A tribute to a remarkably sound solution.

For their work on the development of the modern cochlear implant, which bestows hearing to individuals with profound deafness, Ingeborg Hochmair, Graeme Clark, and Blake Wilson are the 2013 recipients of the Lasker∼DeBakey Clinical Medical Research Award.

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

BACKGROUND: Cochlear nerve deficiency is one of the known causes of congenital sensorineural hearing loss. Management of hearing loss in children with cochlear nerve deficiency poses a multidimensional challenge. The absent or hypoplastic cochlear nerve may prevent electrical stimulation from reaching the brainstem and the auditory cortex. A deficient cochlear nerve can be associated with other inner ear malformations, which may diminish the success of cochlear implantation in those children. Promising results in adults after auditory brainstem implantation led to the expansion of candidacy to include the pediatric populations who were contraindicated for CIs. OBJECTIVE: To review the outcomes of cochlear implantation versus that of auditory brainstem implantation in children with various conditions of the auditory nerve. METHODS: This retrospective chart review study comprised two pediatric groups. The first group consisted of seven ABI recipients with cochlear nerve aplasia and the second group consisted of another seven children with cochlear nerve deficiencies who underwent CI surgery. The participants' auditory skills and speech outcomes were assessed using different tests selected from the Evaluation of Auditory Responses to Speech (EARS) test battery. RESULTS: There were some individual variations in outcomes depending on the status of the auditory nerve. The mean CAP score of the ABI group was 2.87, while the mean SIR score was 0.62. On the other hand, the mean CAP score of the CI group was 1.29, while the mean SIR score was 0.42. CONCLUSION: Our results are in good agreement with the reported auditory perception and speech and language development outcomes of pediatric auditory brainstem implantation. We added to the growing body of literature on the importance of verifying and identifying the status of the cochlear nerve in the decision-making process of the surgical management of those pediatric groups.

Cochlear Implantation in a Patient with Neurofibromatosis Type 2 and an Intracochlear Schwannoma: A Case Report and Literature Review.

A primary intracochlear schwannoma (ICS) is a unique type of vestibular schwannoma (VS); the tumor originates from the terminal branches of the cochlear nerve and is confined to the cochlea. An ICS is the most common subtype of schwannoma in the inner ear. As an ICS is clinically rare, diagnosis and treatment remain challenging. We report a rare case of cochlear implantation (CI) in a patient with neurofibromatosis type 2 and an ICS. The patient exhibited bilateral, profound, sensorineural hearing loss. The tumor on one side was a common VS treated via tumor and acoustic nerve resection and that on the other side an ICS. To ensure auditory rehabilitation via CI, we performed CI while removing part of the ICS via an enlarged round window. Auditory rehabilitation was satisfactory. Thus, ICS patients, especially those who urgently require auditory rehabilitation, can undergo simultaneous CI and (total or partial) tumor removal. However, the long-term results require close observation.

[Cochlear nerve continuity preservation during retrosigmoid ablative osteotomy of the internal auditory canal for advanced vestibular schwannomas]. / Kontinuitätserhalt des Nervus cochlearis bei der retrosigmoidalen ablativen Osteotomie des inneren Gehörgangs bei fortgeschrittenen Vestibularisschwannomen.

The data of 86 patients with retrosigmoid microsurgical resection of vestibular schwannoma in tumor stage Koos II-IV were evaluated. In more than two thirds of the cases it was shown that the cochlear nerve followed the facial nerve, which is easily identified by electroneurography, in recurrent similar patterns in the region of the internal auditory canal. Starting from the fundus, this facilitated early identification and thus preservation of continuity of the cochlear nerve in the course of the internal auditory canal. This was of particular importance when safe functional preservation could not be guaranteed due to tumor size or formation despite intraoperative derivation of somatosenoric potentials, but when the possibility of subsequent hearing rehabilitation with a cochlear implant should be granted. Preoperative MRI sequences gave an indication of the possible nerve courses in some cases, but intraoperative imaging in the internal auditory canal was superior to MRI.

Bimodal stimulation in children with inner ear malformation: One side cochlear implant and contralateral auditory brainstem implant.

OBJECTIVE: To determine audiological outcomes of children who use a cochlear implant (CI) in one ear and an auditory brainstem implant (ABI) in the contralateral ear. DESIGN: Retrospective case review. SETTING: Tertiary referral hospital. PARTICIPANTS: Twelve children followed with CI and contralateral auditory brainstem implant (ABI) by Hacettepe University Department of Otorhinolaryngology and Audiology in Turkey. All children were diagnosed with different inner ear malformations with cochlear nerve aplasia/hypoplasia. CI was planned in the ear with better sound detection during behavioural testing with inserted ear phones and with better CN as seen on MRI. Due to the limited auditory and speech progress with the cochlear implant, ABI was performed on the contralateral ear in all subjects. MAIN OUTCOME MEASURES: Audiological performance and auditory perception skills of children with cochlear nerve deficiency (CND) who use bimodal electrical stimulation with CI and contralateral ABI. RESULTS: Mean age of the subjects was 84.00 ± 33.94 months. Age at CI surgery and ABI surgery was 25.00 ± 10.98 months and 41.50 ± 16.14 months, respectively. However, hearing thresholds only with CI and only with ABI did not reveal significant difference, and auditory perception scores improved with bimodal stimulation. The MAIS scores were significantly improved from unilateral CI to bimodal stimulation (P = .002). Pattern perception and word recognition scores were significantly higher with the bimodal condition when compared to CI only and ABI only conditions. CONCLUSION: Children with CND showed better performance with CI and contralateral ABI combined. Depending on the audiological and radiological results, bimodal stimulation should be advised for children with CND.

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

BACKGROUND: The 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 PRESENTATION: We describe intraoperative neurophysiology monitoring and airway management for the first two ABI procedures in Singapore, conducted for children with congenitally absent cochlear nerves. CONCLUSION: Neurophysiology 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.

Transcanal endoscopic infracochlear vestibular neurectomy: A pilot cadaveric study.

PURPOSE: Effective operative approaches for the treatment of refractory vertigo in Meniere's disease are invasive. Vestibular neurectomy can preserve hearing and has been shown to be effective; however, current approaches require an extensive craniotomy. Transcanal endoscopic approaches to the internal auditory canal (IAC) with cochlear preservation have been recently described and may offer a minimally invasive approach to selectively sectioning the distal vestibular nerves while preserving residual hearing. MATERIALS AND METHODS: Three cadaveric human heads were imaged using high resolution computed tomography (CT). Anatomic analysis of preoperative CT scans showed adequate diameters (>3 mm) of the infracochlear surgical corridor for access to the IAC. A transcanal endoscopic approach was attempted to section the vestibular nerve. Post-operative CT scans were assessed to define the operative tract, determine cochlear preservation and assess cochlear and facial nerve preservation. RESULTS: Transcanal endoscopic approach was successfully performed (n = 3) using 3 mm-diameter, 14 cm-length 0°, 30°, and 45° endoscopes and microsurgical drills. In all cases the tympanomeatal flap and ossicular chain remained intact. Internal auditory canalotomy was performed using angled instruments and confirmed in real time via lateral skull base navigation. The vestibular nerves were readily identified and sectioned with preservation of the facial and cochlear nerves. Post-procedure CT showed no violation of the cochlea. CONCLUSION: A transcanal, infracochlear approach to the IAC may permit a minimally invasive approach to distal vestibular neurectomy in cadavers with appropriate anatomy.

Preserving normal facial nerve function and improving hearing outcome in large vestibular schwannomas with a combined approach: planned subtotal resection followed by gamma knife radiosurgery.

OBJECTIVE: To perform planned subtotal resection followed by gamma knife surgery (GKRS) in a series of patients with large vestibular schwannoma (VS), aiming at an optimal functional outcome for facial and cochlear nerves. METHODS: Patient characteristics, surgical and dosimetric features, and outcome were collected prospectively at the time of treatment and during the follow-up. RESULTS: A consecutive series of 32 patients was treated between July 2010 and June 2016. Mean follow-up after surgery was 29 months (median 24, range 4-78). Mean presurgical tumor volume was 12.5 cm3 (range 1.47-34.9). Postoperative status showed normal facial nerve function (House-Brackmann I) in all patients. In a subgroup of 17 patients with serviceable hearing before surgery and in which cochlear nerve preservation was attempted at surgery, 16 (94.1%) retained serviceable hearing. Among them, 13 had normal hearing (Gardner-Robertson class 1) before surgery, and 10 (76.9%) retained normal hearing after surgery. Mean duration between surgery and GKRS was 6.3 months (range 3.8-13.9). Mean tumor volume at GKRS was 3.5 cm3 (range 0.5-12.8), corresponding to mean residual volume of 29.4% (range 6-46.7) of the preoperative volume. Mean marginal dose was 12 Gy (range 11-12). Mean follow-up after GKRS was 24 months (range 3-60). Following GKRS, there were no new neurological deficits, with facial and hearing functions remaining identical to those after surgery in all patients. Three patients presented with continuous growth after GKRS, were considered failures, and benefited from the same combined approach a second time. CONCLUSION: Our data suggest that large VS management, with planned subtotal resection followed by GKRS, might yield an excellent clinical outcome, allowing the normal facial nerve and a high level of cochlear nerve functions to be retained. Our functional results with this approach in large VS are comparable with those obtained with GKRS alone in small- and medium-sized VS. Longer term follow-up is necessary to fully evaluate this approach, especially regarding tumor control.

[A malignant peripheral nerve sheath tumor developed from the auditory nerve: a case report and a literature review]. / Zlokachestvennaia opukhol' obolochek perifericheskikh nervov, razvivshaiasia iz slukhovogo nerva: sluchai iz praktiki i obzor literatury.

We present a rare clinical case of a patient with a malignant peripheral nerve sheath tumor developed from the auditory nerve as well as a literature review, including 30 reported cases of this disease.

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.

Cavernous hemangioma of the internal auditory canal encasing the VII and VIII cranial nerve complex: case report and review of the literature.

Cavernous angiomas originating in the internal auditory canal are very rare. In the available literature, only 65 cases of cavernomas in this location have been previously reported. We describe the case of a 22-year-old woman surgically treated for a cavernous hemangioma in the left internal auditory canal, mimicking on preoperative magnetic resonance imaging MRI an acoustic neuroma. Neurological symptoms were hypoacusia and dizziness. The cavernous angioma encased the seventh and, partially, the eighth cranial nerve complex. A "nearly total" removal was performed, leaving a thin residual of malformation adherent to the facial nerve. Postoperative period was uneventful; hearing was unchanged, but the patient had a moderate inferior left facial palsy (House-Brackmann grade II) slightly improved during the following weeks. On the basis of the observation of this uncommon case, we propose a revision of the literature and discuss clinical features, differential diagnosis, and treatment.

Navigation-guided transmodiolar approach for auditory nerve implantation via the middle ear in humans.

The aim of this study was to assess the surgical feasibility of a transmodiolar approach via the middle ear cavity for an auditory nerve implantation in humans. In the first part of the study, 6 adult human temporal bones underwent a navigator-guided transmodiolar implantation via the middle ear space after a radical mastoidectomy. In the second part, 122 temporal bone CT scans were analyzed for anatomical parameters relevant to this approach. The nerve implantation was feasible in all temporal bones in laboratory conditions, with a mean target registration error of 0.065 ± 0.0583 mm (n = 6). Evaluation of anatomical parameters on CT scans also supported the feasibility. There was a significant interindividual variation of the modiolar axis and the entry point in relation to visible anatomical landmarks, highlighting the necessity for surgical preplanning.

CE-Chirp® ABR in cerebellopontine angle surgery neuromonitoring: technical assessment in four cases.

Continuous monitoring of wave V of auditory brainstem response (ABR), also called brainstem auditory evoked potential (BAEP), is the most common method used in intraoperative neuromonitoring (IONM) functionality of cochlear nerve during surgery in cerebellopontine angle (CPA). CE-Chirp® ABR represents a recent development of classical ABR. CE-Chirp® is a new acoustic stimulus used in newborn hearing testing, designed to provide enhanced neural synchronicity and faster detection of larger amplitude wave V. In four cases, CE-Chirp® ABR was performed during cerebellopontine angle (CPA) surgery. CE-Chirp® ABR represented a safe and effective method in neuromonitoring functionality of vestibulocochlear nerve. A faster neuromonitoring feedback to surgical equipe was possible with CE-Chirp ABR®.

Hearing preservation surgery for vestibular schwannomas via the retrosigmoid transmeatal approach: surgical tips.

Maximum tumor extirpation with preservation of the facial and cochlear nerve function is the goal of surgery for vestibular schwannoma. To preserve cochlear nerve function, the surgeon must employ a detailed knowledge of microanatomy, precise microsurgical techniques, and persistence. This paper describes the "pearls" of surgical techniques based on the anatomical study inside the mastoid from the view of the retrosigmoid transmeatal approach. A total of 592 consecutive patients underwent surgical removal of unilateral vestibular schwannoma (VS) between January 1994 and December 2009. The hearing preservation rate was 53.7 % for large vestibular schwannomas (>20 mm in diameter) and 74.1 % for tumors of all sizes. The key procedures for hearing preservation surgery are as follows: bloodless microdissection, sufficient coring-debulking, capsular elevation to locate the facial and cochlear nerves both electrophysiologically and by visual observation, sharp dissection of the facial and cochlear nerves, and avoidance of heat and mechanical injury to the nerves, the internal auditory artery, and the brain stem. Besides these techniques, appropriate instruments are essential to preserve hearing. The function of the facial and cochlear nerves should be the foremost concern. Meticulous techniques and the knowledge of microsurgical anatomy lead to hearing preservation with maximum tumor removal.

[The current tendencies and prospects of the neural response telemetry in the rehabilitation of the patients after cochlear implantation].

The objective of the present study was to estimate the potential of the modern technique for telemetry of the neural response during rehabilitation of the patients following cochlear implantation. The methods for the purpose included comparison of the results of intra- and postoperative registration on neural response telemetry (NRT) and evaluation of the influence of perimodiolar localization of electrodes of cochlear implants on the threshold level of stimulation and propagation of excitation inside the cochlea. The results of the study confirm the possibility of using the registration of the electrically evoked auditory nerve potential for fitting the speech processor of the cochlear implant. In addition, it was shown that the application of the perimodiolar electrode significantly narrows the intracochlear excitation distribution profile which enhances the rehabilitative effectiveness of cochlear implantation.

Risk factors and outcomes in patients with cochlear nerve deficiency.

INTRODUCTION: Cochlear nerve deficiency (CND) is a cause of sensorineural hearing loss made by radiologic criteria. There is sparse literature involving audiological outcomes and cochlear implantation (CI) success in patients with CND. METHODS: A retrospective chart review of all patients with sensorineural hearing loss at a tertiary children's hospital from 2000 to 2020 was conducted. Patients with CND on radiographic imaging were included and categorized as hypoplastic, aplastic, or indeterminate. RESULTS: In this study, 53 patients were identified with CND, totaling 70 ears. Of the 53 patients, 30 (56.6 %) were male, 8 (16.0 %) had a family history of childhood hearing loss, 6 (11.3 %) were born preterm, and 11 (23.4 %) required neonatal intensive care admission. The median maternal age was 29 years old [IQR: 27, 35], and 8 (15 %) patients were born to mothers with diabetes. Of the 70 ears, 49 (70 %) utilized conventional hearing aids, 12 (17.1 %) utilized a bone-anchored hearing aid, and 10 (14.3 %) underwent CI. Of the 10 ears implanted, 4 (40 %) ears had nerves classified as hypoplastic, 3 (30 %) as aplastic, and 3 (30 %) as indeterminate. Improvement in pure tone averages compared to preoperative testing was demonstrated in 8 (80 %), and 6 (60 %) displayed improved speech awareness thresholds. CONCLUSION: This study demonstrates that there may be an association between CND and maternal diabetes and NICU admission. There are variable results with hearing amplification options in patients with CND, and further research is needed to better describe the role of CI, bone-anchored hearing aids and conventional hearing aids in patients with CND.

Auditory brainstem implantation: surgical experience and audiometric outcomes in the pediatric population.

OBJECTIVE: Pediatric data regarding treatment via an auditory brainstem implant (ABI) remains sparse. The authors aimed to describe their experience at their institution and to delineate associated demographic data, audiometric outcomes, and surgical parameters. METHODS: An IRB-approved, retrospective chart review was conducted among the authors' pediatric patients who had undergone auditory brainstem implantation between 2012 and 2021. Demographic information including sex, age, race, coexisting syndrome(s), history of cochlear implant placement, average duration of implant use, and follow-up outcomes were collected. Surgical parameters collected included approach, intraoperative findings, number of electrodes activated, and complications. RESULTS: A total of 19 pediatric patients had an ABI placed at the authors' institution, with a mean age at surgery of 4.7 years (range 1.5-17.8 years). A total of 17 patients (89.5%) had bilateral cochlear nerve aplasia/dysplasia, 1 (5.3%) had unilateral cochlear nerve aplasia/dysplasia, and 1 (5.3%) had a hypoplastic cochlea with ossification. A total of 11 patients (57.9%) had a history of cochlear implants that were ineffective and required removal. The mean length of implant use was 5.31 years (0.25-10 years). Two patients (10.5%) experienced CSF-related complications requiring further surgical intervention. The most recent audiometric outcomes demonstrated that 15 patients (78.9%) showed improvement in their hearing ability: 5 with sound/speech awareness, 5 able to discriminate among speech and environmental sounds, and 5 able to understand common phrases/conversation without lip reading. Nine patients (47.4%) are in a school for the deaf and 7 (36.8%) are in a mainstream school with support. CONCLUSIONS: The authors' surgical experience with a multidisciplinary team demonstrates that the retrosigmoid approach for ABI placement in children with inner ear pathologies and severe sensorineural hearing loss is a safe and effective treatment modality. Audiometric outcome data showed that nearly 79% of these patients had an improvement in their environmental and speech awareness. Further multicenter collaborations are necessary to improve these outcomes and potentially standardize/enhance electrode placement.

A Systematic Review and Meta-analysis Examining Outcomes of Cochlear Implantation in Children With Bilateral Cochlear Nerve Deficiency.

OBJECTIVE: To assess hearing and speech outcomes in pediatric patients with bilateral cochlear nerve deficiency (CND) who underwent cochlear implantation (CI) and to identify factors associated with improved outcomes. DATABASES REVIEWED: PubMed, Embase, Web of Science, and Cochran databases were searched following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. METHODS: Studies that reported hearing and speech outcomes of pediatric patients with bilateral CND who underwent CI were included. Demographics, comorbidities, inner ear abnormalities, CND classification (aplasia or hypoplasia), details of diagnostic workup, and outcomes data were extracted. Outcomes were assessed using the four-level auditory performance level (APL) scale. Meta-analysis, using Cochran-Armitage tests, was performed on patients with individual data to assess factors associated with performance. RESULTS: A total of 314 papers were screened, and 40 papers with 378 total patients met inclusion criteria. A total of 339 patients had patient-level data and were included in the meta-analysis. Of the 339 patients, 19% (n = 63) of patients had no measurable stimulation, 28% (n = 95) had improved detection, 22% (n = 76) achieved closed-set speech perception, and 31% (n = 105) achieved open-set speech perception. Patients with cochlear nerve aplasia (p = 0.016) and syndromes (p < 0.001) had significantly worse APL scores relative to patients with cochlear nerve hypoplasia and patients without syndromes, respectively. CONCLUSIONS: While most patients with bilateral CND benefit from CI and almost one-third of patients achieved open-set speech perception, outcomes were heterogenous and one-fifth of patients did not experience measurable benefit from CI.

Functional Outcome After Simultaneous Vestibular Schwannoma Resection and Cochlear Implantation With Intraoperative Cochlear Nerve Monitoring.

OBJECTIVE: Electrically evoked auditory brainstem response audiometry has emerged as a suitable option to intraoperatively assess cochlear nerve function during vestibular schwannoma resection. This study aimed to analyze the functional outcome and implant usage of patients with preserved auditory nerve responses after simultaneous translabyrinthine schwannoma resection and cochlear implantation. STUDY DESIGN: Prospective study. SETTING: Tertiary referral center. METHODS: Patients with unilateral sporadic vestibular schwannoma underwent translabyrinthine tumor resection. Intraoperatively, electrically evoked auditory brainstem response audiometry was performed before and after tumor removal. Cochlear implantation was carried out if positive responses were detected after tumor removal indicating cochlear nerve function. Postoperatively, patients were biannually followed-up to assess aided sound field audiometry and word recognition as well as implant usage. RESULTS: Overall, 26 patients with vestibular schwannoma underwent translabyrinthine schwannoma resection. Out of these patients, 15 had positive cochlear nerve responses after tumor removal and concurrently received a cochlear implant. In 13 patients with histologically confirmed vestibular schwannoma, hearing improved by 23.7 ± 33.2 decibels and word recognition by 25.0 ± 42.4% over a mean follow-up period of 18 months. Overall, 12 included patients were regular cochlear implant users. CONCLUSION: Patients with vestibular schwannoma can benefit substantially from cochlear implantation. Intraoperative assessment of cochlear nerve function using electrically evoked auditory brainstem response audiometry can help to better identify individuals eligible for simultaneous vestibular schwannoma resection and cochlear implantation.

Using a Facial Nerve Stimulator to Record the Auditory Nerve Compound Action Potential to Locate the Auditory Nerve During Vestibular Schwannoma Resection.

BACKGROUND: Improved technology in vestibular neuroma resection and facial nerve protection has become more sophisticated, and the protection of hearing during vestibular schwannoma resection is crucial. Currently, brainstem auditory evoked potential (BAEP), cochlear electrography, and cochlear nerve compound action potential (CNAP) are frequently used. The CNAP waveform is stable; however, the recording electrode can easily affect the procedure and cannot map the auditory nerve. The purpose of the study was to explore a simple method to record the CNAP and map the auditory nerve. METHODS: In this study, CNAP was recorded using a facial nerve bipolar stimulator to localize and protect the auditory nerve. The BAEP click stimulation mode was used. A bipolar stimulator was used as the recording electrode to record CNAP and locate anatomical displacement of the auditory nerve. The CNAP of 40 patients was monitored. Pure tone audiometry, speech discrimination score, and auditory evoked potential (BAEP) evaluations were performed on all patients before and after surgery. RESULTS: Of the 40 patients, 30 patients obtained CNAP during surgery, and the rate of CNAP obtained was significantly higher than that of BAEP. The sensitivity and specificity of decrease in CNAP in predicting significant hearing loss were 88.9% and 66.7%, respectively. The sensitivity and specificity of the disappearance of CNAP in predicting significant hearing loss were 52.9% and 92.3%, respectively. CONCLUSIONS: The bipolar facial nerve stimulator can locate and protect the auditory nerve by recording a stable potential. The CNAP obtained rate was significantly higher than that of BAEP. The disappearance of BAEP during acoustic neuroma monitoring can be used as a standard alert for the surgeon, and decrease in CNAP is an alert for the operator.