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Objectives: Vestibular schwannomas (VS) are rare benign tumours of the vestibular nerve that cause hearing loss. Management strategies include watchful waiting, radiotherapy or surgical resection. Historically, the presence of retrocochlear disease has been considered to be a contra-indication to cochlear implantation (CI). The aim of this systematic review is to assess hearing rehabilitation outcomes for CI recipients with VS, either sporadic or associated with neurofibromatosis type 2, whose tumours have been managed with either observation or radiotherapy. Methods: PubMed, Embase, and Cochrane Library databases were searched from inception through to November 2018. 50 cases from 12 studies met the inclusion criteria. Patient demographics, VS characteristics, management strategy, pre-CI hearing status, electrical promontory stimulation testing, post-CI hearing status and speech perception scores, functional benefits and follow-up length are reported. Results: Radiotherapy and observation groups had similar patient demographics in terms of age at CI, tumour size and duration of deafness. Following CI, 64% and 60% of patients in the radiotherapy and observation groups achieved open-set speech perception, respectively. Pure tone average thresholds (33 vs. 39 dB) and speech scores were also comparable between both groups. Conclusion: Ipsilateral CI in patients with VS that have not been surgically resected can provide beneficial hearing rehabilitation outcomes.

Objective: Review of cochlear implant (CI) outcomes in patients with Neurofibromatosis Type 2 (NF2), implanted in the presence of an ipsilateral vestibular schwannoma (VS). Hearing restoration was combined in some cases with a Bevacizumab regime., Method: Retrospective review of 12 patients, managed over the period 2009-2016, at a tertiary referral multidisciplinary NF2 clinic. The patients are grouped by hearing outcomes to explore likely protective factors, and to generate a proposed decision-making tool for the selection of either CI or Auditory Brainstem Implant (ABI)., Results: Four of the 12 patients achieved speech discrimination without lip-reading. In these individuals there is reason to think that the mechanism of their hearing loss was cochlear dysfunction. A further four patients received benefit to lip-reading and awareness of environmental sound. For such patients their hearing loss may have been due to both cochlear and neural dysfunction. Two patients gained access to environmental sound only from their CI. Two patients derived no benefit from their CIs, which were subsequently explanted. Both these latter patients had had prior ipsilateral tumour surgery, one just before the CI insertion., Conclusion: Cochlear implantation can lead to open set speech discrimination in patients with NF2 in the presence of a stable VS. Use of promontory stimulation and intraoperative electrically evoked auditory brainstem response testing, along with case history, can inform the decision whether to implant an ABI or CI.

In neurofibromatosis type 2 (NF2) bilateral vestibular schwannomas (VS) or their treatment usually results in bilateral hearing loss. Cochlear implantation (CI) was traditionally not used in these patients due to concern that retrocochlear disease would render the implant ineffective. This paper describes the auditory outcomes of CI in 13 patients with NF2 and includes patients with untreated VS and patients undergoing VS removal with cochlear nerve preservation. The non-user rate was 7.7%. Of the active users, median CUNY score was 98%, median BKB score in quiet was 90% and median BKB score in noise was 68%. CI is a viable option in selected patients with NF2.

Objective: To investigate the outcomes from ipsilateral simultaneous or sequential cochlear implantation in patients with neurofibromatosis type 2 (NF2) after vestibular schwannoma removal with cochlear nerve preservation., Study Design: Retrospective case series., Setting: Single tertiary referral NF2 center., Patients: Six patients with NF2., Intervention: Removal of vestibular schwannoma (VS) with preservation of the cochlear nerve and cochlear implantation. Four patients had their surgery via a translabyrinthine approach. Two patients had a retrosigmoid approach. A cochlear implant was inserted at the same time as tumor removal in 4 cases and sequentially in 2 cases., Main Outcome Measures: Surgical and audiometric outcomes using Bamford-Kowal-Bench (BKB) and City of New York University (CUNY) sentence scores., Results: The average age at implantation was 24 years (range, 15-36 yr). Follow-up ranged from 5 to 93 months, with an average of 38 months. All patients had useful hearing in the contralateral ear before surgery. One patient gained no benefit from cochlear implantation and proceeded to have an auditory brainstem implant. Of those that had functional cochlear nerves, the average BKB score in quiet was 64%, BKB score in noise was 42%, and CUNY score with lipreading was 97%. Results varied within the group, but all patients gained significant benefit and continue to use their CI at least intermittantly., Conclusion: The present series demonstrates that in selected cases, cochlear implantation can be successful after a translabyrinthine approach for VS removal and for restoring hearing after failed retrosigmoid hearing preservation surgery. All patients found the cochlear implant offered useful hearing even in the presence of contralateral hearing.

Objective: Hearing loss resulting from bilateral vestibular schwannomas (VSs) has a significant effect on the quality of life of patients with neurofibromatosis Type 2 (NF2). A national consensus protocol was produced in England as a guide for cochlear implantation (CI) and auditory brainstem implantation (ABI) in these patients., Study Design: Consensus statement., Setting: English NF2 Service., Participants: Clinicians from all 4 lead NF2 units in England., Main Outcome Measures: A protocol for the assessment, insertion and rehabilitation of CI and ABI in NF2 patients., Results: Patients should undergo more detailed hearing assessment once their maximum aided speech discrimination score falls below 50% in the better hearing ear. Bamford-Kowal-Bench sentence testing scores below 50% should trigger assessment for auditory implantation, as recommended by the National Institute for Clinical Excellence guidelines on CI. Where this occurs in patients with bilateral stable VS or a unilateral stable VS where the contralateral cochlear nerve was lost at previous surgery, CI should be considered. Where VS surgery is planned, CI should be considered where cochlear nerve preservation is thought possible, otherwise an ABI should be considered. Intraoperative testing using electrically evoked auditory brainstem responses or cochlear nerve action potentials may be used to determine whether a CI or ABI is inserted., Conclusion: The NF2 centers in England agreed on this protocol. Multisite, prospective assessments of standardized protocols for auditory implantation in NF2 provide an essential model for evaluating candidacy and outcomes in this challenging patient population.

Objective: To investigate cochlear implant performance outcomes among patients with Neurofibromatosis type 2 (NF2)., Study Design: Retrospective case series, patient questionnaire, and systematic review of the literature., Setting: Tertiary academic referral center., Patients: All patients with NF2 having an anatomically intact ipsilateral cochlear nerve who underwent cochlear implantation (CI)., Intervention(s): Cochlear implantation., Main Outcome Measures: Postimplantation audiometric performance and patient perceived benefit., Results: Ten patients met study criteria. The median duration of follow-up after CI was 42 months (mean, 46.9 mo; range, 12-97 mo). Five patients received previous microsurgical resection of their ipsilateral vestibular schwannoma, 4 underwent previous stereotactic radiosurgery, and 1 patient had no tumor treatment before CI. Nine subjects achieved sound awareness, 6 attained open-set speech recognition and 7 are daily users. Variables including prolonged auditory deprivation, cochlear ossification, unfavorable electrical promontory stimulation testing, and useful contralateral hearing were associated with poor cochlear implant performance. No statistical associations were found between open-set recognition capacity and previous tumor management strategy, surgical approach, or ipsilateral tumor size., Conclusion: Cochlear implantation is an attractive alternative to auditory brainstem implantation for hearing rehabilitation in patients with NF2. Approximately 70% of patients achieve open-set speech discrimination, many scoring at the ceiling of audiometric testing. Given a favorable risk profile and superior audiometric outcomes, CI should be strongly considered in patients with nonserviceable hearing who have an anatomically intact cochlear nerve, whereas auditory brainstem implantation should be reserved for patients with evidence of cochlear nerve loss. Akin to conventional cochlear implant recipients, prolonged hearing loss, unfavorable electrophysiological testing, and cochlear ossification may predict poor subject performance. Finally, useful hearing in the contralateral ear may present a barrier to daily device use.

Object: The aim of this study was to determine whether patients with neurofibromatosis Type 2 (NF2) who have intact ipsilateral cochlear nerves can have open-set speech discrimination following cochlear implantation., Methods: Records of 7 patients with documented NF2 were reviewed to determine speech discrimination outcomes following cochlear implantation. Outcomes were measured using consonant-nucleus-consonant words and phonemes; Hearing in Noise Test sentences in quiet; and City University of New York sentences in quiet and in noise., Results: Preoperatively, none of the patients had open-set speech discrimination. Five of the 7 patients had previously undergone excision of ipsilateral vestibular schwannoma (VS). One of the patients who received a cochlear implant had received radiation therapy for ipsilateral VS, and another was undergoing observation for a small ipsilateral VS. Following cochlear implantation, 4 of 7 patients with NF2 had open-set speech discrimination following cochlear implantation during extended follow-up (15-120 months). Two of the 3 patients without open-set speech understanding had a prolonged period between ipsilateral VS resection and cochlear implantation (120 and 132 months), and had cochlear ossification at the time of implantation. The other patient without open-set speech understanding had good contralateral hearing at the time of cochlear implantation. Despite these findings, 6 of the 7 patients were daily users of their cochlear implants, and the seventh is an occasional user, indicating that all of the patients subjectively gained some benefit from their implants., Conclusions: Cochlear implantation can provide long-term auditory rehabilitation, with open-set speech discrimination for patients with NF2 who have intact ipsilateral cochlear nerves. Factors that can affect implant performance include the following: 1) a prolonged time between VS resection and implantation; and 2) cochlear ossification.

The auditory midbrain implant (AMI), which is designed for stimulation of the inferior colliculus (IC), is now in clinical trials. The AMI consists of a single shank array (20 contacts) and uses a stimulation strategy originally designed for cochlear implants since it is already approved for human use and we do not yet know how to optimally activate the auditory midbrain. The goal of this study was to investigate the effects of different pulse rates and phase durations on loudness and pitch percepts because these parameters are required to implement the AMI stimulation strategy. Although each patient was implanted into a different region (i.e. lateral lemniscus, central nucleus of IC, dorsal cortex of IC), they generally exhibited similar threshold versus phase duration, threshold versus pulse rate, and pitch versus pulse rate curves. In particular, stimulation with 100 mus/phase, 250 pulse per second (pps) pulse trains achieved an optimal balance among safety, energy, and current threshold requirements while avoiding rate pitch effects. However, we observed large differences across patients in loudness adaptation to continuous pulse stimulation over long time scales. One patient (implanted in dorsal cortex of IC) even experienced complete loudness decay and elevation of thresholds with daily stimulation. Comparing these results with those of cochlear implant and auditory brainstem implant patients, it appears that stimulation of higher order neurons exhibits less and even no loudness summation for higher rate stimuli and greater current leakage for longer phase durations than that of cochlear neurons. The fact that all midbrain regions we stimulated, which includes three distinctly different nuclei, exhibited similar loudness summation effects (i.e. none for pulse rates above 250 pps) suggests a possible shift in some coding properties that is affected more by which stage along the auditory pathway rather than the types of neurons are being stimulated. However, loudness adaptation occurs at multiple stages from the cochlea up to the midbrain.

Cochlear implantation has a limited but definite role in the rehabilitation of certain neurofibromatosis type 2 (NF2) patients. The presence of a dead ear either before, or after, tumour removal does not necessarily imply loss of function in the eighth nerve; in some instances the hearing loss will be cochlear. Promontory or round window electrical stimulation may help to identify those individuals with surviving eighth nerve function. In such patients multichannel cochlear implantation promises a better level of audition than the auditory brain stem implant. This paper highlights such a case and the management problems are discussed.