Contemporary Surgical Management of Vestibular Schwannomas: Analysis of Complications and Lessons Learned Over the Past Decade

Abstract BACKGROUND: Despite advanced microsurgical techniques, more refined instrumentation, and expert team management, there is still a significant incidence of complications in vestibular schwannoma surgery. OBJECTIVE: To analyze complications from the microsurgical treatment of vestibular schwannoma by an expert surgical team and to propose strategies for minimizing such complications. METHODS: Surgical outcomes and complications were evaluated in a consecutive series of 410 unilateral vestibular schwannomas treated from 2000 to 2009. Clinical status and complications were assessed postoperatively (within 7 days) and at the time of follow-up (range, 1–116 months; mean, 32.7 months). RESULTS: Follow-up data were available for 357 of the 410 patients (87.1%). Microsurgical tumor resection was performed through a retrosigmoid approach in 70.7% of cases. Thirty-three patients (8%) had intrameatal tumors and 204 (49.8%) had tumors that were <20 mm. Gross total resection was performed in 306 patients (74.6%). Hearing preservation surgery was attempted in 170 patients with tumors <20 mm, and good hearing was preserved in 74.1%. The main neurological complication was facial palsy (House-Brackmann grade III-VI), observed in 14% of patients (56 cases) postoperatively; however, 59% of them improved during the follow-up period. Other neurological complications were disequilibrium in 6.3%, facial numbness in 2.2%, and lower cranial nerve deficit in 0.5%. Nonneurological complications included cerebrospinal fluid leaks in 7.6%, wound infection in 2.2%, and meningitis in 1.7%. CONCLUSION: Many of these complications are avoidable through further refinement of operative technique, and strategies for avoiding complications are proposed.

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Emerging Indications for Fractionated Gamma Knife Radiosurgery

Neurosurgery ◽

10.1227/neu.0000000000001227 ◽

2017 ◽

Vol 80 (2) ◽

pp. 210-216 ◽

Cited By ~ 31

Author(s):

Emory McTyre ◽

Corbin A. Helis ◽

Michael Farris ◽

Lisa Wilkins ◽

Darrell Sloan ◽

...

Keyword(s):

Gamma Knife ◽

Vestibular Schwannoma ◽

Gamma Knife Radiosurgery ◽

Hearing Preservation ◽

Vestibular Schwannomas ◽

Previously Treated ◽

Immobilization Device ◽

Gamma Knife Perfexion ◽

High Degree

Abstract BACKGROUND: Gamma Knife radiosurgery (GKRS) allows for the treatment of intracranial tumors with a high degree of dose conformality and precision. There are, however, certain situations wherein the dose conformality of GKRS is desired, but single-session treatment is contraindicated. In these situations, a traditional pin-based GKRS head frame cannot be used, because it precludes fractionated treatment. OBJECTIVE: To report our experience in treating patients with fractionated GKRS using a relocatable, noninvasive immobilization system. METHODS: Patients were considered candidates for fractionated GKRS if they had 1 or more of the following indications: a benign tumor >10 cc in volume or abutting the optic pathway, a vestibular schwannoma with the intent of hearing preservation, or a tumor previously irradiated with single-fraction GKRS. The immobilization device used for all patients was the Extend system (Leksell Gamma Knife Perfexion, Elekta, Kungstensgatan, Stockholm). RESULTS: We identified 34 patients treated with fractionated GKRS between August 2013 and February 2015. There were a total of 37 tumors treated including 15 meningiomas, 11 pituitary adenomas, 6 brain metastases, 4 vestibular schwannomas, and 1 hemangioma. At last follow-up, all 21 patients treated for perioptic tumors had stable or improved vision and all 4 patients treated for vestibular schwannoma maintained serviceable hearing. No severe adverse events were reported. CONCLUSION: Fractionated GKRS was well tolerated in the treatment of large meningiomas, perioptic tumors, vestibular schwannomas with intent of hearing preservation, and reirradiation of previously treated tumors.

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HEARING PRESERVATION AFTER INTRACANALICULAR VESTIBULAR SCHWANNOMA RADIOSURGERY

Neurosurgery ◽

10.1227/01.neu.0000335783.70079.85 ◽

2008 ◽

Vol 63 (6) ◽

pp. 1054-1063 ◽

Cited By ~ 60

Author(s):

Ajay Niranjan ◽

David Mathieu ◽

John C. Flickinger ◽

Douglas Kondziolka ◽

L. Dade Lunsford

Keyword(s):

American Academy ◽

Head And Neck ◽

Vestibular Schwannoma ◽

Tumor Resection ◽

Hearing Preservation ◽

Neck Surgery ◽

Head And Neck Surgery ◽

Tumor Control ◽

Gamma Knife Stereotactic Radiosurgery

Abstract OBJECTIVE Tumor control, facial function preservation, and hearing preservation are important criteria for successful management of intracanalicular vestibular schwannomas, whether observation, microsurgery, or radiosurgery is chosen. We collected data prospectively to assess hearing preservation after intracanalicular vestibular schwannoma radiosurgery. METHODS Between 1987 and 2003, 96 patients (65 men and 31 women) underwent gamma knife stereotactic radiosurgery (SRS) for intracanalicular tumors. The median patient age was 54 years (range, 22–80 years). Hearing was graded using the Gardner-Robertson (GR) and the American Academy of Otolaryngology–Head and Neck Surgery classifications. Dose planning was performed on intraoperative stereotactic images using multiple 4-mm isocenters. The median tumor volume was 0.112 mm3 (range, 0.05–0.447 mm3), and the median margin dose was 13 Gy (range, 10–18 Gy). RESULTS The mean and median audiologic follow-up periods were 42 months and 28 months (range, 12–144 months), respectively. Serviceable hearing was preserved in 31 of 40 (77.5%) patients with initial American Academy of Otolaryngology–Head and Neck Surgery Class A hearing. Serviceable hearing was preserved in 40 of 79 (64.5%) patients with GR Grade I or II pre-SRS hearing. Ninety-two patients had GR Grade I, II, or III hearing before SRS, and GR Grade I, II, or III hearing was maintained in 78 patients (85%). Hearing grades improved in 7 patients. Facial and trigeminal nerve function was preserved in all patients. The tumor control rate (freedom from additional intervention) was 99.0% (95 of 96) at a median follow-up of 28 months (range, 12–144 months). One patient underwent tumor resection 18 months after radiosurgery. CONCLUSION SRS is a minimally invasive first-line management option for patients with intracanalicular tumors and provides high rates of hearing preservation with minimal morbidity.

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Diamond knife dissection technique for nerve preservation during resection of large vestibular schwannomas

Neurosurgical Focus: Video ◽

10.3171/2021.7.focvid21104 ◽

2021 ◽

Vol 5 (2) ◽

pp. V8

Author(s):

Julia Shawarba ◽

Cand Med ◽

Matthias Tomschik ◽

Karl Roessler

Keyword(s):

Vestibular Schwannoma ◽

Facial Nerve Palsy ◽

Hearing Preservation ◽

Vestibular Schwannomas ◽

Nerve Preservation ◽

Dissection Techniques ◽

Dissection Technique ◽

Large Vestibular Schwannoma ◽

Facial Function ◽

Diamond Knife

Facial and cochlear nerve preservation in large vestibular schwannomas is a major challenge. Bimanual pincers or plate-knife dissection techniques have been described as crucial for nerve preservation. The authors demonstrate a recently applied diamond knife dissection technique to peel the nerves from the tumor capsule. This technique minimizes the nerve trauma significantly, and complete resection of a large vestibular schwannoma without any facial nerve palsy and hearing preservation is possible. The authors illustrate this technique during surgery of a 2.6-cm vestibular schwannoma in a 27-year-old male patient resulting in normal facial function and preserved hearing postoperatively. The video can be found here: https://stream.cadmore.media/r10.3171/2021.7.FOCVID21104

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Microsurgery for vestibular schwannoma after Gamma Knife surgery: challenges and treatment strategies

Journal of Neurosurgery ◽

10.3171/2014.8.gks141312 ◽

2014 ◽

Vol 121 (Suppl_2) ◽

pp. 150-159 ◽

Cited By ~ 10

Author(s):

Cheng-Chia Lee ◽

Hsiu-Mei Wu ◽

Wen-Yuh Chung ◽

Ching-Jen Chen ◽

David Hung-Chi Pan ◽

...

Keyword(s):

Gamma Knife ◽

Vestibular Schwannoma ◽

Radiation Effects ◽

Tumor Resection ◽

Treatment Strategies ◽

Gamma Knife Surgery ◽

Neurological Outcomes ◽

Radiological Changes ◽

Cyst Development

ObjectResection of vestibular schwannoma (VS) after Gamma Knife surgery (GKS) is infrequently performed. The goals of this study were to analyze and discuss the neurological outcomes and technical challenges of VS resection and to explore strategies for treating tumors that progress after GKS.MethodsIn total, 708 patients with VS underwent GKS between 1993 and 2012 at Taipei Veterans General Hospital. The post-GKS clinical courses, neurological presentations, and radiological changes in these patients were analyzed. Six hundred patients with imaging follow-up of at least 1 year after GKS treatment were included in this study.ResultsThirteen patients (2.2%) underwent microsurgery on average 36.8 months (range 3–107 months) after GKS. The indications for the surgery included symptomatic adverse radiation effects (in 4 patients), tumor progression (in 6), and cyst development (in 3). No morbidity or death as a result of the surgery was observed. At the last follow-up evaluation, all patients, except 1 patient with a malignant tumor, had stable or near-normal facial function.ConclusionsFor the few VS cases that require resection after radiosurgery, maximal tumor resection can be achieved with modern skull-based techniques and refined neuromonitoring without affecting facial nerve function.

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Hearing Preservation Using the Middle Fossa Approach for the Treatment of Vestibular Schwannoma

Neurosurgery ◽

10.1227/neu.0b013e31823110f1 ◽

2011 ◽

Vol 70 (2) ◽

pp. 334-341 ◽

Cited By ~ 26

Author(s):

Joe Walter Kutz ◽

Tyler Scoresby ◽

Brandon Isaacson ◽

Bruce E. Mickey ◽

Christopher J. Madden ◽

...

Keyword(s):

Facial Nerve ◽

Vestibular Schwannoma ◽

Academic Medical Center ◽

Hearing Preservation ◽

Middle Fossa ◽

Middle Fossa Approach ◽

Class A ◽

Facial Function ◽

Grade Iii

Abstract BACKGROUND: The incidence of small vestibular schwannomas in patients with serviceable hearing is increasing because of the widespread use of MRI. The middle fossa approach provides the patient with an opportunity for tumor removal with hearing preservation. OBJECTIVE: To determine the rate of hearing preservation and facial nerve outcomes after removal of a vestibular schwannoma with the use of the middle fossa approach. METHODS: A retrospective case review at a tertiary, academic medical center was performed identifying patients from 1998 through 2008 that underwent removal of a vestibular schwannoma by the middle fossa approach. Preoperative and postoperative audiograms were compared to determine hearing preservation rates. In addition, facial nerve outcomes at last follow-up were recorded. RESULTS: Forty-six patients underwent a middle fossa craniotomy for the removal of a vestibular schwannoma. Of the 38 patients that had class A or class B hearing preoperatively, 24 (63.2%) retained class A or B hearing and 29 (76.3%) retained class A, B, or C hearing. When tumors were 10 mm or less in patients with class A or B preoperative hearing, 22 of 30 patients (73.3%) retained class A or B hearing. When the tumor size was greater than 10 mm in patients with class A or B preoperative hearing, 2 of 8 patients (25%) retained class A or B hearing. At most recent follow-up, 76.1% of patients had House-Brackmann grade I facial function, 13.0% had House-Brackmann grade II facial function, and 10.9% had House-Brackmann grade III facial function. CONCLUSION: Hearing preservation rates are excellent using the middle fossa approach, especially for smaller tumors. No patient experienced long-term facial nerve function worse than House-Brackmann grade III.

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Hearing preservation in patients with vestibular schwannoma treated with Gamma Knife surgery

Journal of Neurosurgery ◽

10.3171/2012.10.jns12880 ◽

2013 ◽

Vol 118 (3) ◽

pp. 571-578 ◽

Cited By ~ 40

Author(s):

Andrew M. Baschnagel ◽

Peter Y. Chen ◽

Dennis Bojrab ◽

Daniel Pieper ◽

Jack Kartush ◽

...

Keyword(s):

Hearing Loss ◽

Gamma Knife ◽

Vestibular Schwannoma ◽

Hearing Preservation ◽

Gamma Knife Surgery ◽

Speech Discrimination ◽

Before And After ◽

Nerve Dysfunction ◽

Preservation Rate

Object Hearing loss after Gamma Knife surgery (GKS) in patients with vestibular schwannoma has been associated with radiation dose to the cochlea. The purpose of this study was to evaluate serviceable hearing preservation in patients with VS who were treated with GKS and to determine if serviceable hearing loss can be correlated with the dose to the cochlea. Methods Forty patients with vestibular schwannoma with serviceable hearing were treated using GKS with a median marginal dose of 12.5 Gy (range 12.5–13 Gy) to the 50% isodose volume. Audiometry was performed prospectively before and after GKS at 1, 3, and 6 months, and then every 6 months thereafter. Hearing preservation was based on pure tone average (PTA) and speech discrimination (SD). Serviceable hearing was defined as PTA less than 50 dB and SD greater than 50%. Results The median cochlear maximum and mean doses were 6.9 Gy (range 1.6–16 Gy) and 2.7 Gy (range 0.7–5.0 Gy), respectively. With a median audiological follow-up of 35 months (range 6–58 months), the 1-, 2-, and 3-year actuarial rates of maintaining serviceable hearing were 93%, 77%, and 74%, respectively. No patient who received a mean cochlear dose less than 2 Gy experienced serviceable hearing loss (p = 0.035). Patients who received a mean cochlear dose less than 3 Gy had a 2-year hearing preservation rate of 91% compared with 59% in those who received a mean cochlear dose of 3 Gy or greater (p = 0.029). Those who had more than 25% of their cochlea receiving 3 Gy or greater had a higher rate of hearing loss (p = 0.030). There was no statistically significant correlation between serviceable hearing loss and age, tumor size, pre-GKS PTA, pre-GKS SD, pre-GKS Gardner-Robertson class, maximum cochlear dose, or the percentage of cochlear volume receiving 5 Gy. On multivariate analysis there was a trend toward significance for serviceable hearing loss with a mean cochlear dose of 3 Gy or greater (p = 0.074). Local control was 100% at 24 months. No patient developed facial or trigeminal nerve dysfunction. Conclusions With a median mean cochlear dose of 2.7 Gy, the majority of patients with serviceable hearing retained serviceable hearing 3 years after GKS. A mean cochlear dose less than 3 Gy was associated with higher serviceable hearing preservation.

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Stereotactic radiosurgery for vestibular schwannomas: average 10-year follow-up results focusing on long-term hearing preservation

Journal of Neurosurgery ◽

10.3171/2016.7.gks161494 ◽

2016 ◽

Vol 125 (Supplement_1) ◽

pp. 64-72 ◽

Cited By ~ 34

Author(s):

Shinya Watanabe ◽

Masaaki Yamamoto ◽

Takuya Kawabe ◽

Takao Koiso ◽

Tetsuya Yamamoto ◽

...

Keyword(s):

Stereotactic Radiosurgery ◽

Tumor Volume ◽

Hearing Preservation ◽

Interquartile Range ◽

Vestibular Schwannomas ◽

Long Term Results ◽

Tumor Control ◽

Univariable Analysis

OBJECTIVEThe aim of this study was to reappraise long-term treatment outcomes of stereotactic radiosurgery (SRS) for vestibular schwannomas (VSs). The authors used a database that included patients who underwent SRS with a unique dose-planning technique, i.e., partial tumor coverage designed to avoid excess irradiation of the facial and cochlear nerves, focusing on tumor control and hearing preservation. Clinical factors associated with post-SRS tumor control and long-term hearing preservation were also analyzed.METHODSThis institutional review board–approved, retrospective cohort study used the authors' prospectively accumulated database. Among 207 patients who underwent Gamma Knife SRS for VSs between 1990 and 2005, 183 (who were followed up for at least 36 post-SRS months) were studied. The median tumor volume was 2.0 cm3 (range 0.05–26.2 cm3). The median prescribed dose at the tumor periphery was 12.0 Gy (range 8.8–15.0 Gy; 12.0 Gy was used in 171 patients [93%]), whereas tumor portions facing the facial and cochlear nerves were irradiated with 10.0 Gy. As a result, 72%–99% of each tumor was irradiated with the prescribed dose. The mean cochlear doses ranged from 2.3 to 5.7 Gy (median 4.1 Gy).RESULTSThe median durations of imaging and audiometric follow-up were 114 months (interquartile range 73–144 months) and 59 months (interquartile range 33–109 months), respectively. Tumor shrinkage was documented in 110 (61%), no change in 48 (27%), and enlargement in the other 22 (12%) patients. A further procedure (FP) was required in 15 (8%) patients. Thus, the tumor growth control rate was 88% and the clinical control rate (i.e., no need for an FP) was 92%. The cumulative FP-free rates were 96%, 93%, and 87% at the 60th, 120th, and 180th post-SRS month, respectively. Six (3%) patients experienced facial pain, and 2 developed transient facial palsy. Serviceable hearing was defined as a pure tone audiogram result better than 50 dB. Among the 66 patients with serviceable hearing before SRS who were followed up, hearing acuity was preserved in 23 (35%). Actuarial serviceable hearing preservation rates were 49%, 24%, and 12% at the 60th, 120th, and 180th post-SRS month, respectively. On univariable analysis, only cystic-type tumor (HR 3.36, 95% CI 1.18–9.36; p = 0.02) was shown to have a significantly unfavorable association with FP. Multivariable analysis followed by univariable analysis revealed that higher age (≥ 65 years: HR 2.66, 95% CI 1.16–5.92; p = 0.02), larger tumor volume (≥ 8 cm3: HR 5.36, 95% CI 1.20–17.4; p = 0.03), and higher cochlear dose (mean cochlear dose > 4.2 Gy: HR 2.22, 95% CI 1.07–4.77; p = 0.03) were unfavorable factors for hearing preservation.CONCLUSIONSStereotactic radiosurgery achieved good long-term results in this series. Tumor control was acceptable, and there were few serious complications in patients with small- to medium-sized VSs. Unfortunately, hearing preservation was not satisfactory. However, the longer the observation period, the more important it becomes to compare post-SRS hearing decreases with the natural decline in untreated cases.

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Radiosurgery for Acoustic Neuromas: Results of Low-dose Treatment

Neurosurgery ◽

10.1227/01.neu.0000073416.22608.b3 ◽

2003 ◽

Vol 53 (2) ◽

pp. 282-288 ◽

Cited By ~ 116

Author(s):

Yoshiyasu Iwai ◽

Kazuhiro Yamanaka ◽

Masato Shiotani ◽

Taichi Uyama

Keyword(s):

Tumor Growth ◽

Low Dose ◽

Tumor Resection ◽

Gamma Knife Radiosurgery ◽

Growth Control ◽

Hearing Preservation ◽

Trigeminal Neuropathy ◽

Tumor Margin ◽

Acoustic Neuromas

Abstract OBJECTIVE The results of radiosurgical treatment of acoustic neuromas have improved by reducing the tumor marginal doses. We report relatively long-term follow-up results (>5 yr) for patients who underwent low-dose radiosurgery. METHODS We treated and followed 51 consecutive patients with unilateral acoustic neuromas who were treated from January 1994 to December 1996 by gamma knife radiosurgery at low doses (≤12 Gy to the tumor margin). The average age of the patients was 55 years (range, 32–76 yr). The treatment volume was 0.7 to 24.9 cm3 (median, 3.6 cm3). The marginal radiation dose was 8 to 12 Gy (median, 12 Gy), and the follow-up period ranged from 18 to 96 months (median, 60 mo). RESULTS Clinical tumor growth control (without tumor resection) was achieved in 96% of patients, and the 5-year tumor growth control rate was 92%. Hearing was preserved in 59% of those with preradiosurgical hearing preservation (Gardner-Robertson Classes 1–4), and improvements (>20 dB of improvement) were noted in 9% of the patients with any hearing. Hearing was preserved at a useful level (Gardner-Robertson Classes 1 and 2) in 56% of patients. Although preexisting trigeminal neuropathy worsened in 4% of the patients, our patients did not experience new facial palsies or trigeminal neuropathies after radiosurgery. Facial spasm occurred in 6% of the patients, and intratumoral bleeding occurred in 4% of patients. CONCLUSION Low-dose radiosurgery (≤12 Gy at the tumor margin) can achieve a high tumor growth control rate and maintain low postradiosurgical morbidity (including hearing preservation) for acoustic neuromas.

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Facial Nerve Outcomes After Vestibular Schwannoma Microsurgical Resection in Neurofibromatosis Type 2

Otolaryngology ◽

10.1177/0194599820954144 ◽

2020 ◽

pp. 019459982095414

Author(s):

Catherine Sobieski ◽

Daniel E. Killeen ◽

Samuel L. Barnett ◽

Bruce E. Mickey ◽

Jacob B. Hunter ◽

...

Keyword(s):

Facial Nerve ◽

Vestibular Schwannoma ◽

Tumor Volume ◽

Tumor Resection ◽

Neurofibromatosis Type ◽

Neurofibromatosis Type 2 ◽

Tumor Diameter ◽

Microsurgical Resection

Objective The aim of this study is to investigate facial nerve outcomes after microsurgical resection in neurofibromatosis type 2 (NF2) compared to sporadic tumors. Study Design Single institutional retrospective chart review. Setting Tertiary referral center. Methods All adult patients with NF2 vestibular schwannoma (VS) or sporadic VS who underwent microsurgical resection from 2008 to 2019 with preoperative magnetic resonance imaging (MRI) and 1 year of postsurgical follow-up were included. The primary outcome measure was postoperative House-Brackmann (HB) facial nerve score measured at first postoperative visit and after at least 10 months. Results In total, 161 sporadic VSs and 14 NF2 VSs met inclusion criteria. Both median tumor diameter (NF2, 33.5 mm vs sporadic, 24 mm, P = .0011) and median tumor volume (NF2, 12.4 cm3 vs sporadic, 2.9 cm3, P = .0005) were significantly greater in patients with NF2. The median follow-up was 24.9 months (range, 12-130.1). Median facial nerve function after 1 year for patients with NF2 was HB 3 (range, 1-6) compared to HB 1 (range, 1-6) for sporadic VS ( P = .001). With multivariate logistic regression, NF2 tumors (odds ratio [OR] = 13.9, P = .001) and tumor volume ≥3 cm3 (OR = 3.6, P = .025) were significantly associated with HB ≥3 when controlling for age, sex, extent of tumor resection, translabyrinthine approach, and prior radiation. Conclusion Tumor volume >3 cm3 and NF2 tumors are associated with poorer facial nerve outcomes 1 year following microsurgical resection.

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Microsurgical Treatment and Follow-Up of KOOS Grade IV Vestibular Schwannoma: Therapeutic Concept and Future Perspective

Frontiers in Oncology ◽

10.3389/fonc.2020.605137 ◽

2020 ◽

Vol 10 ◽

Author(s):

Sae-Yeon Won ◽

Andreas Kilian ◽

Daniel Dubinski ◽

Florian Gessler ◽

Nazife Dinc ◽

...

Keyword(s):

Tumor Progression ◽

Vestibular Schwannoma ◽

Tumor Resection ◽

Residual Tumor ◽

High Rate ◽

Future Perspective ◽

Nerve Function ◽

Repeat Surgery ◽

Therapeutic Concept

PurposeSurgery of KOOS IV vestibular schwannoma remains challenging regarding the balance of extent of tumor resection (EoR) and functional outcome. Our aim was to evaluate the outcome of surgical resection and define a cut-off value for safe resection with low risk for tumor regrowth of KOOS IV vestibular schwannoma.MethodsAll patients presenting at the authors’ institution between 2000 and 2019 with surgically treated KOOS IV vestibular schwannoma were included. Outcome measures included EoR, facial/hearing nerve function, surgical complications and progression of residual tumor during the median follow-up period of 28 months.ResultsIn 58 patients, mean tumor volume was 17.1 ± 9.2 cm3, and mean EoR of 81.6 ± 16.8% could be achieved. Fifty-one patients were available for the follow-up analysis. Growth of residual tumor was observed in 11 patients (21.6%) followed by adjuvant treatment with stereotactic radiosurgery or repeat surgery in 15 patients (29.4%). Overall serviceable hearing preservation was achieved in 38 patients (74.5%) and good facial outcome at discharge was observed in 66.7% of patients, significantly increasing to 82.4% at follow-up. Independent predictors for residual tumor growth was EoR ≤ 87% (OR11.1) with a higher EoR being associated with a very low number of residual tumor progression amounting to 7.1% at follow-up (p=0.008).ConclusionsSubtotal tumor resection is a good therapeutic concept in patients with KOOS IV vestibular schwannoma resulting in a high rate of good hearing and facial nerve function and a very low rate of subsequent tumor progression. The goal of surgery should be to achieve more than 87% of tumor resection to keep residual tumor progression low.

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