Auditory Brainstem Implant Research Articles

An auditory brainstem implant for treatment of unilateral tinnitus: protocol for an interventional pilot study

IntroductionTinnitus may have a very severe impact on the quality of life. Unfortunately, for many patients, a satisfactory treatment modality is lacking. The auditory brainstem implant (ABI) was originally indicated...

Practical and ethical issues for delivery of advanced ENT services in the Indian subcontinent: efforts to 'Bridge the Gap'.

The Indian healthcare industry, one of the largest in the world, caters for 1.3 billion people. The modern middle class addresses its needs by visiting private hospitals, which provide comprehensive services but at a high cost. The low socioeconomic individuals visit government hospitals where all basic services are available, but there is a struggle to provide advanced healthcare. In order to rectify this dichotomous approach, new initiatives are being implemented to provide uniform healthcare across the society. Technological advancements have been rapid and modern methods have reached the shores of India at the same pace as in the western world. In otolaryngology, advanced services especially for restoration of hearing loss and multimodality treatments for head and neck cancers have been two areas where practical and ethical dilemmas have existed to provide the most optimal treatment at subsidized costs. This article explores these two areas as examples to understand the specific problems encountered in delivering advanced ENT care in a low-resource setting in a large populous country. Introduction of government health insurance schemes have helped the poor to make use of advanced healthcare. The highlight of this scheme has been the inclusion of expensive interventions like cochlear and auditory brainstem implantation, whereby cost of the device, surgery and habilitation have all been delivered cost free for eligible children.

Effect of anesthesia on evoked auditory responses in pediatric auditory brainstem implant surgery.

Electrically evoked auditory brainstem responses (EABR) guide placement of the multichannel auditory brainstem implant (ABI) array during surgery. EABRs are also recorded under anesthesia in nontumor pediatric ABI recipients prior to device activation to confirm placement and guide device programming. We examine the influence of anesthesia on evoked response morphology in pediatric ABI users by comparing intraoperative with postoperative EABR recordings. Retrospective review. Seven children underwent ABI surgery by way of retrosigmoid craniotomy. General anesthesia included inhaled sevoflurane induction and propofol maintenance during which EABRs were recorded to confirm accurate positioning of the ABI. A mean of 7.7 ± 2.8 weeks following surgery, the ABI was activated under general anesthesia or sedation (dexmedetomidine) and EABR recordings were made. A qualitative analysis of intraoperative and postoperative waveform morphology was performed. Seven subjects (mean age 20.6 months) underwent nine ABI surgeries (seven primary, two revisions) and nine activations. EABRs were observed in eight of nine postoperative recordings. In three cases, intraoperative EABRs during general anesthesia were similar to postoperative EABRs with sedation. In one case, sevoflurane and propofol were used for intra- and postoperative recordings, and waveforms were also similar. In four cases, amplitude and latency changes were observed for intraoperative versus postoperative EABRs. Similarity of EABR morphology in the anesthetized versus sedated condition suggests that anesthesia does not have a large effect on far-field evoked potentials. Changes in EABR waveform morphology observed postoperatively may be influenced by other factors such as movements of the surface array. 4 Laryngoscope, 130:507-513, 2020.

Expressive Vocabulary Growth After Pediatric Auditory Brainstem Implantation in Two Cases' Spontaneous Productions: A Comparison With Children With Cochlear Implants and Typical Hearing.

Auditory brainstem implants (ABI) are recently being used to restore hearing of children with a congenital hearing loss, due to for instance the absence of auditory nerves. Thus far, the literature has focused on perceptual outcomes. The present study is among the first ones to investigate the spoken language development after implantation. The lexical development of children with ABI is examined longitudinally in comparison to children with typical hearing and children with cochlear implants. Results show that children with ABI still have smaller spoken vocabularies as compared to (hearing) age-matched children with cochlear implants and children with typical hearing. Implications will be discussed.

Novel Statistical Analyses to Assess Hearing Outcomes After ABI Implantation in NF2 Patients: Systematic Review and Individualized Patient Data Analysis

Patients with neurofibromatosis type 2 develop bilateral vestibular schwannomas with progressive hearing loss. Auditory brainstem implants (ABIs) stimulate hearing in the cochlear nuclei and show promise in improving hearing. Here, we assess the impact of ABI on hearing over time by systematically reviewing the literature and re-analyzing available individual patient data. A multidatabase search identified 3 studies with individual patient data of longitudinal hearing outcomes after ABI insertion in adults. Data were collected on hearing outcomes of different sound complexities from sound to speech using an ABI ± lip reading ability plus demographic data. Because of heterogeneity each study was analyzed separately using random effects multilevel mixed linear modeling. Across all 3 studies (n= 111 total) there were significant improvements in hearing over time from ABI placement (P < 0.000 in all). Improvements in comprehension of sounds, words, sentences, and speech occurred over time with ABI use+ lip reading but lip reading ability did not improve over time. All categories of hearing complexity had over 50% comprehension after over 1 year of ABI use and some subsets had over 75% or near 100% comprehension. Vowel comprehension was greater than consonant, and word comprehension was greater than sentence comprehension (P < 0.0001 in both). Age and sex did not predict outcomes. ABIs improve hearing beyond lip reading alone, which represents baseline patient function prior to treatment, and the benefits continue to improve with time. These findings may be used to guide patient counseling regarding ABI insertion, rehabilitation course after insertion, and future studies.

Planning for and Working With Children With an Auditory Brainstem Implant: What Therapists Need to Know

IntroductionInvestigations of auditory brainstem implants (ABIs) in children started around 2012 in the United States. The team at the University of Southern California-Caruso Family Center for Childhood Communication began seeing children, implanted abroad, in 2006. ABIs are indicated for children who cannot benefit from cochlear implants (CIs). The habilitation and educational needs of children with ABIs versus CIs differ.PurposeThis document provides information professionals can use when implementing habilitation programs for children with ABIs.MethodThe University of Southern California-Caruso Family Center for Childhood Communication, as part of the Los Angeles Pediatric ABI team, is conducting an ABI safety and feasibility clinical trial. This article shares experiences from the viewpoint of a multidisciplinary team. The article provides background knowledge, an outcomes review, and considerations to guide ABI intervention.ResultsABIs and CIs differ in the acoustic information they provide. Outcome studies suggest progress is slow with ABIs but that children can develop some auditory or spoken language skills. The children require highly supportive learning experiences. Visual communication support remains important. The considerations outlined reflect the children's need for explicit instruction.ConclusionsWhen serving children with ABIs, therapists must apply their broad knowledge about working with children with hearing loss, tempering that knowledge, and recognizing that auditory access and progress differ with ABIs compared to CIs. Educational and program placement decisions may require unconventional thinking.

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.

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.

Auditory Brainstem Implantation: An Overview

An auditory brainstem implant (ABI) is a surgically implanted central neural auditory prosthesis for the treatment of profound sensorineural hearing loss in children and adults who are not cochlear implant candidates due to a lack of anatomically intact cochlear nerves or implantable cochleae. The device consists of a multielectrode surface array which is placed within the lateral recess of the fourth ventricle along the brainstem and directly stimulates the cochlear nucleus, thereby bypassing the peripheral auditory system. In the United States, candidacy criteria for ABI include deaf patients with neurofibromatosis type 2 (NF2) who are 12 years or older undergoing first- or second-side vestibular schwannoma resection. In recent years, several non-NF2 indications for ABI have been explored, including bilateral cochlear nerve avulsion from trauma, complete ossification of the cochlea due to meningitis, or a severe cochlear malformation not amenable to cochlear implantation. In addition, growing experience with ABI in infants and children has been documented with encouraging outcomes. While cochlear implantation generally remains the first-line option for hearing rehabilitation in NF2 patients with stable tumors or post hearing preservation surgery where hearing is lost but a cochlear nerve remains accessible for stimulation, an ABI is the next alternative in cases where the cochlear nerve is absent and/or if the cochlea cannot be implanted. Herein, we review ABI device design, clinical evaluation, indications, operative technique, and outcomes as it relates to lateral skull base pathology.

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.

The Effect of National Pneumococcal Vaccination Program on Incidence of Postmeningitis Sensorineural Hearing Loss and Current Treatment Modalities.

The aim of the present study was to investigate the effect of the national pneumococcal vaccination program on postmeningitis sensorineural hearing loss (SNHL). Overall, 2751 patients (2615 cochlear implantation and 136 auditory brainstem implantation) who underwent cochlear implantation (CI) and auditory brainstem implantation (ABI) at a tertiary referral hospital otolaryngology clinic were retrospectively analyzed. One hundred sixteen patients with a history of meningitis were included in the study. Patients were evaluated for their age at the time of surgery, gender, computerized tomography (CT) and magnetic resonance imaging (MRI) findings, implant type, side, and incidence before and after the vaccination program. When patients with cochlear implants or ABI were examined, the incidence of meningitis-induced hearing loss was 6.2% in the pre-vaccination period and 0.6% in the post-vaccination period. There is a significant difference between them when compared by chi-square test (p<0.001). The most important finding of the present study is the dramatic decrease in the number of CI and ABI surgeries performed in patients with SNHL due to meningitis. This shows the effectivity of pneumococcal vaccination in this special group of patients. If total ossification is detected on CT of patients with postmeningitis, ABI should be preferred to CI.

A mouthful - airway matters in intraoperative neuromonitoring in auditory brainstem implant surgery for the pediatric patient: a case series

BackgroundThe Auditory brainstem implant (ABI) is a new surgical option for hearing impaired children. Intraoperative neurophysiology monitoring includes brainstem mapping of cranial nerve (CN) IX, X, XI, XII and their motor nuclei, and corticobulbar tract motor-evoked potential. These require laryngeal electrodes and intra-oral pins, posing a challenge to airway management especially in the pediatric airway, where specialized electromyogram (EMG) tracheal tubes are not available.Challenges include determining the optimum position on the endotracheal tube (ETT) in which to place laryngeal electrode, and the increase in external diameter of ETT contributed by the wrapping the electrode around the shaft of ETT; this may necessitate downsizing of the tracheal tube. An appropriate size ETT minimizes displacement, which in turn can affect electrode contact with the vocal cords. Finally, a small thus crowded pediatric airway makes for difficult visualization during placement of intraoral neuromonitoring electrodes. The use of a videolaryngoscope helps determine optimum electrode placement.Case presentationWe describe intraoperative neurophysiology monitoring and airway management for the first two ABI procedures in Singapore, conducted for children with congenitally absent cochlear nerves.ConclusionNeurophysiology cranial nerve IX, X, XII monitoring in the ABI procedure requires intraoral placement of electrodes. Care should be exercised during placement and removal. Vagus nerve monitoring in children requires attention to tube preparation, and consideration should be given to avoidance of airway topicalization.

Performance with an Auditory Brainstem Implant and Contralateral Cochlear Implant in Pediatric Patients

Objective: To assess bimodal auditory performance in children with a cochlear implant (CI) and contralateral auditory brainstem implant (ABI). Methods: This is a retrospective case review performed at a tertiary referral center. Four patients with cochlear nerve deficiency initially underwent cochlear implantation but were not benefiting from their devices and underwent ABI in the contralateral ear. The main outcome measures included age-appropriate speech perception and production assessments. Results: Three subjects performed better on their auditory perception assessments using both of their devices than with either device alone. One subject had only preliminary outcomes, but subjectively performed best with both devices. Conclusions: We observed continued improvement in CI performance over time, even if no benefit was evident before the decision for ABI. This could suggest that ABI and CI have a synergistic effect, or it could simply be the adaptive ability of the developing brain to utilize the signals coming from these devices. There is preliminary evidence to support choosing the ear contralateral to the CI for an ABI in a pediatric patient with bilateral cochlear nerve deficiency.

Paediatric auditory brainstem implantation: The South Asian experience

IntroductionPaediatric 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. MethodStudy 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. ResultsAll 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. ConclusionABI 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.

Novel method of fitting of children with auditory brainstem implants

ObjectivesTo develop a reliable and objective fitting method for use with young children with an auditory brainstem implant (ABI). Materials and methodsSubjects were 17 young children implanted with an ABI with the mean age 2 years and 4 months (8–64 months). Evoked auditory brainstem response (eABR) measurements were performed intraoperatively and at activation in order to record the auditory response and non-auditory side effects. Each child was tested to observe any subjective responses to the electric stimuli and non-auditory side effects. All children were fitted based on the postoperative eABR. The minimum follow up time was 12 months. ResultsIntraoperatively an eABR could be obtained in all children. The responses were recordable from 75–100% of all electrodes. At initial stimulation eABR were recordable in all children. The eABR was obtained in 79.7% of all electrodes (25–100%) with a mean eABR threshold of 22.3 nC. eABR without any non-auditory stimulation was recorded on all electrodes in 11 children. Mixed eABR and non-auditory responses were recorded on 2–6 electrodes in 6 children. The subjective auditory responses for at least 1 electrode were noted in 15 children. In the 2 remaining cases the auditory response was obtained only when the device was activated. In all children the subjective responses were within the estimated dynamic range for each electrode. Each child was able to accept up to 100% of volume of the created map. The non-auditory response was observed only on children and electrodes with mixed eABR and non-auditory responses. The mean CAP score at 6 months after the activation was 2.4 (1–4). ConclusionseABR seems to be a reliable tool to judge ABI electrode placement and a reliable method for fitting of young children with an ABI. The data suggest that eABR-based fitting helps children to more quickly achieve auditory perception and development.

Comprehensive review of the extended middle cranial fossa approach.

To review the current literature on the extended middle cranial fossa (xMCF) approach and to provide a comprehensive description of the relevant anatomy, indications, surgical technique, results, and complications. The xMCF approach expands the surgical exposure provided by the sMCF approach, allowing access to the internal auditory canal, cerebellopontine angle, prepontine cistern, anterior petrous apex, petrous carotid artery, Meckel's cave, cavernous sinus, mid and upper clivus, and posterior lesions approaching the jugular foramen. Preservation of serviceable hearing is possible with success rates approximating 50% in vestibular schwannoma and meningioma resection, and facial nerve outcome is excellent. The xMCF is an important approach for difficult to access lesions that additionally offers the possibility of hearing preservation. This approach is also useful for vascular lesions, auditory brainstem implantation, and lesions of mid-brainstem.

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.

Cochlear Implantation: An Overview.

A cochlear implant (CI) is a surgically implanted device for the treatment of severe to profound sensorineural hearing loss in children and adults. It works by transducing acoustic energy into an electrical signal, which is used to stimulate surviving spiral ganglion cells of the auditory nerve. The past 2 decades have witnessed an exponential rise in the number of CI surgeries performed. Continual developments in programming strategies, device design, and minimally traumatic surgical technique have demonstrated the safety and efficacy of CI surgery. As a result, candidacy guidelines have expanded to include both pre and postlingually deaf children as young as 1 year of age, and those with greater degrees of residual hearing. A growing proportion of patients are undergoing CI for off-label or nontraditional indications including single-sided deafness, retrocochlear hearing loss, asymmetrical sensorineural hearing loss (SNHL) in adults and children with at least 1 ear that is better than performance cut-off for age, and children less than 12 months of age. Herein, we review CI design, clinical evaluation, indications, operative technique, and outcomes. We also discuss the expanding indications for CI surgery as it relates to lateral skull base pathology, comparing CI to auditory brainstem implants, and address the concerns with obtaining magnetic resonance imaging (MRI) in CI recipients.

Assessing the Benefit-Risk Profile for Pediatric Implantable Auditory Prostheses.

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

ObjectiveTo assess auditory brainstem implant (ABI) outcomes in children with a prospective study. MethodsTwelve 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. ResultsTwelve 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. ConclusionsABI 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.