservation for Type I (no drop in amplitude) and Type II (drop with a concurrent phase shift), while Type III (drop without concurrent phase shift) had more surgery induced hearing loss. ECochG potentials measured through the implant could provide valuable feedback during the electrode insertion. Both the amplitude and phase of the ECochG response are important to consider. More data needs to be evaluated to better understand the impact of the different signal components to design an automated system to alert the surgeon ahead of damaging the cochlea.

Electrode array design determines scalar position, dislocation rate and angle and postoperative speech perception

Purpose

The aim of this study is to examine the scalar dislocation rate in straight and perimodiolar electrode arrays in relation to cochlear morphology. Furthermore, we aim to analyze the specific dislocation point of electrode arrays depending on their design and shape and to correlate these results to postoperative speech perception.

Methods

We conducted a comparative analysis of patients (ears: n = 495) implanted between 2013 and 2018 with inserted perimodiolar or straight electrode arrays from Cochlear™ or MED-EL. CBCT (cone beam computed tomography) was used to determine electrode array position (scalar insertion, intra-cochlear dislocation, point of dislocation and angular insertion depth). Furthermore, cochlear morphology was measured. The postoperative speech discrimination was compared regarding electrode array dislocation, primary scalar insertion and angular insertion depth.

Results

The electrode array with the highest rate of primary SV insertions was the CA; the electrode array with the highest rate of dislocations out of ST was the Flex^Soft. We did not find significantly higher dislocation rates in cochleostomy-inserted arrays. The angle of dislocation was electrode array design-specific. A multivariate nonparametric analysis revealed that the dislocation of the electrode array has no significant influence on postoperative speech perception. Nevertheless, increasing angular insertion depth significantly reduced postoperative speech perception for monosyllables.

Conclusion

This study demonstrates the significant influence of electrode array design on scalar location, dislocation and the angle of dislocation itself. Straight and perimodiolar electrode arrays differ from each other regarding both the rate and place of dislocation. Insertion via cochleostomy does not lead to increased dislocation rates in any of the included electrode arrays. Furthermore, speech perception is significantly negatively influenced by angular insertion depth.

Cochlear Implantation in Elderly Patients with Residual Hearing

This retrospective study aimed to investigate the range of hearing levels in a cochlear implant (CI) elderly population receiving electric-acoustic-stimulation (EAS) or electric-stimulation (ES) alone. The investigation evaluates the degree of hearing preservation (HP) and the speech comprehension resulting from EAS or ES-only to identify audiometric factors that predict adequate EAS and ES use. We analyzed the pure tone audiometry and speech perception in quiet and noise preoperatively and 12-months after activation of 89 elderly adults (age of 65 years old or older), yielding in total 97 CIs. Thirty-two (33.1%) patients were potential EAS candidates preoperatively, of which 18 patients used EAS at the time of first fitting and the other 14 patients continued to use their residual hearing for EAS at 12-months. Post-treatment, patients with EAS system and ES-only users’ with longer electrodes showed better results in monosyllable word scores in quiet than ES-only users with shorter electrodes. A similar trend was revealed for the speech recognition in noise. Patients with an EAS system benefit from maintaining their natural residual hearing. Nevertheless, strict preoperative patient selection is warranted particularly in elderly patients, in whom the hearing thresholds for EAS indication differ slightly from that in younger adults.

Initial Hearing Preservation Is Correlated With Cochlear Duct Length in Fully-inserted Long Flexible Lateral Wall Arrays

OBJECTIVES

To characterize the relationship between cochlear duct length (CDL) and initial hearing preservation among cochlear implant recipients of a fully inserted 31.5 mm flexible lateral wall electrode array.

STUDY DESIGN

Retrospective review.

SETTING

Tertiary academic referral center.

PATIENTS

Adult cochlear implant recipients who presented preoperatively with unaided hearing detection thresholds of ≤ 65 dB HL at 125 Hz and underwent cochlear implantation with a 31.5 mm flexible lateral wall array.

INTERVENTION

Cochlear implantation with a hearing preservation surgical approach.

MAIN OUTCOME MEASURES

Computed tomography was reviewed to determine CDL. Hearing preservation was characterized by the shift in low-frequency pure-tone average (LFPTA; 125, 250, and 500 Hz), and shift in individual unaided hearing detection thresholds at 125, 250, and 500 Hz.

RESULTS

Nineteen patients met the criteria for inclusion. The mean CDL was 34.2 mm (range: 30.8-36.5 mm). Recipients experienced a mean LFPTA shift of 27.6 dB HL (range: 10-50 dB HL). Significant, negative correlations were observed between CDL and smaller threshold shifts at individual frequencies and LFPTA (p ≤ 0.048).

CONCLUSION

A longer CDL is associated with greater likelihood of preserving low-frequency hearing with long arrays. Low-frequency hearing preservation is feasible with fully inserted long flexible arrays within the initial months after cochlear implantation. Preoperative measurement of CDL may facilitate a more individualized approach in array selection to permit optimal cochlear coverage while enhancing hearing preservation outcomes.

Unilateral Cochlear Implants for Severe, Profound, or Moderate Sloping to Profound Bilateral Sensorineural Hearing Loss: A Systematic Review and Consensus Statements

Importance

Cochlear implants are a treatment option for individuals with severe, profound, or moderate sloping to profound bilateral sensorineural hearing loss (SNHL) who receive little or no benefit from hearing aids; however, cochlear implantation in adults is still not routine.

Objective

To develop consensus statements regarding the use of unilateral cochlear implants in adults with severe, profound, or moderate sloping to profound bilateral SNHL.

Design, Setting, and Participants

This study was a modified Delphi consensus process that was informed by a systematic review of the literature and clinical expertise. Searches were conducted in the following databases: (1) MEDLINE In-Process & Other Non-Indexed Citations and Ovid MEDLINE, (2) Embase, and (3) the Cochrane Library. Consensus statements on cochlear implantation were developed using the evidence identified. This consensus process was relevant for the use of unilateral cochlear implantation in adults with severe, profound, or moderate sloping to profound bilateral SNHL. The literature searches were conducted on July 18, 2018, and the 3-step Delphi consensus method took place over the subsequent 9-month period up to March 30, 2019.

Main Outcomes and Measures

A Delphi consensus panel of 30 international specialists voted on consensus statements about cochlear implantation, informed by an SR of the literature and clinical expertise. This vote resulted in 20 evidence-based consensus statements that are in line with clinical experience. A modified 3-step Delphi consensus method was used to vote on and refine the consensus statements. This method consisted of 2 rounds of email questionnaires and a face-to-face meeting of panel members at the final round. All consensus statements were reviewed, discussed, and finalized at the face-to-face meeting.

Results

In total, 6492 articles were identified in the searches of the electronic databases. After removal of duplicate articles, 74 articles fulfilled all of the inclusion criteria and were used to create the 20 evidence-based consensus statements. These 20 consensus statements on the use of unilateral cochlear implantation in adults with SNHL were relevant to the following 7 key areas of interest: level of awareness of cochlear implantation (1 consensus statement); best practice clinical pathway from diagnosis to surgery (3 consensus statements); best practice guidelines for surgery (2 consensus statements); clinical effectiveness of cochlear implantation (4 consensus statements); factors associated with postimplantation outcomes (4 consensus statements); association between hearing loss and depression, cognition, and dementia (5 consensus statements); and cost implications of cochlear implantation (1 consensus statement).

Conclusions and Relevance

These consensus statements represent the first step toward the development of international guidelines on best practices for cochlear implantation in adults with SNHL. Further research to develop consensus statements for unilateral cochlear implantation in children, bilateral cochlear implantation, combined electric-acoustic stimulation, unilateral cochlear implantation for single-sided deafness, and asymmetrical hearing loss in children and adults may be beneficial for optimizing hearing and quality of life for these patients.

Cochlear implantation for tinnitus in adults with bilateral hearing loss: protocol of a randomised controlled trial

INTRODUCTION

Tinnitus is the perception of sound without an external stimulus, often experienced as a ringing or buzzing sound. Subjective tinnitus is assumed to origin from changes in neural activity caused by reduced or lack of auditory input, for instance due to hearing loss. Since auditory deprivation is thought to be one of the causes of tinnitus, increasing the auditory input by cochlear implantation might be a possible treatment. In studies assessing cochlear implantation for patients with hearing loss, tinnitus relief was seen as a secondary outcome. Therefore, we will assess the effect of cochlear implantation in patients with primarily tinnitus complaints.

METHOD AND ANALYSIS

In this randomised controlled trial starting in January 2021 at the ENT department of the UMC Utrecht (the Netherlands), patients with a primary complaint of tinnitus will be included. Fifty patients (Tinnitus Functional Index (TFI) >32, Beck's Depression Index <19, pure tone average at 0.5, 1, 2 and 4 kHz: bilateral threshold between 50 and ≤75 dB) will be randomised towards cochlear implantation or no intervention. Primary outcome of the study is tinnitus burden as measured by the TFI. Outcomes of interest are tinnitus severity, hearing performances (tinnitus pitch and loudness, speech perception), quality of life, depression and patient-related changes. Outcomes will be evaluated prior to implantation and at 3 and 6 months after the surgery. The control group will receive questionnaires at 3 and 6 months after randomisation. We expect a significant difference between the cochlear implant recipients and the control group for tinnitus burden.

ETHICS AND DISSEMINATION

This research protocol was approved by the Institutional Review Board of the University Medical Center (UMC) Utrecht (NL70319.041.19, V5.0, January 2021). The trial results will be made accessible to the public in a peer-review journal.

TRIAL REGISTRATION NUMBER

Trial registration number NL8693; Pre-results.

The Effect of Ultra-slow Velocities on Insertion Forces: A Study Using a Highly Flexible Straight Electrode Array

OBJECTIVE

The present study sought to 1) characterize insertion forces resulting from a flexible straight electrode array (EA) inserted at slow and ultra-slow insertion velocities, and 2) evaluate if ultra-slow velocities decrease insertion forces independent of other variables.

BACKGROUND

Low insertion forces are desirable in cochlear implant (CI) surgery to reduce trauma and preserve hearing. Recently, ultra-slow insertion velocities (lower than manually feasible) have been shown to produce significantly lower insertion forces using other EAs.

METHODS

Five flexible straight EAs were used to record insertion forces into an inelastic artificial scala tympani model. Eleven trial recordings were performed for each EA at five predetermined automated, continuous insertion velocities ranging from 0.03 to 1.6 mm/s.

RESULTS

An ultra-slow insertion velocity of 0.03 mm/s resulted in a median insertion force of 0.010 N at 20 mm of insertion depth, and 0.026 N at 24.3 mm-the final insertion depth. These forces represent only 24 to 29% of those measured using 1.6 mm/s. After controlling for insertion depth of the EA into the artificial scala tympani model and trial insertion number, decreasing the insertion velocity from 0.4 to 0.03 mm/s resulted in a 50% decrease in the insertion forces.

CONCLUSION

Using the tested EA ultra-slow velocities can decrease insertion forces, independent of variables like insertion depth. Our results suggest ultra-slow velocities can reduce insertion forces at least 60%, compared with humanly feasible continuous velocities (≥0.9 mm/s).

Preimplant Hearing Threshold: An Important Predictor of Hearing Preservation in Cochlear Implantation With Lateral Wall Electrodes

OBJECTIVE

To evaluate the outcomes and association factors of long-term hearing preservation (HP) in cochlear implantation with lateral wall (LW) electrode arrays.

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary academic center.

PATIENTS

Thirty-four consecutive ears from 32 patients with a ≤ 80 dB HL preoperative low-frequency pure-tone average of 250 to 500 Hz were included.

INTERVENTION

Cochlear implantation with LW electrode arrays and the intention of achieving HP.

MAIN OUTCOME MEASURES

HP classifications according to the HEARRING group and functional HP methods (≤ 85 dB HL of pure-tone threshold at 250 Hz) at 1 year postoperatively.

RESULTS

Based on the HEARRING classification, complete, partial, and minimal HP was achieved in 7 ears (21%), 12 ears (35%), and 4 ears (12%), respectively. Under functional classification, 14 ears (41%) exhibited functional hearing after surgery. The average threshold shift was 17.1 dB HL (SD = 16.9 dB HL). Among various clinical features, a ≤ 60 dB HL preimplant pure-tone threshold of 250 Hz was associated with HP outcome in both classifications (OR = 12.95, 95% CI = 1.29-130.01, p = 0.029 in HEARRING classification; OR = 14.36, 95% CI = 1.07-191.40, p = 0.044 in functional classification). The following parameters were not associated with HP (p > 0.05): patient demographics, surgical aspects (insertion route and depth), electrode array size, scalar electrode position, and presence of comorbidity.

CONCLUSION

With LW electrode arrays, HP was achieved in 68% of HEARRRING group patients and 41% of functional classification patients. A ≤ 60 dB HL preimplant pure-tone threshold of 250 Hz was significantly associated with an increased rate of long-term HP.

Initial hearing preservation outcomes of cochlear implantation with a slim perimodiolar electrode array

OBJECTIVE

To assess the slim modiolar array as a hearing preservation electrode.

METHODS

Retrospective chart review of adult, post-lingual CI recipients implanted with slim modiolar array Sept 2016 to July 2017 in a tertiary referral center. Baseline audiograms were obtained within six months of initial CI evaluation. Patients with low frequency pure tone average (LFPTA) (125, 250, 500 Hz) <80 dB were considered HP candidates. Postoperative audiograms were obtained within 48 h before activation. Successful HP was considered as (1) retention of LFPTA threshold <80 dB and (2) change in threshold from pre- to post-operative.

RESULTS

Sixty-three patients received the slim perimodiolar array and 42 were HP candidates. Post-operative audiograms were obtained for 39 of 42 patients an average of 28.92 days after surgery. 56.4% of HP candidates retainedLFPTA <80 dB. Mean ΔLFPTA was 24.15 dB (±16.14; p < 0.001). 56.4% of HP candidates experienced Δ LFPTA <20 dB; 69.2% <30 dB. Functional hearing preservation was more successful in lower frequencies where starting thresholds were better - 78% with LFPTA <50 dB retained serviceable hearing at activation. The postoperative change was similar in each low frequency (Δ125 Hz: mean 21.25 +/- 14.76 (N = 28); Δ250 Hz: 26.28 +/- 19.29 (N = 39); Δ500 Hz: 25.00 +/- 17.73 (N = 39)).

CONCLUSIONS

The slim perimodiolar array is moderately effective at immediate hearing preservation. In subjects with preoperative audiometric profiles similar to those in prior EAS trials, immediate HP is comparable.

Comparison of Speech Recognition and Localization Ability in Single-sided Deaf Patients Implanted With Different Cochlear Implant Electrode Array Designs

OBJECTIVE

Choice of electrode array (EA) design and differences in outcome are major concerns both to patients with single-sided deafness (SSD) and to surgeons before cochlear implant (CI) surgery. The present work investigates the effects of EA design on 1) insertion depths, and 2) audiological outcomes of SSD CI recipients.

STUDY DESIGN

Retrospective study.

SETTING

Tertiary academic center.

PATIENTS

Forty patients with acquired SSD matched according to duration of deafness MAIN OUTCOME MEASURES:: Fourteen CI recipients were implanted with a perimodiolar electrode (cochlear perimodiolar [CPM]), 12 with a shorter lateral wall electrode (cochlear lateral wall [CLW]), and 14 with a longer lateral wall electrode array (medEl lateral wall [MLW]). Postoperative rotational tomography was evaluated to determine cochlear size and EA angle of insertion depth (AID). Binaural speech comprehension in noise (in three configuration presentations) and localization ability were assessed 12 months postoperatively with CI.

RESULTS

AID was significantly deeper in MLW (mean 527.94 degrees) compared with the CPM (mean 366.35 degrees) and CLW groups (mean 367.01 degrees). No significant difference in AID was seen between the CPM and CLW groups (difference 0.66 degrees). Cochlear sizes revealed no significant differences between any groups. All three groups showed significant improvement in head shadow effect (difference on average CPM: 6.3 dB SPL, CLW 5 dB SPL, and MLW 4.05 dB SPL) and localization ability at 12 months postoperatively (difference on average CPM: 19.72 degrees, CLW: 24 degrees, and MLW: 12.9 degrees). No significant difference in the extent of audiological benefit was observed between any groups.

CONCLUSION

No effect on binaural benefit was apparent from the selection of the three EA designs in SSD CI recipients. Further studies focusing on subjective results, sound quality, and music perception depending on EA design in SSD CI recipients are needed.

Do Impedance Changes Correlate With a Delayed Hearing Loss After Hybrid L24 Implantation?

OBJECTIVES

Preservation of residual hearing is one of the main goals in present cochlear implantation surgery. Especially for this purpose, smaller and softer electrode carriers were developed that are to be inserted through the round window membrane to minimize trauma. By using these electrodes and insertion technique, residual hearing can be preserved in a large number of patients. Unfortunately, some of these patients with initially preserved residual hearing after cochlear implantation lose it later on. The reason for this is unknown but it is speculated about a correlation with an increase in impedance, since increased impedance values are linked to intracochlear inflammation and tissue reaction. Our hypothesis for this study design was that an increase in impedance predicts changes in residual hearing under clinical conditions.

DESIGN

Data of all adult patients (N = 122) receiving a Hybrid-L24 cochlear implant at our center between 2005 and early 2015 were retrospectively evaluated. Impedance values in Common Ground mode as measured during clinical routine and referring audiological test data (audiometric thresholds under headphones) were collected. Changes between consecutive measurements were calculated for impedance values and hearing thresholds for each patient. Correlations between changes in impedances and acoustic hearing thresholds were calculated. Average values were compared as well as patients with largest impedance changes within the observation period were evaluated separately.

RESULTS

Group mean values of impedances were between 5 and 7 kΩ and stable over time with higher values on basal electrode contacts compared with apical contacts. Average hearing thresholds at the time of initial fitting were between 40 to 50 dB (250 Hz) and 90 dB (1 kHz) with a loss of about 10 dB compared with preoperative values. Correlation between impedance changes and threshold changes was found, but too inconsistently to imply a true relationship. When evaluating the 20 patients with the largest impedance changes during the observation period (all >1 kΩ from one appointment to the next one), some patients were found where hearing loss is timely connected and highly correlated with an unusual impedance change. But large impedance changes were also observed without affecting hearing thresholds and hearing loss was found without impedance change.

CONCLUSIONS

Changes in impedance as measured during clinical routine cannot be taken as an indicator for a late acoustic hearing loss.

Acceptance and Benefits of Electro-Acoustic Stimulation for Conventional-Length Electrode Arrays

BACKGROUND

Prior studies have shown an advantage for electro-acoustic stimulation (EAS) in cochlear implant (CI) patients with residual hearing, but the degree of benefit can vary. The objective was to explore which factors relate to performance with and acceptance of EAS for CI users with conventional-length electrodes.

METHODS

A retrospective chart review was conducted for adults with an average threshold of 75 dB hearing loss or better across 250 and 500 Hz preoperatively (n = 83). All patients underwent cochlear implantation with a conventional-length electrode. Low-frequency audiometric thresholds were measured at initial activation as well as 3 and 12 months postoperatively to determine who met the criteria for EAS. Speech perception for CNC words and AzBio sentences in quiet and +10 dB SNR noise was evaluated 3 and 12 months after activation.

RESULTS

Speech perception in quiet and noise was similar regardless of whether or not the patient was eligible for EAS. Less than half of the patients who met the EAS criteria chose to use it, citing reasons such as physical discomfort or lack of perceived benefit. EAS users performed better on CNC words but not sentence recognition than EAS nonusers.

CONCLUSIONS

EAS use is dependent on audiologic and nonaudiologic issues. Hearing preservation is possible with conventional electrodes, but hearing preservation alone does not guarantee superior speech perception.

Randomized placebo-controlled clinical trial investigating the effect of antioxidants and a vasodilator on overall safety and residual hearing preservation in cochlear implant patients

BACKGROUND

The standard therapy for patients suffering from sensorineural hearing loss is cochlear implantation. The insertion of the electrode array into the cochlea, with potential mechanical trauma and the presence of this foreign body inside the cochlea, may lead to free radical formation and reduced blood perfusion of the cochlea which can result in a loss of residual hearing. Studies have suggested that a particular combination of the antioxidants vitamins A, C and E as well as the vasodilator magnesium (together: ACEMg) may protect the residual hearing.

METHODS

The potential protective effect of ACEMg on residual hearing preservation in cochlear implant (CI) patients was investigated in a single-centre, randomized, placebo-controlled, double-blind phase II clinical trial. CI candidates with some residual hearing in low frequencies receiving MED-EL implants of different FLEX electrode array lengths were treated with ACEMg tablets or placebo respectively 2 days preoperatively and up to 3 months postoperatively. The study objective was to demonstrate that ACEMg is more efficacious than placebo in preserving residual hearing during cochlear implantation by comparing the hearing loss (change in hearing thresholds at 500 Hz from baseline) 3 months after the first fitting between the two treatment groups and to investigate the treatments' safety.

RESULTS

Fifty-one patients were included in the study, which had to be terminated before the recruitment goal was reached because of IMP-resupply mismanagement of one partner. In the intention-to-treat population, 25 patients were treated with ACEMg and 24 patients with placebo. The mean hearing loss at 500 Hz was (± 15.84) 30.21 dB (placebo) or (± 17.56) 26.00 dB (ACEMg) 3 months after the initial fitting. Adjusting the postoperative hearing loss for the baseline residual hearing, planned electrode length and surgeon results in 8.01 dB reduced hearing loss in ACEMg-treated patients compared to placebo-treated ones. The safety analysis revealed that ACEMg was generally well-tolerated with adverse event frequencies below the placebo level.

CONCLUSION

This is the first clinical trial investigating a drug effect on residual hearing in CI patients. These first-in-man data may suggest that a perioperative oral administration of ACEMg is safe and may provide protection of residual hearing in CI patients.

TRIAL REGISTRATION

EU Clinical Trial Register No. 2012-005002-22 . Registered on 6 December 2013.

FUNDING

European Commission FP7-HEALTH-2012-INNOVATION-2.

Intracochlear Electrocochleography: Response Patterns During Cochlear Implantation and Hearing Preservation

OBJECTIVES

Electrocochleography (ECochG) obtained through a cochlear implant (CI) is increasingly being tested as an intraoperative monitor during implantation with the goal of reducing surgical trauma. Reducing trauma should aid in preserving residual hearing and improve speech perception overall. The purpose of this study was to characterize intracochlear ECochG responses throughout insertion in a range of array types and, when applicable, relate these measures to hearing preservation. The ECochG signal in cochlear implant subjects is complex, consisting of hair cell and neural generators with differing distributions depending on the etiology and history of hearing loss. Consequently, a focus was to observe and characterize response changes as an electrode advances.

DESIGN

In 36 human subjects, responses to 90 dB nHL tone bursts were recorded both at the round window (RW) and then through the apical contact of the CI as the array advanced into the cochlea. The specific setup used a sterile clip in the surgical field, attached to the ground of the implant with a software-controlled short to the apical contact. The end of the clip was then connected to standard audiometric recording equipment. The stimuli were 500 Hz tone bursts at 90 dB nHL. Audiometry for cases with intended hearing preservation (12/36 subjects) was correlated with intraoperative recordings.

RESULTS

Successful intracochlear recordings were obtained in 28 subjects. For the eight unsuccessful cases, the clip introduced excessive line noise, which saturated the amplifier. Among the successful subjects, the initial intracochlear response was a median 5.8 dB larger than the response at the RW. Throughout insertion, modiolar arrays showed median response drops after stylet removal while in lateral wall arrays the maximal median response magnitude was typically at the deepest insertion depth. Four main patterns of response magnitude were seen: increases > 5 dB (12/28), steady responses within 5 dB (4/28), drops > 5 dB (from the initial response) at shallow insertion depths (< 15 mm deep, 7/28), or drops > 5 dB occurring at deeper depths (5/28). Hearing preservation, defined as < 80 dB threshold at 250 Hz, was successful in 9/12 subjects. In these subjects, an intracochlear loss of response magnitude afforded a prediction model with poor sensitivity and specificity, which improved when phase, latency, and proportion of neural components was considered. The change in hearing thresholds across cases was significantly correlated with various measures of the absolute magnitudes of response, including RW response, starting response, maximal response, and final responses (p's < 0.05, minimum of 0.0001 for the maximal response, r's > 0.57, maximum of 0.80 for the maximal response).

CONCLUSIONS

Monitoring the cochlea with intracochlear ECochG during cochlear implantation is feasible, and patterns of response vary by device type. Changes in magnitude alone did not account for hearing preservation rates, but considerations of phase, latency, and neural contribution can help to interpret the changes seen and improve sensitivity and specificity. The correlation between the absolute magnitude obtained either before or during insertion of the ECochG and the hearing threshold changes suggest that cochlear health, which varies by subject, plays an important role.

Intracochlear fibrosis and the foreign body response to cochlear implant biomaterials

OBJECTIVE

To report current knowledge on the topic of intracochlear fibrosis and the foreign body response following cochlear implantation (CI).

METHODS

A literature search was performed in PubMed to identify peer-reviewed articles. Search components included "cochlear implant," "Foreign body response (FBR)," and "fibrosis." Original studies and review articles relevant to the topic were included.

RESULTS

Ninety peer-reviewed articles describing the foreign body response or intracochlear fibrosis following CI were included.

CONCLUSIONS

Intracochlear fibrosis following CI represents a significant limiting factor for the success of CI users. Several strategies have been employed to mitigate the foreign body response within the cochlea including drug delivery systems and modifications in surgical technique and electrode design. A better understanding of the FBR has the potential to improve CI outcomes and the next generation of cochlear prostheses.

Earphone and Aided Word Recognition Differences in Cochlear Implant Candidates

OBJECTIVE

Compare word recognition scores for adults undergoing cochlear implant evaluations (CIE) measured using earphones and hearing aids.

STUDY DESIGN

Retrospective review of data obtained during adult CIEs.

SETTING

Tertiary cochlear implant center.

PATIENTS

Two hundred eight ears in 183 subjects with greater than 10% word recognition scores measured with earphones.

INTERVENTIONS/MAIN OUTCOMES MEASURED

Preoperative pure-tone thresholds and word recognition scores measured with earphones and hearing aids.

RESULTS

A review of audiological data obtained from 2012 to 2017 during adult CIEs was conducted. Overall, a weak positive correlation (r = 0.33, 95% confidence interval 0.17-0.40, p < 0.001) was observed between word recognition scores measured with earphones and hearing aids. Earphone to aided differences (EAD) ranged from -38 to +72% (mean 14.3 ± 19.9%). Consistent with EADs, 108 ears (51.9%) had earphone scores that were significantly higher than aided word recognition scores (+EAD), as determined by 95% confidence intervals; for 14 ears (6.7%), earphone scores were significantly lower than aided scores (-EAD). Moreover, of the patients with earphone word recognition scores ≥50%, 82.6% were CI candidates based on aided AzBio+10 dB SNR scores.

CONCLUSION

These results demonstrate the limited diagnostic value of word recognition scores measured under earphones for patients undergoing CIE. Nevertheless, aided word recognition is rarely measured before CIEs, which limits the information available to determine CI candidacy and referral for CIEs. Earlier and routine measurement of aided word recognition may help guide clinical decision making by determining the extent to which patients are achieving maximum benefit with their hearing aids or should consider cochlear implantation.

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

Purpose

To evaluate the insertion results and hearing preservation of a novel slim modiolar electrode (SME) in patients with residual hearing.

Methods

We retrospectively collected the data from the medical files of 17 patients (18 ears) implanted with a SME. All patients had functional low frequency hearing (PTA _{(0.125–0.5 kHz)} ≤ 80 dB HL). The insertion results were re-examined from the postoperative cone-beam computed tomography scans. Postoperative thresholds were obtained at the time of switch-on of the sound processors (mean 43 days) and at latest follow-up (mean 582 days). The speech recognition in noise was measured with the Finnish matrix sentence test preoperatively and at follow-up.

Results

The mean insertion depth angle (IDA) was 395°. Neither scala dislocations nor tip fold over were detected. There were no total hearing losses. Functional low-frequency hearing was preserved in 15/18 (83%) ears at switch-on and in 14/17 (82%) ears at follow-up. According to HEARRING classification, 55% (10/18) had complete HP at switch-on and 41% (7/17) still at follow-up. Thirteen patients (14 ears) were initially fitted with electric–acoustic stimulation and seven patients (8 ears) continued to use it after follow-up.

Conclusions

The preliminary hearing preservation results with the SME were more favorable than reported for other perimodiolar electrodes. The results show that the array may also be feasible for electro-acoustic stimulation; it is beneficial in that it provides adequate cochlear coverage for pure electrical stimulation in the event of postoperative or progressive hearing loss.

Surgical approach for complete cochlear coverage in EAS-patients after residual hearing loss

Introduction

In cases with residual-hearing (RH) loss after cochlear implantation, a safe method is needed to provide full spectral resolution and as much auditory information as possible without implant replacement. Aim of this study was to prove the feasibility of accessing a partially inserted cochlear-implant-electrode for complete insertion to its maximum length through the external ear canal using a transcanal approach.

Methods

Two CI electrodes were customized with 18 stimulating channels. The electrode design enables the use of 12 active channels available for electrical stimulation inside the cochlea both after partial and full insertion. 10 CI electrodes were implanted in 10 fresh human cadaveric temporal bones. After initial partial insertion by posterior tympanotomy, the electrode was inserted to its maximum length via a transcanal approach. Radiographs and CT scans were performed to confirm the electrode position. The electrodes were investigated via x-ray after removal.

Results

X-ray and CT-scans confirmed the electrode prototypes covering an angular insertion depth between 236° to 307° after initial insertion. Accessing the electrode in the middle ear space was feasible and insertion to its full length was successful. Post-insertion CT confirmed insertion of the 28mm and 31.5mm electrode arrays covering an angular insertion depth between 360° and 540° respectively. No tip foldovers were detected.

Conclusion

This study confirms the feasibility of extending the electrode insertion to its maximum insertion length using a transcanal approach in temporal bone specimens. This constitutes a second stage procedure on demand in EAS-surgery. This may be beneficial for EAS-patients providing electrical stimulation beyond the basal turn of the cochlea once the functional residual hearing is lost, without replacing the entire CI.

A New Lateral Wall Electrode: Evaluation of Surgical Handling, Radiographic Placement, and Histological Appraisal of Insertion Trauma

OBJECTIVE

To describe histologic and radiographic findings associated with insertion of a new lateral wall electrode in human temporal bones, as well as quantify the ease of insertion as characterized by multiple cochlear implant surgeons.

SETTING

Multi-institutional cadaveric study.

METHODS

The Slim J electrode was inserted in cadaveric temporal bones via a standard mastoidectomy and facial recess approach. Insertion was performed by five cochlear implant surgeons with no previous experience with the Slim J electrode array. Electrode array insertion was performed via a round window, an extended round window, or a cochleostomy approach. Intracochlear trauma, and angular insertion depth was assessed histologically and radiologically, respectively, after placement of the Slim J electrode array.

RESULTS

Scala tympani insertion was accomplished in all 40 specimens. Thirty-eight specimens (95%) showed minimal trauma (Esrhaghi grade 0 or 1). One patient had rupture of basilar membrane (grade 2 trauma) at 380 degrees. One patient had grade 4 trauma with scalar translocation beginning at 210 degrees. The mean angular insertion depth was 416.4 degrees (range: 338.7-509.2 degrees, SD 44 degrees). Surgical handling was described as easy in 38 cases (95%).

CONCLUSION

In a human cadaveric model the lateral wall Slim J electrode produced minimal intracochlear trauma that was positioned completely within the scala tympani in 97.5% of cases.

Initial surgical and clinical experience with the Nucleus CI532 slim modiolar electrode in the UK

OBJECTIVE

The goal of this work is to describe the first experience in the UK with the slim pre-curved perimodiolar electrode Nucleus CI532 in a continuous series of patients in terms of surgical and clinical reliability and early performance outcomes.

METHOD

In this retrospective review we describe the complication rate (including electrode array tip fold-over), NRT thresholds, hearing preservation, power efficiency and CI performance outcomes in a continuous series of 40 cochlear implants CI532 performed between October 2016 and November 2017 in 17 adults and 13 children with severe to profound hearing loss.

RESULTS

Preliminary data from these groups reveals some low-frequency hearing preservation in the CI532 group although none of the patients were conventional hearing preservation candidates. NRT thresholds, power efficiency, and BKB sentences in quiet were measured at 3 and 6 months post activation. There were no significant differences in these results. The average BKB score in quiet increases from 22% pre-operatively to 58% at 3 months and 70% at 6 months. In addition, although hearing preservation was not an objective, low-frequency thresholds were preserved in 20% of cases at 3 and 6 months post-operatively. Complications were observed in 5 cases, one case with non-device related aerocoele and four related to the device array: two cases of tip roll over, one case of the electrode array being placed extra-cochlea, and one case with the electrode buckling into the middle ear. The last 2 cases were dealt with per-operatively.

DISCUSSION

Our preliminary results with the CI532 implant indicate that it may be reliably placed with standard surgical techniques but care is needed during the deployment of the electrode. Further initial data suggest that switch on and early electrophysiological measures are comparable to the existing CI 512 device. However whilst preliminary, our data suggest that it may be possible to use this electrode for hearing preservation. However, further studies are required to determine its definitive advantage over other electrode designs.

CONCLUSION

CI532 is a reliable device offering good initial results and could be an option for hearing preservation although further studies are required.

The effect of cross-over frequency on binaural hearing performance of adults using electric-acoustic stimulation

Objective: To investigate the effect of varying cross-over frequency (CF) settings for electric-acoustic (EA) stimulation in one ear combined with acoustic (A) hearing in the opposite ear on binaural speech perception, localization and functional performance in real life. Methods: Performance with three different CF settings set according to audiometric-based criterion were compared, following a four week familiarisation period with each, in ten adult cochlear implant recipients with residual hearing in both ears. On completion of all trials participants selected their preferred CF setting. Results: On average, CF settings did not have a significant effect on performance scores. However, higher ratings on device usage were associated with the preferred CF settings. Conclusion: Individuals who use EA + A stimulation may benefit from access to different CF settings to achieve maximal device usage.

Influence of In Vitro Electrical Stimulation on Survival of Spiral Ganglion Neurons

Patients scheduled for cochlear implantation often retain residual hearing in the low frequencies. Unfortunately, some patients lose their residual hearing following implantation and the reasons for this are not well understood. Evidence suggests that electrotoxicity could be one of the factors responsible for this late adverse effect. Therefore, the aim of this study was to investigate the survival of spiral ganglion neurons (SGN) subjected to in vitro electrical stimulation (ES). A stimulation setup was developed to provide defined electrical fields at given points of the chamber. SGN isolated from Sprague Dawley rats (P3-4) were dissociated and cultured in the chamber for 24 h prior to biphasic, pulsed electrical field exposure for another 24 h. The current varied in the range of 0 to 2 mA and the pulse width from 10 to 400 μs. Neurite growth and survival were evaluated with respect to the charge density at the position of the cells. Non-exposed SGN cultures served as control. Charge densities below 2.2 μC·cm^-2·phase^-1 appeared to have no effect on SGN survival and neurite outgrowth. Charge densities above 4.9 μC·cm^-2·phase^-1 were detrimental to almost all cells in culture. After fitting results to a sigmoidal dose response curve, a LD₅₀ of 2.9 μC·cm^-2·phase^-1 was calculated. This screening regarding survival and outgrowth of SGN provides parameters that could be used to further investigate the effect of ES on SGN and to develop possible protection strategies, which could potentially rescue residual hearing in the implanted patients.

Intracochlear administration of steroids with a catheter during human cochlear implantation: a safety and feasibility study

Suppression of foreign body reaction, improvement of electrode-nerve interaction, and preservation of residual hearing are essential research topics in cochlear implantation. Intracochlear pharmaco- or cell-based therapies can open new horizons in this field. Local drug delivery strategies are desirable as higher local concentrations of agents can be realized and side effects can be minimized compared to systemic administrations. When administered locally at accessible, basal parts of the cochlea, drugs reach apical regions later and in much lower concentrations due to poor diffusion patterns in cochlear fluids. Therefore, new devices are needed to warrant rapid distribution of agents into all parts of the cochlea. Five patients received a deep intracochlear injection of triamcinolone with a specifically designed cochlear catheter during cochlear implantation right before inserting a cochlear implant electrode. As a measure for formation of fibrous tissue around the electrode, electrical impedances were measured in the operation room and over 4 months thereafter. No adverse events were observed peri- and postoperatively. The handling of the device was easy. Severe damage to the microstructure of the cochlea was excluded as far as possible by cone beam computed tomography and vestibular testing. A delayed rise of the impedances was seen in the catheter group compared to controls over all regions of the cochlea. A statistical significance, however, was only obtained at the midregion of the cochlea. Consequently, the cochlear catheter is a safe and feasible device for local drug delivery of pharmaceutical agents into deeper regions of the cochlea.

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

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

Electric and Acoustic Stimulation in Cochlear Implant Recipients with Hearing Preservation

Hearing loss affects 30 million people in the United States, and a subset of these patients have normal low-frequency hearing and ski-sloped high-frequency hearing loss. For these patients, hearing aids alone may not provide adequate benefit. Cochlear implantation alone has been utilized to improve speech perception. The addition of high-frequency electric hearing to low-frequency acoustic hearing in these patients is beneficial. Technical improvements have allowed preservation of low-frequency hearing in cochlear implant recipients, allowing for electric and acoustic stimulation in the same ear with significant improvements in speech perception, sound localization, music appreciation, and quality of life.

Postoperative Electrocochleography from Hybrid Cochlear Implant users: An Alternative Analysis Procedure

OBJECTIVE

Shorter electrode arrays and soft surgical techniques allow for preservation of acoustic hearing in many cochlear implant (CI) users. Recently, we developed a method of using the Neural Response Telemetry (NRT) system built in Custom Sound EP clinical software to record acoustically evoked electrocochleography (ECoG) responses from an intracochlear electrode in Nucleus Hybrid CI users (Abbas et al., 2017). We recorded responses dominated by the hair cells (cochlear microphonic, CM/DIF) and the auditory nerve (auditory nerve neurophonic, ANN/SUM). Unfortunately, the recording procedure was time consuming, limiting potential clinical applications. This report describes a modified method to record the ECoG response more efficiently. We refer to this modified technique as the "short window" method, while our previous technique (Abbas et al., 2017) is referred as the "long window" method. In this report, our goal was to 1) evaluate the feasibility of the short window method to record the CM/DIF and ANN/SUM responses, 2) characterize the reliability and sensitivity of the measures recorded using the short window method, and 3) evaluate the relationship between the CM/DIF and ANN/SUM measures recorded using the modified method and audiometric thresholds.

METHOD

Thirty-four postlingually deafened adult Hybrid CI users participated in this study. Acoustic tone bursts were presented at four frequencies (250, 500, 750, and 1000 Hz) at various stimulation levels via an insert earphone in both condensation and rarefaction polarities. Acoustically evoked ECoG responses were recorded from the most apical electrode in the intracochlear array. These two responses were subtracted to emphasize the CM/DIF responses and added to emphasize the ANN/SUM responses. Response thresholds were determined based on visual inspection of time waveforms, and trough-to-peak analysis technique was used to quantify response amplitudes. Within-subject comparison of responses measured using both short and long window methods were obtained from seven subjects. We also assessed the reliability and sensitivity of the short window method by comparing repeated measures from 19 subjects at different times. Correlations between CM/DIF and ANN/SUM measures using the short window recording method and audiometric thresholds were also assessed.

RESULTS

Regardless of the recording method, CM/DIF responses were larger than ANN/SUM responses. Responses obtained using the short window method were positively correlated to those obtained using the conventional long window method. Subjects who had stable acoustic hearing at two different time points had similar ECoG responses at those points, confirming high test-retest reliability of the short window method. Subjects who lost hearing between two different time points showed increases in ECoG thresholds, suggesting that physiologic ECoG responses are sensitive to audiometric changes. Correlations between CM/DIF and ANN/SUM thresholds and audiometric thresholds at all tested frequencies were significant.

CONCLUSION

This study compares two different recording methods. Intracochlear ECoG measures recorded using the short window technique were efficient, reliable, and repeatable. We were able to collect more frequency specific data with the short window method, and observed similar results between the long window and short window methods. Correlations between physiological thresholds and audiometric thresholds were similar to those reported previously using the long window method (Abbas et al., 2017). This is an important finding because it demonstrates that clinically-available software can be used to measure frequency-specific ECoG responses with enhanced efficiency, increasing the odds that this technique might move from the laboratory into clinical practice.

In Vivo Electrocochleography in Hybrid Cochlear Implant Users Implicates TMPRSS3 in Spiral Ganglion Function

Cochlear implantation, a surgical method to bypass cochlear hair cells and directly stimulate the spiral ganglion, is the standard treatment for severe-to-profound hearing loss. Changes in cochlear implant electrode array design and surgical approach now allow for preservation of acoustic hearing in the implanted ear. Electrocochleography (ECochG) was performed in eight hearing preservation subjects to assess hair cell and neural function and elucidate underlying genetic hearing loss. Three subjects had pathogenic variants in TMPRSS3 and five had pathogenic variants in genes known to affect the cochlear sensory partition. The mechanism by which variants in TMPRSS3 cause genetic hearing loss is unknown. We used a 500-Hz tone burst to record ECochG responses from an intracochlear electrode. Responses consist of a cochlear microphonic (hair cell) and an auditory nerve neurophonic. Cochlear microphonics did not differ between groups. Auditory nerve neurophonics were smaller, on average, in subjects with TMPRSS3 deafness. Results of this proof-of-concept study provide evidence that pathogenic variants in TMPRSS3 may impact function of the spiral ganglion. While ECochG as a clinical and research tool has been around for decades, this study illustrates a new application of ECochG in the study of genetic hearing and deafness in vivo.

Using Neural Response Telemetry to Monitor Physiological Responses to Acoustic Stimulation in Hybrid Cochlear Implant Users

OBJECTIVE

This report describes the results of a series of experiments where we use the neural response telemetry (NRT) system of the Nucleus cochlear implant (CI) to measure the response of the peripheral auditory system to acoustic stimulation in Nucleus Hybrid CI users. The objectives of this study were to determine whether they could separate responses from hair cells and neurons and to evaluate the stability of these measures over time.

DESIGN

Forty-four CI users participated. They all had residual acoustic hearing and used a Nucleus Hybrid S8, S12, or L24 CI or the standard lateral wall CI422 implant. The NRT system of the CI was used to trigger an acoustic stimulus (500-Hz tone burst or click), which was presented at a low stimulation rate (10, 15, or 50 per second) to the implanted ear via an insert earphone and to record the cochlear microphonic, the auditory nerve neurophonic and the compound action potential (CAP) from an apical intracochlear electrode. To record acoustically evoked responses, a longer time window than is available with the commercial NRT software is required. This limitation was circumvented by making multiple recordings for each stimulus using different time delays between the onset of stimulation and the onset of averaging. These recordings were then concatenated off-line. Matched recordings elicited using positive and negative polarity stimuli were added off-line to emphasize neural potentials (SUM) and subtracted off-line to emphasize potentials primarily generated by cochlear hair cells (DIF). These assumptions regarding the origin of the SUM and DIF components were tested by comparing the magnitude of these derived responses recorded using various stimulation rates. Magnitudes of the SUM and DIF components were compared with each other and with behavioral thresholds.

RESULTS

SUM and DIF components were identified for most subjects, consistent with both hair cell and neural responses to acoustic stimulation. For a subset of the study participants, the DIF components grew as stimulus level was increased, but little or no SUM components were identified. Latency of the CAPs in response to click stimuli was long relative to reports in the literature of recordings obtained using extracochlear electrodes. This difference in response latency and general morphology of the CAPs recorded was likely due to differences across subjects in hearing loss configuration. The use of high stimulation rates tended to decrease SUM and CAP components more than DIF components. We suggest this effect reflects neural adaptation. In some individuals, repeated measures were made over intervals as long as 9 months. Changes over time in DIF, SUM, and CAP thresholds mirrored changes in audiometric threshold for the subjects who experienced loss of acoustic hearing in the implanted ear.

CONCLUSIONS

The Nucleus NRT software can be used to record peripheral responses to acoustic stimulation at threshold and suprathreshold levels, providing a window into the status of the auditory hair cells and the primary afferent nerve fibers. These acoustically evoked responses are sensitive to changes in hearing status and consequently could be useful in characterizing the specific pathophysiology of the hearing loss experienced by this population of CI users.

Preliminary Outcomes Report for CO2 Laser Assisted Electric-Acoustic Cochlear Implantation

OBJECTIVE

Report on the safety/efficacy of a novel, carbon dioxide (CO2) laser-assisted protocol for hearing-preservation cochlear implantation (HPCI) and electric-acoustic stimulation (EAS).

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral center.

PATIENTS

Adult patients meeting established criteria for HPCI and EAS.

INTERVENTION

Therapeutic/rehabilitative. A standardized protocol used CO2 laser to achieve meticulous hemostasis and perform cochleostomy was evaluated.

MAIN OUTCOME MEASURES

Audiometric assessments included low-tone pure tone average (LtPTA), consonant-nucleus-consonant (CNC), and AzBio scores. Primary outcomes were low-tone hearing-preservation (LtHP) and EAS usage rates. Secondary outcomes included change in LtPTA, outcomes durability, and the rate/onset/presentation of delayed hearing loss (DHL). Subset analyses stratified data by presenting LtPTA and surgeon experience.

RESULTS

Forty-seven patients and 52 ears were included. Mean follow-up was 20.7 ± 12.6 months. When adjusted for preoperative LtPTA less than 60 dB, the LtHP rate was 77%. This was significantly better than for patients with LtPTA more than 60 dB (24%; p < 0.0001). Outcomes were highly durable. EAS usage was excellent in those with LtPTA less than 60 dB (100%). Nine patients developed DHL. Three additional patients (25%) were successfully salvaged via steroids. Both CNC and AzBio scores improved significantly (p < 0.0001) at definitive testing. Speech-hearing scores did not differ significantly between patients using/not using EAS. The complication rate was 3.8%; none were caused by the laser. Surgeon experience was associated with significantly better outcomes.

CONCLUSION

Use of a CO2 laser-assisted HPCI protocol was safe and effective. Outcomes were consistent with contemporary literature reporting. Patient selection and surgeon experience both significantly impacted outcomes.

Hearing Preservation with the Slim Modiolar Electrode Nucleus CI532® Cochlear Implant: A Preliminary Experience

As the indications for cochlear implant have expanded to include younger patients and individuals with greater degrees of residual hearing, increasing emphasis has been placed on atraumatic surgery and the preservation of the cochlear structure. Here, a descriptive prospective randomized study was performed. It was shown that residual hearing preservation is possible 12 months postoperatively with an atraumatic perimodiolar flexible electrode array CI532® (Cochlear Ltd, Sydney, Australia). Residual hearing preservation, considered as < 15 dB, was obtained in 70% of the cases. Better clinical outcomes and performance could be obtained compared with the previous perimodiolar CI512®, but further research and a longer follow-up are necessary to verify the impact of outcomes.

Cochlear implant - state of the art

Cochlear implants are the treatment of choice for auditory rehabilitation of patients with sensory deafness. They restore the missing function of inner hair cells by transforming the acoustic signal into electrical stimuli for activation of auditory nerve fibers. Due to the very fast technology development, cochlear implants provide open-set speech understanding in the majority of patients including the use of the telephone. Children can achieve a near to normal speech and language development provided their deafness is detected early after onset and implantation is performed quickly thereafter. The diagnostic procedure as well as the surgical technique have been standardized and can be adapted to the individual anatomical and physiological needs both in children and adults. Special cases such as cochlear obliteration might require special measures and re-implantation, which can be done in most cases in a straight forward way. Technology upgrades count for better performance. Future developments will focus on better electrode-nerve interfaces by improving electrode technology. An increased number of electrical contacts as well as the biological treatment with regeneration of the dendrites growing onto the electrode will increase the number of electrical channels. This will give room for improved speech coding strategies in order to create the bionic ear, i.e. to restore the process of natural hearing by means of technology. The robot-assisted surgery will allow for high precision surgery and reliable hearing preservation. Biological therapies will support the bionic ear. Methods are bio-hybrid electrodes, which are coded by stem cells transplanted into the inner ear to enhance auto-production of neurotrophins. Local drug delivery will focus on suppression of trauma reaction and local regeneration. Gene therapy by nanoparticles will hopefully lead to the preservation of residual hearing in patients being affected by genetic hearing loss. Overall the cochlear implant is a very powerful tool to rehabilitate patients with sensory deafness. More than 1 million of candidates in Germany today could benefit from this high technology auditory implant. Only 50,000 are implanted so far. In the future, the procedure can be done under local anesthesia, will be minimally invasive and straight forward. Hearing preservation will be routine.