Cochlear Implants to Treat Deafness Caused by Vestibular Schwannomas

Otology & Neurotology 34:1291Y1298 Ó 2013, Otology & Neurotology, Inc.

*Payal Mukherjee, *James D. Ramsden, †Nick Donnelly, †Patrick Axon, ‡Shakeel Saeed, §Paul Fagan, and kRichard M. Irving

*John Radcliffe Hospital, Oxford; ÞAddenbrookes Hospital, Cambridge; þUniversity College Hospital, National Hospital for Neurology and Neurosurgery, Royal National Throat, Nose and Ear Hospital, London, U.K.; §St. Vincent’s Hospital, Sydney, Australia; and kQueen Elizabeth Hospital, Birmingham, U.K.

Objective: Rehabilitation of hearing is complicated in patients including City University of New York (CUNY) in noise and with profound bilateral hearing loss in the presence of sporadic Bamford, Kowal and Bench (BKB) sentence scores. vestibular schwannoma (VS) or neurofibromatosis 2 (NF2), espe- Results: Patients with untreated lesions experienced marked cially if the tumor does not need to be removed. We present the improvement in their BKB and CUNY scores in the implanted outcome of patients who have had a cochlear implant in the tumor ear and were daily cochlear implant users. The improvement affected ear without removal of the primary tumor. was less consistent in the patients who had radiotherapy where Design: This is a retrospective multicentre study investigating only 1 patient attained open set speech discrimination. outcomes of cochlear implantation in profoundly deaf patients Conclusion: Patients with unilateral VS (sporadic or those affected with vestibular schwannoma in the implanted ear. with NF2) whose tumor status was stable, benefited from co- Materials and Methods: Out of 11 implanted patients, 5 re- chlear implantation in their tumor-affected ear. Patients who had quired no treatment for their tumor, whereas 6 had previously radiotherapy also benefited from CI, but their outcomes were undergone radiotherapy. Nine patients experienced NF2, and 2 variable. Key Words: Cochlear implantsVHearing outcomeV had unilateral VS in the only hearing ear. Postoperative hearing ObservationVRadiationVUntreatedVVestibular schwannoma. was assessed with open and closed set speech discrimination, Otol Neurotol 34:1291Y1298, 2013.

Hearing rehabilitation in sporadic vestibular schwan- The effectiveness of CI in untreated VS is unknown. noma (VS) when it affects the only hearing ear poses many Trotter and Briggs (2) cited case reports of 3 patients with challenges. Patients with neurofibromatosis 2 face an even NF2 who were implanted postradiotherapy. All 3 were more complex management dilemma. An auditory brain- daily cochlear implant users. Lustig et al. (4) had also stem implant (ABI) may be an option after tumor exci- reported similar results in their experience of 2 patients. sion; however, hearing results may be limited to detection Neff et al. (3) in a large multicenter study reported a case of environmental sounds or as an aid to lip reading, and series of 6 patients who underwent surgery of their tumors only a few patients get open set speech discrimination (1). with cochlear nerve preservation. All these patients re- A cochlear implant (CI) may be an option in those rare ceived benefit from their cochlear implants. The study cases where the cochlear nerve has been left intact after showed that, despite interruption of blood supply to the tumor resection or in those cases that have been treated cochlear nerve and loss of postoperative hearing, a CI could with radiotherapy (2Y4). In addition, some authors advo- provide significant improvement to hearing. An interesting cate the use of a CI in preference to an ABI, not only be- observation was made by Helbig et al. (6) who implanted cause of better open set speech discrimination with CI but a patient with sporadic VS that required no treatment for also because of the reduced surgical morbidity, risks, and the tumor. The contralateral ear was implanted first. The time associated with the operation (5). tumor-affected ear was sequentially implanted. On 6-month follow-up, the patient attained 80% speech scores on mono- syllabylic testing, and the tumor side matched the results Address correspondence and reprint requests to Payal Mukherjee, of the nontumor side. M.S., FRACS (ORL-HNS), 42 The Esplanade, Thornleigh, Sydney, NSW, One of the factors influencing the hearing outcome of Australia 2120; E-mail: [email protected] Disclosure of Funding: No separate funding was used to finance this a cochlear implant is the length of time an ear has been study. None of the authors had any financial interests in the results of the deaf (7). Therefore, a recently deafened ear with a tumor study or any information presented in the manuscript. may give a good or better outcome than the long deafened

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Copyright © 2013 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited. 1292 P. MUKHERJEE ET AL. contralateral nontumor ear, especially in light of findings who were exceptions had large tumors on the contralateral of equal outcome of hearing in tumor and nontumor side side and were awaiting urgent contralateral tumor removal (6). NF2 patients are surgically often very challenging, and on that side. The sizes were 5.4 and 4.5 cm, respectively CI may provide an alternate safer rehabilitation. (Patients 5 and 6; Table 2). They were implanted with a CI on the stable irradiated side, with a view that if unsuc- METHODS cessful, they would be considered for an ABI placement during tumor removal on the contralateral side. These 2 This is a retrospective multicenter study undertaken to in- patients who were considered for ABIs were assessed in vestigate hearing outcomes in patients implanted with CI in 2 independent multidisciplinary specialized NF2 teams their tumor-affected ear in 2 groups. First, patients whose tumors (one of these teams is a specialized ABI center) and prog- have been stable and required no active treatment, and second, ressed to CI after consensus was reached. patients whose tumors have been implanted after they have been There were some limitations to data collection. Be- stabilized after radiotherapy. The inclusion criteria were bilateral cause this was a multicenter study and the data were profound sensorineural hearing loss in the setting of NF2 or a sporadic vestibular schwannoma with a contralateral dead ear. collected retrospectively, not all patients had PTA mea- All patients had stable tumors, with stable tumors being de- sured. Some centers did not routinely measure hearing fined as tumors that had no growth for at least 2 years. Patients thresholds especially in situations where speech scores were assessed for CI candidacy only after this period, and hence, a without lip reading was zero anyway. Furthermore, we further period passed of observation before they were implanted. did not have tumor measurements for 2 patients with Patients with NF2 had a longer follow-up and observation period. intracanalicular tumors. Tumor measurements were rou- They only became candidates for CI once their only hearing ear tinely made for the CPA component of tumors, as it is this lost hearing, but their total period of observation of the ipsilat- measure that has been traditionally used to guide inter- eral tumor would have been far longer as they would have been vention. The intracanalicular size had therefore not been regularly reviewed in the NF2 clinic for their bilateral VS as well routinely documented. In the above 2 cases, it was also as other tumors. Postoperative hearing was assessed with open and closed set difficult to rectify this by reviewing the original films as speech discrimination, including City University of New York the imaging was recorded on hard copies and no longer (CUNY) in noise and Bamford, Kowal and Bench (BKB) sen- available for review. tence scores. Follow-up audiogram was conducted at 3, 6, and 12 months. Their average hearing threshold (referred to as pure Group A tone average or PTA) was also calculated as per American acad- Patients in this group attained an improvement in open emy guidelines (AAO-HNS) with average decibel hearing at set speech discrimination, although one had a language 0.5-, 1-, 2-, and 3-kHz frequency range. disorder as a result of NF2 and could perform audiometry effectively but not speech testing. RESULTS The first patient (Table 1) had recently lost aidable hearing because of a 4-mm sporadic IAC tumor, and the con- There were 11 patients in the entire series, of which, 9 tralateral ear had been deaf for more than 10 years. She had were affected with NF2. None of the tumors were actively some usable hearing in that ear, so she was implanted in growing. her tumor-affected side after promontory stimulation con- The results were stratified into 2 groups according to firmed a functioning nerve. She had the best result of the the disease burden on the CI candidate ear. The first group, entire patient set with BKB scores at 12 months measuring group A, were the untreated VS patients (5 patients), of 99% in quiet without lip reading from 36% preoperatively. whom, 2 had sporadic VS, and 3 had NF2. In this group, The second patient was diagnosed with a small spo- tumors that occupied the cerebellopontine angle (CPA) radic CPA lesion when she presented for CI assessment were all less than 1.5 cm in size. The second group, group after losing hearing in her only hearing ear. The contra- B (6 patients) were the ipsilaterally irradiated patients lateral ear had been deaf since childhood. Her tumor- who were all affected with NF2. These patients had a spec- free ear was implanted first, and she did poorly, which trum of complexity but generally had tumors, which required resulted in implanting the tumor-affected side as this had treatment to the ipsilateral side, patients with aggressive only recently lost hearing. Although she did better in this phenotypes, patients who presented in a pediatric age group, side compared with the other, her additive benefit when and patients with multiple comorbidities and other sensory she used both implants was far greater than when using 1 deficits. implant alone. This effect was sustained at 12 months. All patients were managed in multidisciplinary teams. The next 3 patients were NF2 patients whose implanted Patients with NF2 were managed in specialized NF2 ipsilateral ears had tumors that were untreated. clinics, whereas sporadic patients were managed in a cra- Patient 3 had an IAC lesion only with the contralateral nial base multidisciplinary team. Implant choice depended ear having no serviceable hearing after surgery 13 years mainly on individual patient preference and to a lesser ex- ago. The lesion was filling the IAC completely but not tent on the practice of different units. All patients were pre- expanding it. Her speech discrimination scores improved viously deaf in the contralateral ear. The contralateral sides postoperatively, and when combined with lip reading, she of all the NF2 patients except 2 had been previously op- experienced a great improvement to her overall commu- erated on and had no functional hearing. The 2 patients nication skills. She was able to return to bingo and win.

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Patient 4 had a CPA lesion with no serviceable hearing in the contralateral ear after surgery 9 years ago. She was diagnosed with a language disorder secondary to the disease. Her speech scores were therefore very poor, with BKB BKB 100% CUNY 87%

Bilat BKB 87% scores without lip reading being zero, although her postoperative PTA improved to 30 dB from 100 dB preoperatively. Patient 5 had a 10-mm CPA lesion with no serviceable

0 BKB 50% hearing. The contralateral ear had partial resection of tumor

V in 1981 and had been stable. His BKB scores improved to

Postoperative (1 yr) 98% in quiet and 68% in noise without lip reading. His preoperative scores were 44% aided with lip reading. He Without LR With LR was a telephone user and was using an MP3 player through aily. bilat-61% in noise his implant when he presented for follow-up. These patients were not considered for any form of treatment on their ipsilateral side because their tumors were stable. This was despite the fact that some patients were relatively young (Patients 1, 4, and 5 who were 58, 61, and

36% BKB: L 99% 65 yr old, respectively) as it was felt that they may not re- Y

64% quire an intracranial procedure for treatment. Patient 1 had Y a small sporadic intracanalicular lesion, which was unlikely R to ever grow, although he was young. Patients 4 and 5, in addition, were NF2 patients and had other comorbidities and preferred not to undergo surgery to the tumors if possible. of 5 yr BKB: L 7 yr2 CUNY: yr 42% with aid and LR BKB: R- 23%, L-2%, BKB CUNY: 17% LR only BKB: 49% (CI only) CUNY: 93% Group B 6 mo PTA 100 dB BKB - 0 PTA 30 dB BKB deafness Preoperative Duration Of the 6 NF2 patients, 3 had tumors 1.5 cm or less. The others had lesions, although stable, measuring 1.9, 2.3, and 3.7 cm, respectively. These patients were also pediatric at age of presentation and had more aggressive phenotypes with multiple comorbidities and other sensory deficits. Three of the 6 patients had also lost their hearing either immediately or within 12 months after radiotherapy. Of these, one was immediate, and this patient had stereotactic July 2010 90K Dec 2008 90K Jan 2009 2009 Medel Sonata ti 100 Advanced Bionics HiRes Medel Flex 28 Sept 2011 5 yr BKB: 44% with aid and LR BKB: 98% in quiet 68% radiotherapy. The other 2 patients had gamma knife treatment and lost all aidable hearing during 12 months after radiation.

dead Only 1 patient in this group attained open set speech

V discrimination. This patient had a 1.3-cm tumor in the CPA. The contralateral tumor had translabyrinthine removal dead ear Advanced Bionics Hi Res dead ear Cochlear Nucleus 5 Nov

V 10 years before and had no serviceable hearing. Her BKB V scores were 82% in quiet and 52% in noise without LR

Summary of results of patients who were implanted with tumors not requiring any treatment (Table 2). The other 5 patients could detect environmental sound useful hearing implanted with little effect ear (tumor stable) Idiopathic loss 10 yr, some Idiopathic loss since childhood, Excised 1996 Excised 2000 only. Those with vision improved their lip reading scores. Patient 5 (Table 2), for instance, was awaiting urgent re-

TABLE 1. moval of a contralateral 5.4 cm left VS, which was complicated by the fact that she also had a facial neuroma on that side causing mild facial weakness. She also had bilateral trigeminal, a right jugular foramen schwannoma, a IAM at CPA only CPA right meningioma on posterior surface of temporal bone, and right ventriculoperitoneal shunt that was inserted before radiation. Her ipsilateral (right) VS measured 2.3 cm NF2 Left:NF2 Fills IAC Right: 13 mm NF2 Left: 10 mm CPA Partially excised 1981 and had been stable since irradiation, although she had Sporadic Left: 4 mm at Sporadic Right: 1.2 cm eventually lost all functional hearing in the months after radiation. At the time of presentation and diagnosis, she already had all these tumors. Within a few months of pre- female female female female male sentation, she developed a right vagal palsy, and in view Patient 4 was diagnosedCPA with indicates a cerebellopontine language angle; disorder IAC, and, internal although acoustic could canal; hear LR, well, lip scored reading; poorly L, on left; speech R, tests. right. She was delighted with her CI and used it d 1. 58 yr old, Patient Cause Ear Contralateral side CI 2. 82 yr old, 3. 79 yr old, 4. 61 yr old, 5. 65 yr old, of the fact that she had a left facial nerve schwannoma (and

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Copyright © 2013 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited. tlg ertlg,Vl 4 o ,2013 7, No. 34, Vol. Neurotology, & Otology AL. ET MUKHERJEE P. 1294 Copyright © 2013 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.

TABLE 2. Results of patients who were implanted following radiotherapy

Post operative (12 mo) Duration of Patient Cause Ear Contralateral side CI deafness Preoperative Without LR With LR 1. 44 yr old, male NF2 Left: 1.5 cm tumor irradiated Right: excised age 23, Cochlear Nucleus Unsure CUNY: 0% with LR No open set speech right facial paresis Freedom March 2009 and hearing aid discriminationVblind and hence unable to LR, some benefit day to day 2: 55 yr old, female NF2 Left: 1.3 cm tumor irradiated Right: excised 1990: Cochlear Nucleus 5 series, 8 yr Dead ears bilaterally, BKB in noise BKB live dead ear October 2010 L ear BKB with LR 46% 54%, BKB in voice with quiet 82% LRV100%, 3: 72 yr old, female NF2 Left: IAC tumor irradiated Right excised 1988: Cochlear Nucleus 2 yr Bilateral dead ears At 3 yr, gets environmental 1993 immediate loss of hearing dead ear July 1995 L ear sound only and facial paresis 4: 26 yr old, female NF2 Left: 19 mm irradiation in R VS: 3.5 cm excised 2008 Cochlear Nucleus 12 mo BKB: 0% BKB: 0% at BKB: 68% November 2009. September 2011 L ear. without LR 6mo at 6 mo Lost all hearing by December 2010. Also has 24 mm R parafalcine Left: BKB 20% Was normal preoperatively. meningioma and 3 further with LR Balance also affected posttreatment lesions one compressing the brainstem 5: 18 yr old, female NF2 Right: 2.3 cm tumor irradiated L VS: 5.4 cm, left facial R cochlear Nucleus 6 mo R preop- 8% BKB BKB, 0% at 36% at 6 mo May 2010: hearing deteriorated neuromaVmild facial Jan 2011 R ear with LR, 0% 6mo June 2010 weakness without LR 6: 20 yr old, female NF2 Left: 3.7 cm tumor irradiated - gamma R: VS and jug foramen CI: Cochlear nucleus 3 6 yr Bilateral dead ears Heard the dog bark but no knife in 2008Vtumor grew post schwannoma excised 2011 L ear speech discrimination. radiation 2005, 2006 with Tumor in cochlear a time of Failed device but patient residualV4.5 cm. OT but good electrical liked the benefit enough responses. to strongly want replacement device CPA indicates cerebellopontine angle; IAC, internal acoustic canal; L, left; R, right; VS, vestibular schwannoma. COCHLEAR IMPLANTS IN VESTIBULAR SCHWANNOMAS 1295 so it was expected that she may lose some facial nerve results, it made an important improvement in the patient’s function on that side in due course), the patient preferred quality of life. She was incredibly sensory deprived, and the radiation for her ipsilateral VS. Her left VS grew within 6 awareness of sound, although not enough to give her open months of the radiation for her right VS and she also de- set speech discrimination, made a dramatic difference to her veloped left facial nerve palsy, so she was assessed for re- life. This patient had the most advanced disease in this series. moval of her large Left VS and left facial nerve schwannoma. She was discussed in 2 separate specialized centers (of which, one is an ABI center) with a view to either implant DISCUSSION her with a cochlear implant on the ipsilateral side or an ABI following tumor removal on the contralateral ear. She Management of sporadic and NF2-associated VS has had a cochlear implant, and although she did not attain evolved over time with ‘‘wait and rescan,’’ an increasingly open set speech discrimination postoperatively, she became popular treatment option for stable tumors. This is largely a more proficient lip reader. Her BKB scores with lip read- due to better imaging, early detection, and increased aware- ing improved from 8% preoperatively to 36% postopera- ness of the growth patterns of these lesions (8), with some tively at 6 months. She subsequently underwent surgery for studies indicating that nearly two-thirds of tumors do not her contralateral tumors and did not require an ABI. grow (8). Studies also indicate that mean tumor growth Likewise,Patient4alsoimprovedherlipreadingscores. rates range from 1.2 to 1.9 mm per year, that NF2 tumors She had lost her ipsilateral hearing after radiation of a 19-mm exhibit a higher annual growth rate (9Y12), and that intra- VS. She had multiple intracranial tumors, and her contra- canalicular tumors do not exhibit significant growth com- lateral VS had been excised 3 years ago. She had a positive pared with tumors occupying the CPA (13). Within these, result on promontory stimulation preoperatively and was there is a higher probability of growth if the tumor exceeds implanted 2 years after radiation. Although she did not at- asizeofmorethan15to20mmintheCPA(13Y15). The tain open set speech scores, her BKB scores with lip reading 2 sporadic tumors in our series (tumor size intracanalicular improved from 20% to 68% at 6 months. and 1.2 cm at the CPA) were considered extremely unlikely Despite the fact that 5 of 6 patients did not attain open to grow beyond 2 years of observation for this reason. set speech discrimination, all patients found their implants useful and were daily users. One patient had device failure (Patient 6, Table 2). She was a 20-year-old woman with a Sporadic Tumors Affecting the Only Hearing Ear left-sided 3.7-cm tumor. Her tumor was irradiated 4 years Sporadic VS with a bilateral profound loss, which is long ago. A component of it had grown after irradiation but had standing on the contralateral side creates a serious handi- then stabilized and had remained so. She was awaiting re- cap. A high proportion of tumors are stable, whereas some moval of a contralateral jugular foramen schwannoma and others may be stabilized with radiotherapy. These patients, 4.5-cm VS, which had recurred after a previous surgery. who do not progress to surgical intervention for their tu- She already had nerve palsies of Cranial Nerves VII to X mors therefore, are not candidates for an ABI. If they have and XII on this contralateral side. She was blind on this side no aidable hearing remaining, this group of patients has (right) and slowly developing blindness in her left eye sec- no options for hearing rehabilitation apart from a cochlear ondary to pressure effects of her right CPA tumors. Because implant. This then creates debate over which side should her left-sided facial and lower cranial nerves were the only be implanted, the tumor-free side that has been deaf over functioning side, as her left eye was the only seeing eye, a prolonged period or the side experiencing recent hear- her left-sided tumor had been treated with radiotherapy, ing loss but is occupied with tumor. In our series, 1 patient although it was on the larger side for radiation. This had pre- was implanted in the nontumor side first. However, she served the function of the cranial nerves on that side while did poorly on that side and required implantation on the stabilizing the tumor and her management decision largely tumor-affected side. This is supported by historical data involved further surgery to the right-sided lesions. Given (7). Thus, the presence of an untreated VS is not a contra- the degree of brainstem distortion caused by the size of the indication for CI and provides new options for hearing tumors and particularly because this would be her third ope- rehabilitation with limited morbidity, to this subgroup of ration on that side, the successful placement of an ABI would patients who would otherwise have no other options. be difficult. Her management rationale was the same as Patient 5. After discussion in 2 independent centers, she had a left-sided CI insertion (her left-sided tumor was stable) Patients Affected With NF2 before her right-sided tumor removal. During operation In NF2, treatment decisions are more complex. With forcochlear implantation, it was noted that she had intraco- treatment of the first side, controversy surrounds the options chlear tumor, although this was unable to be visualized on the of ‘‘wait and rescan’’ versus treating small tumors with preoperative MRI scan. She had good electrical responses hearing preservation surgery (2). Treatment of the second preoperatively. She derived no open set speech discrimi- side is usually advocated if there is hearing deterioration nation from her CI but was able to hear the dog bark. She or tumor enlargement and depends also on the hearing found this very useful, and although her device failed, she status of the first side (2,4). strongly wanted the device replaced. Thus, although the NF2 patients form a spectrum in terms of their com- outcome of her CI was unquantifiable in terms of hearing plexity in managing their hearing. On one hand, some

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Copyright © 2013 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited. 1296 P. MUKHERJEE ET AL. patients have small stable tumors, which do not require from the disease itself to then apply it to the effect of dif- active treatment. On the other end of the spectrum are ferent treatment variables. Hearing in VS may be lost be- patients who are incredibly complex, have multiple co- cause of either cochlear ischemia or infarction. Alternatively, morbidities, large tumor bulk, and multiple intracranial it may also be due to impairment of the cochlear nerve, and for tumors. They are increasingly sensory deprived, with pa- larger tumors, it may be due to effects on brainstem. It may tients being blind and immobile as well as deaf and thereby also be due to a combination of some or all of these factors. can feel isolated from the world. This is more so the case Moreover, position of different tumors may be associated in patients who are diagnosed in a pediatric age group. with different outcomes, such as a tumor, although small, if Many articles have reported that the most important pre- widening the IAC or extending into the cochlea through the dictors of disease severity in NF2 are age at diagnosis and habenula perforata may predispose the cochlear nerve to age at onset of symptoms (16Y19). more trauma through pressure or devascularization and, al- Regardless of where the individual patient lies on the though small, may pose a worse outcome from a CI. spectrum, if their tumor does not require surgical interven- In our study, there was quite a degree of heterogeneity tion, CI offers them hearing rehabilitation without the need within the individual groups as well as between the 2 groups, for an intracranial procedure. ABI surgery carries higher not only relating to differing cause of hearing loss but also surgical risks and morbidity (20), and in comparison, CI related to age difference in between patients, duration of in many centers involves day case surgery (5). Moreover, deafness, and different implants used. Those affected with having a CI does not preclude the opportunity for future NF2 had different degrees of severity of disease and, there- ABI placement if required. fore, differing comorbidities, which were additional confounding factors in the hearing outcome of CI. Because of Factors Influencing Outcomes With CI the presence of so many confounding factors, it was ex- In our study, all patients who were implanted with no tremely difficult to subject these data to statistical analysis, treatment to their tumors received significant benefit and and only observations regarding trends could be made. were daily CI users. In the group of patients who were im- Promontory stimulation using the golf club electrode may planted after having radiotherapy, only 1 of 6 patients re- provide some prognostic information about the integrity of ceived open set speech discrimination. It is likely that this the pathway and the likelihood of success. This was cer- is because of advanced disease in these patients. Certainly, tainly used in some of the cases, and a positive promontory 3 of 6 patients who had presented in a pediatric age group stimulation helped in the decision-making process to pro- had large tumors, and one even had intracochlear tumor seen ceed with implantation. Although there is much contro- at the time of operation. versy about the role and value of this test (25), promontory It is worthy to note that 3 patients lost their hearing after stimulation in our patients using the golf club electrode radiotherapy. However, it was not possible to document the played a small but important role to aid the clinician and dosage of radiation to each tumor and in particular note the the patient in what was sometimes a difficult decision- dosage of radiation exposure to the cochlea. The patients making and counseling process about CI candidacy. came from different units, and each of these patients went A criticism of cochlear implantation in the setting of to different remote centers to have the radiation treatment. vestibular schwannoma is follow-up imaging that is re- No information about their radiation was available at the quired for their tumors. Where MRI is the gold standard, centers, and there were some significant logistical limitations some patients can be continued to be followed up for their to accessing this retrospective data. There were not enough tumor size with a CT scan. If the patient requires an MRI, data, therefore, in this current article to derive conclusive ex- it has been the experience of the centers participating in this planations of the reason of hearing loss after radiotherapy, study that adequate images are able to be attained with an although some temporal bone studies have shown loss of MRI scanner with 1.5 T magnet strength (Fig. 1). There is, spiral ganglion cells after stereotactic radiotherapy (21). however, an artifact, and some patients experience discom- Likewise, studies evaluating the effect of hearing loss after fort at the site of the speech processor, requiring local an- gamma knife (22) found that a change in PTA was signifi- esthetic at the site before imaging (26). There may be some cantly poor at 12 months in patients whose cochlea received limited morbidity associated with this area in some patients, doses of 4.75 Gy or more. Linskey et al. (23) found a mean although if general precautions are taken, these can largely absorption of 5.5 Gy at the inferior portion of the basal turn minimized (26). Alternatively, a device without a magnet and 8.9 Gy at the modiolus of the basal turn after gamma can be used. knife treatment for vestibular schwannoma. Wakym et al. None of the units participating in this current study had (24) found that the pattern of hearing loss was most con- any patients where surgery to the tumor was required on the sistent with cochlear damage as opposed to neural dam- implanted side. We were therefore unable to collect any data age. Nevertheless, the effects of radiotherapy on hearing or make any experience-based comments about the out- and its effect on cochlear implantation needs to be further come of subtotal removal or cochlear nerve preservation studied and perhaps as we acquire more patients who have surgery and CI. Successful results of CI with cochlear nerve been implanted without treatment, further comparisons preservation surgery has already been reported (3), and with can be made. many units now performing subtotal or near-total removal In any case, this is a difficult area to study because we of VS (in preference to preserving facial nerve function), need to first understand the mechanism of hearing loss it is possible that future directions of implantation in these

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FIG. 1. T1-weighted images with gadolinium in a 1.5 Tesla magnet MRI scanner of bilateral vestibular schwannomas after right cochlear implantation. Images A to D progress consecutively from the midbrain to the cerebellopontine angle. patients may reveal promising results. From our experience, may be more advantages in cochlear implantation as opposed however, we are able to observe that a vestibular schwannoma to an ABI, given the lower surgical risk and that the former is not an absolute contraindication for cochlear implantation. does not preclude the future possibility of the latter. The benefits noticed from the observations made from this study has moved the management paradigm of the units involved CONCLUSION for considering CI as a treatment option at a much earlier stage in the planning and also considering it in preference Although there is a great variability in terms of disease for an ABI. spectrum and, therefore, confounding factors in our patients, REFERENCES it was apparent that if the vestibular schwannoma was small and did not require treatment, cochlear implantation can 1. Otto SR, Brackmann DE, Hitselberger WE, Shannon RV, Kuchta J. attain good hearing results in the setting of NF2 or sporadic Multichannel auditory brainstem implant: update on performance in lesions despite the presence of tumor. If the tumor requires 61 patients. J Neurosurg 2002;96:1063Y71. 2. Trotter M, Briggs R. Cochlear implantation in NF2 after radiation radiotherapy, then the patients may still benefit from co- therapy. Otology & Neurotology 2010;31:216Y9. chlear implantation, although their outcome is more vari- 3. Neff B, Wiet M, Lasak J, et al. Cochlear implant in the NF2 patient: able. Patients with very aggressive disease are less likely to long term follow up. Laryngoscope 2007;117:1069Y72. attain open set speech discrimination, and their outcome 4. Lustig L, Yeagle J, Driscoll C, Blevins N, Francis H, Niparko J. measure may be better evaluated by a quality-of-life study. Cochlear implant in NF2 and bilateral vestibular schwannoma. Otol Neurotol 2006;27:512Y18. Most importantly, in this subgroup of patients who require 5. Vincenti V, Pasanisi E, Guida M, Di Trapani G, Sanna M. Hearing no surgical intervention for their tumor, cochlear implan- rehabilitation in neurofibromatosis type 2 patients: cochlear versus tation provides new hope for hearing rehabilitation. There auditory brainstem implantation. Audiol Neurotol 2008;14:273Y80.

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6. Helbig S, Rader T, Bahmer A, Baumann U. A case of bilateral co- noma growth in patients with neurofibromatosis type 2. J Neurosurg chlear implantation in single sided untreated acoustic neuroma. Acta 2002;96:217Y22. Otolaryngol 2009;129:694Y96. 18. Mautner VF, Baser ME, Thakkar SD, Feigen UM, Friedman JM, 7. Ramsden R, Khwaja S, Green K, O-Driscoll M, Mawman D. Ves- Kluwe L. Vestibular schwannoma growth in patients with neurofi- tibular schwannoma in only hearing ear: CI or ABI? Otol Neurotol bromatosis type 2: a longitudinal study. J Neurosurg 2002;96:223Y8. 2005;26:261Y4. 19. Otsuka G, Saito K, Nagatani T, Yoshida J. Age at symptom onset 8. Suryanarayan R, Ramsden R, Saeed S, et al. Vestibular schwannoma: and long-term survival in patients with neurofirmatosis type 2. J role of conservative management. J Laryngol Otol 2010;124:251Y57. Neurosurg 2003;99:480Y3. 9. Yoshimoto Y. Systematic review of the natural history of Vestibular 20. Celis-Aguilar E, Lassaletta L, Gavilan J. Cochlear implantation in Schwannoma. J Neurosurgery 2005;103:59Y63. patients with neurofibromatosis type 2 and patients with vestibular 10. Selesnick HS, Johnson G. Radiologic surveillance of acoustic neu- schwannoma in the only hearing ear. Int J Otolaryngol 2012;2012: romas. Am J Otol 1998;19:846Y9. 157497. 11. Smouha EE, Yoo M, Mohr K, Davis RP. Conservative management 21. Hoistad DL, Ondrew C, Mutlu P, Schachern M, Paparella M, of acoustic neuroma: a meta-analysis and proposed treatment algo- Adams GL. Histopathology of huma temporal bone after cis-platinum, rithm. Laryngoscope 2005;115:450Y4. radiation or both. Otolaryngol Head Neck Surg 1998;118:825Y32. 12. Yamakami I, Uchino Y, Kobayashi E, Yamaura A. Conservative man- 22. Lasak JM, Klish D, Kryzer TC, Hearn C, Gorecki JP, Rine GP. agement, gamma-knife radiosurgery and microsurgery for acoustic Gamma Knife radiosurgery for vestibular schwannoma: early hearing neurinomas: a systematic review of outcome and risk of three thera- outcomes and evaluation of the cochlear dose. Otol Neurotol 2008;29: peutic options. Neurol Res 2003;25:682Y90. 1179Y86. 13. Suryanarayanan R, Lesser THJ. Growth rate of vestibular of vestibular 23. Linskey ME, Johnstone PAS, O’Leary M, Goetsch S. Radiation ex- schwannoma Y what the literature tells us. Otorhinolaryngologist 2007; posure of normal temporal bone structures during stereotactic guided 1:66Y71. gamma knife surgery for vestibular schwannomas. J Neurosurg 2003; 14. Fucci MJ, Buchman CA, Brackmann DE, Berliner KI. Acoustic 98:800Y6. tumour growth: implications for treatment choices. Am J Otol 1999; 24. Wackym A, Runge-Samuelson CL, Nash JJ, et al. Gamma knife 20:495Y9. surgery of vestibular schwannomas: volumetric dosimetry correla- 15. Martin TPC, Tzifa K, Kowalski C, Holder RL, Walsh R, Irving RM. tions to hearing loss suggest stria vascularis devascularisation as a Conservative versus primary surgical treatment of acoustic neuro- mechanism of early hearing loss. Otol Neurotol 2010;31:1480Y87. mas: a comparison of rates of facial nerve and hearing preservation. 25. Kuo SC, Gibson WPR. The role of the promontory stimulation test Clin Otolaryngol 2008;33:228Y35. in cochlear implantation. Cochlear Implants Int 2002;3:19Y28. 16. Mac Nally S, Rutherford S, King A, et al. Outcome from surgery for 26. Tam YC, Graves MJ, Black RT, et al. Magnetic resonance imaging vestibular schwannomas in children. Br J Neurosurg 2009;23:226Y31. in patients with cochlear implants and auditory brainstem implants. 17. Baser ME, Makariou EV, Parry DM. Predictors of vestibular schwan- Cochlear Implants Int 2010;11:48Y51.

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