Systematic Review of Nontumor Pediatric Auditory Brainstem Implant Outcomes

Auditory Brainstem Implant Outcomes in Tumor and Nontumor Patients: A Systematic Review

OBJECTIVE

To elucidate the differences in auditory performance between auditory brainstem implant (ABI) patients with tumor or nontumor etiologies.

DATA SOURCES

PubMed, Embase, and Web of Science Core Collection from 1990 to 2021.

REVIEW METHODS

We included published studies with 5 or more pediatric or adult ABI users. Auditory outcomes and side effects were analyzed with weighted means for closed-set, open-set speech, and categories of auditory performance (CAP) scores. Overall performance was compared using an Adult Pediatric Ranked Order Speech Perception (APROSPER) scale created for this study.

RESULTS

Thirty-six studies were included and underwent full-text review. Data were extracted for 662 tumor and 267 nontumor patients. 83% were postlingually deafened and 17% were prelingually deafened. Studies that included tumor ABI patients had a weighted mean speech recognition of 39.2% (range: 19.6%-83.3%) for closed-set words, 23.4% (range: 17.2%-37.5%) for open-set words, 21.5% (range: 2.7%-48.4%) for open-set sentences, and 3.1 (range: 1.0-3.2) for CAP scores. Studies including nontumor ABI patients had a weighted mean speech recognition of 79.8% (range: 31.7%-84.4%) for closed-set words, 53.0% (range: 14.6%-72.5%) for open-set sentences, and 2.30 (range: 2.0-4.7) for CAP scores. Mean APROSPER results indicate better auditory performance among nontumor versus tumor patients (3.5 vs 3.0, P = .04). Differences in most common side effects were also observed between tumor and nontumor ABI patients.

CONCLUSION

Auditory performance is similar for tumor and nontumor patients for standardized auditory test scores. However, the APROSPER scale demonstrates better ABI performance for nontumor compared to tumor patients.

Ten-year follow-up of auditory brainstem implants: From intra-operative electrical auditory brainstem responses to perceptual results

The auditory brainstem implant (ABI) can provide hearing sensation to individuals where the auditory nerve is damaged. However, patient outcomes with the ABI are typically much poorer than those for cochlear implant recipients. A major limitation to ABI outcomes is the number of implanted electrodes that can produce auditory responses to electric stimulation. One of the greatest challenges in ABI surgery is the intraoperative positioning of the electrode paddle, which must fit snugly within the cochlear nucleus complex. While there presently is no optimal procedure for intraoperative electrode positioning, intraoperative assessments may provide useful information regarding viable electrodes that may be included in patients' clinical speech processors. Currently, there is limited knowledge regarding the relationship between intraoperative data and post-operative outcomes. Furthermore, the relationship between initial ABI stimulation with and long-term perceptual outcomes is unknown. In this retrospective study, we reviewed intraoperative electrophysiological data from 24 ABI patients (16 adults and 8 children) obtained with two stimulation approaches that differed in terms of neural recruitment. The interoperative electrophysiological recordings were used to estimate the number of viable electrodes and were compared to the number of activated electrodes at initial clinical fitting. Regardless of the stimulation approach, the intraoperative estimate of viable electrodes greatly overestimated the number of active electrodes in the clinical map. The number of active electrodes was associated with long-term perceptual outcomes. Among patients with 10-year follow-up, at least 11/21 active electrodes were needed to support good word detection and closed-set recognition and 14/21 electrodes to support good open-set word and sentence recognition. Perceptual outcomes were better for children than for adults, despite a lower number of active electrodes.

Auditory Brainstem Implants in Children with Inner Ear Anomalies: An Indian Perspective

Auditory brainstem implantation (ABI) is a viable option for individuals with inner ear anomalies, or other retro-cochlear pathologies, where cochlear implantation is not a suitable option. Although ABI has its advantages in those populations, most often, ABI is not recommended or accepted by the patients because of its limitations and shortcoming such as open-set word recognition in auditory mode, limited infrastructures for carrying out ABI surgery, and the high cost of implantation. This review highlights the benefits in non-tumor patients with ABI surgery and possible reasons for the limited acceptance of the ABI device from an Indian perspective.

Functional Outcomes of Cochlear Implantation in Children with Bilateral Cochlear Nerve Aplasia

Background and Objectives: Many otologists face a dilemma in the decision-making process of surgical management of patients with cochlear nerve (CN) aplasia. The goal of this study is to provide fresh evidence on cochlear implantation (CI) results in patients with CN aplasia. Materials and Methods: We scrutinized functional outcomes in 37 ears of 21 children with bilateral CN aplasia who underwent unilateral or bilateral CI based on cross-sectional and longitudinal assessments. Results: The Categories of Auditory Performance (CAP) scores gradually improved throughout the 3-year follow-up; however, variable outcomes existed between individuals. Specifically, 90% of recipients with a 1-year postoperative CAP score ≤1 could not achieve a CAP score over 1 even at 3-year postoperative evaluation, while the recipients with a 1-year postoperative CAP score >1 had improved auditory performance, and 72.7% of them were able to achieve a CAP score of 4 or higher. Meanwhile, intraoperative electrically evoked compound action potential was not correlated with postoperative CAP score. Conclusions: Our results further refine previous studies on the clinical feasibility of CI as the first treatment modality to elicit favorable auditory performance in children with CN aplasia. However, special attention should be paid to pediatric patients with an early postoperative CAP score ≤1 for identification of unsuccessful cochlear implants and switching to auditory brainstem implants.

A Retrospective Evaluation to Assess Reliability of Electrophysiological Methods for Diagnosis of Hearing Loss in Infants

Background: An electrophysiological investigation with auditory brainstem response (ABR), round window electrocochleography (RW-ECoG), and electrical-ABR (E-ABR) was performed in children with suspected hearing loss with the purpose of early diagnosis and treatment. The effectiveness of the electrophysiological measures as diagnostic tools was assessed in this study. Methods: In this retrospective case series with chart review, 790 children below 3 years of age with suspected profound hearing loss were tested with impedance audiometry and underwent electrophysiological investigation (ABR, RW-ECoG, and E-ABR). All implanted cases underwent pure-tone audiometry (PTA) of the non-implanted ear at least 5 years after surgery for a long-term assessment of the reliability of the protocol. Results: Two hundred and fourteen children showed bilateral severe-to-profound hearing loss. In 56 children with either ABR thresholds between 70 and 90 dB nHL or no response, RW-ECoG showed thresholds below 70 dB nHL. In the 21 infants with bilateral profound sensorineural hearing loss receiving a unilateral cochlear implant, no statistically significant differences were found in auditory thresholds in the non-implanted ear between electrophysiological measures and PTA at the last follow-up (p > 0.05). Eight implanted children showed residual hearing below 2000 Hz worse than 100 dB nHL and 2 children showed pantonal residual hearing worse than 100 dB nHL (p > 0.05). Conclusion: The audiological evaluation of infants with a comprehensive protocol is highly reliable. RW-ECoG provided a better definition of hearing thresholds, while E-ABR added useful information in cases of auditory nerve deficiency.

Emerging therapies for human hearing loss

INTRODUCTION

More than 5% of the world's population have a disabling hearing loss which can be managed by hearing aids or implanted electrical devices. However, outcomes are highly variable, and the sound perceived by recipients is far from perfect. Sparked by the discovery of progenitor cells in the cochlea and rapid progress in drug delivery to the cochlea, biological and pharmaceutical therapies are currently in development to improve the function of the cochlear implant or eliminate the need for it altogether.

AREAS COVERED

This review highlights progress in emerging regenerative strategies to restore hearing and adjunct therapies to augment the cochlear implant. Novel approaches include the reprogramming of progenitor cells to restore the sensory hair cell population in the cochlea, gene therapy and gene editing to treat hereditary and acquired hearing loss. A detailed review of optogenetics is also presented as a technique that could enable optical stimulation of the spiral ganglion neurons, replacing or complementing electrical stimulation.

EXPERT OPINION

Increasing evidence of substantial reversal of hearing loss in animal models, alongside rapid advances in delivery strategies to the cochlea and learnings from clinical trials will amalgamate into a biological or pharmaceutical therapy to replace or complement the cochlear implant.

Written language skills in children with auditory brainstem implants

PURPOSE

This study aimed to assess the written language skills of children with auditory brainstem implants (ABI).

METHODS

In this study, 15 children (from second to eighth grades) with ABI were evaluated for their written language abilities using a written expression skill assessment form. Five different features of written expression points were scored and analyzed, yielding a composite score for written expression skills.

RESULTS

This study showed that all children with ABI needed more verbal cues than spontaneously written samples. Moreover, these children used short and simple sentences with limited vocabulary and repeated words and sentences. Furthermore, these children were deficient in writing an introduction, the body, and the conclusion paragraphs and could not write events in a logical sequence.

CONCLUSIONS

The written language skills of children with ABI depend on age at implantation, duration of implant use, and additional handicaps. Written expression skills in children with ABI are highly complex skills. The findings highlight the importance of ABI during the critical language development period and the enhancement of training programs for written language skills in children who underwent ABI.

Neurological and developmental outcomes following neonatal encephalopathy treated with therapeutic hypothermia

In randomized trials, therapeutic hypothermia (TH) is associated with reduced prevalence of the composite outcome mortality or neurodevelopmental morbidity in infants with neonatal encephalopathy (NE). Following systematic review, the reduction in prevalence of both mortality and infant neuromorbidity is clear. Among three trials reporting school age outcomes, the effects of NE and TH suggest that such benefit persists into middle childhood, but none of the major trials were powered to detect differences in these outcomes. Cognitive, educational and behavioural outcomes are all adversely affected by NE in children without moderate or severe neuromorbidity. High-quality longitudinal studies of neurocognitive and educational outcomes following NE in the era of TH, including studies incorporating multimodal neuroimaging assessments, are required to characterise deficits more precisely so that robust interventional targets may be developed, and resource planning can occur. Understanding the impact of NE on families and important educational, social, and behavioural outcomes in childhood is critical to attempts to optimise outcomes through interventions.

Cochlear implantation versus auditory brainstem implantation in children with auditory nerve deficiencies

BACKGROUND

Cochlear nerve deficiency is one of the known causes of congenital sensorineural hearing loss. Management of hearing loss in children with cochlear nerve deficiency poses a multidimensional challenge. The absent or hypoplastic cochlear nerve may prevent electrical stimulation from reaching the brainstem and the auditory cortex. A deficient cochlear nerve can be associated with other inner ear malformations, which may diminish the success of cochlear implantation in those children. Promising results in adults after auditory brainstem implantation led to the expansion of candidacy to include the pediatric populations who were contraindicated for CIs.

OBJECTIVE

To review the outcomes of cochlear implantation versus that of auditory brainstem implantation in children with various conditions of the auditory nerve.

METHODS

This retrospective chart review study comprised two pediatric groups. The first group consisted of seven ABI recipients with cochlear nerve aplasia and the second group consisted of another seven children with cochlear nerve deficiencies who underwent CI surgery. The participants' auditory skills and speech outcomes were assessed using different tests selected from the Evaluation of Auditory Responses to Speech (EARS) test battery.

RESULTS

There were some individual variations in outcomes depending on the status of the auditory nerve. The mean CAP score of the ABI group was 2.87, while the mean SIR score was 0.62. On the other hand, the mean CAP score of the CI group was 1.29, while the mean SIR score was 0.42.

CONCLUSION

Our results are in good agreement with the reported auditory perception and speech and language development outcomes of pediatric auditory brainstem implantation. We added to the growing body of literature on the importance of verifying and identifying the status of the cochlear nerve in the decision-making process of the surgical management of those pediatric groups.

Clinical and scientific innovations in auditory brainstem implants

The auditory brainstem implant (ABI) was originally developed to provide rehabilitation of retrocochlear deafness caused by neurofibromatosis type 2 (NF2). Recent studies of the ABI have investigated outcomes in non-NF2 cohorts, such as patients with cochlear nerve aplasia or cochlear ossification and more recently, intractable tinnitus. New technologies that improve the ABI-neural tissue interface are being explored as means to improve performance and decrease side effects. Innovative discoveries in optogenetics and bioengineering present opportunities to continually evolve this technology into the future, enhancing spatial selectivity of neuronal activation in the cochlear nucleus and preventing side effects through reduction in activation of non-target neuronal circuitry. These advances will improve surgical planning and ultimately improve patients’ audiological capabilities. ABI research has rapidly increased in the 21st century and applications of this technology are likely to continually evolve. Herein, we aim to characterize ongoing clinical, basic science, and bioengineering advances in ABIs and discuss future directions of this technology.

Microstructured thin-film electrode technology enables proof of concept of scalable, soft auditory brainstem implants

Auditory brainstem implants (ABIs) provide sound awareness to deaf individuals who are not candidates for the cochlear implant. The ABI electrode array rests on the surface of the cochlear nucleus (CN) in the brainstem and delivers multichannel electrical stimulation. The complex anatomy and physiology of the CN, together with poor spatial selectivity of electrical stimulation and inherent stiffness of contemporary multichannel arrays, leads to only modest auditory outcomes among ABI users. Here, we hypothesized that a soft ABI could enhance biomechanical compatibility with the curved CN surface. We developed implantable ABIs that are compatible with surgical handling, conform to the curvature of the CN after placement, and deliver efficient electrical stimulation. The soft ABI array design relies on precise microstructuring of plastic-metal-plastic multilayers to enable mechanical compliance, patterning, and electrical function. We fabricated soft ABIs to the scale of mouse and human CN and validated them in vitro. Experiments in mice demonstrated that these implants reliably evoked auditory neural activity over 1 month in vivo. Evaluation in human cadaveric models confirmed compatibility after insertion using an endoscopic-assisted craniotomy surgery, ease of array positioning, and robustness and reliability of the soft electrodes. This neurotechnology offers an opportunity to treat deafness in patients who are not candidates for the cochlear implant, and the design and manufacturing principles are broadly applicable to implantable soft bioelectronics throughout the central and peripheral nervous system.

Light-Based Neuronal Activation: The Future of Cranial Nerve Stimulation

Despite advances in implant hardware, neuroprosthetic devices in otolaryngology have sustained evolutionary rather than revolutionary changes over the past half century. Although electrical stimulation has the capacity for facile activation of neurons and high temporal resolution, it has limited spatial selectivity. Alternative strategies for neuronal stimulation are being investigated to improve spatial resolution. In particular, light-based neuronal stimulation is a viable alternative and complement to electrical stimulation. This article provides a broad overview of light-based neuronal stimulation technologies. Specific examples of active research on light-based prostheses, including cochlear implants, auditory brainstem implants, retinal implants, and facial nerve implants, are reviewed.

Methodological Quality of Systematic Reviews and Meta-analyses Published in High-Impact Otolaryngology Journals

OBJECTIVE

To assess the methodological quality of intervention-focused systematic reviews (SRs) and meta-analyses (MAs) published in high-impact otolaryngology journals.

DATA SOURCES

Ovid Medline, Embase, and Cochrane Library.

REVIEW METHODS

A comprehensive search was performed for SR and MA citations from 2012 to 2017 in the 10 highest impact factor otolaryngology journals. Abstracts were screened to identify published manuscripts in which the authors indicated clearly that they were performing an SR or MA. Applying a modified typology of reviews, 4 reviewers characterized the review type as SR, MA, or another review type. A simplified version of the AMSTAR 2 (A MeaSurement Tool to Assess systematic Reviews 2) tool was used to assess the reporting and methodological quality of the SRs and MAs that were focused on interventions.

RESULTS

Search and abstract screening generated 499 manuscripts that identified themselves as performing an SR or MA. A substantial number (85/499, 17%) were review types other than SRs or MAs, including 34 (7%) that were literature reviews. In total, 236 SRs and MAs focused on interventions. Over 50% of these SRs and MAs had weaknesses in at least 3 of the 16 items in the AMSTAR 2, and over 40% had weaknesses in at least 2 of the 7 critical domains. Ninety-nine percent of SRs and MAs provided critically low confidence in the results of the reviews.

CONCLUSION

Intervention-focused SRs and MAs published in high-impact otolaryngology journals have important methodological limitations that diminish confidence in the results of these reviews.

Pediatric Auditory Brainstem Implant Users Compared With Cochlear Implant Users With Additional Disabilities

OBJECTIVES

To evaluate long-term language development in children with prelingual deafness who received auditory brainstem implants (ABIs) compared with children who received cochlear implants (CIs) at the same hospital. Additional non-auditory disabilities were taken into account.

STUDY DESIGN

Retrospective cohort study.

SETTING

Tertiary referral center.

PATIENTS

Ten children with bilateral malformations of the cochlea and/or cochlear nerve who received ABIs, including seven with additional disabilities, and 147 children with CIs as a reference group, including 22 children with additional disabilities.

INTERVENTION

ABIs were implanted at 1.3 to 6.2 years of age. Follow-up ranged from 1.1 to 7.7 years.

MAIN OUTCOME MEASURES

Receptive and expressive language abilities were assessed using the Infant Toddler Meaningful Auditory Integration Scale (IT-MAIS), the Categories of Auditory Performance (CAP), the Meaningful Use of Speech Scale (MUSS), and the Speech Intelligibility Rate (SIR).

RESULTS

Of the 10 children with ABIs, seven had long-term follow-up data. Within 1 year, six of the seven children with ABIs could identify sounds, respond to speech, and use their voice to attract attention. Language skills developed at a slower rate than in children with CIs and reached the same competence level when additional disabilities were absent. These language skills matched, on average, those of children with CIs with additional disabilities.

CONCLUSION

For deaf children with bilateral inner ear malformations, ABIs provide satisfactory auditory input. Children with ABIs are able to develop receptive and expressive language skills comparable to those of children with CIs with additional disabilities. Using this knowledge, preoperative parent counselling can be refined.

Three-Dimensional Surface Reconstruction of the Human Cochlear Nucleus: Implications for Auditory Brain Stem Implant Design

Objective  The auditory brain stem implant (ABI) is a neuroprosthesis placed on the surface of the cochlear nucleus (CN) to provide hearing sensations in children and adults who are not candidates for cochlear implantation. Contemporary ABI arrays are stiff and do not conform to the curved brain stem surface. Recent advancements in microfabrication techniques have enabled the development of flexible surface arrays, but these have only been applied in animal models. Herein, we measure the surface curvature of the human CN and adjoining regions to assist in the design and placement of next-generation conformable clinical ABI arrays. Three-dimensional (3D) reconstructions from ultrahigh T1-weighted brain magnetic resonance imaging (MRI) sequences and histologic reconstructions based on postmortem adult human brain stem specimens were used. Design  This is a retrospective review of radiologic data and postmortem histologic axial sections. Setting  This is set at the tertiary referral center. Participants  Data were acquired from healthy adults. Main Outcome Measures  The main outcome measures are principal curvature values (Kmin and Kmax) and global radius of curvature. Results  The CN was successfully extracted and rendered as a 3D surface in all cases. Significant curvatures of the CN in both histologic and radiographic reconstructions were found with global radius of curvature ranging from 2.08 to 8.5 mm. In addition, local curvature analysis revealed that the surface is highly complex. Conclusion  Detailed rendering of the human CN is feasible using histology and 3D MRI reconstruction and highlights complex surface topography that is not recapitulated by contemporary stiff ABI arrays.

Clinical Profile and Results Obtained in Patients Treated by Auditory Brainstem Implants

INTRODUCTION

Cochlear implants have been able to treat some types of hearing loss, but those related to cochlear nerve impairment made it necessary to find new ways to manage these deficits; leading to auditory brainstem implants (ABI).

AIM

Our objective is to present the clinical profile of patients treated through an ABI and the results obtained from 1997 to 2017.

MATERIAL AND METHODS

On the one hand, patients with statoacoustic nerve tumours (VIIIcranial nerve) were selected, and on the other hand, patients withoutVIII tumours with congenital malformations of the inner ear. Before and after the placement of the ABI, hearing was assessed through tonal audiometry, from which the PTA (Pure Tone Average) and the CAP (Categories of Auditory Performance) scale were obtained.

RESULTS

A total of 20 patients undergoing ABI surgery were included. Eight were of tumour cause (40%) and 12 non-tumour (60%). In 15 subjects (75%) a suboccipital approach was performed and in 5 (25%) translabyrinthine. The mean of active electrodes before the implantation of Cochlear® (Nucleus ABI24) was 13/21 (61.90%) versus 8.5/12 (70.83%) of the Med-el® (ABI Med-el). An improvement in the mean PTA of 118.49dB was found against 46.55dB at 2years. On the CAP scale, values of1 were obtained in the preimplantation and of 2.57 (1-5) in the 2-year revision.

CONCLUSION

The ABI is a safe option, and with good hearing results when the indication is made correctly.

Concepts in Neural Stimulation: Electrical and Optical Modulation of the Auditory Pathways

Understanding the mechanisms of neural stimulation is necessary to improve the management of sensory disorders. Neurons can be artificially stimulated using electrical current, or with newer stimulation modalities, including optogenetics. Electrical stimulation forms the basis for all neuroprosthetic devices that are used clinically. Off-target stimulation and poor implant performance remain concerns for patients with electrically based neuroprosthetic devices. Optogenetic techniques may improve cranial nerve stimulation strategies used by various neuroprostheses and result in better patient outcomes. This article reviews the fundamentals of neural stimulation and provides an overview of recent major advancements in light-based neuromodulation."

Hearing Restoration in Cochlear Nerve Deficiency: the Choice Between Cochlear Implant or Auditory Brainstem Implant, a Meta-analysis

OBJECTIVE

To answer the dilemma clinician's face when deciding between cochlear implant (CI) and auditory brainstem implant (ABI) treatment options in patients with cochlear nerve deficiency (CND).

STUDY DESIGN

Case study supplemented with literature review and meta-analysis.

SETTING

Tertiary referral center.

PATIENT(S)

Child with CHARGE syndrome and congenital deafness.

INTERVENTION(S)

ABI as there was no benefit after bilateral cochlear implantation.

MAIN OUTCOME MEASURES

Speech and language development, quality of life.

RESULTS

In one ear the cochleovestibular nerve was present on magnetic resonance imaging (MRI) without preoperative ABR responses. In the contra lateral ear the nerve could not be identified, despite present ABR responses. Nevertheless, there was no positive outcome with CI. The patient had improved speech and language and quality of life with ABI. Of the 108 patients with CND and CI identified in the literature review, 25% attained open-set speech perception, 34% attained closed-set speech perception, and 41% detected sounds or less. The appearance of the cochlear nerve on MRI was a useful predictor of success, with cochlear nerve aplasia on MRI associated with a smaller chance of a positive outcome post cochlear implantation compared with patients with cochlear nerve hypoplasia.

CONCLUSION

Although patients with (apparent) cochlear nerve aplasia are less likely to benefit from CI, CI before ABI is supported as some patients attain closed or open-set levels of speech perception after cochlear implantation.

Auditory brainstem implantation in children with hearing loss: Effect on speech production

Auditory brainstem implantation (ABI) is a recent technique in children's hearing restoration. Up till now the focus in the literature has mainly been the perceptual outcomes after implantation, whereas the effect of ABI on spoken language is still an almost unexplored area of research. This study presents a one-year follow-up of the volubility of two children with ABI. The volubility of signed and oral productions is investigated and oral productions are examined in more detail. Results show clear developmental trends in both children, indicating a beneficial effect of ABI on spoken language development.

Pediatric Auditory Brainstem Implantation: Surgical, Electrophysiologic, and Behavioral Outcomes

OBJECTIVES

The objectives of this study were to demonstrate the safety of auditory brainstem implant (ABI) surgery and document the subsequent development of auditory and spoken language skills in children without neurofibromatosis type II (NFII).

DESIGN

A prospective, single-subject observational study of ABI in children without NFII was undertaken at the University of North Carolina at Chapel Hill. Five children were enrolled under an investigational device exemption sponsored by the investigators. Over 3 years, patient demographics, medical/surgical findings, complications, device mapping, electrophysiologic measures, audiologic outcomes, and speech and language measures were collected.

RESULTS

Five children without NFII have received ABIs to date without permanent medical sequelae, although 2 children required treatment after surgery for temporary complications. All children wear their device daily, and the benefits of sound awareness have developed slowly. Intra-and postoperative electrophysiologic measures augmented surgical placement and device programming. The slow development of audition skills precipitated limited changes in speech production but had little impact on growth in spoken language.

CONCLUSIONS

ABI surgery is safe in young children without NFII. Benefits from device use develop slowly and include sound awareness and the use of pattern and timing aspects of sound. These skills may augment progress in speech production but progress in language development is dependent upon visual communication. Further monitoring of this cohort is needed to better delineate the benefits of this intervention in this patient population.

Auditory brainstem stimulation with a conformable microfabricated array elicits responses with tonotopically organized components

Auditory brainstem implants (ABIs) restore hearing to deaf individuals not eligible for cochlear implants. Speech comprehension in ABI users is generally poor compared to that of cochlear implant users, and side effects are common. The poor performance may result from activating broad areas and multiple neuronal populations of the cochlear nucleus, however detailed studies of the responses to surface stimulation of the cochlear nucleus are lacking. A conformable electrode array was microfabricated to fit on the rat's dorsal cochlear nucleus (DCN). It hosts 20 small electrodes (each 100 μm diam.). The array was tested by recording evoked potentials and neural activity along the tonotopic axis of the inferior colliculus (IC). Almost all bipolar electrode pairs elicited responses, in some cases with an even, or relatively constant, pattern of thresholds and supra-threshold measures along the long axis of the array. This pattern suggests that conformable arrays can provide relatively constant excitation along the surface of the DCN and thus might decrease the ABI side effects caused by spread of high current to adjacent structures. We also examined tonotopic patterns of the IC responses. Compared to sound-evoked responses, electrically-evoked response mappings had less tonotopic organization and were broader in width. They became more tonotopic when the evoked activity common to all electrodes and the late phase of response were subtracted out, perhaps because the remaining activity is from tonotopically organized principal cells of the DCN. Responses became less tonotopic when inter-electrode distance was increased from 400 μm to 800 μm but were relatively unaffected by changing to monopolar stimulation. The results illustrate the challenges of using a surface array to present tonotopic cues and improve speech comprehension in humans who use the ABI.

Auditory Brainstem Implants: Recent Progress and Future Perspectives

The auditory brainstem implant (ABI) was first developed nearly 40 years ago and provides auditory rehabilitation to patients who are deaf and ineligible for cochlear implant surgery due to abnormalities of the cochlea and cochlear nerve. The aims of the following review are to describe the history of the ABI and innovations leading up to the modern ABI system, as well as highlight areas of future development in implant design.

Paediatric auditory brainstem implantation: The South Asian experience

INTRODUCTION

Paediatric Auditory Brainstem Implantation (ABI) is indicated for children with congenital cochlear aplasia, absent/hypoplastic vestibulocochlear nerve, for whom cochlear implantation is not possible. Knowledge of the anatomical landmarks and variants in anatomy of the brainstem is vital for ABI surgery.

METHOD

Study was done at Auditory implant centre in Madras ENT research foundation, which includes 24 children who had undergone ABI surgery and are being followed up for 1 year, post operatively. Aims were to study the anatomical variants and the outcomes of ABI implantation. To determine if different anatomical variants effect placement of ABI electrode. To assess the patient outcomes by Categories of auditory Performance (CAP) scores and Speech Intelligibility Ratings (SIR) scores.

RESULTS

All the candidates showed gradual improvement in audiological and verbal outcomes after the ABI. The mean CAP and SIR scores after 6 months of AVHT were 2.07 and 1.37 respectively. After 1 year of auditory verbal rehabilitation therapy CAP was 3.42 and SIR was 2.33. Flocculus of the cerebellum can be of different grades. Though, there was difficulty in insertion of the electrode in subjects with anatomical variants, the outcomes were comparable with other subjects.

CONCLUSION

ABI surgery involves frequent anatomical variations surrounding the lateral recess which makes the positioning of the auditory prosthesis difficult. Variants during the surgery can make the placement of ABI electrodes difficult, but promising results were seen all the implantees.

Early experience and health related quality of life outcomes following auditory brainstem implantation in children

OBJECTIVE

To assess auditory brainstem implant (ABI) outcomes in children with a prospective study.

METHODS

Twelve patients with cochlear nerve deficiency received an auditory brainstem implant. Patients were evaluated with age appropriate speech perception and production assessments, and health related quality of life (HRQoL) surveys for parents of subjects and for subjects if age appropriate.

RESULTS

Twelve patients received an ABI without major complications. Eleven out of twelve received some auditory benefit from their ABI. Parental HRQoL ratings were positive for all domains with the exception of communication. Self reported overall HRQoL metrics from two subjects were also positive.

CONCLUSIONS

ABI is a good option for patients who are not eligible for or fail CI. Our findings show that despite varying degrees of postoperative performance, HRQoL ratings were positive. The presence of additional disabilities and health problems resulted in less positive HRQoL outcomes. Our results emphasize the need to assess outcomes in these patients beyond speech perception and communication.

Pediatric Auditory Brainstem Implantation: Impact on Audiological Rehabilitation and Tonal Language Development

OBJECTIVE

This is a retrospective review of the impact of an Auditory Brainstem Implant (ABI) on the audiological rehabilitation and tonal language development of pediatric patients with prelingual profound deafness in Hong Kong.

RESULTS

From January 2009 to February 2015, 11 pediatric patients with profound prelingual deafness received an ABI in Hong Kong (age range 1.67-3.75 years). Etiologies included Cochlear Nerve Deficiency in 7, Severe Cochlear Malformations in 2, and Retrocochlear Deafness in 2. All of them were rehabilitated in Cantonese, a dialect of Chinese. Standard pediatric cochlear implant outcome measurements were used in this study that comprised of the 7-Sound Detection, Syllable Identification, Vowel Identification, Consonant Identification, Tone Imitation, Tone Production and Speech Perception Category. Audiological rehabilitation and speech development outcomes were reviewed. Age-matched outcomes of pediatric cochlear implant users were used for comparisons.

CONCLUSION

Encouraging results of speech development were found, especially with continued use of the ABI. There was considerable variation in outcomes. Children with coexisting developmental and nonauditory cognitive disabilities did not perform as well. Auditory brainstem implantation is a safe and beneficial treatment for profound prelingual deafness in Cantonese-speaking pediatric patients.

Assessing the Benefit-Risk Profile for Pediatric Implantable Auditory Prostheses

BACKGROUND/AIMS

Children with congenital cochleovestibular abnormalities associated with profound hearing loss have few treatment options if cochlear implantation does not yield benefit. An alternative is the auditory brainstem implant (ABI). Regulatory authority device approvals currently include a structured benefit-risk assessment. Such an assessment, for regulatory purposes or to guide clinical decision making, has not been published, to our knowledge, for the ABI and may lead to the design of a research program that incorporates regulatory authority, family, and professional input.

METHODS

Much structured benefit-risk research has been conducted in the context of drug trials; here we apply this approach to device studies. A qualitative framework organized benefit (speech recognition, parent self-report measures) and risk (surgery- and device-related) information to guide the selection of candidates thought to have potential benefit from ABI.

RESULTS

Children with cochleovestibular anatomical abnormalities are challenging for appropriate assessment of candidacy for a cochlear implant or an ABI. While the research is still preliminary, children with an ABI appear to slowly obtain benefit over time. A team of professionals, including audiological, occupational, and educational therapy, affords maximum opportunity for benefit.

CONCLUSIONS

Pediatric patients who have abnormal anatomy and are candidates for an implantable auditory prosthetic require an individualized, multisystems review. The qualitative benefit-risk assessment used here to characterize the condition, the medical need, potential benefits, risks, and risk management strategies has revealed the complex factors involved. After implantation, continued team support for the family during extensive postimplant therapy is needed to develop maximum auditory skill benefit.

Early Communication Development of Children with Auditory Brainstem Implants

The auditory brainstem implant (ABI) is an auditory sensory device that is surgically placed on the cochlear nucleus of the brainstem for individuals who are deaf but unable to benefit from a cochlear implant (CI) due to anatomical abnormalities of the cochlea and/or eighth nerve, specific disease processes, or temporal bone fractures. In the United States, the Food and Drug Administration has authorized a Phase I clinical trial to determine safety and feasibility of the ABI in up to 10 eligible young children who are deaf and either derived no benefit from the CI or were anatomically unable to receive a CI. In this paper, we describe the study protocol and the children who have enrolled in the study thus far. In addition, we report the scores on speech perception, speech production, and language (spoken and signed) for five children with 1-3 years of assessment post-ABI activation. To date, the results indicate that spoken communication skills are slow to develop and that visual communication remains essential for post-ABI intervention.

Auditory Brainstem Implant Array Position Varies Widely Among Adult and Pediatric Patients and Is Associated With Perception

OBJECTIVES

The auditory brainstem implant (ABI) provides sound awareness to patients who are ineligible for cochlear implantation. Auditory performance varies widely among similar ABI cohorts. We hypothesize that differences in electrode array position contribute to this variance. Herein, we classify ABI array position based on postoperative imaging and investigate the relationship between position and perception.

DESIGN

Retrospective review of pediatric and adult ABI users with postoperative computed tomography. To standardize views across subjects, true axial reformatted series of scans were created using the McRae line. Using multiplanar reconstructions, basion and electrode array tip coordinates and array angles from vertical were measured. From a lateral view, array angles (V) were classified into types I to IV, and from posterior view, array angles (T) were classified into types A to D. Array position was further categorized by measuring distance vertical from basion (D1) and lateral from midline (D2). Differences between array classifications were compared with audiometric thresholds, number of active electrodes, and pitch ranking.

RESULTS

Pediatric (n = 4, 2 with revisions) and adult (n = 7) ABI subjects were included in this study. Subjects had a wide variety of ABI array angles, but most were aimed superiorly and posteriorly (type II, n = 7) from lateral view and upright or medially tilted from posterior view (type A, n = 6). Mean pediatric distances were 8 to 42% smaller than adults for D1 and D2. In subjects with perceptual data, electrical thresholds and the number of active electrodes differed among classification types.

CONCLUSIONS

In this first study to classify ABI electrode array orientation, array position varied widely. This variability may explain differences in auditory performance.

Cochlear Implant Outcomes in Cochlea Nerve Aplasia and Hypoplasia

OBJECTIVE

To assess cochlear implant (CI) outcomes, and factors affecting outcomes, for children with aplasia/ hypoplasia of the cochlea nerve. We also developed a new grading system for the nerves of the internal auditory meatus (IAM) and cochlea nerve classification.

STUDY DESIGN

Retrospective patient review.

SETTING

Tertiary referral hospital and cochlear implant program.

PATIENTS

Children 0 to 16 years inclusive with a CI who had absent/hypoplastic cochlea nerve on magnetic resonance imaging (MRI).

INTERVENTION

Cochlear implant.

MAIN OUTCOME MEASURES

MRI, trans-tympanic electrical auditory brainstem response, intraoperative electrical auditory brainstem response, Neural Response Telemetry, Categories of Auditory Perception score, Main mode of communication.

RESULTS

Fifty CI recipients (26 males and 24 females) were identified, 21 had bilateral CIs, 27 had developmental delay. MRI showed cochlea nerve aplasia in 64 ears, hypoplasia in 25 ears, and a normal nerve in 11 ears. Main mode of communication was analyzed for 41 children: 21 (51%) used verbal language (15 speech alone, 5 speech plus some sign, 1 bilingual in speech and sign), and 20 (49%) used sign language (10 sign alone, 9 sign plus some speech, 1 tactile sign). Seventy-three percent of children used some verbal language. Cochlea nerve aplasia/ hypoplasia and developmental delay were both significant factors affecting main mode of communication. Categories of Auditory Performance scores were available for 59 CI ears; 47% with CN Aplasia (IAM nerve grades 0-III) and 89% with CN hypoplasia (IAM nerve grade IV) achieved Categories of Auditory Performance scores of 5 to 7 (some verbal understanding) (p = 0.003).

CONCLUSION

Our results are encouraging and useful when counselling families regarding the likelihood of language outcomes and auditory understanding.

Initial Results of a Safety and Feasibility Study of Auditory Brainstem Implantation in Congenitally Deaf Children

OBJECTIVE

To determine the safety and feasibility of the auditory brainstem implant (ABI) in congenitally deaf children with cochlear aplasia and/or cochlear nerve deficiency.

STUDY DESIGN

Phase I feasibility clinical trial of surgery in 10 children, ages 2 to 5 years, over a 3-year period.

SETTING

Tertiary children's hospital and university-based pediatric speech/language/hearing center.

INTERVENTION(S)

ABI implantation and postsurgical programming.

MAIN OUTCOME MEASURE(S)

The primary outcome measure is the number and type of adverse events during ABI surgery and postsurgical follow-up, including behavioral mapping of the device. The secondary outcome measure is access to and early integration of sound.

RESULTS

To date, nine children are enrolled. Five children have successfully undergone ABI surgery and postoperative behavioral programming. Three children were screen failures, and one child is currently undergoing candidacy evaluation. Expected adverse events have been documented in three of the five children who received the ABI. One child experienced a cerebral spinal fluid leak, which resolved with lumbar drainage. One child demonstrated vestibular side effects during device programming, which resolved by deactivating one electrode. One child experienced postoperative vomiting resulting in an abdominal radiograph. Four children have completed their 1-year follow-up and have speech detection thresholds of 30 to 35 dB HL. Scores on the IT-MAIS/MAIS range from 8 to 31 (out of a total of 40), and the children are demonstrating some ability to discriminate between closed-sets words that differ by number of syllables (pattern perception).

CONCLUSION

ABI surgery and device activation seem to be safe and feasible in this preliminary cohort.

Outcomes following Pediatric Auditory Brainstem Implant Surgery: Early Experiences in a North American Center

There are no approved Food and Drug Administration indications for pediatric auditory brainstem implant (ABI) surgery in the United States. Our prospective case series aims to determine the safety and feasibility of ABI surgery in pediatric patients <5 years old with congenital deafness at a tertiary North American center. The inclusion criterion was pre- or postlinguistic deafness in children not eligible for cochlear implantation. Seventeen candidates were evaluated (mean ± SD: age, 2.52 ± 0.39 years). Four patients underwent ABI surgery (age, 19.2 ± 3.43 months), including 4 primary procedures and 1 revision for device failure. Spontaneous device failure occurred in another subject postoperatively. No major/minor complications occurred, including cerebrospinal fluid leak, facial nerve injury, hematoma, and nonauditory stimulation. All subjects detected sound with environmental awareness, and several demonstrated babbling and mimicry. Poor durability of older implants underscores need for updated technology.