On the Horizon: Cochlear Implant Technology

Cochlear Implantation Is Associated With Reduced Incidence of Dementia in Severe Hearing Loss

OBJECTIVES

Hearing loss is recognized as a potentially modifiable risk factor for dementia in midlife. This study aimed to investigate the association between rehabilitation methods and dementia risk in patients with severe to profound hearing loss.

DESIGN

Using the nationwide population data from South Korea, individuals with severe to profound hearing loss were identified. Individuals aged 40 to 79 were then divided into 3 groups according to the type of auditory rehabilitation they received in the period between 2005 and 2010, namely cochlear implant (CI), hearing aid (HA), or no rehabilitation (NR). No hearing loss (NHL) group (with normal hearing) consisted of individuals without hearing loss. Dementia incidence was followed up to 2022.

RESULTS

The study involved 649 individuals in the CI group, 35,076 in the HA, 16,494 in the NR, and 1,280,788 in the NHL group. The groups that received auditory rehabilitation (HA and CI groups) had a significantly reduced risk of dementia compared with the NR group, with the CI group showing the most pronounced reduction. The CI group demonstrated a lower risk of dementia than the HA group and had a similar dementia risk to the NHL group.

CONCLUSIONS

In individuals with severe to profound hearing loss, rates of dementia were lower in CI users than in HA users. Moreover, the risk of dementia in those undergoing CI surgery is comparable to that of individuals with normal hearing.

Influence of surgeon experience on the incidence of tip fold-over with slim preformed cochlear implant electrodes

PURPOSE

To assess whether increasing experience with implantation of a thin preformed electrode array for perimodiolar insertion reduces the incidence of tip fold-over (TFO).

METHODS

The retrospective study included 100 patients who received a cochlear implant (CI) with the Slim Modiolar (SM) electrode array (Cochlear, Sydney, Australia) at a university CI centre between November 2015 and December 2022. Postoperative radiological imaging was performed to verify electrode position. Surgical reports and radiological images were reviewed and the incidence of TFO was analyzed for three experienced CI surgeons. In addition, the incidence of intraoperative measurements showing evidence of electrode malposition and the mean duration of surgery over time were documented.

RESULTS

129 SM implantations in 100 patients were included. In seven cases (5.4%) TFO was radiologically detected and successfully revised. In eight cases (6.2%), electrophysiological measurements indicated misplacement and the position was corrected during the same surgery. For one surgeon, five out of 67 implantations (7.5%) were affected by TFO, with the frequency of this complication decreasing over time. The average surgery time for all surgeons was 122.2 (± 44.2) minutes, with two surgeons showing a decrease over time.

CONCLUSION

The results show a tendency that the SM electrodes can be implanted with a lower complication rate and faster over time. Therefore, it can be assumed that the implantation of the SM electrode requires a certain amount of practice, even for experienced surgeons. As intraoperative electrophysiological measurements detected 71.4% of all radiologically confirmed TFOs, their use is highly recommended.

Meta-analysis on lexical tone recognition in cochlear implant users

OBJECTIVE

Lexical tone plays a vital role in speech communication in tonal languages. This study investigated lexical tone recognition in cochlear implant (CI) users, and identified potential factors that influence lexical tone recognition in the CI population.

DESIGN

We conducted a systematic search across eleven major databases, evaluated the risk of bias in the included studies, and conducted five meta-analyses.

STUDY SAMPLE

Forty studies that utilised a multi-item alternative forced-choice paradigm were included to evaluate the performance of lexical tone recognition in CI users.

RESULTS

CI users performed worse at recognising lexical tones than normal hearing (NH) controls. Furthermore, bimodal stimulation could benefit lexical tone recognition for CI users in both quiet and noisy conditions. Besides, the pooled results showed a negative correlation between tone recognition accuracy and age at implantation, as well as a positive correlation between tone recognition performance and the duration of CI experience.

CONCLUSIONS

This study indicates that CI users could not recognise lexical tones at the same level as the NH population. The bimodal intervention does have a more positive effect than unimodal implantation regardless of the listening environment. Moreover, earlier implantation and longer experience with the CI could facilitate lexical tone recognition.

Cochlear reimplantation rate, causes, and outcomes: a multicenter study

OBJECTIVE

The current study aimed to evaluate cochlear reimplantation rate, causes, and audiological outcomes in a large group of patients in a multicenter study.

METHODS

This retrospective study was conducted on patients with cochlear reimplantation surgeries between 2000 and 2022 in five academic referral centers. The rate and reasons for cochlear reimplantation surgeries were evaluated. The auditory performance and speech production outcomes were compared before and after cochlear reimplantation surgeries.

RESULTS

Of 9,287 primary cochlear implantation surgeries, 186 reimplantations were performed (a cochlear reimplantation rate of 2%). The highest risk of reimplantation was found 2 to 4 years after primary implantation. Device failure was the main reason for cochlear reimplantation (81.2%). The categories of auditory performance and speech intelligibility rating scores were unchanged or improved in 57 out of 59 patients (96.6%), and 55 out of 59 patients (93.2%), respectively.

CONCLUSION

The cochlear reimplantation rate seems to be relatively low, with the cause of device failure in most cases. While the highest risk of reimplantation happened during the first four years after primary surgery, regular follow-ups are necessary, particularly during this time. The audiological outcomes do not worsen after reimplantation in most patients, and some children may experience some improvements.

Cochlear implants with dexamethasone-eluting electrode arrays reduce foreign body response in a murine model of cochlear implantation and human subjects

The inflammatory foreign body response (FBR) following cochlear implantation (CI) can negatively impact CI outcomes, including increased electrode impedances. This study aims to investigate the long-term efficacy of dexamethasone eluting cochlear implant and locally delivered dexamethasone, a potent anti-inflammatory glucocorticoid on the intracochlear FBR and electrical impedance post-implantation in a murine model and human subjects. The left ears of CX3CR1 +/GFP Thy1 +/YFP (macrophage-neuron dual reporter) mice were implanted with dexamethasone-eluting cochlear implants (Dex-CI) or standard implant (Standard-CI) while the right ear served as unoperated control. Another group of dual reporter mice was implanted with a standard CI electrode array followed by injection of dexamethasone in the middle ear to mimic current clinical practice (Dex-local). Mouse implants were electrically stimulated with serial measurement of electrical impedance. Human subjects were implanted with either standard or Dex-CI followed by serial impedance measurements. Dex-CI reduced electrical impedance in the murine model and human subjects and inflammatory FBR in the murine model for an extended period. Dex-local in the murine model is ineffective for long-term reduction of FBR and electrode impedance. Our data suggest that dexamethasone eluting arrays are more effective than the current clinical practice of locally applied dexamethasone in reducing FBR and electrical impedance.

A full-head model to investigate intra and extracochlear electric fields in cochlear implant stimulation

Objective.Despite the widespread use and technical improvement of cochlear implant (CI) devices over past decades, further research into the bioelectric bases of CI stimulation is still needed. Various stimulation modes implemented by different CI manufacturers coexist, but their true clinical benefit remains unclear, probably due to the high inter-subject variability reported, which makes the prediction of CI outcomes and the optimal fitting of stimulation parameters challenging. A highly detailed full-head model that includes a cochlea and an electrode array is developed in this study to emulate intracochlear voltages and extracochlear current pathways through the head in CI stimulation.Approach.Simulations based on the finite element method were conducted under monopolar, bipolar, tripolar (TP), and partial TP modes, as well as for apical, medial, and basal electrodes. Variables simulated included: intracochlear voltages, electric field (EF) decay, electric potentials at the scalp and extracochlear currents through the head. To better understand CI side effects such as facial nerve stimulation, caused by spurious current leakage out from the cochlea, special emphasis is given to the analysis of the EF over the facial nerve.Main results.The model reasonably predicts EF magnitudes and trends previously reported in CI users. New relevant extracochlear current pathways through the head and brain tissues have been identified. Simulated results also show differences in the magnitude and distribution of the EF through different segments of the facial nerve upon different stimulation modes and electrodes, dependent on nerve and bone tissue conductivities.Significance.Full-head models prove useful tools to model intra and extracochlear EFs in CI stimulation. Our findings could prove useful in the design of future experimental studies to contrast FNS mechanisms upon stimulation of different electrodes and CI modes. The full-head model developed is freely available for the CI community for further research and use.

Investigating Additional Cochlear Parameters: A follow-up systematic review and meta-analysis

Objectives

The movement towards personalization of cochlear implantation has continued to generate interest about variabilities in cochlear size. In a recent meta-analysis, Atalay et al. (2022) examined organ of corti length, cochlear lateral wall, and "A" value and found that most covariates, other than congenital sensorineural hearing loss, did not impact cochlear size via these measurements. However, no meta-analysis exists on how patient-specific variables could impact other cochlear size measurements, such as cochlear height (CH), and "B" value (defined as the distance between opposite lateral walls and perpendicular to "A" value). The purpose of this systematic review and meta-analysis is to examine how patient-specific variables impact additional cochlear size measurements to assist clinical decision-making.

Databases reviewed

A systematic review for cochlear size measurements using PRISMA methodology was performed using PubMed, CINAHL, and MEDLINE from database inception to October 1st, 2022.

Methods

Search terms used included English, cochlea, size, histology, anatomy, and human. Inclusion criteria were measurements for human cochlea, full-text articles, and articles in English. Primary measurements were "B" value and CH, as these measurements differ from the recent meta-analysis on this topic. Cochlear duct length (CDL) was also included. A random-effects continuous model for meta-analysis was performed. Measurements were stratified by gender (male/female) and disease type (sensorineural hearing loss (SNHL)/conductive hearing loss (CHL)).

Results

A total of 7 articles met final inclusion criteria from a total of 674 articles received on initial search, resulting in 2263 total human cochleae. There was a statistical difference between male CDL (n = 681 cochlea) compared to female CDL (n = 657) from four articles (p < 0.001; Cohen's d effect size (ES):0.421; 95% confidence intervals (CI): 0.171, 0.671). The frequency weighted mean for male CDL was 33.5 mm ± 1.8 mm and the frequency weighted mean for female CDL was 32.4 mm ± 1.5 mm with an unstandardized mean difference of 0.854 mm. There was no statistical difference between male "B" value (n = 329) and female "B" value (n = 349) for cochlea from two studies (p = 0.184; Cohen's d ES: 0.410; 95% CI: 0.194, 1.014). The frequency weighted mean for male "B" value was 6.5 mm ± 0.1 mm and the frequency weighted mean for female "B" value was 6.4 mm ± 0.1 mm with an unstandardized mean difference of 0.126 mm. There was no statistical difference between CH for SNHL (n = 282) and CHL (n = 275) from two studies (p = 0.486; ES: 0.085; 95% CI: 0.323, 0.153, F ig. 3). The frequency weighted mean for SNHL CH was 4.6 mm ± 0.8 mm and the frequency weighted mean for CHL CH was 4.3 mm ± 0.8 mm with an unstandardized mean difference of 0.032 mm.

Conclusion

Male CDL is statistically larger than female CDL. There is no statistically significant association between gender or hearing loss type and "B" value or CH. The effect size for all comparisons is small, indicating little practical significance between any existing differences. The results of this study provide two additional cochlear metrics and indicate similar findings to the study by Atalay and colleagues as patient-specific characteristics appear to have no statistically significantly impact on cochlear size.

Comparison of postural control and space perception outcomes between robotic and conventional cochlear implantation in adults

PURPOSE

The aim of the study is to capture the difference between the groups in direct relation to the type of electrode array insertion during cochlear implantation (CI). The robotic insertion is expected to be a more gently option. As recent studies have shown, there is a difference in perception of visual vertical (SVV) and postural control related to the CI. We assume that there can be differences in postural control and space perception outcomes depending on the type of the surgical method.

METHODS

In total, 37 (24 females, mean age ± SD was 42.9 ± 13.0) candidates for CI underwent an assessment. In 14 cases, the insertion of the electrode array was performed by a robotic system (RobOtol, Colin, France) and 23 were performed conventionally. In all of these patients, we performed the same examination before the surgery, the first day, and 3 weeks after the surgery. The protocol consists of static posturography and perception of visual vertical.

RESULTS

The both groups, RobOtol and conventional, responded to the procedure similarly despite the dissimilar electrode insertion. There was no difference between two groups in the dynamic of perception SVV and postural parameters. Patients in both groups were statistically significantly affected by the surgical procedure, SVV deviation appeared in the opposite direction from the implanted ear: 0.90° ± 1.25; - 1.67° ± 3.05 and - 0.19° ± 1.78 PRE and POST surgery (p < 0.001). And this deviation was spontaneously adjusted in FOLLOW-UP after 3 weeks (p < 0.01) in the both groups. We did not find a significant difference in postural parameters between the RobOtol and conventional group, even over time.

CONCLUSION

Although the robotic system RobOtol allows a substantial reduction in the speed of insertion of the electrode array into the inner ear, our data did not demonstrate a postoperative effect on vestibular functions (SVV and posturography), which have the same character and dynamics as in the group with standard manual insertion.

REGISTRATION NUMBER

The project is registered on clinicaltrials.gov (registration number: NCT05547113).

Postural Stability of Adolescents with Late Cochlear Implantation and Hearing Aids: A Non-Randomized Trial

Background: The aim of this study was to assess the neuromuscular control of adolescents with late unilateral cochlear implantation and compare them to adolescents with hearing aids (HAs) while performing a balance task on a platform with the conditions of an activated hearing device (cochlear implant (CI)/HAs) with eyes opened/closed (EO/EC). Methods: Forty-eight adolescents with hearing loss participated in the study and were divided into SG (unilateral CI and HA) and CG (bilateral HA). The evaluation of the postural stability was performed with a force plate during two repeating testing trials with EO/EC. Results: SG was characterized by greater values of vCOP compared to CG (EO), while, in CG, greater values of vCOP were noted in the second trial. The type of hearing device was found to be related to the values of area (EO) (p < 0.001), which were always greater in SG, regardless of the visual perception. Conclusions: Late unilateral CI may impact the activation of different models of the auditory compensatory mechanism than HA, which is related to neuromuscular control. The values of vCOP can be predicted by age in late-CI individuals. Visual perception seems not to be related to the values of the area, which can be impacted both by CI and HA.

Clinical Applications of Intracochlear Electrocochleography in Cochlear Implant Users With Residual Acoustic Hearing

We herein review the use of electrocochleography (ECoG) to assess peripheral auditory system responsiveness in a growing population of cochlear implant (CI) users with preserved hearing in ears with implants. Twenty-eight recently published intracochlear ECoG articles were thoroughly reviewed to investigate the prognostic utility of intraoperative ECoG monitoring to assess hearing preservation, and the clinical applicability of postoperative ECoG for estimating audiometric thresholds and monitoring longitudinal changes in residual acoustic hearing in patients with EAS. Intraoperative ECoG studies have focused on monitoring the changes in the cochlear microphonics (CM) amplitudes during and after electrode insertion. Mixed results have been reported regarding the relationship between changes in CM amplitude in the operating room and changes in hearing thresholds after surgery. Postoperative ECoG studies have shown that CM and auditory nerve neurophonics thresholds correlate significantly with behavioral thresholds. ECoG thresholds sensitively detect changes as residual acoustic hearing decreases over time in some CI users. This indicates its potential clinical value for monitoring the post-implantation status of the peripheral auditory system. Intracochlear ECoG can provide real-time intraoperative feedback and monitor postoperative hearing preservation in a growing population of CI users.

A New Floating Piezoelectric Microphone for Fully Implantable Cochlear Implants in Middle Ear

OBJECTIVE

Our team designed a long-lasting, well-sealed microphone, which uses laser welding and vacuum packaging technology. This study examined the sensitivity and effectiveness of this new floating piezoelectric microphone (NFPM) designed for totally implantable cochlear implants (TICIs) in animal experiments and intraoperative testing.

METHODS

Different NFPM frequency responses from 0.25 to 10 kHz at 90 dB SPL were analyzed using in vivo testing of cats and human patients. The NFPM was tested in different positions that were clamped to the ossicular chains or placed in the tympanic cavity of cats and human patients. Two volunteers' long incus foot and four cats' malleus neck of the ossicular chain were clamped with the NSFM. The output electrical signals from different locations were recorded, analyzed, and compared. The NFPM was removed after the test without causing any damage to the middle-ear structure of the cats. Intraoperative tests of the NFPM were performed during the cochlear implant surgery and the cochlear implant surgery was completed after all tests.

RESULTS

Compared with the results in the tympanic cavity, the NFPM could detect the vibration from the ossicular chain more sensitively in cat experiments and intraoperative testing. We also found that the signal output level of the NFPM decreased as the acoustic stimulation strength decreased in the intraoperative testing.

CONCLUSION

The NFPM is effective in the intraoperative testing, making it feasible as an implantable middle-ear microphone for TICIs.

LEVEL OF EVIDENCE

4 Laryngoscope, 134:937-944, 2024.

Digital Health Literacy: Evaluating the Readability and Reliability of Cochlear Implant Patient Information on the Web

Hearing aids and implants are used to treat hearing loss, with cochlear implants being the most successful option for severe sensorineural hearing loss. Patients frequently use the internet as a trusted source of clinical information before committing to any therapeutic procedure, including receiving a cochlear implant. A health resource's readability and dependability influence its value to patients. Readability refers to how easily language can be understood, whereas reliability refers to the correctness and consistency of the information presented. JAMA standards and the DISCERN tool were used to assess the reliability of the websites listed. For readability analysis, the FRE, FKG and GFI were chosen. The acceptable readability level was set to < 7 for the FKG, GF score over 17 as the equivalent of college-level education and ≥ 80.0 for the FRE. The readability scores vary across the sources, suggesting a range of comprehension levels required for understanding the cochlear implant patient information found on Google. There was a statistical difference detected in Discern score between the groups (p = 0.008). The mean discern score was significantly higher in hospital generated sources when compared to industry (3.13 ± 0.69 vs. 2.11 ± 0.78, p = 0.03).

Features of the speech processing network in post- and prelingually deaf cochlear implant users

The onset of hearing loss can lead to altered brain structure and functions. However, hearing restoration may also result in distinct cortical reorganization. A differential pattern of functional remodeling was observed between post- and prelingual cochlear implant users, but it remains unclear how these speech processing networks are reorganized after cochlear implantation. To explore the impact of language acquisition and hearing restoration on speech perception in cochlear implant users, we conducted assessments of brain activation, functional connectivity, and graph theory-based analysis using functional near-infrared spectroscopy. We examined the effects of speech-in-noise stimuli on three groups: postlingual cochlear implant users (n = 12), prelingual cochlear implant users (n = 10), and age-matched individuals with hearing controls (HC) (n = 22). The activation of auditory-related areas in cochlear implant users showed a lower response compared with the HC group. Wernicke's area and Broca's area demonstrated differences network attributes in speech processing networks in post- and prelingual cochlear implant users. In addition, cochlear implant users maintain a high efficiency of the speech processing network to process speech information. Taken together, our results characterize the speech processing networks, in varying noise environments, in post- and prelingual cochlear implant users and provide new insights for theories of how implantation modes impact remodeling of the speech processing functional networks.

Landmark-based registration of a cochlear model to a human cochlea using conventional CT scans

Cochlear implants can provide an advanced treatment option to restore hearing. In standard pre-implant procedures, many factors are already considered, but it seems that not all underlying factors have been identified yet. One reason is the low quality of the conventional computed tomography images taken before implantation, making it difficult to assess these parameters. A novel method is presented that uses the Pietsch Model, a well-established model of the human cochlea, as well as landmark-based registration to address these challenges. Different landmark numbers and placements are investigated by visually comparing the mean error per landmark and the registrations' results. The landmarks on the first cochlear turn and the apex are difficult to discern on a low-resolution CT scan. It was possible to achieve a mean error markedly smaller than the image resolution while achieving a good visual fit on a cochlear segment and directly in the conventional computed tomography image. The employed cochlear model adjusts image resolution problems, while the effort of setting landmarks is markedly less than the segmentation of the whole cochlea. As a next step, the specific parameters of the patient could be extracted from the adapted model, which enables a more personalized implantation with a presumably better outcome.

Contribution of macrophages to neural survival and intracochlear tissue remodeling responses following cochlear implantation

BACKGROUND

Cochlear implants (CIs) restore hearing to deafened patients. The foreign body response (FBR) following cochlear implantation (post-CI) comprises an infiltration of macrophages, other immune and non-immune cells, and fibrosis into the scala tympani, a space that is normally devoid of cells. This FBR is associated with negative effects on CI outcomes including increased electrode impedances and loss of residual acoustic hearing. This study investigates the extent to which macrophage depletion by an orally administered CSF-1R specific kinase (c-FMS) inhibitor, PLX-5622, modulates the tissue response to CI and neural health.

MAIN TEXT

10- to 12-week-old CX3CR1 + /GFP Thy1 + /YFP mice on C57BL/6J/B6 background was fed chow containing 1200 mg/kg PLX5622 or control chow for the duration of the study. 7 days after starting the diet, 3-channel cochlear implants were implanted in the ear via the round window. Serial impedance and neural response telemetry (NRT) measurements were acquired throughout the study. Electric stimulation began 7 days post-CI until 28 days post-CI for 5 h/day, 5 days/week, with programming guided by NRT and behavioral responses. Cochleae harvested at 10, 28 or 56 days post-CI were cryosectioned and labeled with an antibody against α-smooth muscle actin (α-SMA) to identify myofibroblasts and quantify the fibrotic response. Using IMARIS image analysis software, the outlines of scala tympani, Rosenthal canal, modiolus, and lateral wall for each turn were traced manually to measure region volume. The density of nuclei, CX3CR1 + macrophages, Thy1 + spiral ganglion neuron (SGN) numbers, and the ratio of the α-SMA + volume/scala tympani volume were calculated. Cochlear implantation in control diet subjects caused infiltration of cells, including macrophages, into the cochlea. Fibrosis was evident in the scala tympani adjacent to the electrode array. Mice fed PLX5622 chow showed reduced macrophage infiltration throughout the implanted cochleae across all time points. However, scala tympani fibrosis was not reduced relative to control diet subjects. Further, mice treated with PLX5622 showed increased electrode impedances compared to controls. Finally, treatment with PLX5622 decreased SGN survival in implanted and contralateral cochleae.

CONCLUSION

The data suggest that macrophages play an important role in modulating the intracochlear tissue response following CI and neural survival.

Emerging biotechnologies and biomedical engineering technologies for hearing reconstruction

Hearing impairment is a global health problem that affects social communications and the economy. The damage and loss of cochlear hair cells and spiral ganglion neurons (SGNs) as well as the degeneration of neurites of SGNs are the core causes of sensorineural hearing loss. Biotechnologies and biomedical engineering technologies provide new hope for the treatment of auditory diseases, which utilizes biological strategies or tissue engineering methods to achieve drug delivery and the regeneration of cells, tissues, and even organs. Here, the advancements in the applications of biotechnologies (including gene therapy and cochlear organoids) and biomedical engineering technologies (including drug delivery, electrode coating, electrical stimulation and bionic scaffolds) in the field of hearing reconstruction are presented. Moreover, we summarize the challenges and provide a perspective on this field.

Contribution of macrophages to intracochlear tissue remodeling responses following cochlear implantation and neural survival

Introduction

Cochlear implants (CIs) restore hearing to deafened patients. The foreign body response (FBR) following cochlear implantation (post-CI) comprises an infiltration of macrophages, other immune and non-immune cells, and fibrosis into the scala tympani; a space that is normally devoid of cells. This FBR is associated with negative effects on CI outcomes including increased electrode impedances and loss of residual acoustic hearing. This study investigates the extent to which macrophage depletion by an orally administered CSF-1R specific kinase (c-FMS) inhibitor, PLX-5622, modulates the tissue response to CI and neural health.

Materials and methods

10-12-week-old CX3CR1+/GFP Thy1+/YFP mice on C57Bl6 background with normal hearing were fed chow containing 1200 mg/kg PLX5622 or control chow for the duration of the study. 7-days after starting the diet, 3-channel cochlear implants were implanted ear via the round window. Serial impedance and neural response telemetry (NRT) measurements were acquired throughout the study. Electric stimulation began 7 days post-CI until 28- days post-CI for 5 hrs/day, 5 days/week, with programming guided by NRT and behavioral responses. Cochleae harvested at 10-, 28- or 56-days post-CI were cryosectioned and labeled with antibody against α-smooth muscle actin (α-SMA) to identify myofibroblasts and quantify the fibrotic response. Using IMARIS image analysis software, the outlines of scala tympani, Rosenthal canal, modiolus and lateral wall for each turn were traced manually to measure region volume. Density of nuclei, CX3CR1+ macrophages, Thy1+ spiral ganglion neuron (SGN) numbers and ratio of volume of α-SMA+ space/volume of scala tympani were calculated.

Results

Cochlear implantation in control diet subjects caused infiltration of cells, including macrophages, into the cochlea: this response was initially diffuse throughout the cochlea and later localized to the scala tympani of the basal turn by 56-days post-CI. Fibrosis was evident in the scala tympani adjacent to the electrode array. Mice fed PLX5622 chow showed reduced macrophage infiltration throughout the implanted cochleae across all timepoints. However, scala tympani fibrosis was not reduced relative to control diet subjects. Further, mice treated with PLX5622 showed increased electrode impedances compared to controls. Finally, treatment with PLX5622 decreased SGN survival in implanted and contralateral cochleae.

Discussion

The data suggest that macrophages play an important role in modulating the intracochlear tissue response following CI and neural survival.

Neural Plasticity in Sensorimotor Brain-Machine Interfaces

Brain-machine interfaces (BMIs) aim to treat sensorimotor neurological disorders by creating artificial motor and/or sensory pathways. Introducing artificial pathways creates new relationships between sensory input and motor output, which the brain must learn to gain dexterous control. This review highlights the role of learning in BMIs to restore movement and sensation, and discusses how BMI design may influence neural plasticity and performance. The close integration of plasticity in sensory and motor function influences the design of both artificial pathways and will be an essential consideration for bidirectional devices that restore both sensory and motor function.

Evaluation of the Cognitive Function of Adults with Severe Hearing Loss Pre- and Post-Cochlear Implantation Using Verbal Fluency Testing

Hearing loss is a major public health problem with significant evidence correlating it with cognitive performance. Verbal fluency tests are commonly used to assess lexical access. They provide a great deal of information about a subject's cognitive function. The aim of our study was to evaluate phonemic and semantic lexical access abilities in adults with bilateral severe to profound hearing loss and then to re-evaluate a cohort after cochlear implantation. 103 adult subjects underwent phonemic and semantic fluency tests during a cochlear implant candidacy evaluation. Of the total 103 subjects, 43 subjects underwent the same tests at 3 months post-implantation. Our results showed superior performance in phonemic fluency compared to semantic fluency in subjects prior to implantation. Phonemic fluency was positively correlated with semantic fluency. Similarly, individuals with congenital deafness had better semantic lexical access than individuals with acquired deafness. Results at 3 months post-implantation showed an improvement in phonemic fluency. No correlation was found between the evolution of pre- and post-implant fluency and the auditory gain of the cochlear implant, and we found no significant difference between congenital and acquired deafness. Our study shows an improvement in global cognitive function after cochlear implantation without differentiation of the phonemic-semantic pathway.

Auditory evoked response to an oddball paradigm in children wearing cochlear implants

OBJECTIVE

Although children with cochlear implants (CI) achieve remarkable success with their device, considerable variability remains in individual outcomes. Here, we explored whether auditory evoked potentials recorded during an oddball paradigm could provide useful markers of auditory processing in this pediatric population.

METHODS

High-density electroencephalography (EEG) was recorded in 75 children listening to standard and odd noise stimuli: 25 had normal hearing (NH) and 50 wore a CI, divided between high language (HL) and low language (LL) abilities. Three metrics were extracted: the first negative and second positive components of the standard waveform (N1-P2 complex) close to the vertex, the mismatch negativity (MMN) around Fz and the late positive component (P3) around Pz of the difference waveform.

RESULTS

While children with CIs generally exhibited a well-formed N1-P2 complex, those with language delays typically lacked reliable MMN and P3 components. But many children with CIs with age-appropriate skills showed MMN and P3 responses similar to those of NH children. Moreover, larger and earlier P3 (but not MMN) was linked to better literacy skills.

CONCLUSIONS

Auditory evoked responses differentiated children with CIs based on their good or poor skills with language and literacy.

SIGNIFICANCE

This short paradigm could eventually serve as a clinical tool for tracking the developmental outcomes of implanted children.

Impact of Expanding Eligibility Criteria for Cochlear Implantation - Dynamic Modeling Study

OBJECTIVES

Eligibility criteria for cochlear implantation (CI) are shifting due to technological and surgical improvements. The aim of this study was to explore the impact of further expanding unilateral CI criteria in those with severe hearing loss (HL) (61-80 dBHL) in terms of number of CI recipients, costs, quality of life, and cost-effectiveness.

METHODS

A dynamic population-based Markov model was constructed mimicking the Dutch population in three age categories over a period of 20 years. Health states included severe HL (61-80 dBHL), profound HL (>81 dBHL), CI recipients, and no-CI recipients. Model parameters were based on published literature, (national) databases, expert opinion, and model calibration.

RESULTS

If persons with severe HL would qualify and opt for CI similar to those with profound HL now, this would lead to a 6-7 times increase of new CI recipients and an associated increase in costs (€550 million) and QALYs (54.000) over a 20-year period (incremental cost utility ratio: 10.771 euros/QALY [2.5-97.5 percentiles: 1.252-23.171]). One-way-sensitivity analysis indicated that model outcomes were most sensitive to regaining employment, utility associated with having a CI, and costs of surgery and testing.

CONCLUSION

Our findings suggest that expanding eligibility for CI to persons with severe HL could be a cost-effective use of resources. Clearly, however, it would require a significant increase in diagnostic, operative, and rehabilitative capacity. Our quantitative estimates can serve as a basis for a wider societal deliberation on the question whether such an increase can and should be pursued.

LEVEL OF EVIDENCE

NA Laryngoscope, 133:924-932, 2023.

The 100 Most-Cited Manuscripts in Hearing Implants: A Bibliometrics Analysis

The aim of the study was to characterise the most frequently cited articles on the topic of hearing implants. A systematic search was carried out using the Thomson Reuters Web of Science Core Collection database. Eligibility criteria restricted the results to primary studies and reviews published from 1970 to 2022 in English dealing primarily with hearing implants. Data including the authors, year of publication, journal, country of origin, number of citations and average number of citations per year were extracted, as well as the impact factors and five-year impact factor of journals publishing the articles. The top 100 papers were published across 23 journals and were cited 23,139 times. The most-cited and influential article describes the first use of the continuous interleaved sampling (CIS) strategy utilised in all modern cochlear implants. More than half of the studies on the list were produced by authors from the United States, and the Ear and Hearing journal had both the greatest number of articles and the greatest number of total citations. To conclude, this research serves as a guide to the most influential articles on the topic of hearing implants, although bibliometric analyses mainly focus on citations. The most-cited article was an influential description of CIS.

Zwitterionic Polymer/Polydopamine Coating of Electrode Arrays Reduces Fibrosis and Residual Hearing Loss after Cochlear Implantation

Since the first surgery 50 years ago, cochlear implantation (CI) is the major treatment for patients with severe sensorineural hearing loss. However, unexpected foreign body reactions (FBRs) after surgery are reported in 90% of CI recipients, resulting in the formation of fibrosis in the cochlea and progressive residual hearing loss. Zwitterion modification is universally used to reduce bio-fouling and suppress FBRs but never for CI. In the present study, a zwitterionic coating is developed, which is composed of poly sulfobetaine methacrylate (PSB) and polydopamine (PDA) for cochlear implants. The PSB-PDA coating shows a series of characters for an ideal anti-FBRs material, including super-hydrophilicity, low protein and cell adsorption, long-term stability, and high biocompatibility. Compared to the uncoated controls, PSB-PDA coating inhibits the activation of macrophages and reduces the release of inflammatory factors (TNF-α, IL-1β, NO) and fibrosis-related factors (TGF-β1, α-SMA, collagen I). PSB-PDA coated electrode arrays suppress fibrosis completely and preserve residual hearing significantly in rat CI models. These results suggest that PSB-PDA coating is a novel strategy for anti-fibrosis to improve the outcomes of CI.

Cochlear Reimplantation Rate and Cause: a 22-Year, Single-Center Experience, and a Meta-Analysis and Systematic Review

OBJECTIVES

In terms of cochlear reimplantation, there is no consensus on the definition, range, or calculation formulation for the reimplantation rate. This study aims to put forward a relatively standardized and more explicit definition based on a literature review, calculate the rate of cochlear reimplantation, and examine the classification and distribution of the reimplantation causes.

DESIGN

A systematic review and retrospective study. A relatively clearer definition was used in this study: cochlear reimplantation is the implantation of new electrodes to reconstruct the auditory path, necessitated by the failure or abandonment of the initial implant. Seven English and Chinese databases were systematically searched for studies published before July 23, 2021 regarding patients who accepted cochlear reimplantation. Two researchers independently applied the inclusion and exclusion criteria to select studies and complete data extraction. As the effect size, the reimplantation rate was extracted and synthesized using a random-effects model, and subgroup and sensitivity analyses were performed to reduce heterogeneity. In addition, a retrospective study analyzed data on cochlear reimplantation in a tertiary hospital from April 1999 to August 2021. Kaplan-Meier survival analysis and the log-rank test were adopted to analyze the survival times of cochlear implants and compare them among different subgroups.

RESULTS

A total of 144 articles were included, with 85,851 initial cochlear implantations and 4276 cochlear reimplantations. The pooled rate of cochlear reimplantation was 4.7% [95% CI (4.2% to 5.1%)] in 1989 to 2021, 6.8% [95% CI (4.5% to 9.2%)] before 2000, and 3.2% [95% CI (2.7% to 3.7%)] after 2000 ( P =0.003). Device failures accounted for the largest proportion of reimplantation (67.6% [95% CI (64.0% to 71.3%)], followed by medical reasons (28.9% [95% CI (25.7% to 32.0%)]). From April 1999 to August 2021, 1775 cochlear implants were performed in West China Hospital (1718 initial implantations and 57 reimplantations; reimplantation rate 3.3%). In total, 45 reimplantations (78.9%) were caused by device failure, 10 (17.5%) due to medical reasons, and 2 (3.5%) from unknown reasons. There was no difference in the survival time of implants between adults and children ( P = 0.558), while there existed a significant difference between patients receiving implants from different manufacturers ( P < 0.001).

CONCLUSIONS

The cochlear reimplantation rate was relatively high, and more attention should be paid to formulating a standard definition, calculation formula, and effect assessment of cochlear reimplantation. It is necessary to establish a sound mechanism for long-term follow-up and rigorously conduct longitudinal cohort studies.

Chronic cochlear implantation with and without electric stimulation in a mouse model induces robust cochlear influx of CX3CR1+/GFP macrophages

BACKGROUND

Cochlear implantation is an effective auditory rehabilitation strategy for those with profound hearing loss, including those with residual low frequency hearing through use of hybrid cochlear implantation techniques. Post-mortem studies demonstrate the nearly ubiquitous presence of intracochlear fibrosis and neo-ossification following cochlear implantation. Current evidence suggests post-implantation intracochlear fibrosis is associated with delayed loss of residual acoustic hearing in hybrid cochlear implant (CI) recipients and may also negatively influence outcomes in traditional CI recipients. This study examined the contributions of surgical trauma, foreign body response and electric stimulation to intracochlear fibrosis and the innate immune response to cochlear implantation and the hierarchy of these contributions.

METHODS

Normal hearing CX3CR1+/GFP mice underwent either round window opening (sham), acute CI insertion or chronic CI insertion with no, low- or high-level electric stimulation. Electric stimulation levels were based on neural response telemetry (NRT), beginning post-operative day 7 for 5 h per day. Subjects (n=3 per timepoint) were sacrificed at 4 h, 1,4,7,8,11,14 and 21 days. An unoperated group (n=3) served as controls. Cochleae were harvested at each time-point and prepared for immunohistochemistry with confocal imaging. The images were analyzed to obtain CX3CR1+ macrophage cell number and density in the lateral wall (LW), scala tympani (ST) and Rosenthal's canal (RC).

RESULTS

A ST peri-implant cellular infiltrate and fibrosis occurred exclusively in the chronically implanted groups starting on day 7 with a concurrent infiltration of CX3CR1+ macrophages not seen in the other groups. CX3CR1+ macrophage infiltration was seen in the LW and RC in all experimental groups within the first week, being most prominent in the 3 chronically implanted groups during the second and third week.

CONCLUSIONS

The cochlear immune response was most prominent in the presence of chronic cochlear implantation, regardless of electric stimulation level. Further, the development of intracochlear ST fibrosis was dependent on the presence of the indwelling CI foreign body. An innate immune response was evoked by surgical trauma alone (sham and acute CI groups) to a lesser degree. These data suggest that cochlear inflammation and intrascalar fibrosis after cochlear implantation are largely dependent on the presence of a chronic indwelling foreign body and are not critically dependent on electrical stimulation. Also, these data support a role for surgical trauma in inciting the initial innate immune response.

Implications of Neural Plasticity in Retinal Prosthesis

Retinal degenerative diseases such as retinitis pigmentosa cause a progressive loss of photoreceptors that eventually prevents the affected person from perceiving visual sensations. The absence of a visual input produces a neural rewiring cascade that propagates along the visual system. This remodeling occurs first within the retina. Then, subsequent neuroplastic changes take place at higher visual centers in the brain, produced by either the abnormal neural encoding of the visual inputs delivered by the diseased retina or as the result of an adaptation to visual deprivation. While retinal implants can activate the surviving retinal neurons by delivering electric current, the unselective activation patterns of the different neural populations that exist in the retinal layers differ substantially from those in physiologic vision. Therefore, artificially induced neural patterns are being delivered to a brain that has already undergone important neural reconnections. Whether or not the modulation of this neural rewiring can improve the performance for retinal prostheses remains a critical question whose answer may be the enabler of improved functional artificial vision and more personalized neurorehabilitation strategies.

Battery Lifespan of an Implantable Middle Ear Device

Background: The Carina system (Cochlear Ltd., Sydney, Australia) is a totally implantable device providing acoustic amplification in adult patients with moderate-to-severe sensorineural or mixed hearing loss. One of the main concerns about such a totally implantable device has been represented by the subcutaneous battery lifespan. The aim of this article is to report the analysis of battery performances in a series of Carina-implanted patients after a long follow up. Methods: In this retrospective study, the technical data of a series of patients implanted with the Carina middle ear implant in our clinic have been analysed, extracting the data from the log of telemetric measures. Results: The mean lifespan cutback was 0.43 h/years (from 0 to 0.71 h/year), with a strong negative significant correlation between the follow-up period and the percentage of battery residual lifespan. Conclusion: The lifespan of the Carina’s battery seems consistent with the manufacturer statement of a pluri-decennial lifespan, avoiding the need of an early surgical substitution and providing a full day of use of the system even after up to 12 years from the implantation.

Cochlear implants: Causes, effects and mitigation strategies for the foreign body response and inflammation

Cochlear implants provide effective auditory rehabilitation for patients with severe to profound sensorineural hearing loss. Recent advances in cochlear implant technology and surgical approaches have enabled a greater number of patients to benefit from this technology, including those with significant residual low frequency acoustic hearing. Nearly all cochleae implanted with a cochlear implant electrode array develop an inflammatory and fibrotic response. This tissue reaction can have deleterious consequences for implant function, residual acoustic hearing, and the development of the next generation of cochlear prosthetics. This article reviews the current understanding of the inflammatory/foreign body response (FBR) after cochlear implant surgery, its impact on clinical outcome, and therapeutic strategies to mitigate this response. Findings from both in human subjects and animal models across a variety of species are highlighted. Electrode array design, surgical techniques, implant materials, and the degree and type of electrical stimulation are some critical factors that affect the FBR and inflammation. Modification of these factors and various anti-inflammatory pharmacological interventions have been shown to mitigate the inflammatory/FBR response. Ongoing and future approaches that seek to limit surgical trauma and curb the FBR to the implanted biomaterials of the electrode array are discussed. A better understanding of the anatomical, cellular and molecular basis of the inflammatory/FBR response after cochlear implantation has the potential to improve the outcome of current cochlear implants and also facilitate the development of the next generation of neural prostheses.

A forskolin-loaded nanodelivery system prevents noise-induced hearing loss

Hearing loss is the most common sensory disorder worldwide and may result from age, drugs, or exposure to excessive noise. Crossing the blood-labyrinth barrier to achieve targeted drug delivery to the inner ear is key to the treatment of hearing loss. We designed a nanoparticle (NP)-based system for targeted drug delivery of forskolin (FSK) to the inner ear, driven by the prestin-targeting peptide LS19 ("ligand-receptor type interaction"). In vivo experiments in developing zebrafish embryos (4-96 h past fertilization) and mice confirmed that LS19-FSK specifically targeted and accumulated in zebrafish lateral line neuromasts and mouse outer hair cells (OHCs). LS19 peptide modification enabled LS19-FSK-NPs to rapidly target OHCs with high specificity. Furthermore, the multifunctional LS19-FSK-NPs were successfully delivered to the OHCs via the round window membrane route and exhibited slow-release properties. The sustained release and intracellular accumulation of FSK inhibited apoptosis of OHCs. Compared with LS19-NPs and FSK-NPs, LS19-FSK-NPs provided significantly stronger protection against noise-induced hearing damage, based on auditory brainstem responses at 4, 8, 16, and 32 kHz. Thus, our specially designed targeted nano-delivery system may serve as a basis for future clinical applications and treatment platforms and has the potential to significantly improve the treatment results of many inner ear diseases.

Guidelines for Best Practice in the Audiological Management of Adults Using Bimodal Hearing Configurations

Clinics are treating a growing number of patients with greater amounts of residual hearing. These patients often benefit from a bimodal hearing configuration in which acoustic input from a hearing aid on 1 ear is combined with electrical stimulation from a cochlear implant on the other ear. The current guidelines aim to review the literature and provide best practice recommendations for the evaluation and treatment of individuals with bilateral sensorineural hearing loss who may benefit from bimodal hearing configurations. Specifically, the guidelines review: benefits of bimodal listening, preoperative and postoperative cochlear implant evaluation and programming, bimodal hearing aid fitting, contralateral routing of signal considerations, bimodal treatment for tinnitus, and aural rehabilitation recommendations.

Methods for measuring pre-, intra-, and postoperative skin thickness for cochlear implants

Objective

This study was conducted to determine whether there is a reliable method for measuring the thickness of the retroauricular skin before, during, and after cochlear implantation, which allows the assessment of the optimal force of the external magnet of the cochlear implant (CI).

Methods

The retroauricular skin thickness of 83 patients who received a CI was measured using three different methods. The thickness was measured on pre- and postoperative CT images, as well as intraoperatively. The magnet category chosen by the surgeon was recorded when the implant was switched on and during the first follow-up visit. Correlation analyses were performed on the different skin thickness measurements and between the skin thickness and magnet strength categories.

Results

Only six patients required an exchange of the magnet until the follow-up. Although the median absolute thickness differed significantly between the three measures (p < 0.0001), their thickness values showed highly significant correlations (Pearson's r = 0.457–0.585; p < 0.01). In addition, magnet strength, was significantly correlated with the flap thickness determined pre-, post-, and during surgery. The lowest correlation with magnet strength was found in the intraoperative needle method.

Conclusion

All three measurements methods provided a suitable base for determining the ideal magnetic force. However, of particular interest were the pre- and postoperative CT measurements. The first enabled the early assessment of the required magnetic strength and thus a timely postoperative supply, whereas the latter helped to estimate the need for magnetic strength reduction during follow-up care and the feasibility of an early swith-on.

Real-Time Localization of Cochlear-Implant Electrode Arrays Using Bipolar Impedance Sensing

OBJECTIVE

Surgeons have no direct objective feedback on cochlear-implant electrode array (EA) positioning during insertion, yet optimal hearing outcomes are contingent on placing the EA as close as feasible to viable neural endings. This paper describes a system to non-invasively determine intracochlear positioning of an EA, without requiring any modifications to existing commercial EAs themselves.

METHODS

Electrical impedance has been suggested as a way to measure EA proximity to the inner wall of the cochlea that houses auditory nerve endings-the modiolus. In this paper, we extend prior work and demonstrate for the first time the relationship between bipolar access resistance and proximity of the EA to the modiolus (E-M proximity). We also evaluate two methods for producing direct, real-time estimates of E-M proximity from bipolar impedance measurements.

RESULTS

We show that bipolar access resistance is highly correlated with E-M proximity and can be approximately modeled by a power law function. This one dimensional model is shown to be capable of producing accurate real-time estimates of E-M proximity, but its simplicity also limits the potential for future improvement. To address this challenge, we propose a new prediction approach based on a recurrent neural network, which generated an overall prediction accuracy of 93.7%.

CONCLUSION

Bipolar access resistance is highly correlated with E-M proximity, and can be used to estimate EA positioning.

SIGNIFICANCE

This work shows how impedance sensing can be used to localize an EA during insertion into the small, enclosed cochlear environment, without requiring any modifications to existing clinically used EAs.

Frequency-Following Response (FFR) in cochlear implant users: a systematic review of acquisition parameters, analysis, and outcomes

PURPOSE

To characterize the acquisition parameters, analysis, and results of the frequency-following response (FFR) in cochlear implant users.

RESEARCH STRATEGIES

The search was conducted in Cochrane Library, Latin American and Caribbean Health Sciences Literature (LILACS), Ovid Technologies, PubMed, SciELO, ScienceDirect, Scopus, Web of Science, and gray literature.

SELECTION CRITERIA

Studies on FFR in cochlear implant users or that compared them with normal-hearing people, with no restriction of age, were included. Secondary and experimental studies were excluded. There was no restriction of language or year of publication.

DATA ANALYSIS

The data were analyzed and reported according to the stages in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), 2020. The methodological quality was analyzed with the Joanna Briggs Institute Critical Appraisal Checklist for Analytical Cross-Sectional Studies. Divergences were solved by a third researcher.

RESULTS

Six studies met the inclusion criteria. Only one study was comparative, whose control group comprised normal-hearing people. The variations in acquisition parameters were common and the analysis predominantly approached the time domain. Cochlear implant users had different FFR results from those of normal-hearing people, considering the existing literature. Most articles had low methodological quality.

CONCLUSION

There is no standardized FFR acquisition and analysis protocol for cochlear implant users. The results have a high risk of bias.

Understanding them to understand ourselves: The importance of NHP research for translational neuroscience

Studying higher brain function presents fundamental scientific challenges but has great potential for impactful translation to the clinic, supporting the needs of many patients suffering from conditions that relate to neuronal dysfunction. For many key questions relevant to human neurological conditions and clinical interventions, non-human primates (NHPs) remain the only suitable model organism and the only effective way to study the relationship between brain structure and function with the knowledge and tools currently available. Here we present three exemplary studies of current research yielding important findings that are directly translational to human clinical patients but which would be impossible without NHP studies. Our first example shows how studies of the NHP prefrontal cortex are leading to clinically relevant advances and potential new treatments for human neuropsychiatric disorders such as depression and anxiety. Our second example looks at the relevance of NHP research to our understanding of visual pathways and the visual cortex, leading to visual prostheses that offer treatments for otherwise blind patients. Finally, we consider recent advances in treatments leading to improved recovery of movement and motor control in stroke patients, resulting from our improved understanding of brain stem parallel pathways involved in movement in NHPs. The case for using NHPs in neuroscience research, and the direct benefits to human patients, is strong but has rarely been set out directly. This paper reviews three very different areas of neuroscience research, expressly highlighting the unique insights offered to each by NHP studies and their direct applicability to human clinical conditions.

Approaches for Ear-targeted Delivery Systems in Neurosensory Disorders to avoid Chronic Hearing Loss Mediated Neurological Diseases

BACKGROUND AND OBJECTIVE

Hearing loss is a common audio-vestibular-related neurosensory disability of inner ears, in which patients exhibit clinical symptoms of dizziness, gait unsteadiness, and oscillopsia, at an initial stage. While, if such disorders are untreated for a prolonged duration then the progression of disease into a chronic state significantly decreases GABA level as well as an alteration in the neurotransmission of CNS systems. Hence, to control the progression of disease into a chronic approaches for timely and targeted delivery of the drugs at the site of action in the ear is now attracting the interest of neurologists for effective and safe treatment of such disorders. Among delivery systems, owing to small dimension, better penetration, rate-controlled release, higher bioavailability; nanocarriers are preferred to overcome delivery barriers, improvement in residence time, and enhanced the performance of loaded drugs. Subsequently, these carriers also stabilize encapsulated drugs while also provide an opportunity to modify the surface of carriers to favor guided direction for site-specific targeting. Contrary to this; conventional routes of drug delivery such as oral, intravenous, and intramuscular are poorer in performance because of inadequate blood supply to the inner ear and limited penetration of blood-inner ear barrier.

CONCLUSION

This review summarized novel aspects of non-invasive and biocompatible nanoparticles- based approaches for targeted delivery of drugs into the cochlea of the ear to reduce the rate, and extent of the emergence of any hearing loss mediated neurological disorders.

Expansion of Audiologic Criteria for Pediatric Cochlear Implantation

In 2020, the lower age limit for pediatric cochlear implant candidacy was lowered from 12 to 9 months of age. However, audiometric-based criteria for pediatric cochlear implant candidacy have remained unchanged for more than 20 years, requiring bilateral profound sensorineural hearing loss for children less than 2 years and bilateral severe-to-profound sensorineural hearing loss for children 2 years and older. Despite the static audiometric criteria, there is an increasing literature base demonstrating significant benefits for pediatric cochlear implant recipients who exceed current Food and Drug Administration-labeled indications for cochlear implantation.

Measuring 3D Cochlear Duct Length on MRI: Is It Accurate and Reliable?

BACKGROUND AND PURPOSE

Prior studies have evaluated cochlear length using CT to select the most suitable cochlear implants and obtain patient-specific anatomy. This study aimed to test the accuracy and reliability of cochlear lateral wall length measurements using 3D MR imaging.

MATERIALS AND METHODS

Two observers measured the cochlear lateral wall length of 35 patients (21 men) with postlingual hearing loss using CT and MR imaging. The intraclass correlation coefficient (with 95% confidence intervals) was used to evaluate intraobserver and interobserver reliability for the 3D cochlear measurements.

RESULTS

The mean age of the participants was 39.85 (SD, 16.60) years. Observer 1 measured the mean lateral wall length as 41.52 (SD, 2.25) mm on CT and 41.44 (SD, 2.18) mm on MR imaging, with a mean difference of 0.08 mm (95% CI, -0.11 to 0.27 mm), while observer 2 measured the mean lateral wall length as 41.74 (SD, 2.69) mm on CT and 42.34 (SD, 2.53) mm on MR imaging, with a mean difference of -0.59 mm (95% CI, -1.00 to -0.20 mm). An intraclass correlation coefficient value of 0.90 (95% CI, 0.84-0.94) for CT and 0.69 (95% CI, 0.46-0.82) for MR imaging was obtained for the interobserver reliability for the full-turn cochlear lateral wall length.

CONCLUSIONS

CT-based 3D cochlear measurements show excellent intraobserver and interobserver reliability, while MR imaging-based lateral wall length measurements have good-to-excellent intraobserver reliability and moderate interobserver reliability. These results corroborate the use of CT for 3D cochlear measurements as a reference method and demonstrate MR imaging to be an alternative acquisition technique with comparably reliable results.

Screening Tools and Assessment Methods of Cognitive Decline Associated With Age-Related Hearing Loss: A Review

Strong links between hearing and cognitive function have been confirmed by a growing number of cross-sectional and longitudinal studies. Seniors with age-related hearing loss (ARHL) have a significantly higher cognitive impairment incidence than those with normal hearing. The correlation mechanism between ARHL and cognitive decline is not fully elucidated to date. However, auditory intervention for patients with ARHL may reduce the risk of cognitive decline, as early cognitive screening may improve related treatment strategies. Currently, clinical audiology examinations rarely include cognitive screening tests, partly due to the lack of objective quantitative indicators with high sensitivity and specificity. Questionnaires are currently widely used as a cognitive screening tool, but the subject's performance may be negatively affected by hearing loss. Numerous electroencephalogram (EEG) and magnetic resonance imaging (MRI) studies analyzed brain structure and function changes in patients with ARHL. These objective electrophysiological tools can be employed to reveal the association mechanism between auditory and cognitive functions, which may also find biological markers to be more extensively applied in assessing the progression towards cognitive decline and observing the effects of rehabilitation training for patients with ARHL. In this study, we reviewed clinical manifestations, pathological changes, and causes of ARHL and discussed their cognitive function effects. Specifically, we focused on current cognitive screening tools and assessment methods and analyzed their limitations and potential integration.

Comparison of automated and traditional ECAP recording approaches in clinical practice

OBJECTIVE

The traditional method of recording electrically evoked compound action potentials (ECAPs), as implemented in the MAESTRO clinical software (standard ART), requires manual adjustments during threshold determination through a specialist. The "FineGrain" research tool (FineGrain RT) uses a continuous stimulation paradigm combined with automatic ECAP threshold determination. The aim of this study was to compare the FineGrain RT with standard ART.

DESIGN

ECAPs were recorded with standard ART and the FineGrain RT in paediatric cochlear implant recipients. Different stimulation rates were used for FineGrain ECAP recordings (40, 60, and 76 Hz).

STUDY SAMPLE

Thirteen children (6 - 19 years) participated in this study - nine were bilaterally and four unilaterally implanted, resulting in a total of twenty-two implanted ears.

RESULTS

ECAP threshold determination success rates were similar between the two approaches (92% and 89%) and ECAP thresholds correlated well (r: 0.94, p < 2.2e^-16) with average ART thresholds being lower than FineGrain RT thresholds. FineGrain stimulation with different stimulation rates did not have a significant effect on ECAP thresholds but ECAP thresholds at medial and apical contacts were lower compared to basal contacts.

CONCLUSIONS

TheFineGrain research approach is a reliable replacement for standard ART in clinical practice.

Comprehensive Analysis of Factors Affecting Cochlear Size: A Systematic Review and Meta-analysis

OBJECTIVES

To determine the cochlea's average size in humans and evaluate the relationships between certain covariates and cochlear size.

METHODS

A systematic search on articles on cochlear size and published in English was conducted using Cochrane, PubMed, Web of Science, and Scopus databases up to September 15, 2020. Data were pooled using random-effects with three models. The effect of demographic, clinical, and measurement-related parameters was specifically analyzed. Meta-regression and subgroup analyses were conducted. The overall effect estimation was made for outcomes.

RESULTS

The meta-analysis included 4,708 cochleae from 56 studies. The overall length of the organ of Corti was 32.94 mm (95% confidence interval [CI]: 32.51-33.38). The first and second models revealed that age, gender, country, continent, measurement method (direct, indirect), measured structure ("A" value, cochlear lateral wall), origin (in vivo, in vitro), and type (histology specimens, plastic casts, imaging) of the cochlear material did not affect the cochlear size. However, study populations (general population, patients with a cochlear implant, and patients with congenital sensorineural hearing loss [CSNHL]) were found to affect the outcomes. Compared to the other populations, patients with CSNHL had shorter cochleae. Therefore, we developed a third model and found that the general population and patients with cochlear implants did not differ in cochlear size.

CONCLUSION

This meta-analysis investigated the factors that could affect the cochlear size and found that patients with CSNHL had significantly shorter cochleae, whereas other covariates had no significant effect. Laryngoscope, 2021.

Gene Therapy to the Retina and the Cochlea

Vision and hearing disorders comprise the most common sensory disorders found in people. Many forms of vision and hearing loss are inherited and current treatments only provide patients with temporary or partial relief. As a result, developing genetic therapies for any of the several hundred known causative genes underlying inherited retinal and cochlear disorders has been of great interest. Recent exciting advances in gene therapy have shown promise for the clinical treatment of inherited retinal diseases, and while clinical gene therapies for cochlear disease are not yet available, research in the last several years has resulted in significant advancement in preclinical development for gene delivery to the cochlea. Furthermore, the development of somatic targeted genome editing using CRISPR/Cas9 has brought new possibilities for the treatment of dominant or gain-of-function disease. Here we discuss the current state of gene therapy for inherited diseases of the retina and cochlea with an eye toward areas that still need additional development.

Evolution of drug-eluting biomedical implants for sustained drug delivery

In the field of drug delivery, the most commonly used treatments have traditionally been systemically delivered using oral or intravenous administration. The problems associated with this type of delivery is that the drug concentration is controlled by first pass metabolism, and therefore may not always remain within the therapeutic window. Implantable drug delivery systems (IDDSs) are an excellent alternative to traditional delivery because they offer the ability to precisely control the drug release, deliver drugs locally to the target tissue, and avoid the toxic side effects often experienced with systemic administration. Since the creation of the first FDA-approved IDDS in 1990, there has been a surge in research devoted to fabricating and testing novel IDDS formulations. The versatility of these systems is evident when looking at the various biomedical applications that utilize IDDSs. This review provides an overview of the history of IDDSs, with examples of the different types of IDDS formulations, as well as looking at current and future biomedical applications for such systems. Though there are still obstacles that need to be overcome, ever-emerging new technologies are making the manufacturing of IDDSs a rewarding therapeutic endeavor with potential for further improvements.

Do Patients Benefit From a Cochlear Implant When They Qualify Only in the Presence of Background Noise?

OBJECTIVE

To compare the difference in pre- to postoperative speech performance of patients qualifying for a cochlear implant (CI) in quiet, +10 dB signal-to-noise ratio (SNR), and +5 dB SNR.

STUDY DESIGN

Retrospective.

SETTING

Tertiary referral center.

PATIENTS

Fifty-eight post-lingually deafened, unilateral CI recipients from three Groups were included: 1) those who met CI candidacy criteria with AzBio sentences in quiet, 2) in noise at +10 dB SNR but not in quiet, 3) and in noise at +5 dB SNR but not in quiet or +10 dB SNR.

INTERVENTION

Unilateral CI.

MAIN OUTCOME MEASURES

Pre- and 1 year postoperative speech recognition scores.

RESULTS

Best-aided AzBio speech recognition of individuals in Group 1 improved significantly for all test conditions and improved significantly for Groups 2 and 3 in the +10 and +5 dB SNR test conditions postoperatively. When tested with their CI alone however, while AzBio speech recognition of individuals in Group 1 and Group 2 improved significantly in the quiet and +10 dB SNR conditions, speech recognition was not significantly changed postoperatively under any testing condition for individuals in Group 3.

CONCLUSIONS

While individuals qualifying for a CI only in the +5 dB SNR condition may derive significant benefit from implantation in best aided conditions, speech understanding outcomes can be more variable thus warranting additional counseling before implantation and case-by-case consideration of listening needs and goals.

Toward nanobioelectronic medicine: Unlocking new applications using nanotechnology

Bioelectronic medicine aims to interface electronic technology with biological components and design more effective therapeutic and diagnostic tools. Advances in nanotechnology have moved the field forward improving the seamless interaction between biological and electronic components. In the lab many of these nanobioelectronic devices have the potential to improve current treatment approaches, including those for cancer, cardiovascular disorders, and disease underpinned by malfunctions in neuronal electrical communication. While promising, many of these devices and technologies require further development before they can be successfully applied in a clinical setting. Here, we highlight recent work which is close to achieving this goal, including discussion of nanoparticles, carbon nanotubes, and nanowires for medical applications. We also look forward toward the next decade to determine how current developments in nanotechnology could shape the growing field of bioelectronic medicine. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > Biosensing.

Understanding and treating paediatric hearing impairment

Sensorineural hearing impairment is the most frequent form of hearing impairment affecting 1-2 in 1000 newborns and another 1 in 1000 adolescents. More than 50% of congenital hearing impairment is of genetic origin and some forms of monogenic deafness are likely targets for future gene therapy. Good progress has been made in clinical phenotyping, genetic diagnostics, and counselling. Disease modelling, e.g. in transgenic mice, has helped elucidate disease mechanisms underlying genetic hearing impairment and informed clinical phenotyping in recent years. Clinical management of paediatric hearing impairment involves hearing aids, cochlear or brainstem implants, signal-to-noise improvement in educational settings, speech therapy, and sign language. Cochlear implants, for example, have much improved the situation of profoundly hearing impaired and deaf children. Nonetheless there remains a major unmet clinical need for improving hearing restoration. Preclinical studies promise that we will witness clinical trials on gene therapy and a next generation of cochlear implants during the coming decade. Moreover, progress in generating sensory hair cells and neurons from stem cells spurs disease modelling, drug screening, and regenerative approaches. This review briefly summarizes the pathophysiology of paediatric hearing impairment and provides an update on the current preclinical development of innovative approaches toward improved hearing restoration.

The sensitivity of different methods for detecting abnormalities in auditory nerve function

Background

Cochlear implants (CIs) have become important for the treatment of severe-to-profound sensorineural hearing loss (SNHL). Meanwhile, electrically evoked compound action potentials (ECAPs) and electrically evoked auditory brainstem responses (EABRs), which can be examined and evaluated with minimal patient cooperation, have become more reliable for tone measurement and speech recognition postoperatively. However, few studies have compared the electrophysiological characteristics of the auditory nerve using ECAPs and EABRs under different functional states of the auditory nerve (FSANs). We used guinea pig models in which six electrodes were implanted unilaterally with continuous electrical stimulation (ES) for 4 h. The amplitude growth functions (AGFs) of the alternating polarity ECAP (AP-ECAP) and forward-masking subtraction ECAP (FM-ECAP), as well as the EABR waves under “normal” and “abnormal” FSANs, were obtained.

Results

Both the AP-ECAP and FM-ECAP thresholds were significantly higher than those measured by EABR under both “normal” FSAN and “abnormal” FSANs (p < 0.05). There was a significant difference in the slope values between electrodes 1 and 2 and electrodes 3 and 4 in terms of the AP-ECAP under the “abnormal” FSAN (p < 0.05). The threshold gaps between the AP-ECAP and FM-ECAP were significantly larger under the “abnormal” FSAN than under the “normal” FSAN (p < 0.05).

Conclusions

Both of the ECAP thresholds were higher than the EABR thresholds. The AP-ECAP was more sensitive than the FM-ECAP under the “abnormal” FSAN.

Nanocarriers for drug delivery to the inner ear: Physicochemical key parameters, biodistribution, safety and efficacy

Despite the high incidence of inner ear disorders, there are still no dedicated medications on the market. Drugs are currently administered by the intratympanic route, the safest way to maximize drug concentration in the inner ear. Nevertheless, therapeutic doses are ensured for only a few minutes/hours using drug solutions or suspensions. The passage through the middle ear barrier strongly depends on drug physicochemical characteristics. For the past 15 years, drug encapsulation into nanocarriers has been developed to overcome this drawback. Nanocarriers are well known to sustain drug release and protect it from degradation. In this review, in vivo studies are detailed concerning nanocarrier biodistribution, their pathway mechanisms in the inner ear and the resulting drug pharmacokinetics. Key parameters influencing nanocarrier biodistribution are identified and discussed: nanocarrier size, concentration, surface composition and shape. Recent advanced strategies that combine nanocarriers with hydrogels, specific tissue targeting or modification of the round window permeability (cell-penetrating peptide, magnetic delivery) are explored. Most of the nanocarriers appear to be safe for the inner ear and provide a significant efficacy over classic formulations in animal models. However, many challenges remain to be overcome for future clinical applications.

Non-research industry payments to pediatric otolaryngologists in 2018

OBJECTIVES

To characterize non-research industry payments to pediatric otolaryngologists in 2018.

STUDY DESIGN

Centers for Medicare and Medicaid Services Open Payments program was used to obtain all non-research industry payments to pediatric otolaryngology in 2018. Total payment amount information was obtained for years 2014-2017 for trend analysis. Descriptive statistics were used to analyze the data.

RESULTS

There were 1704 payments to pediatric otolaryngologists in 2018, totaling $163,716 with a median of $17.79. Of the total payments, 74.77% (1274 out of 1704) were under $50. Payments to 299 physicians were reported for 175 different products, the majority of which were associated with otitis media and sinus disease. The nature of the payments included 1579 ($57,120) towards food and beverage, 64 ($46,251) for travel and lodging, 29 ($39,688) for consulting services, 23 ($1075) for education, 4 ($7898) for royalty or license, and 5 ($11,684) for compensation for services such as serving as faculty or a speaker.

CONCLUSION

Our study is the first to investigate industry payments to pediatric otolaryngologists in 2018. Most of the payments were under $50 and mainly for food and beverage. The majority of payments were associated with otitis media and sinus disease.