Auditory brainstem implant (ABI): new frontiers in adults and children

Do auditory brainstem implants favor the development of sensory integration and cognitive functions?

BACKGROUND

Information about the development of cognitive skills and the effect of sensory integration in children using auditory brainstem implants (ABIs) is still limited.

OBJECTIVE

This study primarily aims to investigate the relationship between sensory processing skills and attention and memory abilities in children with ABI, and secondarily aims to examine the effects of implant duration on sensory processing and cognitive skills in these children.

METHODS

The study included 25 children between the ages of 6 and 10 years (mean age: 14 girls and 11 boys) with inner ear and/or auditory nerve anomalies using auditory brainstem implants. Visual-Aural Digit Span Test B, Marking Test, Dunn Sensory Profile Questionnaire were applied to all children.

RESULTS

The sensory processing skills of children are statistically significant and positive, and moderately related to their cognitive skills. As the duration of implant use increases, better attention and memory performances have been observed (p < .05).

CONCLUSION

The study demonstrated the positive impact of sensory processing on the development of memory and attention skills in children with ABI. It will contribute to evaluating the effectiveness of attention, memory, and sensory integration skills, and aiding in the development of more effective educational strategies for these children.

Real-time closed-loop brainstem stimulation modality for enhancing temporal blood pressure reduction

BACKGROUND

Traditional pharmacological interventions are well tolerated in the management of elevated blood pressure (BP) for individuals with resistant hypertension. Although neuromodulation has been investigated as an alternative solution, its open-loop (OL) modality cannot follow the patient's physiological state. In fact, neuromodulation for controlling highly fluctuating BP necessitates a closed-loop (CL) stimulation modality based on biomarkers to monitor the patient's continuously varying physiological state.

OBJECTIVE

By leveraging its intuitive linkage with BP responses in ongoing efforts aimed at developing a CL system to enhance temporal BP reduction effect, this study proposes a CL neuromodulation modality that controls nucleus tractus solitarius (NTS) activity to effectively reduce BP, thus reflecting continuously varying physiological states.

METHOD

While performing neurostimulation targeting the NTS in the rat model, the arterial BP response and neural activity of the NTS were simultaneously measured. To evaluate the temporal BP response effect of CL neurostimulation, OL (constant parameter; 20 Hz, 200 μA) and CL (Initial parameter; 11 Hz, 112 μA) stimulation protocols were performed with stimulation 180 s and rest 600 s, respectively, and examined NTS activity and BP response to the protocols.

RESULTS

In-vivo experiments for OL versus CL protocol for direct NTS stimulation in rats demonstrated an enhancement in temporal BP reduction via the CL modulation of NTS activity.

CONCLUSION

This study proposes a CL stimulation modality that enhances the effectiveness of BP control using a feedback control algorithm based on neural signals, thereby suggesting a new approach to antihypertensive neuromodulation.

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.

Auditory brainstem implants: an analysis of adverse events in the MAUDE database

OBJECTIVE

Auditory Brainstem Implants (ABI) are used to restore hearing in patients lacking appropriate cochlear anatomy and/or cochlear nerve. The objective of this study was to examine the Manufacture and User Facility Device Experience (MAUDE) database to analyze adverse events.

STUDY DESIGN

This is a study of a multi-institutional database maintained by the US FDA.

SETTING

A database analysis was performed via collaboration of multiple clinicians at tertiary referral centers.

METHODS

The MAUDE database was queried for Medical Device Reports (MDRs) relating to ABIs. MDRs were identified using the advanced search term "Implant, Auditory Brainstem" and reviewing all reports with the basic search term "Brainstem Implant". All collected reports were individually reviewed.

RESULTS

A total of 265 individual patient reports were reviewed, of which 55 reports met inclusion criteria. Reports regarding audiologic outcome included failure to provide hearing benefit (n = 27), implant failure/device malfunction (n = 10), and device non-use (n = 6). Postoperative complications included local skin infection (n = 3), CSF leak (n = 3), elevated ICP (n = 1), surgical site dehiscence (n = 1), swelling (n = 1), seroma formation requiring drainage (n = 1), and meningitis (n = 2). Two patients had dislodged magnets during 1.5 Tesla MRI acquisition. There were 35 instances of full explantation of the device and 1 partial removal; 13 patients had a new device implanted following explantation.

CONCLUSIONS

Poor hearing results, device failure, and non-use were commonly reported causes for explanation in this analysis. This information can aid physicians in counseling patients and family members and managing device expectations.

Conversion of a medical implant into a versatile computer-brain interface

BACKGROUND

Information transmission into the human nervous system is the basis for a variety of prosthetic applications. Spinal cord stimulation (SCS) systems are widely available, have a well documented safety record, can be implanted minimally invasively, and are known to stimulate afferent pathways. Nonetheless, SCS devices are not yet used for computer-brain-interfacing applications.

OBJECTIVE

Here we aimed to establish computer-to-brain communication via medical SCS implants in a group of 20 individuals who had been operated for the treatment of chronic neuropathic pain.

METHODS

In the initial phase, we conducted interface calibration with the aim of determining personalized stimulation settings that yielded distinct and reproducible sensations. These settings were subsequently utilized to generate inputs for a range of behavioral tasks. We evaluated the required calibration time, task training duration, and the subsequent performance in each task.

RESULTS

We could establish a stable spinal computer-brain interface in 18 of the 20 participants. Each of the 18 then performed one or more of the following tasks: A rhythm-discrimination task (n = 13), a Morse-decoding task (n = 3), and/or two different balance/body-posture tasks (n = 18; n = 5). The median calibration time was 79 min. The median training time for learning to use the interface in a subsequent task was 1:40 min. In each task, every participant demonstrated successful performance, surpassing chance levels.

CONCLUSION

The results constitute the first proof-of-concept of a general purpose computer-brain interface paradigm that could be deployed on present-day medical SCS platforms.

Extraordinary Speech and Language Outcomes After Auditory Brainstem Implantation: Guidance From a Case Study

PURPOSE

Large individual differences and poor speech recognition outcomes are routinely observed in most patients who have received auditory brainstem implants (ABIs). A case report of an ABI recipient with exceptionally good speech recognition outcomes presents an opportunity to better understand the core information processing mechanisms that underlie variability and individual differences in outcomes.

METHOD

A case study is reported of an adult ABI recipient (ID-006) with postlingually acquired, Neurofibromatosis Type 2 (NF2)-related hearing loss who displayed exceptional postoperative speech recognition scores. A novel battery of assessment measures was used to evaluate ID-006's auditory, cognitive, and linguistic information processing skills.

RESULTS

Seventeen years following ABI activation, ID-006 scored 77.6% correct on the AzBio Sentences in quiet. On auditory processing tasks, ID-006 scored higher on tasks with meaningful sentences and much lower on tasks that relied exclusively on audibility. ID-006 also demonstrated exceptionally strong abilities on several cognitive and linguistic information processing tasks.

CONCLUSIONS

Results from a novel battery of information processing tests suggest that ID-006 relies extensively on top-down predictive processing and cognitive control strategies to efficiently encode and process auditory information provided by his ABI. Results suggest that current measures of outcomes and benefits should be expanded beyond conventional speech recognition measures to include more sensitive and robust measures of speech recognition as well as neurocognitive measures such as executive function, working memory, and lexical access.

Advancements in prevention and intervention of sensorineural hearing loss

The inner ear is a complex and difficult organ to study, and sensorineural hearing loss (SNHL) is a multifactorial sensorineural disorder with characteristics of impaired speech discrimination, recognition, sound detection, and localization. Till now, SNHL is recognized as an incurable disease because the potential mechanisms underlying SNHL have not been elucidated. The risk of developing SNHL is no longer viewed as primarily due to environmental factors. Instead, SNHL seems to result from a complicated interplay of genetic and environmental factors affecting numerous fundamental cellular processes. The complexity of SNHL is presented as an inability to make an early diagnosis at the earliest stages of the disease and difficulties in the management of symptoms during the process. To date, there are no treatments that slow the neurodegenerative process. In this article, we review the recent advances about SHNL and discuss the complexities and challenges of prevention and intervention of SNHL.

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.

Analysis of Long-Term Cochlear Implantation Outcomes and Correlation With Imaging Characteristics in Patients With Common Cavity Deformity

Object

To investigate the long-term development of auditory and speech in patients with common cavity deformity (CCD) after cochlear implantation (CI) and its relationship to imaging characteristics.

Methods

Twenty-three CCD patients and 59 age- and sex-matched CI children with normal inner ear structure were recruited. The auditory and speech development of these two groups were evaluated at 0, 1, 3, 6, 12, and 18 months after CI activation using four parent reports questionnaires [Categories of Auditory Performance (CAP), Speech Intelligibility Rating (SIR), Meaningful Auditory Integration Scale/Infant-Toddler Meaningful Auditory Integration Scale (MAIS/ITMAIS), and Meaningful Use of Speech Scale (MUSS)]. Computed tomography-based 3-dimensional reconstruction of the surgical side of 18 CCD children was performed, the volume and surface area were calculated. Correlation analysis was performed on the imaging performance and post-operative outcomes.

Results

The percentages of MAIS/IT-MAIS scores and CAP scores at different evaluation time points are significantly different (p < 0.05). When comparing SIR results across time points, significant growth was observed in most of the comparisons. In addition, significant differences (p < 0.05) are observed among the percentages of MUSS scores at different time points except the comparison between 0 and 1 month after CI activation. Patients in the CCD group had poorer auditory and speech performances at different stages after CI compared with those in the control group. According to the reconstruction of CCD patients, the volume ranged from 12.21 to 291.96 mm³; the surface area ranged from 27.81 to 284.7 mm². When the lumen surface area was <190.45 mm² or the volume was <157.91 mm³, the survival time for CCD children to achieve a CAP score of 4 after CI was significantly shorter.

Conclusion

Cochlear implantation are less effective in CCD patients than in patients with normal inner ear structures, but they can still achieve significant improvement post-operatively. The morphology and size of the inner ear vary in CCD patients, which reflects the degree of inner ear development influences the outcome after CI surgery.

Internal auditory canal hypoplasia associated with bilateral vestibulocochlear nerve aplasia and deviant facial nerve course: A case report and MRI findings

The evaluation of internal auditory canals and cochlea has gained significant importance due to the increasing number of cochlear implantations worldwide. This region's anatomical study is essential for cochlear implant surgery using magnetic resonance imaging as the method of choice. We report a case of a 6-year-old male patient diagnosed with a rare bilateral malformation of the internal auditory canals associated with an aberrant course of the facial nerve and vestibulocochlear nerve aplasia. This report raises the importance of identifying this rare malformation for appropriate management and reinforces awareness of possible complications.

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.

Low-Intensity Ultrasound Causes Direct Excitation of Auditory Cortical Neurons

Cochlear implantation is the first-line treatment for severe and profound hearing loss in children and adults. However, deaf patients with cochlear malformations or with cochlear nerve deficiencies are ineligible for cochlear implants. Meanwhile, the limited spatial selectivity and high risk of invasive craniotomy restrict the wide application of auditory brainstem implants. A noninvasive alternative strategy for safe and effective neuronal stimulation is urgently needed to address this issue. Because of its advantage in neural modulation over electrical stimulation, low-intensity ultrasound (US) is considered a safe modality for eliciting neural activity in the central auditory system. Although the neural modulation ability of low-intensity US has been demonstrated in the human primary somatosensory cortex and primary visual cortex, whether low-intensity US can directly activate auditory cortical neurons is still a topic of debate. To clarify the direct effects on auditory neurons, in the present study, we employed low-intensity US to stimulate auditory cortical neurons in vitro. Our data show that both low-frequency (0.8 MHz) and high-frequency (>27 MHz) US stimulation can elicit the inward current and action potentials in cultured neurons. c-Fos staining results indicate that low-intensity US is efficient for stimulating most neurons. Our study suggests that low-intensity US can excite auditory cortical neurons directly, implying that US-induced neural modulation can be a potential approach for activating the auditory cortex of deaf patients.

Effects of Age at Auditory Brainstem Implantation: Impact on Auditory Perception, Language Development, Speech Intelligibility

OBJECTIVE

To study the effect of age at auditory brainstem implant (ABI) surgery on auditory perception, language, and speech intelligibility.

STUDY DESIGN

Retrospective single cohort design.

SETTING

Tertiary referral center.

PATIENTS

In this study, 30 pediatric ABI users with no significant developmental issues were included. Participants were divided into two groups, according to age at surgery (Early Group: < 3 yr old [n = 15], Late Group: ≥ 3 yr old [n = 15]). Groups were matched by duration of ABI use and participants were evaluated after 5 years (±1 yr) experience with their device. The mean age at ABI surgery was 22.27 (ranged ± 6.5) months in the early group, 45.53 (ranged ± 7.9) months in the late group.

INTERVENTION(S)

Retrosigmoid craniotomy and ABI placement.

MAIN OUTCOME MEASURE(S)

Auditory perception skills were evaluated using the Meaningful Auditory Integration Scale and Categories of Auditory Performance from the Children's Auditory Perception Test Battery. We used a closed-set pattern perception subtest, a closed-set word identification subtest, and an open-set sentence recognition subtest. Language performance was assessed with the Test of Early Language Development and Speech Intelligibility Rating, which was administered in a quiet room.

RESULTS

In this study, the results demonstrated that the Early Group's auditory perception performance was better than the Late Group after 5 years of ABI use, when children had no additional needs (U = 12, p < 0.001). Speech intelligibility was the most challenging skill to develop, in both groups. Due to multiple regression analysis, we found that auditory perception categories can be estimated with speech intelligibility scores, pattern perception scores, receptive language scores, and age at ABI surgery variables in ABI users with no additional handicaps.

CONCLUSIONS

ABI is a viable option to provide auditory sensations for children with cochlear anomalies. ABI surgery under age 3 is associated with improved auditory perception and language development compared with older users.

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.

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."

Validation of the Egyptian Arabic Assessment of Auditory Skills development using children with Cochlear Implants

INTRODUCTION

Audition is the gateway to spoken language, and infants' early accomplishments in acquiring the sound structure of their native language lays a critical ground work for subsequent learning. The development of pre-lingual auditory perceptual skills for cochlear implanted children is crucial for initial development of oral language.

OBJECTIVE

The aims of the present study were to validate the Egyptian Arabic Assessment of Auditory Skills, and to track the development of auditory skills in Egyptian children fitted with CI during the first three years post implantation.

METHODS

The study included 90 Arabic Egyptian children attending the phoniatric unit, Kasr El Aini hospital. Their chronological age ranged from 36 to 72 months. The study lasted for 18 months from July 2015 to January 2017. The children were divided into six groups according to their cochlear age i.e., amount of implant experience. An Arabic assessment chart of auditory skills was tailored that included six auditory skills' domains; detection, identification, short term auditory memory, supra-segmental discrimination, segmental discrimination and linguistic auditory processing. This chart was then used to develop an assessment tool which was then applied to all the study participants. All children had bilateral Sensorineural Hearing Loss (SNHL) since birth. None of the participants had prior Cochlear Implant (CI), but all had tried conventional hearing aids. All participants were implanted unilateral, with CI devices. All met selection criteria applied in the Egyptian national insurance committee for cochlear implantation.

RESULTS

All auditory skills domains improved with cochlear age. There was significant improvement between 1-6 and 7-12 months in the scores of the Detection (DET) domain. There was significant difference between 1-6 and 7-12 months, 7-12 and 13-18 months, 19-24 and 25-30 months in the scores of the Identification (IDENT) domain. Regarding the Short Term Auditory Memory (STAM) domain scores and the Supra-segmental Discrimination (SSD) domain scores there was significant difference between all the groups. Regarding the Segmental Discrimination (SGD) domain scores, there was significant difference between group 1-6 and 7-12 months, 7-12 and 13-18 months, 19-24 and 25-30 months, 25-30 and 31-36 months. Regarding the Linguistic Auditory Processing (LAP) domain, there was significant difference between group 1-6 and 7-12 months, 7-12 and 13-18 months, 25-30 and 31-36 months.

CONCLUSIONS

Children fitted with Cochlear Implants (CIs) appeared to show improvement in acquisition of auditory skills over a period of three years that followed a hierarchy of development dependent on the cochlear age.

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

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

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 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.

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.

Surgical anatomy of lateral recess in paediatric auditory brainstem implant patients and its clinical correlates including grades of flocculus

INTRODUCTION

Auditory brainstem implant (ABI), a standard technique in treatment of profound sensorineural hearing loss in patients with neurofibromatosis 2, is now being increasingly employed in children with congenital bilateral sensorineural hearing loss, as in Michele's deformity. A detailed knowledge of the relevant surgical anatomy of the lateral recess and its anatomical landmarks including the flocculus, the choroid plexus and the root entry zones of facial-vestibulocochlear and glossopharyngeal-vagus nerve complexes and their anatomical variants is mandatory, as it is the conduit for electrode array placement. The placement of electrode may be eased or impeded by these variations.

MATERIALS AND METHODS

Thirty-two children with congenital bilateral hearing loss underwent surgery through retromastoid suboccipital approach for placement of auditory brainstem implant. The preoperative anatomy was reviewed in detail during procedure and again later in the operative videos.

RESULTS

The flocculus was classified into four grades based on its anatomy and relations. Among these, grade II (11 children) was the commonest while grade IV (five children) was least common. Choroid plexus was variable in size across grades of flocculus. Difficulty in defining the anatomy was significantly more (p value = 0.003) in the group with higher grade flocculus (grade III and IV) than in lower grade flocculus (grade I and II).

CONCLUSION

The flocculus in these patients is classifiable into one of the four grades and the surgical nuances such as difficulty in defining the anatomy for placement of ABI are dependent on the characteristics exhibited by the floccular anatomy and relations.

Auditory brainstem implant in postmeningitis totally ossified cochleae

INTRODUCTION

An auditory brainstem implant (ABI) is an option for auditory rehabilitation in patients with totally ossified cochleae who cannot receive a conventional cochlear implant.

OBJECTIVE

To evaluate the outcomes in audiometry and speech perception tests after the implantation of an ABI via the extended retrolabyrinthine approach in patients with postmeningitis hearing loss.

MATERIALS AND METHODS

Ten patients, including children and adults, with postmeningitis hearing loss and bilateral totally ossified cochleae received an ABI in a tertiary center from 2009 to 2015. The extended retrolabyrinthine approach was performed in all the patients by the same surgeons. A statistical analysis compared pure tonal averages and speech perception tests before and at least 12 months after the ABI activation.

RESULTS

Eight patients (80%) showed improvements in tonal audiometry and the word and vowel perception tests after an average follow-up of 3.3 years. Two patients recognized up to 40% of the closed-set sentences without lip-reading. Two patients had no auditory response.

CONCLUSIONS

The ABI improved hearing performance in audiometry and speech perception tests in cases of postmeningitis hearing loss. The extended retrolabyrinthine approach is a safe surgical option for patients with postmeningitis hearing loss and bilateral totally ossified cochleae.

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.

Responses of neurons in the feline inferior colliculus to modulated electrical stimuli applied on and within the ventral cochlear nucleus; Implications for an advanced auditory brainstem implant

Auditory brainstem implants (ABIs) can restore useful hearing to persons with deafness who cannot benefit from cochlear implants. However, the quality of hearing restored by ABIs rarely is comparable to that provided by cochlear implants in persons for whom those are appropriate. In an animal model, we evaluated elements of a prototype of an ABI in which the functions of macroelectrodes on the surface of the dorsal cochlear nucleus would be integrated with the function of multiple penetrating microelectrodes implanted into the ventral cochlear nucleus. The surface electrodes would convey most of the range of loudness percepts while the intranuclear microelectrodes would sharpen and focus pitch percepts. In the present study, stimulating electrodes were implanted chronically on the surface of the animal's dorsal cochlear nucleus (DCN) and also within their ventral cochlear nucleus (VCN). Recording microelectrodes were implanted into the central nucleus of the inferior colliculus (ICC). The electrical stimuli were sinusoidally modulated stimulus pulse trains applied on the DCN and within the VCN. Temporal encoding of neuronal responses was quantified as vector strength (VS) and as full-cycle rate of neuronal activity in the ICC. VS and full-cycle AP rate were measured for 4 stimulation modes; continuous and transient amplitude modulation of the stimulus pulse trains, each delivered via the macroelectrode on the surface of the DCN and then by the intranuclear penetrating microelectrodes. In the proposed clinical device the functions of the surface and intranuclear microelectrodes could best be integrated if there is minimal variation in the neuronal responses across the range of modulation depth, modulation frequencies, and across the four stimulation modes. In this study VS did vary as much as 34% across modulation frequency and modulation depth within a stimulation mode, and up to 40% between modulation modes. However, these intra- and inter-mode variances differed for different stimulation rates, and at 500 Hz the inter-mode differences in VS and across the range of modulation frequencies and modulation depths was<Roman> = </Roman>24% and the intra-modal differences were<Roman> = </Roman>15%. The findings were generally similar for rate encoding of modulation depth, although the depth of transient amplitude modulation delivered by the surface electrode was weakly encoded as full-cycle rate. Overall, our findings support the concept of a clinical ABI that employs surface stimulation and intranuclear microstimulation in an integrated manner.

Electrically Evoked Auditory Event-Related Responses in Patients with Auditory Brainstem Implants: Morphological Characteristics, Test-Retest Reliability, Effects of Stimulation Level, and Association with Auditory Detection

OBJECTIVE

This study aimed to (1) characterize morphological characteristics of the electrically evoked cortical auditory event-related potentials (eERPs) and explore the potential association between onset eERP morphology and auditory versus nonauditory stimulation; (2) assess test-retest reliability of onset eERPs; (3) investigate effects of stimulation level on onset eERPs; and (4) explore the feasibility of using the onset eERP to estimate the lowest stimulation level that can be detected for individual stimulating electrodes in patients with auditory brainstem implants (ABIs).

DESIGN

Study participants included 5 children (S1 to S5) and 2 adults (S6 to S7) with unilateral Cochlear Nucleus 24M ABIs. Pediatric ABI recipients ranged in age from 2.6 to 10.2 years (mean: 5.2 years) at the time of testing. S6 and S7 were 21.2 and 24.6 years of age at the time of testing, respectively. S6 and S7 were diagnosed with neurofibromatosis II (NF2) and implanted with an ABI after a surgical removal of the tumors. All pediatric subjects received ABIs after being diagnosed with cochlear nerve deficiency. The lowest stimulation level that could be detected (behavioral T level) and the estimated maximum comfortable level (C level) was measured for individual electrodes using clinical procedures. For electrophysiological measures, the stimulus was a 100-msec biphasic pulse train that was delivered to individual electrodes in a monopolar-coupled stimulation mode at stimulation levels ranging from subthreshold to C levels. Electrophysiological recordings of the onset eERP were obtained in all subjects. For studies evaluating the test-retest reliability of the onset eERP, responses were measured using the same set of parameters in two test sessions. The time interval between test sessions ranged from 2 to 6 months. The lowest stimulation level that could evoke the onset eERP was defined as the objective T level.

RESULTS

Onset eERPs were recorded in all subjects tested in this study. Inter- and intrasubject variations in morphological characteristics of onset eERPs were observed. Onset eERPs with complex waveforms were recorded for electrodes that evoked nonauditory sensations, based on feedback from subjects, as well as for electrodes without any indications of nonauditory stimulations. Onset eERPs in patients with ABIs demonstrated good test-retest reliability. Increasing stimulation levels resulted in increased eERP amplitudes but showed inconsistent effects on response latencies in patients with ABIs. Objective and behavioral T levels were correlated.

CONCLUSIONS

eERPs could be recorded in both non-NF2 and NF2 patients with ABIs. eERPs in both ABI patient groups show inter- and intrasubject variations in morphological characteristics. However, onset eERPs measured within the same subject in this study tended to be stable across study sessions. The onset eERP can potentially be used to estimate behavioral T levels in patients with ABIs. Further studies with more adult ABI recipients are warranted to investigate whether the onset eERP can be used to identify electrodes with nonauditory stimulations.

Favorable Long-Term Functional Outcomes and Safety of Auditory Brainstem Implants in Nontumor Patients

BACKGROUND

Auditory brainstem implants (ABIs) were designed to restore hearing in deaf patients with auditory tumors or those unable to receive cochlear implants. Although ABIs may help some patients, their long-term outcomes have been rarely studied.

OBJECTIVE

To assess the long-term benefits and safety of ABIs in nontumor patients with sensorineural hearing loss (SNHL).

METHODS

We retrospectively reviewed the histories of 15 deaf patients (8 females, 7 males; mean age, 15.5 yr; range, 1-56 yr) who received ABIs for treatment of SNHL at our hospital from July 2008 to November 2015. These included 11 children with narrow internal auditory canals and 4 deaf adults with severe cochlear ossification. In each patient, a 12-channel ABI electrode was placed in the cochlear nucleus complex via a retrosigmoid approach. Auditory performance was evaluated using the Categories of Auditory Performance (CAP) index and sound detection and word identification tests.

RESULTS

One year after ABI placement, 13 of 15 patients showed adequate or significantly improved auditory function based on the CAP scores at the last follow-up. Generally, adult patients tended to show better CAP scores (3.50) than pediatric patients (2.15), but the difference was not significant (P = .058). Postoperative complications included electrode migration, cerebrospinal fluid leakage, nonauditory stimulation, and minor seizures without severe sequelae or mortality.

CONCLUSION

ABIs show favorable functional outcomes and long-term safety in nontumor deaf patients with limited treatment options. Collectively, our data indicate that ABIs represent an important treatment option for SNHL.

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.

Auditory brainstem implant program development

OBJECTIVE

Auditory brainstem implants (ABIs), which have previously been used to restore auditory perception to deaf patients with neurofibromatosis type 2 (NF2), are now being utilized in other situations, including treatment of congenitally deaf children with cochlear malformations or cochlear nerve deficiencies. Concurrent with this expansion of indications, the number of centers placing and expressing interest in placing ABIs has proliferated. Because ABI placement involves posterior fossa craniotomy in order to access the site of implantation on the cochlear nucleus complex of the brainstem and is not without significant risk, we aim to highlight issues important in developing and maintaining successful ABI programs that would be in the best interests of patients.

DATA SOURCES

Especially with pediatric patients, the ultimate benefits of implantation will be known only after years of growth and development. These benefits have yet to be fully elucidated and continue to be an area of controversy. The limited number of publications in this area were reviewed.

REVIEW METHODS

Review of the current literature was performed.

RESULTS

Disease processes, risk/benefit analyses, degrees of evidence, and U.S. Food and Drug Administration approvals differ among various categories of patients in whom auditory brainstem implantation could be considered for use.

CONCLUSION

We suggest sets of criteria necessary for the development of successful and sustaining ABI programs, including programs for NF2 patients, postlingually deafened adult nonneurofibromatosis type 2 patients, and congenitally deaf pediatric patients. Laryngoscope, 127:1909-1915, 2017.

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.

Experiences from Auditory Brainstem Implantation (ABIs) in four paediatric patients

INTRODUCTION

Indications for auditory brainstem implants (ABIs) have been widened from patients with neurofibromatosis type 2 (NF2) to paediatric patients with congenital cochlear malformations, cochlear nerve hypoplasia/aplasia, or cochlear ossification after meningitis. We present four ABI surgeries performed in children at Uppsala University Hospital in Sweden since 2009.

METHODS

Three children were implanted with implants from Cochlear Ltd. (Lane Cove, Australia) and one child with an implant from MedEl GMBH (Innsbruck, Austria). A boy with Goldenhar syndrome was implanted with a Cochlear Nucleus ABI24M at age 2 years (patient 1). Another boy with CHARGE syndrome was implanted with a Cochlear Nucleus ABI541 at age 2.5 years (patient 2). Another boy with post-ossification meningitis was implanted with a Cochlear Nucleus ABI24M at age 4 years (patient 3). A girl with cochlear aplasia was implanted with a MedEl Synchrony ABI at age 3 years (patient 4). In patients 1, 2, and 3, the trans-labyrinthine approach was used, and in patient 4 the retro-sigmoid approach was used.

RESULTS

Three of the four children benefited from their ABIs and use it full time. Two of the full time users had categories of auditory performance (CAP) score of 4 at their last follow up visit (6 and 2.5 years postoperative) which means they can discriminate consistently any combination of two of Ling's sounds. One child has not been fully evaluated yet, but is a full time user and had CAP 2 (responds to speech sounds) after 3 months of ABI use. No severe side or unpleasant stimulation effects have been observed so far. There was one case of immediate electrode migration and one case of implant device failure after 6.5 years.

CONCLUSION

ABI should be considered as an option in the rehabilitation of children with similar diagnoses.

The electrically evoked cortical auditory event-related potential in children with auditory brainstem implants

OBJECTIVE

This study explored the feasibility of measuring electrically evoked cortical auditory event-related potentials (eERPs) in children with auditory brainstem implants (ABIs).

DESIGN

Five children with unilateral ABIs ranging in age from 2.8 to 10.2 years (mean: 5.2 years) participated in this study. The stimulus was a 100-msec biphasic pulse train that was delivered to individual electrodes in a monopolar stimulation mode. Electrophysiological recordings of the onset eERP were conducted in all subjects.

RESULTS

The onset eERP was recorded in four subjects who demonstrated auditory perception. These eERP responses showed variations in waveform morphology across subjects and stimulating electrode locations. No eERPs were observed in one subject who received no auditory sensation from ABI stimulation.

CONCLUSIONS

eERPs can be recorded in children with ABIs who develop auditory perception. The morphology of the eERP can vary across subjects and also across stimulating electrode locations within subjects.

Nervus Intermedius Guides Auditory Brainstem Implant Surgery in Children with Cochlear Nerve Deficiency

OBJECTIVE

To investigate the anatomic features of the nervus intermedius and cranial nerve VII in children with cochlear nerve deficiency and to verify whether the nervus intermedius can provide an additional landmark to help guide placement of the auditory brainstem implant electrode.

STUDY DESIGN

Case series with chart review.

SETTING

Tertiary referral center.

SUBJECTS AND METHODS

High-definition video was captured during retrosigmoid surgery in 64 children (mean age, 3.91 ± 2.83 years) undergoing auditory brainstem implant placement. These videos were examined with particular reference to the number and variety of nervus intermedius bundles and any associated facial nerve anomalies.

RESULTS

Absence of cranial nerves VI, VII, and VIII was observed in 3, 6, and all 64 children, respectively. Fifteen children had several abnormalities of the facial nerve in the cerebellopontine angle. Anatomic identification of the facial nerve and the bundles composing the nervus intermedius was possible in 46 children. In 12 children, identification was possible with the assistance of intraoperative monitoring. The number of bundles composing the nervus intermedius varied from 1 to 6. The nervus intermedius and cranial nerve IX were useful landmarks for identifying the foramen of Luschka of the lateral recess.

CONCLUSION

The nervus intermedius provides an additional landmark during auditory brainstem microsurgery since it was identified in all subjects. The nervus intermedius anatomy and its topographic relationship with the neurovascular structures around the foramen of Luschka have been described for the first time in children with cochlear nerve deficiency.

Self-reported benefit, sound perception, and quality-of-life in patients with auditory brainstem implants (ABIs)

CONCLUSION

The majority of the patients used their auditory brainstem implants (ABIs) all the time, reporting that he/she would make the decision to receive an implant again if the decision were reconsidered. The findings support that the ABI is a valuable treatment in patients with type 2 neurofibromatosis (NF2) and in children with congenital inner ear and nerve anomalies or cochlear ossification.

OBJECTIVE

To evaluate the patients who underwent ABI implantation in Uppsala during 1993-2013. This study analyzed patients' implant use, perception of environmental sounds, perceived benefit from the implant, and quality-of-life (QoL).

METHOD

The NF2-patients (n = 20) comprised the majority of the patients, and there were a few non-NF2 pediatric patients (n = 4). The exclusion criteria included deceased patients (n = 4) and patients with no hearing sensations from the implant, or those with an inactivated ABI (n = 2). The data were collected from a questionnaire survey.

RESULTS

Eleven adult patients and two pediatric patients answered the questionnaires. Eight of the adult patients used their implants 'always'. The two children always used their implants. Hearing problems had the largest negative effect on the QoL. The non-users and the users scored equally on the NFTI-QoL.

Systematic Review of Nontumor Pediatric Auditory Brainstem Implant Outcomes

OBJECTIVE

The auditory brainstem implant (ABI) was initially developed for patients with deafness as a result of neurofibromatosis type 2. ABI indications have recently extended to children with congenital deafness who are not cochlear implant candidates. Few multi-institutional outcome data exist. Herein, we aim to provide a systematic review of outcomes following implantation of the ABI in pediatric patients with nontumor diagnosis, with a focus on audiometric outcomes.

DATA SOURCES

PubMed, Embase, and Cochrane.

REVIEW METHODS

A systematic review of literature was performed using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) recommendations. Variables assessed included age at implantation, diagnosis, medical history, cochlear implant history, radiographic findings, ABI device implanted, surgical approach, complications, side effects, and auditory outcomes.

RESULTS

The initial search identified 304 articles; 21 met inclusion criteria for a total of 162 children. The majority of these patients had cochlear nerve aplasia (63.6%, 103 of 162). Cerebrospinal fluid leak occurred in up to 8.5% of cases. Audiometric outcomes improved over time. After 5 years, almost 50% of patients reached Categories of Auditory Performance scores >4; however, patients with nonauditory disabilities did not demonstrate a similar increase in scores.

CONCLUSION

ABI surgery is a reasonable option for the habilitation of deaf children who are not cochlear implant candidates. Although improvement in Categories of Auditory Performance scores was seen across studies, pediatric ABI users with nonauditory disabilities have inferior audiometric outcomes.

Retrosigmoid Craniotomy for Auditory Brainstem Implantation in Adult Patients with Neurofibromatosis Type 2

Objective To report our technique and experience using a retrosigmoid craniotomy approach for auditory brainstem implantation (ABI) placement in adult neurofibromatosis type 2 (NF2) patients. Design Retrospective case series. Setting Single-center study, Boston, Massachusetts, United States. Participants All NF2 patients who underwent evaluation at Massachusetts Eye and Ear Infirmary and surgery at Massachusetts General Hospital from 2009 to 2013 were reviewed. Six cases of retrosigmoid craniotomy for ABI surgery in five adult NF2 patients were identified. The clinical history, operative course, and outcomes in these patients were reviewed. Main Outcome Measures Postoperative complications and audiological outcomes. Results Indications for ABI surgery were profound hearing loss associated with growth or treatment of bilateral vestibular schwannomas. In all cases, a retrosigmoid craniotomy was performed for tumor resection and ABI placement without complication. Electrode placement was confirmed intraoperatively using electrical-evoked auditory brainstem responses. The ABI was activated in the awake patient 4 to 6 weeks postoperatively. Audiological testing was used to evaluate sound detection and speech perception with the ABI. There were no cases of cerebrospinal fluid leak. Conclusion Retrosigmoid craniotomy is a safe and effective means to provide access to the cochlear nucleus for ABI placement following tumor resection in the adult NF2 patient. Preliminary data indicate that this approach has few complications while offering benefits for hearing. The retrosigmoid craniotomy should be considered a reasonable alternative to the traditional translabyrinthine approach for placement of the ABI in deaf patients who are not candidates for the cochlear implant.

Auditory brainstem implant candidacy in the United States in children 0-17 years old

OBJECTIVES

The auditory brainstem implant (ABI) is an option for hearing rehabilitation in profoundly deaf patients ineligible for cochlear implantation. Over the past decade, surgeons have begun implanting ABIs in pediatric patients who are unable to receive cochlear implants due to congenital or acquired malformations of the inner ear. No study has examined the potential population-level demand for ABIs in the United States (US). Herein, we aim to quantify the potential need for pediatric ABIs.

METHODS

A systematic literature review was conducted to identify studies detailing the rates of congenital cochlear and/or cochlear nerve (CN) anomalies. Absolute indications for ABI include bilateral cochlea or CN aplasia (Group A), and relative indications for ABI include bilateral cochlea or CN hypoplasia (Group B). Data was subsequently correlated to the US Census Bureau, the National Health Interview Survey, and the Gallaudet Research Institute to provide an estimation of pediatric ABI candidates.

RESULTS

Eleven studies documented rates of bilateral findings. Bilateral cochlea aplasia was identified in 0-8.7% of patients and bilateral CN aplasia in 0-4.8% of patients (Group A). Bilateral cochlea hypoplasia was identified in 0-8.7% of patients and bilateral CN hypoplasia in 0-5.4% of patients (Group B). Using population-level sensorineural hearing loss data, we roughly estimate 2.1% of potential implant candidates meet absolute indications for an ABI in the United States.

CONCLUSION

Congenital cochlear and cochlear nerve anomalies are exceedingly rare. This study provides the first preliminary estimate of cochlea and CN aplasia/hypoplasia at the population level albeit with limitations based on available data. These data suggest the need for dedicated ABI centers to focus expertise and management.

Methods and preliminary outcomes of pediatric auditory brainstem implantation

OBJECTIVE

The objective was to provide information about methods used and preliminary outcomes for pediatric ABI (auditory brainstem implant).

STUDY DESIGN

An analysis of outcome was performed in children who received an ABI.

METHODS

Twelve children received a MED-EL ABI system. Progress in audition and language was monitored through parental reports, questionnaires, profiles, and closed-set tests.

RESULTS

The median number of active electrodes was 9 of 12. Seven of 12 users consistently respond to sound, and 5 of 12 do not. Highest performers can recognize words in small sets and have begun to use some words.

CONCLUSION

Auditory brainstem implants appear to be beneficial for some pediatric patients who cannot benefit from traditional cochlear implant surgery. Benefits in the short-term can be recognition of environmental sounds, recognition of some words and very commonly used phrases, and the beginning use of words. Although some of our ABI users demonstrate no response to sound, they do want to wear their sound processors all waking hours. The cause of lack of response may be related to the second intervention, which might have led to displacement of the electrode array, or presence of additional handicaps or syndromes. However, the results are less than optimal. The relatively short postoperative follow-up duration is a considered weakness of this study.

Auditory brainstem implants (ABIs)--20 years of clinical experience in Uppsala, Sweden

CONCLUSIONS

Even though sound perception may be limited after treatment with an auditory brainstem implant (ABI), it provides benefits and should be selectively offered to patients. Importantly the patients must be motivated, given reasonable expectations of outcome and offered long-term rehabilitation with a considerable 'learn to listen' period with the implant device.

OBJECTIVES

To describe the clinical experiences and results of 24 ABI surgeries performed in Uppsala University Hospital between 1993 and 2013.

METHODS

Most patients (n = 20) suffered from neurofibromatosis type 2 (NF2); a few patients (n = 4) were paediatric non-NF2 patients. The files were searched for information on the presurgery size of the vestibular schwannoma, whether the patient had undergone gamma knife treatment, the surgical approach, the side effects of the surgery and of the use of the implant, the electrode activation pattern and implant use, and categories of auditory performance (CAP) score.

RESULTS

Our results show that many patients greatly benefited from an ABI, and most of the patients used their implants even though the hearing improvements usually consisted of awareness of surrounding sounds and improved lip-reading. No severe side effects were observed from implant stimulation.