Resection of large vestibular schwannomas: facial nerve preservation in the context of surgical approach and patient-assessed outcome

Management and outcomes of large and giant vestibular schwannomas. Experience in 567 cases over 35 years

PURPOSE

(1) Study the preoperative predictive factors (such as duration of symptoms, tumor size, and cystic component) and their effects on the type of resection and facial nerve (FN) outcomes. (2) Analyze the intraoperative predictive factors, such as the extent of resection and intraoperative FN stimulation. (3) Compare our approaches (enlarged translabyrinthine approach, transotic and transcochlear approaches) to other approaches (retro sigmoid) and review the literature comparing different approaches. (4) To inquire if the surgical decision (total vs. non-total removal) and outcomes (complications and facial nerve function) of large and giant VS surgery have changed during 35 years at Gruppo Otologico.

METHODS

A total of 567 cases out of 3707 were enrolled. The inclusion criteria were patients with tumors > 30 mm extrameatal diameter undergoing a translabyrinthine approach with a minimum follow-up of 12 months.

RESULTS

The mean duration of symptoms was 35.9 months, pronounced more in the elderly (53.4 months) than in younger individuals (33.9 months). The mean tumor diameter was 36.6 mm, and 50.4% of them were cystic. Total resection (TR), near-total resection (NTR), subtotal resections (STR), and partial resection (PR) were achieved in 73.2%, 7.4%, 10.2%, and 9.1% of cases, respectively. Regrowth was observed only after STR and PR (20.7% and 44.2%, respectively). We excluded the sacrificed facial nerves (no.86) from the results of the FN outcomes. Postoperatively, FN outcomes were as follows: HB I-II 42.2%, HB III 46.9%, and HB IV-VI 10.8%. Younger individuals underwent TR in 403 (79.3%) cases, against 12 (20.3%) elderly individuals. Non-total resections (NTR/STR/PR) were performed in 47 (79.7%) cases in the elderly as against 105 (20.7%) in younger individuals. For experience effect, there were increased cases of NTR, STR, and PR (18.8% before 2004, 28.9% ≥ 2004), while the rate of complications decreased (24.8% before 2004, 13.1% ≥ 2004).

CONCLUSION

TR and NTR are good strategies for tumor control and FN outcomes. Preoperatively, longer symptom duration, profound deafness, and tumor diameter of ≥ 4 cm adversely influence facial nerve outcome after surgery. Conversely, cystic tumors may have a favorable influence. Additionally, intact FN responding to a stimulus after tumor resection anticipates good long-term FN (HB I-III) outcomes. With experience, operating time decreases and there may be an increase in poor outcomes of FN due to the high rate of operated giant tumors. Long-term follow-up is recommended.

Evaluating the effectiveness and complications of the Retrosigmoid, Translabyrinthine and Middle Fossa approaches in vestibular Schwannoma surgical management: a comprehensive systematic review and meta-analysis of 6,889 patients

Surgical resection stands as one of the potential therapeutic methods for vestibular schwannomas (VS). However, in the management of patients with VS, there is limited literature directly comparing the Retrosigmoid approach (RSA) with the Translabyrinthine Approach (TLA) and Middle Fossa Approach (MFA). This gap arises because the MFA is typically reserved for smaller intracanalicular tumors, while the RSA and TLA are preferred for larger lesions. Our objective was to assess and compare the outcomes and safety profile of these three different surgical approaches. A comprehensive search was performed on PubMed, Embase, and Cochrane Library for studies comparing RSA with TLA and MFA in patients with VS. The main outcomes of interest were hearing preservation, facial nerve function, extent of resection, and postoperative complications. Statistical analyses were performed using Review Manager. The I2 test was employed for heterogeneity assessment, while the risk of bias was evaluated utilizing ROBINS-I. We included 6,889 patients from 32 observational studies. RSA was used to manage VS in 3,352 (48,7%) patients. Our comparative hearing preservation analysis revealed no significant difference in patient improvement between RSA and MFA, with a risk ratio (RR) of 1.18 (95% CI: 0.76-1.85, p = 0.46, I2:0%). Late facial nerve preservation comparing RSA and TLA showed RR = 0.91(95% CI: 0.77-1.07, p = 0.25, I2:32%), while RSA with MFA a RR = 0.98 (95% CI: 0.92-1.04, p = 0.53, I2:87%). The cerebrospinal fluid (CSF) leak showed no significant difference in risk RR = 1.18 (95% CI: 0.92-1.51, p = 0.21; I2:0%) and RR = 1.14 (95% CI: 0.70-1.83; p = 0.60, I2:26%) comparing RSA with TLA and MFA respectively. The evidence synthesized in this meta-analysis suggests equivalent hearing preservation and facial nerve function in managing VS patients across the different RSA and MFA surgical approaches analyzed. However, in comparison to TLA and MFA, RSA stood out exhibiting fewer occurrences of postoperative complications consisting of hydrocephalus, and CSF leaks.

Characterization of facial nerve outcomes following radiosurgery for vestibular schwannoma: a meta-analysis

PURPOSE

Gamma Knife radiosurgery (GKRS) is a precise and efficacious treatment modality for vestibular schwannoma (VS) with favorable cranial nerve preservation rates. This study aims to better characterize facial nerve (FN) outcomes in VS after GKRS.

METHODS

A query of six medical databases was conducted following PRISMA guidelines. Eligible studies exclusively reported VS managed with single-fraction GKRS and included House-Brackmann (HB) scale assessments prior to and following GKRS. Data was analyzed using random-effects modeling, and FN preservation was defined as HB I or II at last follow-up.

RESULTS

Data was analyzed from 15 articles with 3,155 patients at an mean age of 55.0 years. Mean tumor volume, radiation dose, follow-up, tumor control, and hearing preservation were 4.28 cm3, 13.3 Gy, 59.4 months, 92.7%, and 62.6%, respectively. The pooled FN preservation rate was 92.9%. Mean preoperative tumor volume > 2.5 cm3 and age > 60 years were significantly associated with worse preoperative FN function (p = 0.019, p = 0.023, respectively). Normal FN function (HB = 1) at last follow up was 95.8% for VS volume < 2.5 cm3 and 89.4% with larger volumes (p < 0.001). Doses ≤ 13 Gy were significantly associated with superior FN preservation (96.5%) compared to higher doses (p < 0.001). Tumor control and hearing preservation were not significantly associated with FN preservation.

CONCLUSION

This meta-analysis identifies tumor volume and radiation dose as prognostic factors for FN preservation. A FN preservation rate of 93% may be expected at five years after GKRS. This study provides a unique characterization of FN outcome that should be considered in the management of VS.

Intraoperative monitoring and early recognition of facial nerve root in vestibular schwannoma surgery

The removal of vestibular schwannomas carries a risk of facial palsy. This study aims to evaluate the usefulness and technical aspects of intraoperative monitoring (IOM) for the facial nerve. A total of 96 patients who underwent surgery for vestibular schwannoma were retrospectively investigated. The cohort was divided into two groups: those with intraoperative facial nerve monitoring (IOM group) and those without IOM (non-IOM group). Preoperative and postoperative facial nerve functions were assessed using the House-Brackmann (HB) scale immediately after surgery, at discharge, and at the 1-year follow-up. HB grade I and II were classified as satisfactory outcomes, HB grade III and IV as intermediate, and HB grade V and VI as poor. Facial nerve functions were compared between the groups. Additionally, the ratio of satisfactory results was investigated in the IOM group, focusing on whether the root exit zone (REZ) was identified at an early or late stage of surgery. Among the 65 (67%) patients in the IOM group and 31 (32%) patients in the non-IOM group, there were no differences in demographic and tumor characteristics. The extent of resection varied from subtotal to gross total removal, with no statistical differences between the groups. Although facial nerve function was more favorably preserved in the non-IOM group immediately after surgery, this trend reversed at discharge and the 1-year follow-up, showing significant statistical differences. In the IOM group, more patients achieved satisfactory outcomes when the REZ was identified early compared to late during tumor resection. Intraoperative facial nerve monitoring provides more satisfactory outcomes in preserving nerve function in vestibular schwannoma surgery. Early recognition of the REZ may contribute to improved surgical outcomes.

Likelihood-of-harm/help of microsurgery compared to radiosurgery in large vestibular schwannoma

PURPOSE

It has been shown that in large vestibular schwannomas (VS), radiosurgery (SRS) is inferior with respect to tumor control compared to microsurgical resection (SURGERY). However, SURGERY poses a significantly higher risk of facial-function deterioration (FFD). The aim of this study was to illustrate the effectiveness in terms of number-needed-to-treat/operate (NNO), number-needed-to-harm (NNH), and likelihood-of-harm/help (LHH) by comparing both treatment modalities in large VS.

METHODS

This was a retrospective, dual-center cohort study. Tumor size was classified by Hannover Classification. Absolute risk reduction and risk increase were used to derive additional estimates of treatment effectiveness, namely NNO and NNH. LHH was then calculated by a quotient of NNH/NNO to illustrate the risk-benefit-ratio of SURGERY.

RESULTS

Four hundred and forty-nine patients treated met the inclusion criteria. The incidence of tumor recurrence was significantly higher in SRS (14%), compared to SURGERY (3%) resulting in ARR of 11% and NNO of 10. At the same time, SURGERY was related to a significant risk of FFD resulting in an NNH of 12. Overall, the LHH calculated at 1.20 was favored SURGERY, especially in patients under the age of 40 years (LHH = 2.40), cystic VS (LHH = 4.33), and Hannover T3a (LHH = 1.83) and T3b (LHH = 1.80).

CONCLUSIONS

Due to a poorer response of large VS to SRS, SURGERY is superior with respect to tumor control. One tumor recurrence can be prevented, when 10 patients are treated by SURGERY instead of SRS. Thus, LHH portrays the benefit of SURGERY in large VS even when taking raised FFD into account.

Retrosigmoid versus middle fossa approach for hearing and facial nerve preservation in vestibular schwannoma surgery: A systematic review and comparative meta-analysis

BACKGROUND

Vestibular schwannomas (VS) are benign tumors arising from vestibular nerve's Schwann cells. Surgical resection via retrosigmoid (RS) or middle fossa (MF) is standard, but the optimal approach remains debated. This meta-analysis evaluated RS and MF approaches for VS management, emphasizing hearing preservation and Cranial nerve seven (CN VII) outcomes stratified by tumor size.

METHODS

Systematic searches across PubMed, Cochrane, Web of Science, and Embase identified relevant studies. Hearing and CN VII outcomes were gauged using the American Academy of Otolaryngology-Head and Neck Surgery, Gardner Robertson, and House-Brackmann scores.

RESULTS

Among 7228 patients, 56 % underwent RS and 44 % MF. For intracanalicular tumors, MF recorded 38 % hearing loss, compared to RS's 54 %. In small tumors (<1.5 cm), MF showed 41 % hearing loss, contrasting RS's lower 15 %. Medium-sized tumors (1.5 cm-2.9 cm) revealed 68 % hearing loss in MF and 55 % in RS. Large tumors (>3cm) were only reported in RS with a hearing loss rate of 62 %.

CONCLUSION

Conclusively, while MF may be preferable for intracanalicular tumors, RS demonstrated superior hearing preservation for small to medium-sized tumors. This research underlines the significance of stratified outcomes by tumor size, guiding surgical decisions and enhancing patient outcomes.

Long-term quality of life outcomes in patients undergoing microsurgical resection of vestibular schwannoma

Background

While previous studies have assessed patient reported quality of life (QOL) of various vestibular schwannoma (VS) treatment modalities, few studies have assessed QOL as related to the amount of residual tumor and need for retreatment in a large series of patients. Objective: To assess patient reported QOL outcomes following VS resection with a focus on extent of resection and retreatment.

Methods

A retrospective chart review was performed using single-center institutional data of adult patients who underwent VS resection by the senior authors between 1989-2018 at Loyola University Medical Center. The Penn Acoustic Neuroma Quality of Life (PANQOL) survey was sent to all patients via postal mail.

Results

Fifty-five percent of 367 total patients were female with a mean age of 61.6 years (SD 12.63). The mean period between surgery and PANQOL response was 11.4 years (IQR: 4.74-7.37). The median tumor size was 2 cm (IQR: 1.5-2.8). The mean total PANQOL score was 70 (SD 19). Patients who required retreatment reported lower overall scores (μdiff = -10.11, 95% CI: -19.48 to -0.74; p = 0.03) and face domain scores (μdiff = -20.34, 95% CI: -29.78 to -10.91; p < .001). There was no association between extent of resection and PANQOL scores in any domain.

Conclusion

In an analysis of 367 patients who underwent microsurgical resection of VS, extent of resection did not affect PANQOL scores in contrast to previous reports in the literature, while the need for retreatment and facial function had a significant impact on patient-reported outcomes.

Facial Nerve Preservation With Inferior Long-Axis Dissection of Large Vestibular Schwannomas

OBJECTIVE

To describe a tumor resection using the inferior long-axis (ILA) technique for cisternal facial nerve dissection in large vestibular schwannomas (VS).

STUDY DESIGN

Retrospective case series from 2018 to 2021.

SETTING

Tertiary academic medical center.

PATIENTS

Patients who underwent surgical resection with ILA facial nerve dissection of VS (>2.0 cm measured parallel to the petrous ridge) and had at least 3-month follow-up.

INTERVENTIONS

Cisternal facial nerve dissection during retrosigmoid or translabyrinthine approach using standardized ILA technique developed by author R.N.

MAIN OUTCOME MEASURES

Immediate postoperative and last follow-up facial nerve function with House-Brackmann scores of I to II defined as "good" facial nerve function and House-Brackmann scores III to VI defined as "poor" function. Extent of resection was also assessed.

RESULTS

A total of 48 patients underwent large VS resection with ILA dissection of tumor off of the facial nerve from 2018 to 2021. Mean (standard deviation) tumor size was 3.11 (0.76) cm. Mean (standard deviation) follow-up was 9.2 (9.0) months. Gross-total resection or near-total resection were achieved in 75% (radiographic estimate) to 83% (surgeon estimate) of cases. End-of-case facial nerve stimulation at 0.05 mAmp with a response of at least 240 mV was achieved in 80.4% of patients. Good facial nerve function was observed in 72% immediately postoperatively, 70% 1-month postoperatively, and 82% of patients at last follow-up.

CONCLUSIONS

The ILA technique is now the method of choice of the senior surgeon (R.N.) when performing microsurgical dissection of the cisternal facial nerve, with which he has achieved high rates of total or near-total resection with excellent facial nerve preservation.

Large Vestibular Schwannoma: A Two-Stage Surgery

Treatment of large vestibular schwannoma (VS) has historically centered on total resection of the lesion. Staged surgery has been used for VS that is highly vascularized, unexpected events during surgery, and thinned and stretched facial nerve with serious adherence causing difficult dissection. We present a case of a patient with a large VS resected through a two-stage surgery through the same retrosigmoid craniotomy.

A comparative study of microsurgery and gamma knife radiosurgery in vestibular schwannoma evaluating tumor control and functional outcome

Background

Both stereotactic radiosurgery (SRS) and microsurgical resection (SURGERY) are available as treatment options for sporadic vestibular schwannoma (VS). There are very few direct comparative studies comparing both treatment modalities in large cohorts allowing detailed subgroup analysis. This present study aimed to compare the nuances in the treatment of VS by SURGERY and SRS in 2 highly specialized neurosurgical centers.

Methods

This is a retrospective bicentric cohort study. Data from patients treated between 2005 and 2011 were collected retrospectively. Recurrence-free survival (RFS) was assessed radiographically by contrast-enhanced magnetic resonance imaging.

Results

The study population included N = 901 patients with a mean follow-up of 7 years. Overall, the incidence of recurrence was 7% after SURGERY, and 11% after SRS with superior tumor control in SURGERY in the Kaplan-Meier-analysis (P = 0.031). In small tumors (Koos I and II), tumor control was equivalent in both treatment arms. In large VS (Koos III and IV), however, RFS was superior in SURGERY. The extent of resection correlated with RFS (P < .001). Facial and hearing deterioration was similar in both treatment arms in small VS, but more pronounced in SURGERY of large VS. Tinnitus, vertigo, imbalance, and trigeminal symptoms were more often improved by SURGERY than SRS.

Conclusions

SRS can achieve similar tumor control compared to SURGERY in smaller VS (Koos I and II)-with similar postinterventional morbidities. In large VS (Koos III and IV), long-term tumor control of SRS is inferior to SURGERY. Based on these results, we suggest that if combination therapy is chosen, the residual tumor should not exceed the size of Koos II.

Surgical Outcomes After Total or Subtotal Resection of Large Vestibular Schwannoma: A Single-Institution Experience

BACKGROUND

Patients with large vestibular schwannomas have various surgical outcomes. The aim of this study is to evaluate facial nerve outcome and surgical complications in patients who underwent total and subtotal resection.

METHODS

Between October 2008 and September 2020, 72 patients underwent surgery in Rajavithi Hospital. Of these, 48 had total or subtotal resection. We classified these participants into two groups: VS ≥3 cm (Group A, n=30); and VS <3 cm (Group B, n=18). Both groups were compared in terms of clinical presentation, imaging data, facial nerve outcomes, and surgical complications. The retrosigmoid approach was used in each case, and all patients had follow-up for at least 1 year. Chi-square and Fisher's exact test were used for statistical analysis.

RESULTS

The mean tumor size in Group A was 3.8 cm compared with 1.5 cm in Group B. In Group A, clinical signs of hearing dysfunction, gait ataxia, and facial paresthesia were present in 96.7%, 66.7%, 50% of patients respectively, compared with 100%, 5.6%, and 11.1% respectively in Group B. Radiographic signs of hydrocephalus were observed in 56.7% of Group A subjects, and 5.6% of those in Group B. At 1 year follow-up, 40% of patients with large VS and 94.4% of patients with small to medium size VS had good facial nerve outcomes (House-Brackmann [HB] facial grading scale grade I-III). Significant differences between the two groups were found only in gait ataxia (p<0.001), facial paresthesia (p=0.006), radiographic signs of hydrocephalus (p=0.002), facial nerve outcome 1 month (p<0.001) and facial nerve outcome 1 year (p<0.001).

CONCLUSION

In patients with large size VS, microsurgical resection had poor facial nerve outcomes compared with those of their counterparts with small to medium size VS. Planned subtotal resection with postoperative radiosurgery might attain superior facial nerve outcomes and result in better quality of life in subjects with large VS.

The combined TL-RS approach: Advantages and disadvantages of working 360 degrees around the sigmoid sinus

Abstract Objective: To highlight the advantages and disadvantages of the combined translabyrinthine (TL) and classic retrosigmoid (RS) approach. Design: Retrospective chart review. Setting: National Tertiary Referral Center for skull base pathology. Participants: Twenty-two patients with very large cerebellopontine angle tumors were resected using the combined TL-RS approach. Main outcome measures: Preoperative patient characteristics, including age, sex, and hearing loss. Tumor characteristics, pathology, and size. Intraoperative outcome: Tumor removal. Postoperative outcomes included facial nerve function, residual tumor growth, and neurological deficits. Results: Thirteen patients had schwannoma, eight had meningioma, and one had both. The mean age was 47 years, mean tumor size was 39 × 32 × 35 mm (anterior-posterior, medial-lateral, craniocaudal), and mean follow-up period was 80 months. Tumor control was achieved in 13 patients (59%), and nine (41%) had residual tumor growth that required additional treatment. Seventeen patients (77%) had postoperative HouseBrackmann (HB) facial nerve function grade 12, one had HB grade 3, one HB V, and three HB VI. Conclusion: Combining TL and RS approach may be helpful in safely removing large meningiomas and schwannomas in selected cases. This valuable technique should be considered when sufficient exposure cannot be achieved with the TL or RS approach alone.

Preoperative Facial Nerve Palsy in Patients With Vestibular Schwannoma: Clinical Features and Postoperative Functional Prognosis in a Case Series of 34 Among 1228 Consecutive Patients

BACKGROUND

Facial nerve palsy is a rare presenting symptom of vestibular schwannomas and has not been investigated in detail.

OBJECTIVE

To investigate the incidence, clinical features, and postoperative long-term outcomes of facial nerve function in patients with vestibular schwannomas causing preoperative facial nerve palsy.

METHODS

After excluding patients with neurofibromatosis type 2 and those with prior treatment, 1228 consecutive patients who underwent vestibular schwannoma surgery were retrospectively investigated. Patients with and without preoperative facial nerve palsy were compared statistically to clarify their clinical features.

RESULTS

Preoperative tumoral facial nerve palsy was seen in 34 patients (2.8%). Their clinical features included older age, having large cystic tumors with significant meatal extension, and showing abnormal electrogustometric responses, compared with patients without preoperative facial nerve palsy. Owing to the frequent insufficient intraoperative responses on facial nerve electromyography, the tumor resection rate was lower in the group with preoperative facial nerve palsy (mean: 95.2%). Among the 33 patients with sufficient follow-up data (mean: 63.9 mo), additional treatment was required only in 1 patient and facial nerve function improved in 25 patients (75.8%) within 2 yr postoperatively.

CONCLUSION

Facial nerve palsy is a rare preoperative symptom that occurs in less than 3% of patients with vestibular schwannoma. Tumor resection in such patients tends to be challenging owing to their advanced age, having large cystic tumors with significant meatal extension, and difficulties in intraoperative facial nerve monitoring, but surgical decompression of the facial nerve can assist in the improvement of their long-term functions.

Accuracy and outcomes of diffusion tensor imaging tractography in resection for vestibular schwannoma for facial nerve preservation

BACKGROUND

Impairment of facial nerve (FN) function is a common postoperative complication in surgical resections of Vestibular Schwannomas (VS). Diffusion tensor imaging (DTI) tractography creates in vivo imaging of the anatomical location of white matter tracts that can be preoperatively used to visualize the displaced FN. We present an analysis of patients who underwent DTI tractography imaging prior to VS resection.

METHODS

Patient charts were reviewed from March 2012 to April 2015 who underwent DTI tractography prior to surgical resection for VS. Reliability of this measure was compared to the intraoperative FN location as determined by the surgeon. House Brackmann (HB) score was used to assess facial nerve function.

RESULTS

A total of 11 patients were included with a mean age of 43 years (range: 19-64) and mean follow-up length of 11.9 months (range: 3.1-34.2). The average maximum tumor diameter was 2.82 cm (range: 1.7-4.2). DTI tractography was accurate in 90.9% (10/11) of patients. Postoperatively, 72.7% (8/11) had a HB score of I or II, 18.2% (2/11) had a HB score of III, and 9.1% (1/11) had a HB score of IV.

CONCLUSIONS

Facial nerve visualization for VS resection can be accurately visualized using DTI tractography. This modality may lead to reduction of postoperative FN damage.

Clinical Studies and Pre-clinical Animal Models on Facial Nerve Preservation, Reconstruction, and Regeneration Following Cerebellopontine Angle Tumor Surgery-A Systematic Review and Future Perspectives

Background and purpose: Tumorous lesions developing in the cerebellopontine angle (CPA) get into close contact with the 1st (cisternal) and 2nd (meatal) intra-arachnoidal portion of the facial nerve (FN). When surgical damage occurs, commonly known reconstruction strategies are often associated with poor functional recovery. This article aims to provide a systematic overview for translational research by establishing the current evidence on available clinical studies and experimental models reporting on intracranial FN injury.

Methods: A systematic literature search of several databases (PubMed, EMBASE, Medline) was performed prior to July 2020. Suitable articles were selected based on predefined eligibility criteria following the Preferred Reporting Items for Systematic Reviews and Meta Analyses (PRISMA) guidelines. Included clinical studies were reviewed and categorized according to the pathology and surgical resection strategy, and experimental studies according to the animal. For anatomical study purposes, perfusion-fixed adult New Zealand white rabbits were used for radiological high-resolution imaging and anatomical dissection of the CPA and periotic skull base.

Results: One hundred forty four out of 166 included publications were clinical studies reporting on FN outcomes after CPA-tumor surgery in 19,136 patients. During CPA-tumor surgery, the specific vulnerability of the intracranial FN to stretching and compression more likely leads to neurapraxia or axonotmesis than neurotmesis. Severe FN palsy was reported in 7 to 15 % after vestibular schwannoma surgery, and 6% following the resection of CPA-meningioma. Twenty-two papers reported on experimental studies, out of which only 6 specifically used intracranial FN injury in a rodent (n = 4) or non-rodent model (n = 2). Rats and rabbits offer a feasible model for manipulation of the FN in the CPA, the latter was further confirmed in our study covering the radiological and anatomical analysis of perfusion fixed periotic bones.

Conclusion: The particular anatomical and physiological features of the intracranial FN warrant a distinguishment of experimental models for intracranial FN injuries. New Zealand White rabbits might be a very cost-effective and valuable option to test new experimental approaches for intracranial FN regeneration. Flexible and bioactive biomaterials, commonly used in skull base surgery, endowed with trophic and topographical functions, should address the specific needs of intracranial FN injuries.

Radiomics-Based Prediction of Long-Term Treatment Response of Vestibular Schwannomas Following Stereotactic Radiosurgery

OBJECTIVE

Stereotactic radiosurgery (SRS) is one of the treatment modalities for vestibular schwannomas (VSs). However, tumor progression can still occur after treatment. Currently, it remains unknown how to predict long-term SRS treatment outcome. This study investigates possible magnetic resonance imaging (MRI)-based predictors of long-term tumor control following SRS.

STUDY DESIGN

Retrospective cohort study.

SETTING

Tertiary referral center.

PATIENTS

Analysis was performed on a database containing 735 patients with unilateral VS, treated with SRS between June 2002 and December 2014. Using strict volumetric criteria for long-term tumor control and tumor progression, a total of 85 patients were included for tumor texture analysis.

INTERVENTION(S)

All patients underwent SRS and had at least 2 years of follow-up.

MAIN OUTCOME MEASURE(S)

Quantitative tumor texture features were extracted from conventional MRI scans. These features were supplied to a machine learning stage to train prediction models. Prediction accuracy, sensitivity, specificity, and area under the receiver operating curve (AUC) are evaluated.

RESULTS

Gray-level co-occurrence matrices, which capture statistics from specific MRI tumor texture features, obtained the best prediction scores: 0.77 accuracy, 0.71 sensitivity, 0.83 specificity, and 0.93 AUC. These prediction scores further improved to 0.83, 0.83, 0.82, and 0.99, respectively, for tumors larger than 5 cm.

CONCLUSIONS

Results of this study show the feasibility of predicting the long-term SRS treatment response of VS tumors on an individual basis, using MRI-based tumor texture features. These results can be exploited for further research into creating a clinical decision support system, facilitating physicians, and patients to select a personalized optimal treatment strategy.

Surgical management for large vestibular schwannomas: a systematic review, meta-analysis, and consensus statement on behalf of the EANS skull base section

BACKGROUND AND OBJECTIVE

The optimal management of large vestibular schwannomas continues to be debated. We constituted a task force comprising the members of the EANS skull base committee along with international experts to derive recommendations for the management of this problem from a European perspective.

MATERIAL AND METHODS

A systematic review of MEDLINE database, in compliance with the PRISMA guidelines, was performed. A subgroup analysis screening all surgical series published within the last 20 years (January 2000 to March 2020) was performed. Weighted summary rates for tumor resection, oncological control, and facial nerve preservation were determined using meta-analysis models. This data along with contemporary practice patterns were discussed within the task force to generate consensual recommendations regarding preoperative evaluations, optimal surgical strategy, and follow-up management.

RESULTS

Tumor classification grades should be systematically used in the perioperative management of patients, with large vestibular schwannomas (VS) defined as > 30 mm in the largest extrameatal diameter. Grading scales for pre- and postoperative hearing (AAO-HNS or GR) and facial nerve function (HB) are to be used for reporting functional outcome. There is a lack of consensus to support the superiority of any surgical strategy with respect to extent of resection and use of adjuvant radiosurgery. Intraoperative neuromonitoring needs to be routinely used to preserve neural function. Recommendations for postoperative clinico-radiological evaluations have been elucidated based on the surgical strategy employed.

CONCLUSION

The main goal of management of large vestibular schwannomas should focus on maintaining/improving quality of life (QoL), making every attempt at facial/cochlear nerve functional preservation while ensuring optimal oncological control, thereby allowing to meet patient expectations. Despite the fact that this analysis yielded only a few Class B evidences and mostly expert opinions, it will guide practitioners to manage these patients and form the basis for future clinical trials.

Clinical Predictors of Facial Nerve Outcomes After Surgical Resection of Vestibular Schwannoma

OBJECTIVE

To identify clinical predictors of facial nerve (FN) outcomes after microsurgical resection of vestibular schwannoma (VS).

STUDY DESIGN

Prospective cohort study.

SETTING

Academic medical center.

METHODS

Consecutive patients undergoing VS resection from November 2017 to October 2019 were included. FN function was evaluated with the House-Brackmann (HB) scale and stratified into good (HB I-II) and poor (HB III-VI) function. Analyses included descriptive statistics, correlation, and logistic regression.

RESULTS

Of 256 patients who met criteria (mean age, 47.7 years; 62.5% female), 227 (88.7%) achieved good FN function postoperatively and 238 (93.0%) at latest follow-up (mean, 154.8 days). Operative approaches consisted of translabyrinthine (50.8%), retrosigmoid (25.0%), and middle fossa craniotomies (24.2%). Extent of resection was decided intraoperatively, and gross or near total resection was accomplished in 237 (92.6%) cases. Postoperative HB grade correlated with latest HB grade (0.615, P < .001). Factors associated with good postoperative FN function included small tumor size (≤15 mm; odds ratio [OR], 2.425; P = .042), gross or near total resection (OR, 3.170; P = .041), and ≥100-µV intraoperative FN electromyographic response to a 0.05-mA stimulus (OR, 22.242; P < .001). Factors associated with good FN function at latest follow-up included gross total resection (OR, 7.764; P = .003) and ≥100-µV FN electromyographic response (OR, 8.518; P < .001), accounting for surgical approach and tumor size.

CONCLUSION

Microsurgical resection of VS can be accomplished with excellent FN outcomes. Gross total resection and ≥100-µV intraoperative FN electromyographic response predicted excellent FN outcomes. Immediate postoperative FN function is a prognosticator of long-term FN function.

Near Total Versus Gross Total Resection of Large Vestibular Schwannomas: Facial Nerve Outcome

BACKGROUND

Large vestibular schwannomas (VSs) with brainstem compression are generally reserved for surgical resection. Surgical aggressiveness must be balanced with morbidity from cranial nerve injury. The purpose of the present investigation is to evaluate the clinical presentation, management modality, and patient outcomes following near total resection (NTR) vs gross total resection (GTR) of large VSs.

OBJECTIVE

To assess facial nerve outcome differences between GTR and NTR patient cohorts.

METHODS

Between January 2010 and March 2018, a retrospective chart review was completed to capture patients continuously who had VSs with Hannover grades T4a and T4b. NTR was decided upon intraoperatively. Primary data points were collected, including preoperative symptoms, tumor size, extent of resection, and postoperative neurological outcome.

RESULTS

A total of 37 patients underwent surgery for treatment of large and giant (grade 4a and 4b) VSs. Facial nerve integrity was preserved in 36 patients (97%) at the completion of surgery. A total of 27 patients underwent complete resection, and 10 had near total (>95%) resection. Among patients with GTR, 78% (21/27) had House-Brackmann (HB) grade I-II facial nerve function at follow-up, whereas 100% (10/10) of the group with NTR had HB grade I-II facial nerve function. Risk of meningitis, cerebrospinal fluid leak, and sinus thromboses were not statistically different between the 2 groups. There was no stroke, brainstem injury, or death. The mean follow-up was 36 mo.

CONCLUSION

NTR seems to offer a benefit in terms of facial nerve functional outcome compared to GTR in surgical management of large VSs without significant risk of recurrence.

"Large and giant vestibular schwannomas: overall outcomes and the factors influencing facial nerve function"

(1) To study the overall outcomes of patients surgically treated for large/giant vestibular schwannomas (VSs) and (2) to identify and analyze preoperative and intraoperative prognostic factors influencing facial nerve (FN) outcome. A retrospective clinical study was conducted at a quaternary referral otology and skull-base center. A total of 389 cases were enrolled. The inclusion criteria were patients with tumor > 30 mm undergoing surgery with a minimum follow-up of 12 months. Neurofibromatosis-II, previous radiotherapy, revision surgeries, preoperative FN House-Brackmann (HB) grade > I, partial resections, incomplete records, or those lost to follow-up for a minimum period of 1 year were excluded. In addition, partial resections and cases where FN was sacrificed intraoperatively were also excluded and were analyzed separately. The mean duration of symptoms was 35.4 months, pronounced more in elderly (58.3 months) than in younger individuals (28.4 months). Mean tumor diameter was 36 mm and 52.7% was cystic. Total resection (TR), near total resection (NTR), and subtotal resections (STR) were achieved in 77.4%, 9.5%, and 13.2% of cases, respectively. Regrowth was observed only after STR (19.6%). Good (HB I-II), moderate (HB III), and poor (HB IV-VI) FN functions were observed in 36.8%, 51.7%, and 11.6% cases, respectively. Younger individuals underwent TR in 259 (86.9%) cases against 42 (46.2%) in elderly individuals. Non-total resections (NTR/STR) were performed in 49 (53.8%) cases in elderly as against 39(13.1%) in younger individuals. Good FN outcome was observed in 28 (57.1%) cases of non-total resections in elderly as against 13 (33.3%) cases in younger individuals. On multiple logistic regression analysis, size of the tumor, preoperatively prolonged duration of symptoms, profound deafness, and antero-superiorly located FN with respect to the tumor played a detrimental role in the final facial nerve outcome postoperatively. On the contrary, in large tumors (3-3.9 cm), presence of vertigo/disequilibrium had a relatively better impact on final FN outcome. Partial resections accounted for 41(7.8%) cases and FN was interrupted in 71(13.6%) cases in total. Factors detrimental to better FN outcome were giant VSs (> 4 cm), antero-superiorly located FN intratumorally, preoperatively prolonged duration of symptoms, and profound deafness. In large tumors (3-3.9 cm), presence of vertigo/disequilibrium had a better impact on FN outcome. Understandably, cases with TR in comparison with NTR/STR had worse FN outcomes. In comparison with younger patients, elderly patients underwent higher NTR/STR resulting in better FN outcomes. The above factors can be used as prognosticators for patient counseling and surgical decision making.

Long term phonatory function following acoustic neuroma surgery: a cohort study

Background: Acoustic neuroma (AN) is a well-recognized cause of neurological morbidity, peripheral facial paralysis being one of the most prevalent. Phonatory dysfunction in the late post-operative term has not been properly addressed so far.Objective: The objective of this study is to describe the outcomes of phonatory function on the long-term follow-up of AN surgery and identify its prognostic factors.Material and methods: This cohort study included patients submitted to AN surgery from 1999 to 2014, with a mean follow up of 6.4 ± 4.5 years. To evaluate the phonatory function, we performed a combination of noninvasive acoustic and aerodynamic measurements including vocal intensity and stability, maximum declination rate of the glottal airflow (MDR) and transglottal pressure scale (TP).Results: 101 patients were studied. 25 (24.7%) presented a deficit in phonatory function. Women comprised 56% and the mean age was 42.4 ± 13.8 years (range19-80). 100% presented reduced expiratory airflow capacity with excessive manifestation of the laryngeal musculature (TP > 1,23s ;MDR/z/<MDR/s/). Dysphonic patients presented more neurofibromatosis II (NF II) (40% vs 12.7% p = .002), large tumors (3.8 ± 1.1 p = .002) and needed less surgeries (≥256.7% vs 74.6%, p = .0073) in univariate analysis. NFII and tumor size were predictive of dysphonia according to multivariate analysis (NFII-OR 5.57, p = .006; tumor size-each 1 cm, OR1.68, p = .062).Conclusion: The late postoperative prevalence of dysphonia corresponded to 24.7%. Dysphonia could be secondary to the hyperfunction of laryngeal musculature explained by the reduced expiratory airflow found in our patients. Tumor size and NF II were predictors for the occurrence of dysphonia in the present study.HighlightsThe comprise of phonation function can be a morbidity of AN surgeryNF II and tumor size were predictive of dysphonia on late postoperative periodData of hypofunction secondary to the phonatory hyperfunction were unanimous in the dysphonic patients.The early diagnosis and treatment of phonation function could avoid alterations of pneumophono-articulatory coordination and projection deficiency.

Clinical outcomes of resecting scarpa's ganglion during vestibular schwannoma surgery

Vestibular schwannomas are slow-growing tumors arising from the Schwann cells of the vestibular nerve. Scarpa's ganglion, the vestibular nerve ganglion, is located within the internal auditory meatus. Surgical treatment of vestibular schwannomas carries the potential of resecting Scarpa's ganglion along with the tumor. No prior studies have evaluated outcomes based on the presence of Scarpa's ganglion within tumor specimens. The neurosurgery patient records were queried for patients who underwent surgical resection of vestibular schwannomas at the University of Missouri Healthcare between January 1, 2008 and December 31, 2018. Inclusion criteria consisted of minimum age of 18, imaging demonstrating an eighth nerve tumor, surgical resection thereof, and a final pathological diagnosis of WHO grade I schwannoma. Data were collected retrospectively. The histological slides of the tumors were reviewed, and the presence or absence of the ganglion was noted. Outcomes analyzed included postoperative dizziness, hearing, and facial nerve function. Fifty-two patients met inclusion criteria. Ten (19%) resected tumors contained portions of the ganglion. No difference in risk of resection of ganglion occurred based on the surgical approach (p = 0.2454). Mean follow-up duration was 24.6 months ± 26.2 standard deviation. No differences in postoperative hearing or dizziness (p = 0.8483 and p = 0.3190 respectively) were present if Scarpa's ganglion was resected. House-Brackmann classification of facial nerve function at last follow-up was similar (p = 0.9190). Resection of Scarpa's ganglion with vestibular schwannomas does not increase risk of post-operative dizziness, facial nerve weakness, or hearing loss.

Comparison between retrosigmoid and translabyrinthine approaches for large vestibular schwannoma: focus on cerebellar injury and morbidities

This study aimed to compare the surgical outcomes and morbidities of retrosigmoid and translabyrinthine approaches for large vestibular schwannoma (VS), with a focus on cerebellar injury and morbidities. Eighty-six consecutive patients with large VS, with a maximal extrameatal diameter > 3.0 cm, were reviewed between August 2010 and September 2018. The surgical outcomes, operating time, volume change of perioperative cerebellar edema, and inpatient rehabilitation related to cerebellar morbidities were compared between the two approaches. In total, 53 and 33 patients underwent the retrosigmoid and translabyrinthine approaches, respectively. The median follow-up time was 34.5 months. Surgical outcomes, including the extent of resection, tumor recurrence, and facial nerve preservation, showed no significant differences between the two groups. Patients who underwent the retrosigmoid approach showed a marginal trend for postoperative lower cranial nerve (LCN) dysfunction (P = 0.068). Although the approaching procedure time was longer in the translabyrinthine group, the tumor resection time was significantly longer in the retrosigmoid group (P = 0.001). The median change in the volume of the perioperative cerebellar edema was significantly larger in the retrosigmoid group (P < 0.001) and significantly related to the retrosigmoid approach, solid VS, and tumor resection time. Most cerebellar and LCN deficits were transient; however, the patients in the retrosigmoid group underwent inpatient rehabilitation more than those in the translabyrinthine group (P = 0.018). Both surgical approaches show equivalent surgical outcomes. Notably, the translabyrinthine approach for large VS has advantages in that it reduces cerebellar injury and related morbidities.

Benign Intracranial Lesions - Radiotherapy: An Overview of Treatment Options, Indications and Therapeutic Results

BACKGROUND

Radiation Therapy (RT) is an established treatment option for benign intracranial lesions. The aim of this study is to display an update on the role of RT concerning the most frequent benign brain lesions and tumors.

METHODS

Published articles about RT and meningiomas, Vestibular Schwannomas (VSs), Pituitary Adenomas (PAs), Arteriovenous Malformations (AVMs) and craniopharyngiomas were reviewed and extracted data were used.

RESULTS

In meningiomas RT is applied as an adjuvant therapy, in case of patientrefusing surgery or in unresectable tumors. The available techniques are External Beam RT (EBRT) and stereotactic ones such as Stereotactic Radiosurgery (SRS), Fractionated Stereotactic RT (FSRT), Intensity Modulated RT (IMRT) and proton-beam therapy. The same indications are considered in PAs, in which SRS and FSRT achieve excellent tumor control rate (92-100%), acceptable hormone remission rates (>50%) and decreased Adverse Radiation Effects (AREs). Upon tumor growth or neurological deterioration, RT emerges as alone or adjuvant treatment against VSs, with SRS, FSRT, EBRT or protonbeam therapy presenting excellent tumor control growth (>90%), facial nerve (84-100%), trigeminal nerve (74-99%) and hearing (>50%) preservation. SRS poses an effective treatment modality of certain AVMs, demonstrating a 3-year obliteration rate of 80%. Lastly, a combination of microsurgery and RT presents equal local control and 5-year survival rate (>90%) but improved toxicity profile compared to total resection in case of craniopharyngiomas.

CONCLUSION

RT comprises an effective treatment modality of benign brain and intracranial lesions. By minimizing its AREs with optimal use, RT projects as a potent tool against such diseases.

Keyhole retrosigmoid approach for large vestibular schwannomas: strategies to improve outcomes

OBJECTIVE There are numerous treatment strategies in the management for large vestibular schwannomas, including resection only, staged resections, resections followed by radiosurgery, and radiosurgery only. Recent evidence has pointed toward maximal resection as being the optimum strategy to prevent tumor recurrence; however, durable tumor control through aggressive resection has been shown to occur at the expense of facial nerve function and to risk other approach-related complications. Through a retrospective analysis of their single-institution series of keyhole neurosurgical approaches for large vestibular schwannomas, the authors aim to report and justify key techniques to maximize tumor resection and reduce surgical morbidity. METHODS A retrospective chart review was performed at the Centre for Minimally Invasive Neurosurgery. All patients who had undergone a keyhole retrosigmoid approach for the resection of large vestibular schwannomas, defined as having a tumor diameter of ≥ 3.0 cm, were included in this review. Patient demographics, preoperative cranial nerve status, perioperative data, and postoperative follow-up were obtained. A review of the literature for resections of large vestibular schwannomas was also performed. The authors' institutional data were compared with the historical data from the literature. RESULTS Between 2004 and 2017, 45 patients met the inclusion criteria for this retrospective chart review. When compared with findings in a historical cohort in the literature, the authors' minimally invasive, keyhole retrosigmoid technique for the resection of large vestibular schwannomas achieved higher rates of gross-total or near-total resection (100% vs 83%). Moreover, these results compare favorably with the literature in facial nerve preservation (House-Brackmann I-II) at follow-up after gross-total resections (81% vs 47%, p < 0.001) and near-total resections (88% vs 75%, p = 0.028). There were no approach-related complications in this series. CONCLUSIONS It is the experience of the senior author that complete or near-complete resection of large vestibular schwannomas can be successfully achieved via a keyhole approach. In this series of 45 large vestibular schwannomas, a greater extent of resection was achieved while demonstrating high rates of facial nerve preservation and low approach-related and postoperative complications compared with the literature.

Adaptive hybrid surgery analysis (AHSA) for adjuvant gamma knife radiosurgery treatment of vestibular schwannoma residuals

OBJECTIVES

Adaptive Hybrid Surgery Analysis (AHSA, Brainlab, Munich, Germany) is a software application generating in real-time conceptual dose plans for tumor residuals but has so far not been assessed for usability in a Gamma Knife (Elekta, Stockholm, Sweden) radiosurgery practice. We aimed to compare AHSA stereotactic radiosurgery dose plans with Leksell Gamma Plan (LGP, Elekta, Stockholm, Sweden) plans for adjuvant radiosurgical treatment of Vestibular Schwannoma (VS) residuals.

PATIENTS AND METHODS

In this retrospective comparative study, we compared the automatically calculated AHSA dose plans with clinical LGP treatment plans in 13 patients radiosurgically treated for VS residuals. We first created an LGP template based on our specific constraints to organs at risk (OAR), and a tumor prescription volume coverage of minimum 98%. As most proximal anatomy at risk is not manually contoured in our practice, OARs (i.e. brainstem, optic apparatus and cochlea) in the planning images were automatically segmented in Elements Anatomical Mapping and imported into the AHSA software for re-planning and comparison with the LGP dose plans.

RESULTS

There was no significant difference in tumor coverage and conformity index between the LGP and AHSA dose planning data, with the mean and maximal dose to the brainstem slightly higher in the latter.

CONCLUSION

The AHSA dose plans for adjuvant radiosurgical treatment of VS residuals were comparable to those of LGP used in our Gamma Knife practice, confirming the usability of AHSA in the management of Vestibular Schwannoma in a Gamma Knife practice.

A-train clusters and the intermedius nerve in vestibular schwannoma patients

OBJECTIVE

EMG "A-train" activity correlates with postoperative facial palsy after vestibular schwannoma (VS) surgery. An intermedius nerve separate from the facial nerve increases A-trains without significant impact on function. We investigate occurrence of A-train "clusters", A-trains over a majority of channels within a short time frame.

METHODS

Data from 217 patients with first surgery for VS were evaluated retrospectively. Continuous EMG recorded with 9 channels was evaluated for A-train patterns. "Clusters" of A-trains were identified, i.e. A-trains within 3 seconds over a majority of channels. Relation to a separate intermedius, tumor size and facial palsy was evaluated.

RESULTS

Correlations between A-trains and postoperative facial palsy were higher in patients without separate intermedius (r = 0.562 versus r = 0.194). Clusters were identified in 107 patients (49.3%), separate intermedius in 109 (50.2%), with significant association of both (p < 0.001, Chi-Square test). Excluding clusters slightly increased correlation of A-trains to facial nerve function.

CONCLUSIONS

A-train clusters have limited relevance for predicting postoperative paresis. However, they should be regarded as warning signs, suggesting the presence of a separate intermedius nerve.

SIGNIFICANCE

A-train "clusters" are a sign of hyperactivity of the facial nerve due to a separate intermedius nerve and may confound intraoperative monitoring during VS surgery.

Intentional Subtotal Resection of Vestibular Schwannoma: A Reexamination

Background  Treatment of vestibular schwannomas (VS) remains controversial. Historical surgical series prioritized gross total resections (GTR); however, near total resections (NTR) and intentional subtotal resections (STR) aiming at improving cranial nerve outcomes are becoming more popular. Objective  The main purpose of this article is to assess the tumor control and facial nerve outcomes in VS patients treated with STR or NTR. Methods  VS patients undergoing STR or NTR at our institution between 1984 and 2016 were retrospectively reviewed. Patient demographics, extent of tumor resection, facial nerve injury, tumor recurrence, and need for Gamma Knife radiosurgery were analyzed. Facial nerve outcomes were quantified using House-Brackmann (HB) scores. Tumor regrowth was defined by the San Francisco criteria. Results  Four-hundred fifty-seven VS resections were performed in a 32-year period. Sixty cases met inclusion criteria. The mean (range) follow-up duration was 30.9 (12-103) months. The STR cohort ( n  = 33) demonstrated regrowth in 12 patients (36.3%) at an average of 23.6 months. The NTR cohort ( n  = 27) did not experience tumor recurrence. Risk of tumor recurrence was positively correlated with preoperative tumor size ( p  = 0.002), size of residual tumor ( p  < 0.001), and STR ( p  < 0.001). Facial nerve outcomes of HB1-2 were observed in the majority of patients in both cohorts (74.1% NTR, 56% STR), though NTR was associated with a higher likelihood of facial nerve recovery ( p  = 0.003). Conclusion  GTR remains the gold standard as long as facial nerve outcomes remain acceptable. NTR achieved superior tumor control and higher likelihood of facial nerve recovery compared with STR.

Case Report: Facial Nerve Bifurcation Noted During Resection of Vestibular Schwannoma

BACKGROUND AND IMPORTANCE

Resection of cerebellopontine angle tumors is challenging because the proximity of the facial nerve puts it at risk of inadvertent injury and subsequent dysfunction. It is critical to consider variations in anatomy and be aware of the potential deviations in the course of the nerve in order to avoid damage.

CLINICAL PRESENTATION

We present a case of a facial nerve bifurcation identified during resection of a vestibular schwannoma.

CONCLUSION

This is the only reported case of proximal facial nerve bifurcation. We review what is known about variations in proximal facial nerve anatomy, the rates of facial nerve injury after schwannoma resection, and the importance of neuromonitoring in identifying the nerve and predicting function postoperatively. Ultimately, understanding possible anatomic variations in the nerve is critical to minimize iatrogenic injury during surgery.

Adaptive Hybrid Surgery: Paradigm Shift for Patient-centered Neurosurgery

The surgical management of cerebral and skull base lesions has evolved greatly in the last few decades. Still, a complete resection of lesions abutting critical neurovascular structures carries significant morbidity. Stereotactic radiosurgery (SRS) has emerged as an increasingly accepted treatment option. Minimally invasive, SRS results in excellent tumor control and low complication rates in patients with moderate-size tumors. The management of large cerebral and skull base tumors remains a formidable challenge. In such large tumors, radical surgical extirpation offers a significantly higher risk of neurological deficit, and SRS alone cannot be used because of the elevated incidence of radiation-induced complications known to be associated with large-volume tumors. With increasing treatment volumes, SRS-associated tumor control rates decrease and complication rates increase. Planned subtotal resection (STR) with adjuvant SRS (adaptive hybrid surgery [AHS]) has gained increasing interest in recent years as a multimodal approach. In AHS, a planned STR (aimed at decreasing surgical morbidity) followed by SRS to a preplanned residual tumor aids in harnessing advantages offered by both approaches. Although intuitive and reasonable, this paradigm shift from maximal resection at all cost has not been adopted widely. Combining open microsurgery with SRS requires a good understanding of both surgical and SRS modalities and their respective safety-efficacy features. We present a review and discussion on AHS as a modern, multidisciplinary treatment approach. Available data and views are discussed for vestibular schwannoma (VS) as a sample tumor. Other indications for AHS are mentioned in brief.

Systematic review and meta-analysis of the technique of subtotal resection and stereotactic radiosurgery for large vestibular schwannomas: a “nerve-centered” approach

OBJECTIVE

During the last decade, the primary objective for large vestibular schwannoma (VS) management has progressively shifted, from tumor excision to nerve preservation by using a combined microsurgical and radiosurgical approach. The aim of this study was to provide a systematic review and meta-analysis of the available literature regarding the combined strategy of subtotal resection (STR) followed by stereotactic radiosurgery (SRS) for large VSs.

METHODS

The authors performed a systematic review and meta-analysis in compliance with the PRISMA guidelines for article identification and inclusion using the PubMed, Embase, and Cochrane databases. Established inclusion criteria were used to screen all identified relevant articles published before September 2017 without backward date limit.

RESULTS

The authors included 9 studies (248 patients). With a weighted mean follow-up of 46 months (range 28–68.8 months), the pooled rate of overall tumor control was 93.9% (95% CI 91.0%–96.8%). Salvage treatment (second STR and/or SRS) was necessary in only 13 (5.24%) of 18 patients who experienced initial treatment failure. According to the House-Brackmann (HB) grading scale, functional facial nerve preservation (HB grade I–II) was achieved in 96.1% of patients (95% CI 93.7%–98.5%). Serviceable hearing after the combined approach was preserved in 59.9% (95% CI 36.5%–83.2%).

CONCLUSIONS

A combined approach of STR followed by SRS was shown to have excellent clinical and functional outcomes while still achieving a tumor control rate comparable to that obtained with a total resection. Longer-term follow-up and larger patient cohorts are necessary to fully evaluate the rate of tumor control achieved with this approach.

Preoperative diffusion tensor imaging-fiber tracking for facial nerve identification in vestibular schwannoma: a systematic review on its evolution and current status with a pooled data analysis of surgical concordance rates

OBJECTIVE Total tumor excision with the preservation of neurological function and quality of life is the goal of modern-day vestibular schwannoma (VS) surgery. Postoperative facial nerve (FN) paralysis is a devastating complication of VS surgery. Determining the course of the FN in relation to a VS preoperatively is invaluable to the neurosurgeon and is likely to enhance surgical safety with respect to FN function. Diffusion tensor imaging-fiber tracking (DTI-FT) technology is slowly gaining traction as a viable tool for preoperative FN visualization in patients with VS. METHODS A systematic review of the literature in the PubMed, Cochrane Library, and Web of Science databases was performed in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and those studies that preoperatively localized the FN in relation to a VS using the DTI-FT technique and verified those preoperative FN tracking results by using microscopic observation and electrophysiological monitoring during microsurgery were included. A pooled analysis of studies was performed to calculate the surgical concordance rate (accuracy) of DTI-FT technology for FN localization. RESULTS Fourteen studies included 234 VS patients (male/female ratio 1:1.4, age range 17-75 years) who had undergone preoperative DTI-FT for FN identification. The mean tumor size among the studies ranged from 29 to 41.3 mm. Preoperative DTI-FT could not visualize the FN tract in 8 patients (3.4%) and its findings could not be verified in 3 patients (1.2%), were verified but discordant in 18 patients (7.6%), and were verified and concordant in 205 patients (87.1%). CONCLUSIONS Preoperative DTI-FT for FN identification is a useful adjunct in the surgical planning for large VSs (> 2.5 cm). A pooled analysis showed that DTI-FT successfully identifies the complete FN course in 96.6% of VSs (226 of 234 cases) and that FN identification by DTI-FT is accurate in 90.6% of cases (205 of 226 cases). Larger studies with DTI-FT-integrated neuronavigation are required to look at the direct benefit offered by this specific technique in preserving postoperative FN function.

Long-Term Facial Nerve Outcomes after Microsurgical Resection of Vestibular Schwannomas in Patients with Preoperative Facial Nerve Palsy

Objectives  This study aimed at evaluating facial nerve outcomes in vestibular schwannoma patients presenting with preoperative facial nerve palsy. Design  A retrospective review. Setting  Single-institution cohort. Participants  Overall, 368 consecutive patients underwent vestibular schwannoma resection. Patients with prior microsurgery or radiosurgery were excluded. Main Outcome Measures  Incidence, House-Brackmann grade. Results  Of 368 patients, 9 had confirmed preoperative facial nerve dysfunction not caused by prior treatment, for an estimated incidence of 2.4%. Seven of these nine patients had Koos grade 4 tumors. Mean tumor diameter was 3.0 cm (range: 2.1-4.4 cm), and seven of nine tumors were subtotally resected. All nine patients were followed up clinically for ≥ 6 months. Of the six patients with a preoperative House-Brackmann grade of II, two improved to grade I, three were stable, and one patient worsened to grade III. Of the three patients with grade III or worse, all remained stable at last follow-up. Conclusions  Preoperative facial nerve palsy is rare in patients with vestibular schwannoma; it tends to occur in patients with relatively large lesions. Detailed long-term outcomes of facial nerve function after microsurgical resection for these patients have not been reported previously. We followed nine patients and found that eight (89%) of the nine patients had either stable or improved facial nerve outcomes after treatment. Management strategies varied for these patients, including rates of subtotal versus gross-total resection and the use of stereotactic radiosurgery in patients with residual tumor. These results can be used to help counsel patients preoperatively on expected outcomes of facial nerve function after treatment.

Patient- versus physician-reported facial disability in vestibular schwannoma: an international cross-sectional study

OBJECTIVE

Patient-reported outcomes are increasingly used in studies of vestibular schwannoma (VS); however, few studies have examined self-evaluated facial nerve function and its relation to physician-reported outcomes. The primary objective of this study was to compare patient self-evaluations of facial disability with physician-evaluated facial nerve status and with self-evaluations of a healthy control group. The second objective was to provide insight into the controversial subject of the optimal initial management of small- and medium-sized VSs; consequently, the authors compared patient-reported facial nerve disability following treatment via observation (OBS), Gamma Knife surgery (GKS), or microsurgery (MS). Lastly, the authors sought to identify risk factors for facial nerve dysfunction following treatment for small- and medium-sized VSs.

METHODS

All patients with a VS 3 cm or smaller that was singly treated with OBS, GKS, or MS at either of 2 independent treatment centers between 1998 and 2008 were retrospectively identified. Longitudinal facial nerve measures and clinical data, including facial nerve evaluation according to the House-Brackmann (HB) grading system, were extracted from existing VS databases. Supplementing the objective data were Facial Disability Index (FDI) scores, which were obtained via survey of patients a mean of 7.7 years after initial treatment.

RESULTS

The response rate among the 682 eligible patients was 79%; thus, data from a total of 539 patients were analyzed. One hundred forty-eight patients had been managed by OBS, 247 with GKS, and 144 with MS. Patients who underwent microsurgery had larger tumors and were younger than those who underwent OBS or GKS. Overall, facial nerve outcomes were satisfactory following treatment, with more than 90% of patients having HB Grade I function at the last clinical follow-up. Treatment was the major risk factor for facial nerve dysfunction. Almost one-fifth of the patients treated with MS had an objective decline in facial nerve function, whereas only 2% in the GKS group and 0% in the OBS cohort had a decline. The physical subscale of the FDI in the VS patients was highly associated with HB grade; however, the social/well-being subscale of the FDI was not. Thus, any social disability caused by facial palsy was not detectable by use of this questionnaire.

CONCLUSIONS

The majority of patients with small- and medium-sized VSs attain excellent long-term facial nerve function and low facial nerve disability regardless of treatment modality. Tumor size and microsurgical treatment are risk factors for facial nerve dysfunction and self-reported disability. The FDI questionnaire is sensitive to the physical but not the social impairment associated with facial dysfunction.

Surgical treatment of sporadic vestibular schwannoma in a series of 1006 patients

The management of sporadic vestibular schwannoma (VS) has evolved in the last decades. The aim of this study was to analyse the evolution in surgical outcomes of VSs operated by a neurotological team between 1990 and 2006 by different approaches. A monocentric retrospective review of medical charts of 1006 patients was performed. In order to assess eventual changes and progress, the 17-years period was divided in three periods, each one comprehending 268 VS (1990-1996), 299 VS (1997-2001), and 439 VS (2002-2006). Mean follow-up was 5.9 ± 2.4 years. Overall, complete VS removal was achieved in 99.4% of cases. Mortality rate was 0.3%, meningitis and CSF leaks were observed in 1.2 % and 9 % of the cases, respectively. CSF leakage decreased from 11.6% to 7.1% between the first and last period (p < 0.01) as well as revision surgery from 3.4 % to 0.9 % (p < 0.05). Facial nerve was anatomically preserved in 97.7% of cases. At one year, a good facial nerve function was observed in 85.1% of patients (grade I and II of House-Brackmann grading scale), which ranged between the first and last period from 78.4% to 87.6% (p <0.05). At one year, hearing preservation was obtained in 61.6% of patients, which increased from the first period to the last one from 50.9% to 69.0% (p < 0.05) (class A+B+C from the AAO-HNS classification). Useful hearing (class A+B) was observed in 33.5% of cases overall, with 21.8% and 42% in the first and last period, respectively (p < 0.01). Surgical outcomes of sporadic vestibular schwannoma have improved concerning facial nerve function outcomes, hearing preservation and cerebrospinal fluid (CSF) leaks, mainly due to the neuro-otological team's experience. Functional results after complete microsurgical removal of large VS depend on experience gained on small VS removal.

Prognostic Indices for Predicting Facial Nerve Outcome following the Resection of Large Acoustic Neuromas

This study analyzes the simple ratio of anterior-to-posterior extension of large (>2.5 cm) acoustic neuromas relative to the internal auditory canal (ICA; anterior-posterior [A/P] index) as a tool for predicting risk of facial nerve (FN) injury. In total, 105 patients who underwent microsurgical resection for large acoustic neuromas were analyzed retrospectively. House-Brackmann (HB) scores were assessed immediately postoperatively, at 1 month, and at 1 year. Lateral-medial, inferior-superior, A/P, and maximum diameters were measured from preoperative magnetic resonance images. These measurements and the A/P index were analyzed using univariable and multivariable statistical models to assess relationship to FN outcomes. The retrosigmoid, translabyrinthine, and combined approaches were used, and the extent of resection was evaluated. For every 1 standard deviation increase in the A/P index, a patient was 3.87 times more likely have a higher postoperative HB score ( p  < 0.0001). Accordingly, for every 1-mm increase anterior to the IAC, a patient was 16% more likely have a higher postoperative HB score ( p  < 0.001). After controlling for tumor size, a patient was still 3.82 times more likely have a higher postoperative HB score for every 1 standard deviation increase in the A/P index ( p  < 0.0001). While larger tumor size trended toward worse postoperative HB scores, it was not statistically significant. Our prognostic index may be useful to assess the risk of FN injury preoperatively for large acoustic neuromas, while also providing information about the tumor-nerve relationship.

Preserving normal facial nerve function and improving hearing outcome in large vestibular schwannomas with a combined approach: planned subtotal resection followed by gamma knife radiosurgery

Objective

To perform planned subtotal resection followed by gamma knife surgery (GKRS) in a series of patients with large vestibular schwannoma (VS), aiming at an optimal functional outcome for facial and cochlear nerves.

Methods

Patient characteristics, surgical and dosimetric features, and outcome were collected prospectively at the time of treatment and during the follow-up.

Results

A consecutive series of 32 patients was treated between July 2010 and June 2016. Mean follow-up after surgery was 29 months (median 24, range 4–78). Mean presurgical tumor volume was 12.5 cm³ (range 1.47–34.9). Postoperative status showed normal facial nerve function (House–Brackmann I) in all patients. In a subgroup of 17 patients with serviceable hearing before surgery and in which cochlear nerve preservation was attempted at surgery, 16 (94.1%) retained serviceable hearing. Among them, 13 had normal hearing (Gardner–Robertson class 1) before surgery, and 10 (76.9%) retained normal hearing after surgery. Mean duration between surgery and GKRS was 6.3 months (range 3.8–13.9). Mean tumor volume at GKRS was 3.5 cm³ (range 0.5–12.8), corresponding to mean residual volume of 29.4% (range 6–46.7) of the preoperative volume. Mean marginal dose was 12 Gy (range 11–12). Mean follow-up after GKRS was 24 months (range 3–60). Following GKRS, there were no new neurological deficits, with facial and hearing functions remaining identical to those after surgery in all patients. Three patients presented with continuous growth after GKRS, were considered failures, and benefited from the same combined approach a second time.

Conclusion

Our data suggest that large VS management, with planned subtotal resection followed by GKRS, might yield an excellent clinical outcome, allowing the normal facial nerve and a high level of cochlear nerve functions to be retained. Our functional results with this approach in large VS are comparable with those obtained with GKRS alone in small- and medium-sized VS. Longer term follow-up is necessary to fully evaluate this approach, especially regarding tumor control.

Facial Nerve Function and Quality of Resection in Large and Giant Vestibular Schwannomas Surgery Operated By Retrosigmoid Transmeatal Approach in Semi-sitting Position with Intraoperative Facial Nerve Monitoring

INTRODUCTION

Large and giant vestibular schwannomas pose a real problem in their management. The preservation of facial nerve function may limit tumor resection despite the use of intraoperative monitoring of the facial nerve. In Algeria, vestibular schwannomas represent 5% of all intracranial tumors operated on, 80.5% of which are large or giant.

METHODS

From January 2010 to December 2015, 151 large and giant vestibular schwannomas were operated in our department. Tumor diameter was between 30 and 60 mm. The most common presenting symptom was hearing loss, which was observed in 41.66% of all our patients. All patients were operated in the semi-sitting position with opening of the posterior wall of the internal auditory canal and under continuous intraoperative facial nerve function monitoring.

RESULTS

Tumor resection was total in 126 patients. Anatomic preservation of the facial nerve was the reason for nontotal resection in 25 patients. The facial nerve was anatomically preserved in 149 patients. Two years after surgery, the facial nerve function was grade I-II House-Brackmann (H-B) score in 124 cases (82%), grade III-IV H-B score in 21 cases (14%), and grade V-VI H-B score in 06 cases (04%). The status and the improvement of postoperative facial nerve function depend on 4 factors: anatomic preservation of nerve, stimulation threshold, cystic form, and the presence of train activity.

CONCLUSIONS

The development of anesthesia techniques and microsurgery and the systematic use of intraoperative monitoring of the facial nerve have allowed us to move from a life preservation era to another era of preservation of function.

Functional outcome and complications after the microsurgical removal of giant vestibular schwannomas via the retrosigmoid approach: a retrospective review of 16-year experience in a single hospital

BACKGROUND

Intracranial vestibular schwannoma still remain to be difficulty for its unique microsurgical technique and preservation of neuro-function, as well as reducing common complications that may arise in surgery.

METHODS

We consecutively enrolled 657 unilateral giant (>4 cm diameter) vestibular schwannoma patients treated in Huashan Hospital via the suboccipital retrosigmoid approach in the past 16 years. The extension of tumor removal, surgical mortality, facial nerve function, hearing, and the other main short and long-term complications were the studied parameters.

RESULTS

Gross total resection was performed in 556 patients (84.6%); near-total resection was achieved in 99 patients (15.1%). The mortality rate is 0.6%. The main short-term complications included 'new' deafness (47.6%), intracranial infection (7.6%), lower cranial nerve defects (7.5%) and pneumonia (6.2%). The facial nerve was preserved anatomically in 589 cases (89.7%). Good facial nerve functional outcome (House-Brackmann Grades I and II) postoperatively was achieved in 216 patients (32.9%). Other 308 cases (46.9%) were House-Brackmann grade III, and 133 patients (20.2%) were House-Brackmann grade IV-VI. Follow-up data were available for 566 of the 657 patients (86.1%). The common long-term complications were hearing loss (85.2%), facial paralysis (HB grade IV-VI, 24.4%) and facial numbness (15.7%).

CONCLUSIONS

Trends in the data lead the authors to suggest that the microsurgical technique, intraoperative nerve monitoring, and multidisciplinary cooperation, were the keys to improving prognostic outcomes in giant intracranial vestibular schwannoma patients.

Intraoperative auditory steady-state monitoring during surgery in the cerebellopontine angle for estimation of postoperative hearing classes

OBJECTIVE Brainstem auditory evoked potentials (BAEPs) have been used for intraoperative monitoring of the auditory nerve for many years. However, BAEPs yield limited information about the expected postoperative hearing quality and speech perception. The auditory steady-state response (ASSR) enables objective audiograms to be obtained in patients under anesthesia. These ASSRs could be used for intraoperative estimation of hearing classes to improve the postoperative outcome and quality of life. Studies investigating the clinical use of ASSRs during total intravenous anesthesia are currently lacking. The work presented in this article therefore investigates the application of ASSRs for intraoperative estimation of hearing classes. METHODS In 43 patients undergoing surgery for vestibular schwannoma, ASSR measurements were performed at the beginning and end of the surgical procedure. ASSR stimuli consisted of 80-dB hearing level amplitude-modulated tones with 5-minute duration, 90-Hz modulation, and 3 different carrier frequencies: 500, 1000, and 2000 Hz. Stimulation was performed unilaterally with and without contralateral masking, using single and combined carriers. Evoked responses were recorded and analyzed in the frequency domain. ASSRs were compared with extraoperative hearing classes and BAEPs using ANOVA, correlation, and receiver operating characteristic statistics. RESULTS ASSRs yielded high and consistent area under the curve (AUC) values (mean 0.83) and correlation values (mean -0.63), indicating reliable prediction of hearing classes. Analysis of BAEP amplitude changes showed lower AUC (mean 0.79) and correlation values (0.63, 0.37, and 0.50 for Waves I, III, and V, respectively). Latencies showed low AUC values (mean 0.6) and no significant correlation. Combination of several carriers for simultaneous evaluation reduced ASSR amplitudes and respective AUC values. Contralateral masking did not show a significant effect. CONCLUSIONS ASSRs robustly estimate hearing class in patients under total intravenous anesthesia, even when using short measurement durations. The method provides a diagnostic performance that exceeds conventional BAEP monitoring and enables objective and automated evaluation. On the basis of these findings, continuous intraoperative auditory monitoring could become a promising alternative or adjunct to BAEPs.

Surgical Treatment of Giant Vestibular Schwannomas: Facial Nerve Outcome and Tumor Control

BACKGROUND

Surgical treatment of giant vestibular schwannomas (GVS) is challenging. The philosophy of incomplete tumor resection may balance the preservation of facial nerve function and long-term tumor control.

OBJECTIVE

We aimed to evaluate the outcome of facial nerve function and tumor control in treating GVS via our institutional surgical strategy.

METHODS

From September 2009 to August 2014, 218 patients who underwent surgical treatment of GVS were enrolled in our study. The clinical features, extent of resections, facial nerve outcome, and the tumor regrowth free rate of these patients were retrospectively analyzed. The treatment strategy of this disease was discussed.

RESULTS

All patients had anatomic preservation of the facial nerve. Gross total resection (GTR) was achieved in 58 patients (28.6%), near-total resection (NTR) in 103 (50.7%), and subtotal resection (STR) in 42 (20.7%). Two patients died because of postoperative complications. After a mean follow-up of 39.7 ± 18.3 months, a favorable facial nerve outcome was achieved in 58.6%, 79.6%, and 83.3% of patients who underwent GTR, NTR, and STR, respectively. During follow-up, 20 patients had tumor regrowth and were treated by stereotactic radiosurgery (SRS), and tumor regrowth free rates were 96.6%, 92.2%, and 76.2% in GTR, NTR, and STR, respectively. The extent of resection was the independent risk factor for poor facial nerve function (P = 0.006).

CONCLUSIONS

A surgical philosophy of prioritizing facial nerve preservation over total tumor resection was recommended in treatment of GVS. Favorable facial nerve outcome and tumor control were achieved after NTR of the tumors.

Surgical management of skull base tumors

AIM

To present a review of the contemporary surgical management of skull base tumors.

BACKGROUND

Over the last two decades, the treatment of skull base tumors has evolved from observation, to partial resection combined with other therapy modalities, to gross total resection and no adjuvant treatment with good surgical results and excellent clinical outcomes.

MATERIALS AND METHODS

The literature review of current surgical strategies and management of skull base tumors was performed and complemented with the experience of Barrow Neurological Institute.

RESULTS

Skull base tumors include meningiomas, pituitary tumors, sellar/parasellar tumors, vestibular and trigeminal schwannomas, esthesioneuroblastomas, chordomas, chondrosarcomas, and metastases. Surgical approaches include the modified orbitozygomatic, pterional, middle fossa, retrosigmoid, far lateral craniotomy, midline suboccipital craniotomy, and a combination of these approaches. The selection of an appropriate surgical approach depends on the characteristics of the patient and the tumor, as well as the experience of the neurosurgeon.

CONCLUSION

Modern microsurgical techniques, diagnostic imaging, intraoperative neuronavigation, and endoscopic technology have remarkably changed the concept of skull base surgery. These refinements have extended the boundaries of tumor resection with minimal morbidity.

A Systematic Analysis of the Reliability of Diffusion Tensor Imaging Tractography for Facial Nerve Imaging in Patients with Vestibular Schwannoma

Surgeons need to visualize the facial nerve reliably in relation to the vestibular schwannoma (VS) in surgical planning. Diffusion tensor imaging (DTI) tractography has enabled unprecedented in vivo preoperative visualization. We collected data to measure the accuracy of DTI for an accurate location of the nerve in preoperative VS resection planning. A PubMed search for relevant studies was conducted. Inclusion criteria were gross total resection of VS, preoperative DTI identification of the facial nerve, and intraoperative cranial nerve localization by the surgeon. Exclusion criteria were tumors other than VS and unsuccessful preoperative location of the cranial nerve. Accuracy rate was calculated by comparing the intraoperative and preoperative locations detailed by DTI. The query identified 38 cases of VS that fit our inclusion criteria. Overall, 89% had surgical findings that agreed with the DTI location of the facial nerve. Of these cases, 32 patients had a postoperative House-Brackmann grade I or II. Our findings suggest that DTI is a reliable method for facial nerve imaging. Implementation of this technique may help decrease facial nerve injury during surgery. Limitations and further studies are needed to better understand what factors correlate with successful location of the facial nerve and DTI in patients with VS.