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Vestibular Schwannoma (VS), previously known as acoustic neuroma, constitutes the majority of tumours found in the cerebellopontine angle (CPA). Most guidelines for managing CPA tumours have been developed by high-income countries (HICs). However, these guidelines often fall short in addressing the unique challenges encountered in low- and middle-income countries (LMICs), such as Pakistan. In LMICs, issues related to a limited healthcare workforce, inadequate infrastructure, and constrained financial resources hinder the effective implementation of these HIC-derived guidelines. Additionally, it has been observed that VS tends to present at a larger size in LMICs compared to HICs. Given that VS is the predominant type of CPA tumour and other types are covered under separate guidelines, this article aims to provide practical, contextspecific recommendations for the screening, diagnosis, and management of Vestibular Schwannoma in LMIC settings. Our focus is to bridge the gap in care strategies and adapt them to the resource constraints and clinical realities of LMICs.

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Surgical removal remains the primary treatment for most brain tumours. However, radiosurgery presents an effective, less invasive alternative or additional treatment for certain types. Our goal was to explore radiosurgery's roles in treating various brain tumours, focussing on its application in low- and middle-income countries (LMICs). We reviewed all relevant systematic reviews, metaanalyses, and guidelines to determine the most effective radiosurgical approaches. Additionally, we consulted a panel of experts with over ten years of experience in LMICs, such as Pakistan. For brain tumours, stereotactic radiosurgery should generally follow a confirmed histopathological diagnosis. Exceptions include tumours identified through Magnetic Resonance Imaging (MRI), like Vestibular Schwannoma (VS), pre-diagnosed Neurofibromatosis type 2 (NF2), multiple typical meningiomas, and metastases with a known histology from another site. While radiosurgery is gaining traction as a primary and adjunct treatment in some LMICs, the lack of regional guidelines, trained personnel, and collaboration among specialists hinders its wider adoption. Addressing these gaps is crucial for expanding radiosurgical care in these regions.

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OBJECTIVE: To review the literature on the diagnosis and treatment of vestibular schwannoma. METHODS: Task force members were educated on knowledge synthesis methods, including electronic database search, review and selection of relevant citations, and critical appraisal of selected studies. Articles written in English or Portuguese on vestibular schwannoma were eligible for inclusion. The American College of Physicians' guideline grading system and the American Thyroid Association's guideline criteria were used for critical appraisal of evidence and recommendations for therapeutic interventions. RESULTS: The topics were divided into 2 parts: (1) Diagnosis - audiologic, electrophysiologic tests, and imaging; (2) Treatment - wait and scan protocols, surgery, radiosurgery/radiotherapy, and systemic therapy. CONCLUSIONS: Decision making in VS treatment has become more challenging. MRI can diagnose increasingly smaller tumors, which has disastrous consequences for the patients and their families. It is important to develop an individualized approach for each case, which highly depends on the experience of each surgical team.

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BACKGROUND: The association between programed cell death-ligand 1 (PD-L1) and tumor-infiltrating lymphocytes (TILs) in vestibular schwannoma (VS) has been investigated in a few studies. These published studies report a difference in the PD-L1 positivity rate in malignant peripheral nerve sheath tumors. We examined PD-L1 expression and lymphocyte infiltration in patients with VS who had undergone surgical resection and investigated the association between PD-L1 expression and clinicopathological features. METHODS: The expression of PD-L1, CD8, and Ki-67 in 40 VS tissue specimens was investigated using immunohistochemistry, and a clinical review of the patients was performed. RESULTS: Of the 40 VS samples, 23 (57.5%) were positive for PD-L1 and 22 (55%) were positive for CD8. No significant differences in age, tumor size, pure-tone audiometry, speech discrimination, or Ki-67 expression were observed between patients in the PD-L1-positive and PD-L1-negative groups. A higher level of CD8-positive cell infiltration was observed in PD-L1-positive tumors than in PD-L1-negative tumors. CONCLUSION: We demonstrated that PD-L1 was expressed in VS tissues. Although no correlation was identified between clinical characteristics and PD-L1 expression, the association between PD-L1 and CD8 was confirmed. Thus, additional research on targeting PD-L1 is necessary to improve immunotherapy for VS in the future.

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Objective: The perfusion profile of vestibular schwannomas (VSs) and the factors that influence it have yet to be determined. Materials and Methods: Twenty patients with sporadic VS were analyzed by calculating parameters related to the extravascular extracellular space (EES)-the volume transfer constant between a vessel and the EES (Ktrans); the EES volume per unit of tissue volume (Ve); and the rate transfer constant between EES and blood plasma (Kep)-as well as the relative cerebral blood volume (rCBV), and by correlating those parameters with the size of the tumor and its structure (solid, cystic, or heterogeneous). Results: Although Ktrans, Ve, and Kep were measurable in all tumors, rCBV was measurable only in large tumors. We detected a positive correlation between Ktrans and rCBV (r = 0.62, p = 0.031), a negative correlation between Ve and Kep (r = -0.51, p = 0.021), and a positive correlation between Ktrans and Ve only in solid VSs (r = 0.64, p = 0.048). Comparing the means for small and large VSs, we found that the former showed lower Ktrans (0.13 vs. 0.029, p < 0.001), higher Kep (0.68 vs. 0.46, p = 0.037), and lower Ve (0.45 vs. 0.83, p < 0.001). The mean Ktrans was lower in the cystic portions of cystic VSs than in their solid portions (0.14 vs. 0.32, p < 0.001), as was the mean Ve (0.37 vs. 0.78, p < 0.001). There were positive correlations between the solid and cystic portions for Ktrans (r = 0.71, p = 0.048) and Kep (r = 0.74, p = 0.037). Conclusion: In VS, tumor size appears to be consistently associated with perfusion values. In cystic VS, the cystic portions seem to have lower Ktrans and Ve than do the solid portions.

Objetivo: O perfil de perfusão do schwannoma vestibular (SV) não tem sido estudado, nem os fatores que o influenciam. Materiais e Métodos: Vinte pacientes com SV esporádico foram analisados usando Ktrans, Ve, Kep e rCBV e correlacionados com tamanho e estádio cístico. Resultados: Ktrans, Ve e Kep foram medidos em todos os casos. rCBV só foi possível em tumores grandes. Ktrans e rCBV estavam correlacionados positivamente (r = 0,62, p = 0, 0 31 ) . Ve e Kep estavam negativamente correlacionados (r = ­0,51, p = 0,021). Ktrans estava correlacionado positivamente com Ve em SVs sólidos (r = 0,64, p = 0,048). Em SVs pequenos, Ktrans foi menor (0,13 vs 0,029, p < 0,001), Kep foi maior (0,68 vs 0,46, p = 0,037) e Ve foi menor (0,45 vs 0,83, p < 0,001) que nos SVs grandes. Ktrans e Ve foram menores dentro dos cistos que nas porções solidas dos SVs císticos (0,14 vs 0,32, p < 0,001; 0,37 vs 0,78, p < 0.001, respectivamente). Foi encontrada correlação positiva em Ktrans (r = 0,71, p = 0,048) e Kep (r = 0,74, p = 0,037) entre as áreas sólidas e císticas. Conclusão: Nos SVs, o tamanho está consistentemente associado com os valores da perfusão. Nos SVs císticos, as porções císticas parecem ter valores menores de Ktrans e Ve do que nas porções sólidas.

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Abstract Objective: The perfusion profile of vestibular schwannomas (VSs) and the factors that influence it have yet to be determined. Materials and Methods: Twenty patients with sporadic VS were analyzed by calculating parameters related to the extravascular extracellular space (EES)—the volume transfer constant between a vessel and the EES (Ktrans); the EES volume per unit of tissue volume (Ve); and the rate transfer constant between EES and blood plasma (Kep)—as well as the relative cerebral blood volume (rCBV), and by correlating those parameters with the size of the tumor and its structure (solid, cystic, or heterogeneous). Results: Although Ktrans, Ve, and Kep were measurable in all tumors, rCBV was measurable only in large tumors. We detected a positive correlation between Ktrans and rCBV (r = 0.62, p = 0.031), a negative correlation between Ve and Kep (r = -0.51, p = 0.021), and a positive correlation between Ktrans and Ve only in solid VSs (r = 0.64, p = 0.048). Comparing the means for small and large VSs, we found that the former showed lower Ktrans (0.13 vs. 0.029, p < 0.001), higher Kep (0.68 vs. 0.46, p = 0.037), and lower Ve (0.45 vs. 0.83, p < 0.001). The mean Ktrans was lower in the cystic portions of cystic VSs than in their solid portions (0.14 vs. 0.32, p < 0.001), as was the mean Ve (0.37 vs. 0.78, p < 0.001). There were positive correlations between the solid and cystic portions for Ktrans (r = 0.71, p = 0.048) and Kep (r = 0.74, p = 0.037). Conclusion: In VS, tumor size appears to be consistently associated with perfusion values. In cystic VS, the cystic portions seem to have lower Ktrans and Ve than do the solid portions.

Resumo Objetivo: O perfil de perfusão do schwannoma vestibular (SV) não tem sido estudado, nem os fatores que o influenciam. Materiais e Métodos: Vinte pacientes com SV esporádico foram analisados usando Ktrans, Ve, Kep e rCBV e correlacionados com tamanho e estádio cístico. Resultados: Ktrans, Ve e Kep foram medidos em todos os casos. rCBV só foi possível em tumores grandes. Ktrans e rCBV estavam correlacionados positivamente (r = 0,62, p = 0, 0 31 ) . Ve e Kep estavam negativamente correlacionados (r = -0,51, p = 0,021). Ktrans estava correlacionado positivamente com Ve em SVs sólidos (r = 0,64, p = 0,048). Em SVs pequenos, Ktrans foi menor (0,13 vs 0,029, p < 0,001), Kep foi maior (0,68 vs 0,46, p = 0,037) e Ve foi menor (0,45 vs 0,83, p < 0,001) que nos SVs grandes. Ktrans e Ve foram menores dentro dos cistos que nas porções solidas dos SVs císticos (0,14 vs 0,32, p < 0,001; 0,37 vs 0,78, p < 0.001, respectivamente). Foi encontrada correlação positiva em Ktrans (r = 0,71, p = 0,048) e Kep (r = 0,74, p = 0,037) entre as áreas sólidas e císticas. Conclusão: Nos SVs, o tamanho está consistentemente associado com os valores da perfusão. Nos SVs císticos, as porções císticas parecem ter valores menores de Ktrans e Ve do que nas porções sólidas.

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OBJECTIVE: This study aimed to evaluate the possibilities of artefact reduction using different anatomical implant positions with the Bonebridge bone-conduction hearing implant 602 for a patient with an acoustic neuroma requiring regular diagnostic magnetic resonance imaging of the tumour position. METHOD: Three implant positions and magnetic resonance imaging examinations with and without customised sequences for metal artefact suppression were investigated. The diagnostic usefulness was rated by a radiologist (qualitative evaluation), and the relation between the area of artefact and the total head area was calculated (quantitative evaluation). RESULTS: Following the qualitative analysis, the radiologist rated the superior to middle fossa implant placement significantly better for diagnostic purposes, which is in agreement with the calculated artefact ratio (p < 0.0001). The customised slice-encoding metal artifact correction view-angle tilting metal artifact reduction technique sequences significantly decreased the relative artefact area between 5.13 per cent and 25.02 per cent. The smallest mean artefact diameter was found for the superior to middle fossa position with 6.80 ± 1.30 cm (range: 5.42-9.74 cm; reduction of 18.65 per cent). CONCLUSION: The application of artefact reduction sequencing and special anatomical implant positioning allows regular magnetic resonance imaging in patients with the bone-conduction hearing implant 602 without sacrificing diagnostic imaging quality for tumour diagnosis.

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Abstract Objective: To review the literature on the diagnosis and treatment of vestibular schwannoma. Methods: Task force members were educated on knowledge synthesis methods, including electronic database search, review and selection of relevant citations, and critical appraisal of selected studies. Articles written in English or Portuguese on vestibular schwannoma were eligible for inclusion. The American College of Physicians' guideline grading system and the American Thyroid Association's guideline criteria were used for critical appraisal of evidence and recommendations for therapeutic interventions. Results: The topics were divided into 2 parts: (1) Diagnosis - audiologic, electrophysiologic tests, and imaging; (2) Treatment - wait and scan protocols, surgery, radiosurgery/radiotherapy, and systemic therapy. Conclusions: Decision making in VS treatment has become more challenging. MRI can diagnose increasingly smaller tumors, which has disastrous consequences for the patients and their families. It is important to develop an individualized approach for each case, which highly depends on the experience of each surgical team.

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OBJECTIVES: There are few known predictive factors for response to gamma-knife radiosurgery (GKRS) in vestibular schwannoma (VS). We investigated the predictive role of pretreatment dynamic contrast-enhanced (DCE)-MRI parameters regarding the tumor response after GKRS in sporadic VS. METHODS: This single-center prospective study enrolled participants between April 2017 and February 2019. We performed a volumetric measurement of DCE-MRI-derived parameters before GKRS. The tumor volume was measured in a follow-up MRI. The pharmacokinetic parameters were compared between responders and nonresponders according to 20% or more tumor volume reduction. Stepwise multivariable logistic regression analyses were performed, and the diagnostic performance of DCE-MRI parameters for the prediction of tumor response was evaluated by receiver operating characteristic curve analysis. RESULTS: Ultimately, 35 participants (21 women, 52 ± 12 years) were included. There were 22 (62.9%) responders with a mean follow-up interval of 30.2 ± 5.7 months. Ktrans (0.036 min-1 vs. 0.057 min-1, p = .008) and initial area under the time-concentration curve within 90 s (IAUC90) (84.4 vs. 143.6, p = .003) showed significant differences between responders and nonresponders. Ktrans (OR = 0.96, p = .021) and IAUC90 (OR = 0.97, p = .004) were significant differentiating variables in each multivariable model with clinical variables for tumor response prediction. Ktrans showed a sensitivity of 81.8% and a specificity of 69.2%, and IAUC90 showed a sensitivity of 100% and a specificity of 53.8% for tumor response prediction. CONCLUSION: DCE-MRI (particularly Ktrans and IAUC90) has the potential to be a predictive factor for tumor response in VS after GKRS. KEY POINTS: •Pretreatment prediction of gamma-knife radiosurgery response in vestibular schwannoma is still challenging. •Dynamic contrast-enhanced MRI could have predictive value for the response of vestibular schwannoma after gamma-knife radiosurgery.

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INTRODUCTION: Hearing rehabilitation with cochlear implants has attracted increasing interest also for patients with cochleovestibular schwannoma. The authors report their experience with the surgical management of tumors with rare transmodiolar or transmacular extension and outcomes after cochlear implantation (CI). METHODS: This retrospective case series included nine patients with either primary intralabyrinthine tumors or secondary invasion of the inner ear from the internal auditory canal. The primary endpoint with CI, performed in six patients, was word recognition score at 65 dB SPL (sound pressure level). Secondary endpoints were intra- and postoperative electrophysiological parameters, impedance measures, the presence of a wave V in the electrically evoked (via the CI) auditory brainstem responses, the specifics of postoperative CI programming, and adverse events. RESULTS: Hearing rehabilitation with CI in cases of transmodiolar tumor growth could be achieved only with incomplete tumor removal, whereas tumors with transmacular growth could be completely removed. All six patients with CI had good word recognition scores for numbers in quiet conditions (80-100% at 65 dB SPL, not later than 6 to 12 months post CI activation). Four of these six patients achieved good to very good results for monosyllabic words within 1-36 months (65-85% at 65 dB SPL). The two other patients, however, had low scores for monosyllables at 6 months (25 and 15% at 65 dB SPL, respectively) with worsening of results thereafter. CONCLUSIONS: Cochleovestibular schwannomas with transmodiolar and transmacular extension represent a rare entity with specific management requirements. Hearing rehabilitation with CI is a principal option in these patients.

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OBJECTIVE: Socioeconomic risk factors may contribute to geographic variation in diseases, but studies are limited due to lack of large available cohorts. METHOD: A geographic analysis was performed of the association between socioeconomic risk factors and the distribution of vestibular schwannomas in adults diagnosed with sporadic vestibular schwannomas through the National Health Services in the West of Scotland from 2000 to 2015. RESULTS: A total of 511 sporadic vestibular schwannomas were identified in a population of over 3.1 million. Prevalence of vestibular schwannomas were lowest in cases with good health (-0.64, 95 per cent confidence interval: -0.93,-0.38; p = 0.002) and level 1 qualifications (-0.562, 95 per cent confidence interval: -0.882 to -0.26; p = 0.01). However, these risk factors did not demonstrate consistent linearity of correlations. Prevalence was lower in people originating from European Union accession countries from April 2001 to March 2011 (-0.63, 95 per cent confidence interval: -0.84 to -0.43; p = 0.002). No correlation between distribution of vestibular schwannomas and socioeconomic risk factors met our threshold criteria (± 0.7). CONCLUSION: This study demonstrated that there is little variation in distribution of vestibular schwannomas by socioeconomic risk factors.

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INTRODUCTION: Hearing rehabilitation with cochlear implants has attracted increasing interest also for patients with cochleovestibular schwannoma. The authors report their experience with the surgical management of tumors with rare transmodiolar or transmacular extension and outcomes after cochlear implantation (CI). METHODS: This retrospective case series included nine patients with either primary intralabyrinthine tumors or secondary invasion of the inner ear from the internal auditory canal. The primary endpoint with CI, performed in six patients, was word recognition score at 65 dB SPL (sound pressure level). Secondary endpoints were intra- and postoperative electrophysiological parameters, impedance measures, the presence of a wave V in the electrically evoked (via the CI) auditory brainstem responses, the specifics of postoperative CI programming, and adverse events. RESULTS: Hearing rehabilitation with CI in cases of transmodiolar tumor growth could be achieved only with incomplete tumor removal, whereas tumors with transmacular growth could be completely removed. All six patients with CI had good word recognition scores for numbers in quiet conditions (80-100% at 65 dB SPL, not later than 6 to 12 months post CI activation). Four of these six patients achieved good to very good results for monosyllabic words within 1-36 months (65-85% at 65 dB SPL). The two other patients, however, had low scores for monosyllables at 6 months (25 and 15% at 65 dB SPL, respectively) with worsening of results thereafter. CONCLUSIONS: Cochleovestibular schwannomas with transmodiolar and transmacular extension represent a rare entity with specific management requirements. Hearing rehabilitation with CI is a principal option in these patients.

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Objective: To analyze the role of facial nerve motor evoked potentials in predicting facial nerve function in vestibular schwannoma surgery. Methods: In a retrospective clinical study of 226 patients with acoustic neuroma, admitted to our hospital from January 2016 to May 2019, were investigated by facial nerve motor evoked potentials (FNMEP) elicited by multi-pulse transcranial electrical motor cortex stimulation from. For recording the same electrode set-up was used as for continuous EMG monitoring of the orbicularis oculi,oris muscles and mentalis. Pre-surgical (opening dural), intraoperative and post-surgical (closing dural) FNMEP amplitudes and latencies were recorded. End (closing dura) to start (opening dura) amplitude ratios were compared to early-term(3 day after surgery) facial nerve function by House-Brackmann(HB) Grading. Results: 201 patients(88.9%) get a total tumor resection, 15 patients (6.6%) were a subtotal resection, 10 patients(4.4%) were a partial resection. 100 percent of patients had a integrated anatomical preservation of facial nerves, there were four (1.8%) death cases in this group. Reliable FNMEPs were obtained in all patients. The ratio of end-operative to start-operative FNMEP-amplitude showed a negative correlation with early facial nerve function. Correlation was especially close with early function: an amplitude preservation rate of 85.3% led to HB Ⅰ or Ⅱ in 190(84.1%) patients, of 45.6% to HB Ⅲ in 17(7.5%) patients, of 23.1% to HB Ⅳ in 13(5.8%) patients and of 6.7% to HB Ⅴor Ⅵ in 6(2.7%) patients. There was a negative correlation between FNMEP amplitude ratio and post-surgical early HB grading(r=-0.895, P=0.000). Conclusion: FNMEP was highly reliable in predicting early postoperative facial function of the resection of vestibular schwannoma, was a valid protection technique of facial nerve.

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OBJECTIVE: Little is known about the long term (greater than 10 years) quality of life in patients with vestibular schwannoma. This study aimed to evaluate long-term outcomes in patients with vestibular schwannoma. METHOD: A retrospective cohort study was performed across 2 academic institutions, with patients followed at least 10 years after vestibular schwannoma surgery (2000 to 2007). Telephone interviews were used to assess quality of life using the Glasgow Benefit Inventory and short form 12 item (version 2) health survey. RESULTS: A total of 99 out of 110 patients were included. Increasing age and symptom burden were associated with poorer quality of life (p = 0.01 and 0.02, respectively). The presence of imbalance, headache and facial nerve dysfunction were all associated with poorer quality of life scores (p = 0.01, 0.04 and 0.02, respectively). CONCLUSION: Identifying and managing post-operative symptoms may improve quality of life in vestibular schwannoma patients and can guide clinical decision making.

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BACKGROUND: The use of Gamma Knife radiosurgery (GKRS) for recurrent or residual vestibular schwannoma (VS) after microsurgery (MS) has been investigated in several retrospective studies. The purpose of this study was to identify potential risk factors for both neurologic deterioration and tumor progression after GKRS for previously operated VSs in a prospective setting. METHODS: Patients who underwent GKRS for previously operated and histopathologically confirmed VS between 1998 and 2015 were prospectively followed-up. Risk factors for therapy side effects and predictors for tumor control were investigated in uni- and multivariate analyses. RESULTS: A total of 160 individuals with a median age of 55 years were included. Median tumor volume prior to GKRS was 1.40 cm3 (range, 0.06-35.80 cm3). After a median follow-up of 36 months, hearing and facial nerve function were serviceable (modified Gardner-Robertson and House-Brackmann grades I and II) in 7 (5%) and 82 (55%) patients, respectively. Deterioration to a nonserviceable facial nerve function after GKRS was found in 3% (3/89) and tended to increase with rising tumor volume (odds ratio, 1.65 per cm3; 95% confidence interval, 1.00-2.71; P = 0.051). Median tumor volume prior to GKRS was higher in patients with radiologic (P = 0.020) or clinical tumor progression (P < 0.001). Critical tumor volume prior to GKRS to predict clinical and radiologic tumor progression was 1.30 cm3 (P < 0.001) and 3.30 cm3 (P = 0.019), respectively. However, in multivariate analyses, none of the analyzed variables were found to independently predict tumor progression. CONCLUSIONS: Intended submaximal resection followed by GKRS is a viable treatment for VS. Because tumor remnant size after MS is an important predictor for recurrence after adjuvant GKRS, both brainstem and cerebellar decompression and maximal safely achievable resection should remain major goals of microsurgery.

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Objective To investigate the clinical value of three-dimensional sampling perfection with application optimized contrasts using different flip angle evolutions (3D-SPACE) sequence in preoperative evaluation of acoustic neuroma.Methods Totally 57 patients with acoustic neuroma confirmed by surgery and pathology were enrolled.All patients underwent preoperative routine head MR and 3D-SPACE sequence.The position,size and shape of the tumors were observed,and the display rate of surrounding cranial nerves was evaluated with 3D-SPACE sequence.The results were compared with those of conventional MRI and operation.Results All 57 patients were found with single tumor.The tumor in 1 patient (1/57,1.75％) limited in the internal auditory canal,and those in another 56 patients (56/57,98.25％) exceed the internal auditory canal crossing growth.The inner auditory canal fundus in 26 patients (26/57,45.61 ％) were completely filled by the tumors,while those in another 31 patients (31/57) were uncompletely filled.3D-SPACE sequence showed 21 patients (21/57,36.84％) with solid type lesions,35 patients (61.40％,35/57) with solid with cystic type lesions and 1 patient (1/57,1.76％) with cystic type lesion.The coincidence rate of lesion types showed with 3D-SPACE sequence and intraoperative findings was 85.96 ％ (49/57).The display rate of trigeminal nerve internal cisternal segment,lower cranial nerves cisternal segment,abducens nerve cisternal segment,facial nerve internal acoustic meatus segment,facial nerve cisternal segment and acoustic nerve cisternal segment was 100％ (57/57),100％(57/57),75.44％ (43/57),50.88％ (29/57),17.53％ (10/57) and 19.30％ (11/57),respectively,all significantly increased compared with those of conventional MRI (all P＜0.05).Conclusion 3D-SPACE sequence can accurately display the relationship between tumor and adjacent cranial nerves,therefore has important clinical value in preoperative evaluation of acoustic neuroma.

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Over the past 50 years, the focus of acoustic neuroma surgery has shifted from low mortality and tumor resection to retention of neurological function. Hearing preservation is another point in addition to facial nerve function preservation. Hearing preservation rates overall ranged from 2% to 93% in recent studies. Characteristics such as approach, pre-operative neurological function, tumor size, nerve of origin and fundal fluid of the internal auditory canal have been reported as possible influencing factors. This review provides a summary of recent studies and describes the prognostic factors that predict hearing preservation.

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BACKGROUND: Hearing restoration after translabyrinthine vestibular schwannoma resection is a challenge. Because the cochlea can begin to ossify a few months after cochlear or labyrinthine injury, the time interval for cochlear implant surgery is limited. To avoid complete ossification and to prolong the time interval until cochlear implantation, it is possible to insert a placeholder (depth gauge) into the cochlea and perform the cochlear implant surgery at a later time point (two-stage approach). OBJECTIVE: The aim of this retrospective case series was to present the outcomes after restoration of hearing with cochlea implants in six patients and to evaluate the use of the depth gauge in practice. METHODS: The hearing outcome of all patients with (n = 3) and without (n = 3) insertion of a depth gauge was measured with the Freiburg monosyllabic test without background noise at 65 dB. The first measurement was performed prior to the translabyrinthine vestibular schwannoma resection, the last measurement was performed up to 48 months after cochlear implantation. RESULTS: All 6 patients reached 22.5 ± 36.57% prior to vestibular schwannoma resection and 41.3 ± 26% 12 months after cochlear implantation. The understanding values of the patients with a depth gauge were 25.8 ± 16% after 12 months which is below the values of the other patients with 56.6 ± 25.0%. No severe intraoperative or postoperative complications occurred in any patient. CONCLUSION: The two-stage approach for cochlear implantation with depth gauge insertion following labrynthine incision and intact nerve appears to represent a very promising and safe variation for hearing restoration. Intensified research on this approach seems to be justified and necessary.

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Objective To observe the influence of different tumor resection extent on facial nerve function and tumor recurrence in acoustic neuroma surgery.Methods A total of 118 patients with acoustic neuroma operated by the same surgeon from January 2009 to December 2015 were enrolled retrospectively.All patients were treated via suboccipital retrosigmoid transmeatal approach.The neartotal resection strategy was used during operation.Part of the tumors closely adhered to the facial nerveswere not removed forcibly.If there was tumor residue partly,the internal auditory canal was not drilled open.The relationship between facial nerve function or tumor recurrence and tumor resection degree was analyzed.The patients with recurrent tumor were treated with Gamma knife.Results In 118 patients,1 patient (0.8％) died during the operation.The follow-up time ranged from 8-90 months.The total resection rate of acoustic neuroma was 19.5％ (23/118),the near-total resection rate was 74.6％(88/118),and subtotal resection rate was 5.9 ％ (7/118).The recurrence rate was 16.1％ (19/118),in total resection group was 0,in near-total resection group was 15.9％ (14/88),in subtotal resection group was 5/7,there was significant difference (x2 =21.980,P ＜ 0.01).The good rate of facial nerve function after procedure was 90.7％ (107/118),in total resection group was 73.9％ (17/23),in near-total resection group was 95.5 ％ (84/88),in subtotal resection group was 6/7,and there was significant difference between total resection group and near-total resection group (x2 =14.168,P ＜ 0.05).After Gamma knife treatmentthe tumor volume increased again in 3 patients (2.5 ％) during the follow up period,and they were reoperated.Conclusions After near-total resection of acoustic neuroma,the assisted Gamma knife therapy may effectively control the growth of acoustic neuroma,and significantly improve the retention rate of facial nerve function.For the improvement of the quality of life,it is a feasible treatment scheme in the patients with tumors closely adhered to the facial nerves.

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OBJECTIVE To explore the significance of intraoperative auditory monitoring(IAMA) in surgery of acoustic neuroma and to compare the value of auditory brainstem response(ABR) and cochlear nerve action potential(CNAP) in auditory monitoring.METHODS Retrospective analysis of 12 cases of acoustic neuroma from January 2016 to December 2016 was performed.All patients have a practical hearing(AAO-HNS,grade class a,b),the ABR waveform can be elicited,wave v differentiation,All tumors were removed via posterior sigmoid sinus approach.RESULTS ABR waveform of all patients were prolonged with different degrees of change(0.68±0.41) ms compared with the preoperative data.Amplitude of CNAP diverse in different individuals,with an average prolong compared to the data before operation(0.25±0.16) ms.In all 12 cases,8 (66.7％) patients remained usable hearing after the operation,4 cases(33.3％) failed to have a usable hearing.Among these 4 patients,3 showed disappearance of wave v,1 patient showed wave v latency prolong in the ABR,meanwhile,2 patients showed P1 dissapear,2 patients showed P1 latency prolong in CNAP.The intraoperative auditory monitoring could play a role in preventing the hearing damage in the procedure.Drilling,noise,surgical nerve stretch or thermal injury may cause the hearing damage.A 5 minutes pause could get some degree of regain,with the amplitude rise again.CONCLUSION A combination use of the ABR and CNAP monitoring has a certain significance in surgery of acoustic neuroma.ABR waveform is stable and reliable,but costs longer time;CNAP stack quickly and improve monitoring sensitivity,but waveform varies.Vibration and noise caused by drilling,nerve stretch during operation and heat damage can be monitored timely.Combined use of ABR and CNAP monitoring can enhance the auditory preservation rate during acoustic neuroma surgery.