Auditory Brainstem Implantation: An Overview

Comparing Speech Recognition Outcomes Between Cochlear Implants and Auditory Brainstem Implants in Patients With NF2-Related Schwannomatosis

OBJECTIVE

To compare cochlear implant (CI) and auditory brainstem implant (ABI) performance in patients with NF2-related schwannomatosis (NF2).

STUDY DESIGN

Historical cohort.

SETTING

Tertiary academic center.

PATIENTS

A total of 58 devices among 48 patients were studied, including 27 ABIs implanted from 1997 to 2022 and 31 CIs implanted from 2003 to 2022. Three patients had bilateral ABIs, three had bilateral CIs, three had an ABI on one side and a CI on the other, one had a CI that was later replaced with an ipsilateral ABI, and one had an ABI and CI concurrently on the same side.

INTERVENTIONS

CI or ABI ipsilateral to vestibular schwannoma.

MAIN OUTCOME MEASURES

Open-set speech perception, consonant-nucleus-consonant word scores, and AzBio sentence in quiet scores.

RESULTS

Among all patients, 27 (47%) achieved open-set speech perception, with 35 (61%) daily users at a median of 24 months (interquartile range [IQR], 12-87 mo) after implantation. Comparing outcomes, CIs significantly outperformed ABIs; 24 (77%) CIs achieved open-set speech perception compared with 3 (12%) ABIs, with median consonant-nucleus-consonant and AzBio scores of 31% (IQR, 0-52%) and 57% (IQR, 5-83%), respectively, for CIs, compared with 0% (IQR, 0-0%) and 0% (IQR, 0-0%), respectively, for ABIs. Patients with ABIs were younger at diagnosis and at implantation, had larger tumors, and were more likely to have postoperative facial paresis.

CONCLUSION

Many patients with NF2-associated vestibular schwannoma achieved auditory benefit with either a CI or an ABI; however, outcomes were significantly better in those patients who were able to receive a CI. When disease and anatomy permit, hearing rehabilitation with a CI should be considered over an ABI in these patients. Tumor management strategies that increase the ability to successfully use CIs should be strongly considered given the high risk of losing bilateral functional acoustic hearing in this population.

Electrically evoked auditory responses: A classification for brainstem implant placement in Neurofibromatosis Type 2

OBJECTIVE

In auditory brainstem implant (ABI) surgery, array placement may be optimized by electrophysiological information of adequate brainstem activation gained from electrically evoked auditory brainstem responses (EABR). This study aims 1) to characterize in detail the EABR from ABI implantation, 2) to introduce an EABR Classification Scheme, and 3) to analyze data for their correlation with individual patients' findings.

METHODS

Out of a continuous series of 54 patients who received an ABI between 2005 and 2019, 23 Neurofibromatosis Type 2 patients with complete documentation of 154 recordings were selected for offline analysis and for development and evaluation of a new EABR Classification Scheme comprising Class A: three vertex positive peaks, Class B:two peaks, Class C: a combination of one peak and a second melted double peak, Class D: one sole vertex positive peak and Class E: no peaks.

RESULTS

All 23 subjects showed EABR at final ABI position and experienced auditory sensations at first activation. The most frequent morphology consisted of two peaks, Classes B and C. Identified mean latencies were for P1 0.42 ms (±0.095), P2 1.42 ms (±0.244) and P3 2.41 ms (±0.329). Peak latencies correlated positively with tumor extensions (p < 0.005).

CONCLUSIONS

This study provides clear instructions on optimal EABR performance and evaluation.

SIGNIFICANCE

The new EABR Classification Scheme relies on a fast "online" identification of vertex positive peaks at the estimated post-artifact phase. The variability in EABR morphology provides an individual snapshot of the actual structural and functional status of the brainstem.

Hearing Rehabilitation in Vestibular Schwannoma

The most common complaint among patients with vestibular schwannoma (VS) is hearing loss. This significantly affects the quality of life before, during, and after treatment for patients with VS. Untreated hearing loss in VS patients may even lead to depression and feelings of social isolation. A variety of devices are available for hearing rehabilitation for patients with vestibular schwannoma. These include contralateral routing of hearing signals (CROSs), bone-anchored hearing devices, auditory brainstem implants (ABI), and cochlear implants. In the United States, ABI is approved for patients 12 years of age and older with neurofibromatosis type 2. In the past few years, cochlear implantation has been offered simultaneously or sequentially with tumor resection or irradiation, or even to patients whose VS have been monitored with serial imaging. However, determining the functional integrity of the auditory nerve in patients with vestibular schwannoma is a challenge. This review article consists of (1) the pathophysiology of vestibular schwannoma (VS), (2) hearing loss in VS, (3) treatment of VS and associated hearing loss, (4) options for auditory rehabilitation in patients with VS with their individual benefits and limitations, and (5) challenges in hearing rehabilitation in this cohort of patients to determine auditory nerve functionality. (6) Future directions.

Topological supramolecular network enabled high-conductivity, stretchable organic bioelectronics

Intrinsically stretchable bioelectronic devices based on soft and conducting organic materials have been regarded as the ideal interface for seamless and biocompatible integration with the human body. A remaining challenge is to combine high mechanical robustness with good electrical conduction, especially when patterned at small feature sizes. We develop a molecular engineering strategy based on a topological supramolecular network, which allows for the decoupling of competing effects from multiple molecular building blocks to meet complex requirements. We obtained simultaneously high conductivity and crack-onset strain in a physiological environment, with direct photopatternability down to the cellular scale. We further collected stable electromyography signals on soft and malleable octopus and performed localized neuromodulation down to single-nucleus precision for controlling organ-specific activities through the delicate brainstem.

Piezoelectric bone conduction hearing implant Osia® - audiological and quality of life benefits

&lt;b&gt;Introduction:&lt;/b&gt; Nowadays, there are many options to treat hearing-impaired patients: tympanoplastic surgery, hearing aids and a wide range of implantable devices.&lt;/br&gt;&lt;/br&gt; &lt;b&gt;Aim:&lt;/b&gt; The aim of this study is to present the mid-term audiological and quality of life benefits after the implantation of Osia®, an active piezoelectric bone conduction hearing implant. &lt;/br&gt;&lt;/br&gt; &lt;b&gt;Material and methods:&lt;/b&gt; The state of the tissues in the implanted area, as well as audiological and quality of life results were analyzed at six, nine and twelve months after implantation in a group of four adult patients with bilateral mixed hearing loss (1 after bilateral canal-wall-down mastoidectomy, 2 with chronic simple otitis media and after myringoplasty in the opposite ear, 1 with bilateral otosclerosis and after stapedotomy in the opposite ear). &lt;/br&gt;&lt;/br&gt; &lt;b&gt;Results:&lt;/b&gt; No postoperative complications were found in any of the cases. One year after surgery the mean audiological gain in FF PTA4 (pure tone average for 0.5, 1, 2, and 4 kHz) was 52.2 ± 3.5 dB in comparison to the unaided situation, the mean speech understanding with Osia® in quiet was 90 ± 8.2% for 50 dB SPL, 98.8 ± 2.5% for 65 dB SPL and 100 ± 0% for 80 dB SPL, and the mean speech understanding with Osia® in noise was 37.5% ± 23.6 for 50 dB SPL, 93.8 ± 4.8% for 65 dB SPL and 98.8 ± 2.5% for 80 dB SPL. There was also an evident improvement in the quality of hearing as well as in the quality of life, measured by APHAB (Abbreviated Profile of Hearing Aid Benefit) and SSQ (Speech, Spatial and Qualities of Hearing Scale). &lt;/br&gt;&lt;/br&gt; &lt;b&gt;Conclusions:&lt;/b&gt; The Osia® is an effective treatment option for patients with bilateral mixed hearing loss. The mid-term audiological and quality of life results are excellent, but further observations including bigger groups of patients and a longer follow- -up are required.

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.

Detailed insight in intraoperative eABR measurements to assist auditory brainstem implantation in a patient with neurofibromatosis type 2

Auditory brainstem implant (ABI) is used to provide auditory sensations in patients with neurofibromatosis type 2 who lost their hearing due to a surgical removal of the tumor. ABI surgery, implant activation and follow-up sessions present unique challenges including the exact placement of the electrode pad in the lateral recess of the IVth ventricle, identification of electrodes that trigger non-auditory sensation and their deactivation which lowers the number of electrodes responsible for hearing, changes of T- and C-levels across follow-up sessions. We present a complete procedure using an example case starting from the surgical part with the detailed description of intraoperative eABR measurement as a guidance for pad placement to the ABI activation and first fitting sessions with auditory sensation assessment. Since the first ABI electrode pad position presented non-satisfactory intraoperative eABR results it was decided to move the pad slightly which resulted in better eABR (more electrodes with auditory responses). The discussed patient demonstrated great auditory and speech perception results after the first ABI fitting (which included three sessions over 2 consecutive days). Repositioning of the ABI electrode pad during the surgery was carried out taking into account the intraoperative eABR results and this led to an overall positive outcome for the patient. The placement of ABI electrode pad is crucial for later auditory results. This study provides detailed insight in this very specialized procedure that is not performed in every clinic and adds to the knowledge of intraoperative navigation using eABR measurements during ABI surgery.

Diagnostic Accuracy of Intracochlear Test Electrode for Acoustic Nerve Monitoring in Vestibular Schwannoma Surgery

OBJECTIVES

Cochlear implants (CIs) are a well-known hearing restoration option for patients with vestibular schwannoma (VS) in cases of neurofibromatosis type-2 and, more recently, for patients with sporadic VS. One of the main limitations when performing CI during VS surgery is the capability to preserve the acoustic nerve (AN) anatomically and functionally. Significant efforts have been directed toward developing an intraoperative testing method for monitoring the AN function to determine if, after tumor removal, it is suitable for conducting stimuli delivered by a CI. However, all these methods have significant limitations, and none of them have documented diagnostic efficacy. To overcome these limitations and to obtain reliable information before CI insertion, a minimally invasive intracochlear test electrode (TE) has been recently developed. This TE has demonstrated to be suitable to test the integrity of the AN before CI in patients without any residual hearing by recording electrically evoked auditory brainstem responses (EABR). The present study constitutes the next phase of this research, which was to determine the usefulness of EABR obtained intraoperatively with the intracochlear TE after the resection of a VS and to calculate its diagnostic accuracy to assess the functionality of the AN for CI.

DESIGN

This was a prospective, multicenter study of diagnostic accuracy. It was conducted in three tertiary referral centers between January 2015 and 2018. This study was designed following the Standards for Reporting of Diagnostic Accuracy Studies (STARD) statement guidelines. The STARD statement are guidelines to improve the completeness and transparency of reports of diagnostic accuracy studies. The diagnostic accuracy of the EABR evoked with the intracochlear TE after tumor removal was studied. Accuracy, sensitivity, specificity, positive predictive value, and negative predictive value were calculated. Patients eligible for the study were consecutive adults undergoing surgery for VS with simultaneous CI. The test under evaluation (index test) was the EABR obtained with the intracochlear TE after resection of the tumor. The reference test (gold standard) was the presence of auditory perception with the CI, defined as the presence of sound detection on an audiogram at 500, 1000, 2000, and 4000 Hz of no greater than 50 dB. In all the cases, auditory perception was verified by the presence of a positive EABR evoked with the CI.

RESULTS

Twenty-one patients were included during the study period; seven patients were excluded from the diagnostic efficacy analysis due to inconclusive EABR results or absence of the gold standard to compare (they did not finally receive the CI). Thus, the outcome of the gold standard was assessed in 14 cases: 9 cases had positive EABR, all of them obtained auditory perception with the CI, and 5 cases had negative EABR, only one case had auditory perception with the CI, which constitutes the only false negative of this study. Accuracy of the TE was 93% (95% confidence interval, 66 to 100%), sensitivity 90% (95% confidence interval, 71 to 100%), specificity 100% (95% confidence interval, 100 to 100%), positive predictive value 100% (95% confidence interval, 100 to 100%), and negative predictive value 80% (95% confidence interval, 45 to 100%).

CONCLUSIONS

EABR elicited with the intracochlear TE had a diagnostic accuracy of 93% for predicting auditory perception with CIs after VS removal. These results suggest that the intracochlear TE can be used intraoperatively after tumor removal to test the integrity of the AN as a useful tool to complement the surgeon's perception for decision-making regarding implantation.

The evaluation of a surgery and the short-term benefits of a new active bone conduction hearing implant - the Osia®

Introduction

Modern medicine offers a wide spectrum of different hearing devices, and bone conduction implants can be found among them.

Objective

The presentation of the outcomes of the implantation of a new active bone conduction hearing implant – the Osia®, and its comparison with the well-known passive transcutaneous system – the Baha® Attract.

Methods

Eight adult patients with bilateral mixed hearing loss were randomly divided into two groups. Group 1 was implanted with the Osia®, and group 2 was implanted with the Baha® Attract. The details of the surgery were analyzed, along with the functional and audiological results.

Results

In all the cases, the surgery was successful, and the healing uneventful. In both groups, it was observed that pure tone audiometry and speech audiometry in free field improved significantly after the implantation (mean gain in pure tone audiometry for the Osia group 42.8 dB SPL and for the Baha group 38.8 dB SPL). In the Osia group, the results after the surgery were much better than with the Baha® 5 Power processor on the Softband. The patients implanted with the Osia® evaluated the quality of their hearing as being superior to those implanted with the Baha® Attract. There was an evident improvement in the abbreviated profile of hearing aid benefit questionnaire and in the speech, spatial and qualities of hearing scale for both systems. In the abbreviated profile of hearing aid benefit, changes were more evident in the Osia group (in global score 49% vs. 37.2%).

Conclusion

Implantation of the Osia® is an effective treatment option for the patients with bilateral mixed hearing loss. The surgery is safe but more complex and time-consuming than the Baha® Attract implantation. The preliminary audiological results as well as the overall quality of life indicate that the Osia® is a better solution than the Baha® Attract. However, future studies should be carried out to make further observations in a larger group of patients, and with longer follow-up.