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The Laryngoscope C 2013 The American Laryngological, V Rhinological and Otological Society, Inc. Cochlear Implantation in Patients With Vestibular Schwannoma: A Single United Kingdom Center Experience Irumee Pai, MSc, FRCS; Vikram Dhar, FRCS; Catherine Kelleher, BA; Terry Nunn, MSc; Steve Connor, MRCP, FRCR; Dan Jiang, PhD, FRCS; Alec Fitzgerald O’Connor, FRCS Objectives/Hypothesis: To evaluate the outcome of cochlear implantation (CI) in patients with vestibular schwannoma (VS). Study Design: A retrospective case series from a tertiary auditory implant center. Methods: A retrospective case note review was carried out to evaluate patients with bilateral profound hearing loss and VS who underwent unilateral CI within the Auditory Implant Centre at St. Thomas’ Hospital, London, between 2000 and 2012. This included both bilateral VS with neurofibromatosis type 2 (NF2) and unilateral sporadic VS. Outcome measures included speech perception with Bamford-Kowal-Bench and City University of New York sentences, sound-field thresholds with warble tones, and the subjective benefits reported by patients. Results: The study included five patients with NF2 and bilateral VS and two patients with sporadic unilateral VS. The standard preoperative audiologic assessment for CI often could not be carried out in NF2 patients. Preoperative testing was more complete in the two patients with sporadic VS. The audiologic outcome was variable. Open-set speech perception was achieved in three out of five NF2 patients, and another reported significant improvement in environmental sound perception and ease of communication. The outcome was overall better in patients with sporadic VS, both of whom were able to use the telephone in their implanted ear. Conclusions: Good speech perception can be achieved in some cases, and CI should be considered as an option for auditory rehabilitation in patients with VS. Key Words: Cochlear implants, vestibular schwannoma, neurofibromatosis type 2. Level of Evidence: 4. Laryngoscope, 123:2019–2023, 2013 INTRODUCTION Auditory rehabilitation for profound sensorineural hearing loss in patients with bilateral vestibular schwannoma (VS) associated with neurofibromatosis type 2 (NF2), or those with sporadic VS and profound hearing loss in their contralateral ear, poses a great therapeutic challenge. This is particularly the case in patients with NF2, who often have other medical comorbidities and eventually develop multiple disabilities including blindness. There are a number of potential pathophysiologic mechanisms by which hearing loss occurs in VS. In a cadaveric study by Roosli et al.,1 a number of changes were found in the cochlea in association with unilateral From the Auditory Implant Centre (I.P., V.D., C.K., T.N., D.J., A.F.O.), Department of Diagnostic Imaging (S.C.), St Thomas’ Hospital, London, United Kingdom Editor’s Note: This Manuscript was accepted for publication January 28, 2013. This study was an oral presentation at the joint 6th International Congress of the World Federation of Skull Base Societies and 10th European Skull Base Society Congress, Brighton, United Kingdom, May 16, 2012. The authors have no funding, financial relationships, or conflicts of interest to disclose. Send correspondence to Dan Jiang, PhD, FRCS, Auditory Implant Department, St. Thomas’ Hospital, Westminster Bridge Road, London SE1 7EH, United Kingdom. E-mail: [email protected] DOI: 10.1002/lary.24056 Laryngoscope 123: August 2013 sporadic VS, including loss of inner and outer hair cells, spiral ganglia degeneration, and precipitates in the endolymph and perilymph. The cochlea may also be directly invaded by the tumor.2 The cochlear nerve function can be compromised, usually through compression, but it may be directly infiltrated by tumor.3 Hearing may deteriorate further following treatment of VS. Even with hearing-preservation surgical techniques such as middle fossa and retrosigmoid approaches, retention of useful hearing is not always possible. If the cochlear nerve is structurally preserved during surgical resection, hearing loss may still occur, probably due to direct neuronal disruption and/or compromise of the vascular supply to the cochlea.4 A number of studies have shown a correlation between hearing loss following stereotactic radiotherapy and radiation dose delivered to the cochlea, in both single and fractionated doses.5–7 Until recently, active intervention for profound sensorineural hearing loss in these two groups of patients was limited to auditory brainstem implant (ABI) following tumor removal. Whilst ABI can provide useful auditory percepts and improve communication especially in conjunction with lip reading, open-set speech recognition is uncommon.8 Of late, there has been a growing interest in cochlear implantation (CI) as an alternative option for auditory rehabilitation in patients with VS who have residual cochlear nerve function. Although reported Pai et al.: CI in Vestibular Schwannoma 2019 audiologic outcomes are variable,9–11 a recent review by Celis-Aguilar et al. suggests that CI is a reasonable option for these patients.12 In this article, we present the experience from our single tertiary referral center with CI both for bilateral VS with NF2 and for unilateral sporadic VS and discuss the management considerations for the two unique groups of patients. MATERIALS AND METHODS A retrospective case note review was carried out to evaluate patients with bilateral profound hearing loss and VS who underwent unilateral CI within the Auditory Implant Centre at St. Thomas’ Hospital, London, between 2000 and 2012. This included both sporadic and NF2-associated VS patients. The study was reviewed by the institutional clinical governance review board and was exempted from the formal ethical approval process. Preoperative audiologic assessment included pure-tone audiometry, sound-field with warble tones, and speech perception testing using Bamford-Kowal-Bench (BKB) sentences and City University of New York (CUNY) sentences with lip reading at 70 dBA sound presentation level. In patients who had no auditory perception, transtympanic electrical promontory stimulation (EPS) was performed to determine gap detection as a surrogate measure of the cochlear nerve function (starting at a pulse rate of 50 Hz and gap length of 250 ms). Radiologic evaluation by serial magnetic resonance imaging (MRI) was carried out by a single consultant neuro-otology radiologist, with particular attention to the rate of tumor growth and detailed assessment of the tumor involvement of the cochlea. Intraoperative findings including electrode insertion depth and neural response telemetry were recorded, as well as any postoperative complications. Outcome measures included sound-field thresholds, BKB, CUNY, and the subjective benefits reported by patients. RESULTS Over the 10-year period, seven patients with VS and bilateral profound hearing loss received a unilateral cochlear implant. Five patients had NF2 with bilateral tumors. Of the two patients with unilateral sporadic VS, one had a 30-year history of profound sensorineural hearing loss of unknown etiology in the contralateral ear, which had never been aided. The other patient had identified the nontumor ear as the better hearing ear, still deriving some benefits from an acoustic hearing aid, but overall fell within the CI criteria and was unwilling to receive an implant in his better hearing (nontumor) ear. Both sporadic VS patients therefore received an implant in the tumor ear. The mean age at implantation was 35.0 years in the NF2 group (range, 18.2–49.8) and 82.4 years in the sporadic group (range, 76.3–88.4). The management of VS in the ear to be implanted was variable and had included surgical resection only (n 5 3), surgery followed by interval gamma knife radiotherapy for control of further growth (n 5 1), gamma knife radiotherapy only (n 5 1), fractionated stereotactic radiotherapy (n 5 1), and observation with serial imaging and no intervention (n 5 1). All four patients who Laryngoscope 123: August 2013 2020 had had surgery were NF2 patients, and the resection was via the retrosigmoid approach in all cases. As can be seen in Table I, the standard preoperative audiologic assessment for CI was largely impossible to carry out in NF2 patients, and testing often had to be abandoned, as they found the tests unmanageable. All five NF2 patients underwent EPS testing, of which four had positive gap detection. The other patient had a negative response with a needle electrode on the promontory but had a positive response with a ball electrode in the round window. Some preoperative audiologic testing was possible in the two patients with sporadic VS. Tumor invasion of the cochlea was evident on MRI in four of five NF2 patients but not in either sporadic VS patient. Implanted devices were Advanced Bionics (Advanced Bionics AG Laubisr€ utistrasse 28, 8712 St€ afa, Switzerland) Clarion AB-5100H, Cochlear Nucleus Freedom CI24RE(ST), Cochlear (Cochlear Headquarters, University Avenue, Macquarie University NSW 2109 Australia) Nucleus CI422, and Advanced Bionics HiRes 90K. No attempt was made to remove intracochlear tumor before insertion of the electrode in any of the cases. Full insertion was achieved in all patients except one NF2 patient (patient 3), where the electrode buckled at 180-degree insertion because of obstruction of the scala tympani adjacent to the internal auditory canal. In only two NF2 patients (patients 4 and 5) did intraoperative neural response telemetry display a compound action potential. There were no surgical complications, and all patients made an uneventful recovery. Two of the NF2 patients (patients 2 and 3) had no open-set speech perception postoperatively. Nonetheless, patient 3 was highly satisfied with the implant and reported that he was able to recognize familiar music and identify some words without lip reading (follow-up, 11 months). Patient 2 had no auditory perception postimplantation. Patient 1 performed very well initially, with BKB score of 78% and CUNY score of 93% at 1 week after switch-on. However, his medical condition deteriorated steadily over the following few months with rapid progression of visual impairment and worsening implant performance, and he died 28 months after implantation. Patient 4 had a good outcome, with BKB and CUNY scores of 63% and 94%, respectively, at 3 months. He reported that he was able to have group conversations with family members and listen to audio books. Patient 5, who was the latest patient to receive an implant, also performed well, with BKB and CUNY scores of 89% and 94%, respectively, at 3 months. He was able to have a one-to-one conversation in a quiet restaurant and enjoy music again. All NF2 patients who are alive wear their device all day. Both sporadic VS patients had significant improvement in sound-field thresholds. One had no appreciable change on either speech perception test, and the other showed improvement in the CUNY score only. Nevertheless, both patients are highly satisfied CI users; despite the relatively low open speech perception scores postimplantation, they are able to use the telephone in their implanted ear and wear their implant all day (mean follow-up, 31 months). Pai et al.: CI in Vestibular Schwannoma TABLE I. Demographics, Preoperative Audiologic Assessment, and Postoperative Outcome. Patient 1 Patient 2 Patient 3 Patient 4 Patient 5 Patient 6 Age at CI, yr 28.7 36.1 18.2 42.1 49.8 88.4 76.3 Etiology Visual impairment NF2 Yes NF2 No NF2 Yes NF2 Yes NF2 No Sporadic No Sporadic No Treatment for VS before CI Surgery Surgery then interval GK Surgery Fractionated radiotherapy Surgery Monitoring only GK Tumor size in implanted ear before CI, mm 16 3 7 Unknown 26 3 19 20 3 12 332 433 23 3 15 Preoperative AC, dBHL EPS NR Yes NR No* NR Yes NR Yes NR Yes 90 Not performed 90 Not performed Preoperative BKB, % NA NA NA NA 0 Postoperative BKB, % 78 at 1 wk NR 2 at 3 mo 11 at 1 wk, 63 at 3 mo 0 50 at 1 wk, 89 at 3 mo 14 28 at 3 mo 24 10 at 1 wk, 54 at 3 mo Patient 7 0 13 at 1 wk, 0 at 9 mo 9 Preoperative CUNY, %† NA NA 0 Postoperative CUNY, %† 93 at 1 wk, 28 at 1 yr NR 10 at 3 mo 62 at 1 wk, 94 at 3 mo 85 at 1 wk, 94 at 3 mo Preoperative sound field, dBA NA NA NR NA NA Postoperative sound field, dBA Deceased NT NT 35 at 3 mo 30 at 1 wk 36 at 1 wk 40 at 3 mo 36 at 3 mo 28 mo after CI 47 mo after CI No No No No No 52 64 22 at 1 wk, 61 at 9 mo 51 *Positive round window stimulation. † With lip reading. AC 5 air conduction (averaged over 0.5, 1, 2, and 4 kHz); BKB 5 Bamford-Kowal-Bench; CI 5 cochlear implantation; CUNY 5 City University of New York; EPS 5 electrical promontory stimulation; GK 5 gamma knife; NA 5 unable to perform test; NF2 5 neurofibromatosis type 2; NR 5 no response; NT 5 not tested; VS 5 vestibular schwannoma. In patients 1 and 2, progressive growth of all NF2associated tumors was observed, including the VS in the implanted ear, and they died 28 and 47 months after implantation, respectively. In patient 3, there has been no further tumor growth since implantation (follow-up, 16 months). The other two NF2 patients who received their implant in the last 12 months have not had repeat imaging to date (patients 4 and 5). There has been no change in the tumor size in either sporadic VS patient. DISCUSSION With advances in our understanding of NF2 and VS molecular biology, a number of novel therapeutic agents are emerging13,14 that may potentially control tumor progression and improve quality of life. It is hoped that these will in turn facilitate a more active management of the associated disabilities such as profound hearing loss and provide a longer window of opportunity for interventions. In our experience, it was largely impossible to implement the standard audiologic CI assessment protocol preoperatively, particularly in NF2 patients. Whilst it is likely that the preoperative assessment will always require some degree of modification, especially when there are other comorbidities such as visual impairment, our findings emphasize the importance of working closely with the NF2 multidisciplinary team and encouraging an early referral to the implant team, even if the patients are not yet meeting the criteria for CI. More comprehenLaryngoscope 123: August 2013 sive audiologic assessment and closer monitoring of the inevitable deterioration in their hearing will aid better counseling concerning their options and the optimal timing of interventions that may maximize improvement in quality of life. Furthermore, thorough preoperative assessment when patients are still able will facilitate further refinement of implant candidacy criteria, which may lead to a better and more consistent outcome. When there was no auditory percept preoperatively (all five NF2 patients), EPS was performed to assess the functional integrity of the cochlear nerve. To date only those with positive electrical promontory or round window stimulation have received a cochlear implant in our unit. However, the literature suggests that the absence of EPS responses does not necessarily preclude CI. There have been reported cases of successful CIs in NF2 patients, despite negative EPS response.11,15 Nonetheless, it should also be borne in mind that evidence from CI in non-VS patients suggests a correlation between no EPS response and poorer speech perception outcome.16 Until the precise implication of the absent EPS response can be established, or a more reliable predictor of the cochlear nerve function found, the decision whether or not to implant in its absence will need to be made on a case-bycase basis after a full discussion with the patient. Thorough radiologic evaluation is crucial when CI is being considered in VS patients. A combination of thin-section T2-weighted (T2w) and gadoliniumenhanced imaging is required to assess the status of the cochlea. The presence of fibrosis or calcification Pai et al.: CI in Vestibular Schwannoma 2021 subsequent to previous surgery results in loss of the increased T2w signal of the cochlea lumen, with possible increased T1w signal and minor enhancement. Transmodiolar extension of schwannoma is associated with loss of the increased T2w signal of the cochlea lumen and similar enhancement characteristics to an intracanalicular tumor. Each scenario may impede the advancement of the electrode, thus influencing electrode choice and route of insertion. The presence of schwannoma in the middle ear may represent transotic extension or be emanating from the tympanic segment of the facial nerve. The postsurgical distortion of the internal auditory meatus (IAM) makes it difficult to assess the anatomy and integrity of the nerves within the IAM or the location of any residual intracanalicular tumor. The timing of CI surgery is another subject of interest. There are reported cases of simultaneous translabyrinthine excision of VS and CI.17–19 This approach has the obvious advantage of sparing the patient another major surgery. In addition, it avoids the potential pitfall of cochlear fibrosis or ossification, which may follow labyrinthectomy.18 However, the main concern about this strategy is that, even if the cochlear nerve is structurally intact following removal of VS, it may not necessarily be functioning. One of the important considerations following CI surgery is radiologically monitoring the tumor growth. Although a number of devices are deemed to be MRI compatible up to 1.5 T, there are potential risks, including device damage, magnet displacement, and migration. Alternative options are removal of the magnet and the use of a magnetless device. There is also a significant artifact (shadow) surrounding the implanted cochlear stimulator. Our current policy is to perform full intracranial and whole spine MRI just before implantation. Subsequent monitoring is usually with computed tomography for the brain and temporal bone, and, if there is a specific indication for MRI, a CI-compatible protocol is used with a compression head bandage, leaving the magnet in place if in keeping with the manufacturer’s guidelines. The audiologic outcomes were variable in our series of patients with VS undergoing CI. Open-set speech perception was achieved in three of five NF2 patients, and another reported significant improvement in environmental sound perception and ease of communication. The outcome was overall better in patients with sporadic VS, both of whom were able to use the telephone in their implanted ear. At present, all five surviving patients are consistent and satisfied users of their device. It is uncertain which speech perception tests are the most appropriate outcome measures in these patients. In our experience, patients often found it difficult to complete postoperative testing in one session due to fatigue, and the scores obtained may not necessarily be representative of their abilities. It is also possible that the standard CI assessment battery used in our study was not always sensitive enough for detecting the small but significant improvement in speech perception in these specific subgroups of CI patients. This may explain, at least in part, the discrepancy between the scores obtained and the subjective improvement in real Laryngoscope 123: August 2013 2022 life reported by some patients. Careful consideration should therefore be given to the choice of outcome measures in future studies. Direct comparisons between the efficacy of CI for auditory rehabilitation in these patients and that of ABI are difficult due to the differences in the patient populations and outcome criteria used for reporting of the results, and the available evidence is limited to small case series. Nonetheless, the audiologic outcome is likely to be better with CI than with ABI, as the electrical stimulus is presented accurately to the acoustic pathway as long as the cochlear nerve is functioning. In a study by Vincenti et al.,15 patients with NF2 performed better with CI than ABI, although the outcome was variable in both groups. Two recently published review articles on the subject reached a similar conclusion.8,12 With CI becoming the favored option, there is increasing emphasis placed on preservation of the cochlear nerve, where possible, during surgical resection. CONCLUSION In our experience, although there is variability in outcome, speech perception can be achieved in some cases, and CI should be considered as an option for auditory rehabilitation in patients with VS. Some modification of the standard CI assessment protocol is likely to be necessary, and highly specific radiologic evaluation is essential. We recommend early referral to the auditory implant team for more comprehensive assessment and monitoring of hearing loss progression, so that more appropriate and timely patient selection for intervention can be achieved. BIBLIOGRAPHY 1. Roosli C, Linthicum FH Jr., Cureoglu S, Merchant SN. Dysfunction of the cochlea contributing to hearing loss in acoustic neuromas: an underappreciated entity. Otol Neurotol 2012;33:473–480. 2. Falcioni M, Taibah A, Di Trapani G, Khrais T, Sanna M. Inner ear extension of vestibular schwannomas. Laryngoscope 2003;113:1605–1608. 3. Linthicum FH Jr, Brackmann DE. Bilateral acoustic tumors. A diagnostic and surgical challenge. Arch Otolaryngol 1980;106:729–733. 4. Cueva RA, Thedinger BA, Harris JP, Glasscock ME. Electrical promontory stimulation in patients with intact cochlear nerve and anacusis following acoustic neuroma surgery. Laryngoscope 1992;102:1220–1224. 5. Timmer FC, Hanssens PE, van Haren AE, et al. Gamma knife radiosurgery for vestibular schwannomas: results of hearing preservation in relation to the cochlear radiation dose. Laryngoscope 2009;119:1076– 1081. 6. Thomas C, Di Maio S, Ma R, et al. Hearing preservation following fractionated stereotactic radiotherapy for vestibular schwannomas: prognostic implications of cochlear dose. J Neurosurg 2007;107:917–926. 7. Lasak JM, Klish D, Kryzer TC, Hearn C, Gorecki JP, Rine GP. Gamma knife radiosurgery for vestibular schwannoma: early hearing outcomes and evaluation of the cochlear dose. Otol Neurotol 2008;29:1179–1186. 8. Sanna M, Di Lella F, Guida M, Merkus P. Auditory brainstem implants in NF2 patients: results and review of the literature. Otol Neurotol 2012;33:154–164. 9. Lustig LR, Yeagle J, Driscoll CL, Blevins N, Francis H, Niparko JK. Cochlear implantation in patients with neurofibromatosis type 2 and bilateral vestibular schwannoma. Otol Neurotol 2006;27:512–518. 10. Neff BA, Wiet RM, Lasak JM, et al. Cochlear implantation in the neurofibromatosis type 2 patient: long-term follow-up. Laryngoscope 2007;117:1069–1072. 11. Trotter MI, Briggs RJ. Cochlear implantation in neurofibromatosis type 2 after radiation therapy. Otol Neurotol 2010;31:216–219. 12. Celis-Aguilar E, Lassaletta L, Gavilan J. Cochlear implantation in patients with neurofibromatosis type 2 and patients with vestibular schwannoma in the only hearing ear. Int J Otolaryngol 2012; 2012:157497. Pai et al.: CI in Vestibular Schwannoma 13. Blakeley JO, Evans DG, Adler J, et al. Consensus recommendations for current treatments and accelerating clinical trials for patients with neurofibromatosis type 2. Am J Med Genet 2011;158A:24–41. 14. Fong B, Barkhoudarian G, Pezeshkian P, Parsa AT, Gopen Q, Yang I. The molecular biology and novel treatments of vestibular schwannomas. J Neurosurg 2011;115:906–914. 15. Vincenti V, Pasanisi E, Guida M, Di Trapani G, Sanna M. Hearing rehabilitation in neurofibromatosis type 2 patients: cochlear versus auditory brainstem implantation. Audiol Neurootol 2008;13:273–280. 16. Kuo SC, Gibson WP. The role of the promontory stimulation test in cochlear implantation. Cochlear Implants Int 2002;3:19–28. Laryngoscope 123: August 2013 17. Zanetti D, Campovecchi CB, Pasini S, Nassif N. Simultaneous translabyrinthine removal of acoustic neuroma and cochlear implantation. Auris Nasus Larynx 2008;35:562–568. 18. Aristegui M, Denia A. Simultaneous cochlear implantation and translabyrinthine removal of vestibular schwannoma in an only hearing ear: report of two cases (neurofibromatosis type 2 and unilateral vestibular schwannoma). Otol Neurotol 2005;26:205–210. 19. Ahsan S, Telischi F, Hodges A, Balkany T. Cochlear implantation concurrent with translabyrinthine acoustic neuroma resection. Laryngoscope 2003;113:472–474. Pai et al.: CI in Vestibular Schwannoma 2023