A Cross-sectional Survey of the North American Skull Base Society: Current Practice Patterns of Vestibular Schwannoma Evaluation and Management in North America

Quantification of Fat Graft Retention in the Translabyrinthine Approach Using Magnetic Resonance Imaging Volumetric Analysis

OBJECTIVE

To characterize the viability and volume of autologous free fat grafts over time, determine clinical/patient factors that may affect free fat graft survival and assess the clinical impact of free fat graft survival on patient outcomes in the translabyrinthine approach for lateral skull base tumor resection.

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary neurotologic referral center.

PATIENTS

Forty-two adult patients who underwent translabyrinthine craniotomy for resection of a lateral skull base tumor with the mastoid defect filled by autologous abdominal fat graft and subsequently underwent more than one postoperative magnetic resonance imaging (MRI) scans of the brain.

INTERVENTIONS

Mastoid obliteration with abdominal fat after craniotomy, postoperative MRI.

MAIN OUTCOME MEASURES

Rate of fat graft volume loss, fraction retention of original fat graft volume, initial fat graft volume, time to steady-state fat graft retention, rate of postoperative cerebrospinal fluid (CSF) leak, and/or pseudomeningocele formation.

RESULTS

Patients were followed postoperatively with MRI for a mean of 31.6 months with a mean of 3.2 postoperative MRIs per patient. Initial graft size was a mean of 18.7 cm3 with a steady-state fat graft retention of 35.5%. Steady-state graft retention (<5% loss per year) was achieved at a mean of 24.96 months postoperatively. No significant association was found in multivariate regression analysis of clinical factors impact on fat graft retention and CSF leak/pseudomeningocele formation.

CONCLUSIONS

In the use of autologous abdominal free fat graft for filling mastoid defects after translabyrinthine craniotomy, there is a logarithmic decline in fat graft volume over time, reaching steady state in 2 years. Rates of CSF leak or pseudomeningocele formation were not significantly affected by initial volume of the fat graft, rate of fat graft resorption, nor the fraction of original fat graft volume at steady state. In addition, no analyzed clinical factors significantly influenced fat graft retention over time.

Introducing an Evidence-Based Approach to Wait-And-Scan Management of Sporadic Vestibular Schwannoma

The advent of MRI has led to more sporadic vestibular schwannomas diagnosed today than ever before. Despite the average patient being diagnosed in their sixth decade of life with a small tumor and minimal symptoms, population-based data demonstrate that more tumors per capita are treated today than ever before. Emerging natural history data justify either an upfront treatment approach or the "Size Threshold Surveillance" approach. Specifically, if the patient elects to pursue observation, then existing data support the tolerance of some growth during observation in appropriately selected patients up until a specific size threshold range (about 15 mm of CPA extension). The current article discusses the rationale behind a shift in the existing observation management approach, where initial detection of growth typically begets treatment, and outlines the application of a more flexible and nuanced approach based on existing evidence.

Radiation for Sporadic Vestibular Schwannoma

Stereotactic radiosurgery (SRS) is a valid option for most patients undergoing treatment of small- and medium-sized vestibular schwannoma. Predictors of hearing preservation are the same for observation or surgery: when pretreatment hearing is normal, the tumor is smaller, and when a cerebrospinal fluid fundal cap exists. Hearing outcomes are poor when hearing loss exists pre-treatment. Rates of facial and trigeminal neuropathy are higher post-treatment after fractionated plans than single-fraction SRS. Subtotal resection and adjuvant radiation appears to offer patients with large tumors optimal outcomes for hearing, tumor control, and cranial nerve function versus gross total resection.

Comparing Patient Satisfaction After Upfront Treatment Versus Wait-and-Scan for Small Sporadic Vestibular Schwannoma

OBJECTIVE

Management of small vestibular schwannoma (VS) remains controversial, as patients are typically candidates for all three management options including microsurgery, stereotactic radiosurgery, or wait-and-scan. This study compares patient satisfaction across treatment modalities in patients with small VS.

STUDY DESIGN

Cross-sectional study.

SETTING

Survey distributed to members of the Acoustic Neuroma Association and Mayo Clinic patients.

METHODS

Patients with small (<1 cm in any location) sporadic VS who completed at least one survey regarding treatment history and patient satisfaction were included.

RESULTS

Among 346 patients with small VS, 106 (31%) underwent microsurgery, 78 (23%) radiosurgery, 152 (44%) wait-and-scan, and 10 (3%) multimodal treatment. Collectively, 307 (89%) patients indicated "Yes, I am happy with my treatment type and in hindsight I would not change anything," and 39 (11%) indicated "No, in hindsight I would have chosen a different treatment type." Satisfaction differed significantly by treatment group with 85, 86, 96, and 40% of patients in the microsurgery, radiosurgery, wait-and-scan, and multimodal groups reporting that they were satisfied with treatment, respectively ( p < 0.001). Satisfaction also differed significantly among those undergoing upfront treatment with microsurgery or radiosurgery (81%), initial wait-and-scan followed by treatment (88%), and wait-and-scan only groups (96%; p = 0.001). Specifically, the wait-and-scan only group demonstrated greater satisfaction compared with the other two treatment strategies ( p < 0.05 for both).

CONCLUSIONS

Patient satisfaction with the management of small VS is generally high. Management with wait-and-scan, even if treatment is eventually pursued, may offer higher patient satisfaction compared with upfront treatment.

Predicting Extent of Microsurgical Resection of Sporadic Vestibular Schwannoma

OBJECTIVE

Develop a predictive model for incomplete microsurgical resection of sporadic vestibular schwannoma (VS).

STUDY DESIGN

Historical cohort.

SETTING

Tertiary referral center.

PATIENTS

Patients with sporadic VS.

INTERVENTIONS

Microsurgery with preoperative intent of gross total resection.

MAIN OUTCOME MEASURES

Patient and tumor characteristics that influence extent of resection.

RESULTS

Among 603 patients, 101 (17%) had intracanalicular tumors and 502 (83%) had tumors with cerebellopontine angle (CPA) extension. For patients with CPA tumors, 331 (66%) underwent gross total resection and 171 (34%) underwent near-total or subtotal resection (NTR-STR). Multivariable modeling identified older age at surgery, larger linear tumor size, and absence of a fundal fluid cap as predictive of NTR-STR ( p < 0.001). From this model, one can estimate that a 20-year-old with a tumor that has less than 10 mm of CPA extension and a present fundal fluid cap has a predicted probability of NTR-STR of 0.01 (or 1%), whereas a 70-year-old with a tumor that has 30 mm or greater CPA extension and absence of a fundal fluid cap has a predicted probability of NTR-STR of 0.91 (or 91%). Among the 171 patients who underwent NTR-STR, 24 required secondary treatment at the time of last follow-up.

CONCLUSION

The primary predictors of incomplete microsurgical resection of VS include older age at surgery, larger linear tumor size, and absence of a fundal fluid cap. These factors can be used to estimate the likelihood of NTR-STR, aiding in preoperative discussions regarding future surveillance and potential need of secondary treatment, as well as shared clinical decision making.

Degree of preoperative hearing loss predicts time to early mobilization following vestibular schwannoma microsurgery

OBJECTIVE

To test the hypothesis that severe to profound preoperative hearing loss predicts less acute postoperative vestibulopathy following microsurgical removal of vestibular schwannoma (VS) allowing for earlier postoperative mobilization and hospital discharge.

METHODS

Patients with VS who underwent microsurgery and were found to have preoperative severe to profound hearing loss (pure tone average [PTA] > 70 dB HL) were matched 1:1 by age and tumor size to a group of randomly selected controls with preoperative serviceable hearing.

RESULTS

A total of 57 patients met inclusion criteria and were matched to controls. Median age at the time of microsurgery was 56 years. The median PTA and WRS for cases were 91 dB HL (interquartile range [IQR] 78-120) and 0% (IQR 0-0), respectively. Median tumor size was 14.2 mm (IQR 10.9-20.9). A total of 35 (61%) patients exhibited nystagmus after surgery associated with acute vestibular deafferentation. Median time to ambulation in the hallway was 2 days. Controls exhibited similar tumor size (12.7 mm, p = 0.11) and age (57 years, p = 0.52). Preoperative hearing loss did not predict severity or duration of postoperative nystagmus or days to discharge; however, those with Class D hearing exhibited a shorter time to ambulation (p = 0.04).

CONCLUSION

Following microsurgical removal of VS, preoperative profound hearing loss was associated with a shorter time to postoperative mobilization; however, there were no observed associations with duration or severity of nystagmus and time to hospital discharge. Although not a predictor of nystagmus, preoperative profound hearing loss may portend quicker recovery from clinically significant postoperative vestibulopathy.

Decision Making on Vestibular Schwannoma: Lessons from a Multidisciplinary Board

BACKGROUND

Management of vestibular schwannoma (VS) is a complex process aimed at identifying a clinical indication for fractionated stereotactic radiotherapy (sRT) or radiosurgery, microsurgical resection, or wait and scan (WS). We describe the experience of our VS multidisciplinary team (MDT) at a tertiary university referral center created for diagnosis, treatment, and follow-up of VS patients.

METHODS

We conducted a retrospective study on 132 consecutive patients referred to the MDT and managed by observation (WS), microsurgery, or fractionated sRT. The analysis included patient age, tumor size, hearing level, facial nerve function, tumor control, complications, and quality of life questionnaires.

RESULTS

Among the patients, 21% were subjected to microsurgery, 10% to sRT, and 69% to WS. The median follow-up time was 30 months. Outcomes based on different management modalities are described. Statistically significant differences among groups were detected in terms of quality of life (physical domain).

CONCLUSIONS

MDT may provide the best individualized therapy for VS patients compared with a single gold-standard strategy.

Defining current practice patterns of vestibular schwannoma management in Italy: results of a nationwide survey

Objective

Despite the increasing incidence rate of vestibular schwannomas (VS), controversies in their management are still present.

Methods

A 35-item multiple-choice survey investigating the current practice patterns of VS care was sent to the members of the Italian Society of Otolaryngology, Head and Neck Surgery (SIO) and of the Italian Society of Neurosurgery (SINCH).

Results

Among 66 respondents, 37 (56.0%) claimed to be actively involved in VS management. Most interviewees (35.1%) declared > 20 years of experience and 59.5% claimed to work in an academic practice. The number of cases evaluated in each centre per year varied widely, with 54.0% evaluating > 25 cases/year and only 13.6% > 100 cases/year. Multidisciplinary care for VS evaluation was confirmed by 50.0% of respondents, and multidisciplinary surgical care by 62.2%. Observation and surgery were the most common management options proposed. Further details regarding VS care are presented.

Conclusions

The present study provides the first overview on the current practice patterns of VS care in Italy. Although integrated in most centres, a multidisciplinary model of care needs to be encouraged. Wide heterogeneity in experience and practices is mostly influenced by the surgeon’s different specialties and by the lack of shared guidelines.

The biological underpinnings of radiation therapy for vestibular schwannomas: Review of the literature

OBJECTIVE

Radiation therapy is a mainstay in the treatment of numerous neoplasms. Numerous publications have reported good clinical outcomes for primary radiation therapy for Vestibular Schwannomas (VS). However, there are relatively few pathologic specimens of VSs available to evaluate post-radiation, which has led to a relative dearth in research on the cellular mechanisms underlying the effects of radiation therapy on VSs.

METHODS

Here we review the latest literature on the complex biological effects of radiation therapy on these benign tumors-including resistance to oxidative stress, mechanisms of DNA damage repair, alterations in normal growth factor pathways, changes in surrounding vasculature, and alterations in immune responses following radiation.

RESULTS

Although VSs are highly radioresistant, radiotherapy is often successful in arresting their growth.

CONCLUSION

By better understanding the mechanisms underlying these effects, we could potentially harness such mechanisms in the future to potentiate the clinical effects of radiotherapy on VSs.

LEVEL OF EVIDENCE

N/A.

Quality of life in vestibular schwannoma: a comparison of three surgical techniques

OBJECTIVE

Through years, interest in quality of life (QoL) among patients affected by vestibular schwannoma (VS) has increased. The expansion of the indications for endoscopic ear surgery allowed the development of the transcanal transpromontorial surgery (TTS) for VS removal. The objective of the present study was to assess QoL in a cohort of VS patients operated on by translabyrinthine (TL), retrosigmoid (RS) and TTS approach.

METHODS

The study was conducted on 111 patients who underwent surgery for VS between January 2017 and January 2020 at two different institutions. Patients fulfilled three questionnaires during follow-up: Glasgow Benefit Inventory, Depression Anxiety Stress Scales-21 and Penn Acoustic Neuroma Quality-Of-Life. The association between sex, age, date of surgery, tumor size, post-operative facial nerve (FN) function and QoL outcomes was assessed.

RESULTS

An overall subjective impairment was demonstrated in all groups. Age, Koos staging and FN functions were associated to distinct QoL outcomes.

CONCLUSIONS

QoL decreases in patients surgically treated for VS. The TTS may allow improved scores in many domains, confirming to be a subjectively well-tolerated technique.

Working Toward Consensus on Sporadic Vestibular Schwannoma Care: A Modified Delphi Study

OBJECTIVE

To address variance in clinical care surrounding sporadic vestibular schwannoma, a modified Delphi study was performed to establish a general framework to approach vestibular schwannoma care. A multidisciplinary panel of experts was established with deliberate representation from key stakeholder societies. External validity of the final statements was assessed through an online survey of registered attendees of the 8th Quadrennial International Conference on Vestibular Schwannoma.

STUDY DESIGN

Modified Delphi method.

METHODS

The panel consisted of 16 vestibular schwannoma experts (8 neurotology and 8 neurosurgery) and included delegates representing the AAOHNSF, AANS/CNS tumor section, ISRS, and NASBS. The modified Delphi method encompassed a four-step process, comprised of one prevoting round to establish a list of focus areas and three subsequent voting rounds to successively refine individual statements and establish levels of consensus. Thresholds for achieving moderate consensus, at ≥67% agreement, and strong consensus, at ≥80% agreement, were determined a priori. All voting was performed anonymously via the Qualtrics online survey tool and full participation from all panel members was required before procession to the next voting round.

RESULTS

Through the Delphi process, 103 items were developed encompassing hearing preservation (N = 49), tumor control and imaging surveillance (N = 20), preferred treatment (N = 24), operative considerations (N = 4), and complications (N = 6). As a result of item refinement, moderate (4%) or strong (96%) consensus was achieved in all 103 final statements. Seventy-nine conference registrants participated in the online survey to assess external validity. Among these survey respondents, moderate (N = 21, 20%) or strong (N = 73, 71%) consensus was achieved in 94 of 103 (91%) statements, and no consensus was reached in 9 (9%). Of the four items with moderate consensus by the expert panel, one had moderate consensus by the conference participants and three had no consensus.

CONCLUSION

This modified Delphi study on sporadic vestibular schwannoma codifies 100% consensus within a multidisciplinary expert panel and is further supported by 91% consensus among an external group of clinicians who regularly provide care for patients with vestibular schwannoma. These final 103 statements address clinically pragmatic items that have direct application to everyday patient care. This document is not intended to define standard of care or drive insurance reimbursement, but rather to provide a general framework to approach vestibular schwannoma care for providers and patients.

Management von Patienten mit Vestibularisschwannomen Typ IV

Hintergrund Vestibularisschwannome (VS) sind benigne Tumoren, die anhand der Hannover-Klassifikation bzw. der Koos-Klassifizierung eingeteilt werden. Trotz der umfangreichen Literatur sind die Klinik und die Behandlungskonzepte speziell bei großen VS selten beschrieben.

Material und Methoden Zwischen 2003 und 2018 wurden 61 Patienten mit VS Typ IV durch die Arbeitsgruppe Schädelbasischirurgie am Klinikum Dortmund behandelt. Die radiologischen und klinischen Daten wurden retrospektiv ausgewertet. Zudem erfolgte eine Subgruppenanalyse zwischen Patienten mit und ohne Kompression des IV. Ventrikels.

Ergebnisse Neben einer Hörminderung bei 55 Patienten (90 %) hatten die meisten Patienten multiple Symptome wie eine Trigeminusaffektion bei 16 (26 %), eine Fazialisparese bei 7 (12 %), eine Ataxie bei 27 (45 %) und Symptome eines Hirndruckanstiegs durch einen Hydrozephalus bei 4 Patienten (7 %). Bei Patienten mit einem VS Typ IVb wurde signifikant häufiger eine Ataxie, eine tonsilläre Herniation bzw. ein Hydrozephalus festgestellt. Eine komplette Resektion wurde in 48 Patienten (78 %) erreicht und eine weitestgehende Tumorentfernung in 12 Patienten (20 %). In der Langzeituntersuchung zeigten 90 % einen günstigen Outcome bezüglich des Nervus facialis (House-und-Brackman-Grad I–III). 6 Patienten (10 %) benötigten einen dauerhaften ventrikulo-peritonealen Shunt. Mehr als 90 % der Patienten erzielten einen Karnofsky-Index > 70 %.

Diskussion VS Typ IV sind häufig assoziiert mit Hydrozephalus, Ataxie, multiplen Hirnnervenausfällen und gelegentlich Zeichen eines intrakraniellen Druckanstiegs. Die primäre mikrochirurgische Resektion ist weiterhin eine entscheidende Therapieoption.

The Influence of Vestibular Schwannoma Tumor Volume and Growth on Hearing Loss

OBJECTIVE

To ascertain the relationship among vestibular schwannoma (VS) tumor volume, growth, and hearing loss.

STUDY DESIGN

Retrospective cohort study.

SETTING

Single tertiary center.

SUBJECTS AND METHODS

Adults with observed VS and serviceable hearing at diagnosis were included. The primary outcome was the development of nonserviceable hearing as estimated using the Kaplan-Meier method. Associations of tumor volume with baseline hearing were assessed using Spearman rank correlation coefficients. Associations of volume and growth with the development of nonserviceable hearing over time were assessed using Cox proportional hazards models and summarized with hazard ratios (HRs).

RESULTS

Of 230 patients with VS and serviceable hearing at diagnosis, 213 had serial volumetric tumor data for analysis. Larger tumor volume at diagnosis was associated with increased pure-tone average (PTA) (P < .001) and decreased word recognition score (WRS) (P = .014). Estimated rates of maintaining serviceable hearing at 6 and 10 years following diagnosis were 67% and 49%, respectively. Larger initial tumor volume was associated with development of nonserviceable hearing in a univariable setting (HR for 1-cm³ increase: 1.36, P = .040) but not after adjusting for PTA and WRS. Tumor growth was not significantly associated with time to nonserviceable hearing (HR, 1.57; P = .14), although estimated rates of maintaining serviceable hearing during observation were poorer in the group that experienced growth.

CONCLUSION

Larger initial VS tumor volume was associated with poorer hearing at baseline. Larger initial tumor volume was also associated with the development of nonserviceable hearing during observation in a univariable setting; however, this association was not statistically significant after adjusting for baseline hearing status.

Can an Imaging Marker of Consistency Predict Intraoperative Experience and Clinical Outcomes for Vestibular Schwannomas? A Retrospective Review

Objective  The main purpose of this article is to determine if vestibular schwannoma consistency as determined by tissue intensity on T2-weighted magnetic resonance imagings (MRIs) is predictive of intraoperative experience and postoperative clinical outcomes. Study Design  Retrospective chart review. Setting  Tertiary referral center. Patients  Seventy-seven patients diagnosed with vestibular schwannomas who were treated with microsurgical resection. Intervention  Diagnostic. Main Outcome Measures  Intraoperative measures include totality of resection, surgical time and cranial nerve VII stimulation and postoperative measures include House-Brackmann grade and perioperative complications. Results  Tumor consistency determined via tissue intensity on MRI was only found to correlate with surgical time, with a softer tumor being associated with a longer surgical time ( p  < 0.0001). However, this was primarily driven by tumor volume with larger tumors being associated with longer surgical time based on multivariate analysis. None of the other intraoperative or postoperative measures considered were found to correlate with tumor consistency. Conclusions  Tumor consistency determined by MRI is not predictive of intraoperative experience or postoperative outcomes in vestibular schwannomas. Tumor volume is the strongest driver of these outcome measures as opposed to tumor consistency.

A Cross-Sectional Survey of the North American Skull Base Society Part 3: The State of Lateral Skull Base Surgery Training in North America

Introduction  Optimal management of vestibular schwannoma (VS) demands involvement of an experienced multidisciplinary team. As the number of training programs in neurotology and skull base neurosurgery continues to rise, ensuring that trainees are capable of evidence-based decision-making and treatment, whether microsurgical or radiosurgical, is of paramount importance. The purpose of this study is to characterize the landscape of neurotologic and neurosurgical fellowship training programs in North America, with special reference to VS management. Methods  A 64-item web-based survey assessing VS practice trends was devised by members of the North American Skull Base Society (NASBS) Research Task Force and distributed electronically to NASBS membership via SurveyMonkey as a cross-sectional study. Participation was entirely voluntary and there was no remuneration for survey completion. The survey link was active from November 29 to December 14, 2016. Results  Of 719 members of the NASBS who were emailed a survey link, a total of 57 were returned (8%) completed surveys. Of all respondents, 51 (89%) claimed to have formal training in skull base neurosurgery or neurotology. Thirty-three respondents (65%) were skull base neurosurgeons while the remainder were neurotologists ( n  = 18; 35%). Institutions with fellowship programs tended to have a higher surgical, radiosurgical, and overall case volume than those with a residency program alone. However, 20% of respondents at institutions with fellowship programs reported evaluating less than 50 new diagnoses of VS per year and 12% reported a surgical case volume of less than 10 cases per year. Conclusion  As the number of skull base training programs expands, it is our duty to ensure that trainees gain sufficient experience to enter independent practice with the ability to exercise informed decision-making and safely perform VS surgery and radiosurgery. In the current training climate, implementing multidisciplinary care models, formalized training requirements, and emerging surgical simulators will support the development of minimum proficiencies in VS care.