Conservative management of vestibular schwannomas - second review of a prospective longitudinal study

Vestibular Schwannoma International Study of Active Surveillance Versus Stereotactic Radiosurgery: The VISAS Study

PURPOSE

The present study assesses the safety and efficacy of stereotactic radiosurgery (SRS) versus observation for Koos grade 1 and 2 vestibular schwannoma (VS), benign tumors affecting hearing and neurological function.

METHODS AND MATERIALS

This multicenter study analyzed data from Koos grade 1 and 2 VS patients managed with SRS (SRS group) or observation (observation group). Propensity score matching balanced patient demographics, tumor volume, and audiometry. Outcomes measured were tumor control, serviceable hearing preservation, and neurological outcomes.

RESULTS

In 125 matched patients in each group with a 36-month median follow-up (P = .49), SRS yielded superior 5- and 10-year tumor control rates (99% CI, 97.1%-100%, and 91.9% CI, 79.4%-100%) versus observation (45.8% CI, 36.8%-57.2%, and 22% CI, 13.2%-36.7%; P < .001). Serviceable hearing preservation rates at 5 and 9 years were comparable (SRS 60.4% CI, 49.9%-73%, vs observation 51.4% CI, 41.3%-63.9%, and SRS 27% CI, 14.5%-50.5%, vs observation 30% CI, 17.2%-52.2%; P = .53). SRS were associated with lower odds of tinnitus (OR = 0.39, P = .01), vestibular dysfunction (OR = 0.11, P = .004), and any cranial nerve palsy (OR = 0.36, P = .003), with no change in cranial nerves 5 or 7 (P > .05). Composite endpoints of tumor progression and/or any of the previous outcomes showed significant lower odds associated with SRS compared with observation alone (P < .001).

CONCLUSIONS

SRS management in matched cohorts of Koos grade 1 and 2 VS patients demonstrated superior tumor control, comparable hearing preservation rates, and significantly lower odds of experiencing neurological deficits. These findings delineate the safety and efficacy of SRS in the management of this patient population.

Management of sporadic intracanalicular vestibular schwannomas: A critical review and International Stereotactic Radiosurgery Society (ISRS) practice guidelines

BACKGROUND

The choice of an appropriate strategy for intracanalicular vestibular schwannoma (ICVS) is still debated. We conducted a systematic review and meta-analysis with the aim to compare treatment outcomes amongst management strategies (conservative surveillance (CS), microsurgical resection (MR), or stereotactic radiosurgery (SRS)) aiming to inform guideline recommendations on behalf of the International Stereotactic Radiosurgery Society (ISRS).

METHODS

Using PRISMA guidelines, we reviewed manuscripts published between January 1990 and October 2021 referenced in PubMed or Embase. Inclusion criteria were peer-reviewed clinical studies or case series reporting a cohort of ICVS managed with CS, MR, or SRS. Primary outcome measures included tumor control, the need for additional treatment, hearing outcomes, and posttreatment neurological deficits. These were pooled using meta-analytical techniques and compared using meta-regression with random effect.

RESULTS

Forty studies were included (2371 patients). The weighted pooled estimates for tumor control were 96% and 65% in SRS and CS series, respectively (P < .001). Need for further treatment was reported in 1%, 2%, and 25% for SRS, MR, and CS, respectively (P = .001). Hearing preservation was reported in 67%, 68%, and 55% for SRS, MR, and CS, respectively (P = .21). Persistent facial nerve deficit was reported in 0.1% and 10% for SRS and MR series, respectively (P = .01).

CONCLUSIONS

SRS is a noninvasive treatment with at least equivalent rates of tumor control and hearing preservation as compared to MR, with the caveat of better facial nerve preservation. As compared to CS, upfront SRS is an effective treatment in achieving tumor control with similar rates of hearing preservation.

Outcomes and Prognostic Factors in the Treatment of Intracanalicular Vestibular Schwannomas Using Gamma Knife Stereotactic Radiation

BACKGROUND

No gold standard has been developed for the therapy of intracanalicular vestibular schwannomas (IVS). Options for treatment include a conservative approach, microsurgery, or radiosurgery. Although the efficacy of these treatment has been well-documented, little is known about the determinants of outcome in IVSs following radiosurgery. Therefore, we examined the results in relation to age, gender, tumor volume, distance to fundus, microcyst existence, and radiosensitivity in this group. In addition, we investigated possible predictors of facial nerve function and hearing preservation.

METHODS

Ninety-four patients with unilateral IVS were included in the evaluation (52 women and 42 males). The patients were separated into younger and older age groups based on their median age (55 years). The median IVS volume was 138 mm3, microcysts were identified in 16 tumors, and 63 tumors were adjacent to the fundus. The data were analyzed using Statistica software package ver. 13.3.

RESULTS

At final follow-up, a statistically significant decrease in tumor volume and no statistically significant decline in hearing were noted, but no differences between age groups were found. The sex had no effect on overall tumor growth control, facial nerve preservation, or hearing preservation. Localization of IVS close to the fundus and the presence of tumor microcysts had no effect on the control of tumor growth, preservation of hearing, and sparing of facial nerve following radiosurgery. Cochlear dose had no influence on hearing preservation. Higher tumor volume was associated with its pseudoprogression during early follow-up and a greater risk of hearing loss.

CONCLUSIONS

Age, sex, tumor volume, proximity to the fundus, and the existence of a microcyst were not predictive of radiosensitivity nor preservation of facial nerve function and hearing, based on the findings. There was no effect of cochlear dose on hearing. Initial greater tumor volume was associated with an increased probability of tumor pseudoprogression.

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.

Schwannomas of Brain and Spinal Cord

Schwannomas are benign tumors originating from the Schwann cells of cranial or spinal nerves. The most common cranial schwannomas originate from the eight cranial nervevestibular schwannomas (VS). VS account for 6-8% of all intracranial tumors, 25-33% of the tumors localized in the posterior cranial fossa, and 80-94% of the tumors in the cerebellopontine angle (CPA). Schwannomas of other cranial nerves/trigeminal, facial, and schwannomas of the lower cranial nerves/are much less frequent. According to the World Health Organization (WHO), intracranial and intraspinal schwannomas are classified as Grade I. Some VS are found incidentally, but most present with hearing loss (95%), tinnitus (63%), disequilibrium (61%), or headache (32%). The neurological symptoms of VSs are mainly due to compression on the surrounding structures, such as the cranial nerves and vessels, or the brainstem. The gold standard for the imaging diagnosis of VS is MRI scan. The optimal management of VSs remains controversial. There are three main management options-conservative treatment or "watch-and-wait" policy, surgical treatment, and radiotherapy in all its variations. Currently, surgery of VS is not merely a life-saving procedure. The functional outcome of surgery and the quality of life become issues of major importance. The most appropriate surgical approach for each patient should be considered according to some criteria including indications, risk-benefit ratio, and prognosis of each patient. The approaches to the CPA and VS removal are generally divided in posterior and lateral. The retrosigmoid suboccipital approach is a safe and simple approach, and it is favored for VS surgery in most neurosurgical centers. Radiosurgery is becoming more and more available nowadays and is established as one of the main treatment modalities in VS management. Radiosurgery (SRS) is performed with either Gamma knife, Cyber knife, or linear accelerator. Larger tumors are being increasingly frequently managed with combined surgery and radiosurgery. The main goal of VS management is preservation of neurological function - facial nerve function, hearing, etc. The reported recurrence rate after microsurgical tumor removal is 0.5-5%. Postoperative follow-up imaging is essential to diagnose any recurrence.

A Subset of Intracanalicular Vestibular Schwannomas Demonstrates Minimal Growth Over a 10-Year Period

OBJECTIVE

Vestibular schwannomas (VS) commonly undergo magnetic resonance imaging (MRI) surveillance, but long-term data to support the ideal frequency is limited. Herein, we aim to investigate intracanalicular VS growth predictors and long-term growth rates (GR).

STUDY DESIGN

Retrospective chart review.

SETTING

Two tertiary care centers.

PATIENTS

Sporadic intracanalicular VS with initial conservative management and at least two sequential MRIs.

INTERVENTION

Serial MRI.

MAIN OUTCOME MEASURES

VS were categorized by baseline internal auditory canal tertile sublocalization (fundus, midpoint, porus) and size (≤100, 100-200, >200 mm3). Throughout follow-up, volumetric GR (mm3/yr) were determined (baseline-3 yrs, 3-5 yrs, 5-10 yrs) and treatment rates were assessed.

RESULTS

Ninety-nine intracanalicular VS were identified (mean follow-up of 6.1 ± 4.5 yrs). Mean GR before 5-year follow-up were comparable for baseline tertile involvement and size. After 5-year follow-up, mean GR of VS involving the fundus at baseline were lower than those involving the midpoint and fundus (6.17 ± 21.16 and 119.74 ± 117.57 mm3/yr, respectively; p = 0.034). Mean GR of VS with less than or equal to 100 mm3 at baseline (-7.29 ± 25.44 mm3/yr) were lower than those with 100 to 200 mm3 (86.55 ± 103.99 mm3/yr; p = 0.011) and more than 200 mm3 (45.70 ± 35.71 mm3/yr; p = 0.031). Vestibular schwannomas involving the midpoint and fundus had greater treatment rates compared with VS involving only the fundus (p < 0.001).

CONCLUSIONS

Baseline tertile involvement and size may predict long-term intracanalicular VS growth where fundal tumors or those less than or equal to 100 mm3 exhibit little long-term growth. Extending surveillance after 5-year follow-up may be reasonable for fundal VS.

Long-term natural history and patterns of sporadic vestibular schwannoma growth: A multi-institutional volumetric analysis of 952 patients

BACKGROUND

The current study aims to characterize the natural history of sporadic vestibular schwannoma volumetric tumor growth, including long-term growth patterns following initial detection of growth.

METHODS

Volumetric tumor measurements from 3505 serial MRI studies were analyzed from unselected consecutive patients undergoing wait-and-scan management at three tertiary referral centers between 1998 and 2018. Volumetric tumor growth was defined as a change in volume ≥20%.

RESULTS

Among 952 patients undergoing observation, 622 experienced tumor growth with initial growth-free survival rates (95% CI) at 1, 3, and 5 years following diagnosis of 66% (63-69), 30% (27-34), and 20% (17-24). Among 405 patients who continued to be observed despite demonstrating initial growth, 210 experienced subsequent tumor growth with subsequent growth-free survival rates at 1, 3, and 5 years following initial growth of 77% (72-81), 37% (31-43), and 24% (18-31). Larger tumor volume at initial growth (HR 1.13, P = .02) and increasing tumor growth rate (HR 1.31; P < .001) were significantly associated with an increased likelihood of subsequent growth, whereas a longer duration of time between diagnosis and detection of initial growth was protective (HR 0.69; P < .001).

CONCLUSIONS

While most vestibular schwannomas exhibit an overall propensity for volumetric growth following diagnosis, prior tumor growth does not perfectly predict future growth. Tumors can subsequently grow faster, slower, or demonstrate quiescence and stability. Larger tumor size and increasing tumor growth rate portend a higher likelihood of continued growth. These findings can inform timing of intervention: whether upfront at initial diagnosis, after detection of initial growth, or only after continued growth is observed.

Hearing loss and volumetric growth rate in untreated vestibular schwannoma

OBJECTIVE

In this study, the authors aimed to clarify the relationship between hearing loss and tumor volumetric growth rates in patients with untreated vestibular schwannoma (VS).

METHODS

Records of 128 treatment-naive patients diagnosed with unilateral VS between 2012 and 2018 with serial audiometric assessment and MRI were reviewed. Tumor growth rates were determined from initial and final tumor volumes, with a median follow-up of 24.3 months (IQR 8.5-48.8 months). Hearing changes were based on pure tone averages, speech discrimination scores, and American Academy of Otolaryngology-Head and Neck Surgery hearing class. Primary outcomes were the loss of class A hearing and loss of serviceable hearing, estimated using the Kaplan-Meier method and with associations estimated from Cox proportional hazards models and reported as hazard ratios.

RESULTS

Larger initial tumor size was associated with an increased risk of losing class A (HR 1.5 for a 1-cm3 increase; p = 0.047) and serviceable (HR 1.3; p < 0.001) hearing. Additionally, increasing volumetric tumor growth rate was associated with elevated risk of loss of class A hearing (HR 1.2 for increase of 100% per year; p = 0.031) and serviceable hearing (HR 1.2; p = 0.014). Hazard ratios increased linearly with increasing growth rates, without any evident threshold growth rate that resulted in a large, sudden increased risk of hearing loss.

CONCLUSIONS

Larger initial tumor size and faster tumor growth rates were associated with an elevated risk of loss of class A and serviceable hearing.

Prediction of Hearing Preservation in Vestibular Schwannoma Surgery According to Tumor Size and Anatomic Extension

OBJECTIVE

Vestibular schwannoma (VS) surgery is feasible for various tumor sizes that are inappropriate for wait and scan or radiosurgery. The predictive value of 2 grading systems was investigated for postoperative hearing preservation (HP) in a large series.

STUDY DESIGN

Retrospective analysis.

SETTING

Neurosurgical patient database of the University of Erlangen was queried between 2014 and 2017.

METHODS

Retrospective single-center analysis on 138 VSs operated on via a retrosigmoidal approach. The mean tumor size was 20.4 mm (SD, 7.6 mm) with fundal infiltration in 67.4%. The overall resection rate was 93.5%. Tumors were classified preoperatively by the 3-tier Erlangen grading system depending on size or the anatomically based 4-tier Koos grading system.

RESULTS

Preoperative hearing preservation was found in 70.3% of patients and was significantly correlated to tumor size (P = .001). For Erlangen grading, a mean postoperative serviceable hearing preservation rate of 32% was achieved: 83.3% for tumors <12 mm, 30.3% for tumors between 12 and 25 mm, and 5.3% for tumors >25 mm. In contrast, according to Koos grading, postoperative serviceable hearing preservation was 100% for grade 1 tumors (meatal), 35.6% for grade 2 (cisternal), 23.1% for grade 3 (brainstem contact), and 21.7% for grade 4 (brainstem compression). Of the total cohort, 86% had normal or nearly normal postoperative facial function (House-Brackmann grades 1 and 2).

CONCLUSION

Surgery on small VSs can achieve excellent hearing preservation. Different grading has a significant influence on and correlates with postoperative hearing preservation. Tumor size seems more important than anatomic relationship.

Intracanalicular Vestibular Schwannoma: A Systematic Review and Meta-analysis of Therapeutics Outcomes

OBJECTIVE

To perform a systematic review and meta-analysis summarizing the current evidence on the management of intracanalicular vestibular schwannoma.

DATA SOURCES

Embase (1947-), Medline (1946-), Cochrane library (1947-), Scopus (2010-), and CINAHL (1961-) were searched from 1969 to October 5, 2019 (50 years).

STUDY SELECTION

A search strategy was performed to identify patients with vestibular schwannoma confined to the internal auditory canal without extension to the cerebellopontine angle. Studies with patients aged less than 18, Neurofibromatosis type 2, revision cases, and non-English language were excluded.

DATA EXTRACTION

A standardized collection sheet was used for the extracted data and a quality assessment was performed using the Newcastle-Ottawa Scale with the comparability criterion omitted.

DATA SYNTHESIS

Seventy-one studies were included with 24 on observation, 14 on radiotherapy, and 34 on surgery. The primary outcome was serviceable hearing preservation. Secondary outcomes were preservation of facial nerve function, growth, involution, and dizziness. Sub-analysis on the type of surgery and type of radiotherapy were performed. Excel 2016 with MIX 2.0 Pro add-on package was used to analyze the data and create forest plots. Data were presented in proportion with a 95% confidence interval.

CONCLUSIONS

Serviceable hearing was observed in 31% of patients after observation, 56% after radiotherapy, and 51% after surgical treatment with mean follow-up time of 4.04 years, 4.92 years, and 2.23 years, respectively. Facial nerve function was found to be best preserved in both observation and radiotherapy groups. Vestibular schwannoma growth occurred in 33% of patients under observation. Involution occurred in 2% of patients under observation and in 38% after radiotherapy.

Predicting Potential of Rapid Tumor Growth in Small to Medium Vestibular Schwannomas on the Basis of Sway Assessed Using Posturography

OBJECTIVE

The relationship between quantitative posturography results and growth of vestibular schwannomas (VSs) during conservative management has not been studied. We aimed to clarify the relationship between the presence of disequilibrium based on posturographic measurement and VS growth.

METHODS

This retrospective, single-center study included 53 patients with VSs (Koos stage I or II) managed conservatively after initial diagnosis. Radiographic progression was considered present if 20% volumetric growth was observed over the imaging interval. Posturography was performed at initial diagnosis, and sway velocity (SV) and sway area were calculated. Tumor growth-free survival was estimated using the Kaplan-Meier method.

RESULTS

Mean follow-up period was 2.87 ± 2.58 years, up to tumor growth detection or last follow-up magnetic resonance imaging. Tumor growth incidence was 40.8% and 61.2% at 2 and 5 years, respectively. Cerebellopontine angle extension and SV with eyes open were related to tumor growth. Tumor growth-free survival of patients with cerebellopontine angle extension and patients with intracanalicular tumor at 2 years was 37.3% and 76.4%, respectively. Tumor growth-free survival of patients with SV >2.06 cm/second and patients with SV ≤2.06 cm/second at 2 years was 30.8% and 68.9%, respectively. The Cox hazard model demonstrated a significant risk for future tumor growth with SV >2.06 cm/second (relative risk, 2.475; 95% confidence interval, 1.11-5.37, P = 0.027).

CONCLUSIONS

We demonstrated a positive correlation between SV with eyes open and future tumor growth. Posturographic data are objective and quantitative; thus, SV may be a potential predictor of future growth of VSs.

Gamma knife surgery in the treatment of intracanalicular vestibular schwannomas

OBJECTIVE

According to the literature, gamma knife surgery (GKS) is a promising method for intracanalicular vestibular schwannoma (IVS) management, providing excellent tumor growth control rates (91%-100%) and good hearing preservation rates (41%-76%), but this evidence originates primarily from a small series of patients. The aim of this study was to present the outcomes of GKS in the largest group of patients with IVS studied to date, with particular emphasis on the long-term outcomes of treatment.

METHODS

The study included 136 consecutive patients with unilateral IVS, who underwent GKS in 2011-2015. Mean age of the patients was 54 ± 12.6 years. All patients were operated on with a 192-source cobalt-60 gamma knife unit. All patients had complete follow-up documentation and the mean duration of the follow-up was 52 ± 13.8 months (6-83 months). Neurological status (facial and trigeminal nerve), hearing and instability/dizziness presence were determined prior to GKS, immediately after the procedure, and during the follow-up visits.

RESULTS

Tumor growth control was obtained in 124/136 (~91.2%) patients. Hearing improvement was observed in 32/136 (23.5%) patients, and there was a distinct cluster of 9 patients (6.6%) regaining serviceable hearing after GKS, whereas in 36 patients (26.5%) was stable. Four patients developed facial nerve dysfunction, including 3 periodic hemifacial spasm and 1 partial paresis, which resolved spontaneously within 12 months of GKS. None of the operated patients showed new, debilitating neurological deficits, including trigeminal sensory disturbances or hydrocephalus.

CONCLUSIONS

GKS is a highly effective treatment for IVS, associated with low morbidity and good tumor growth control.

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.

EAONO position statement on Vestibular Schwannoma: Imaging Assessment Question: How should growth of Vestibular Schwannoma be defined?

The relevance of defining the growth of vestibular schwannoma (VS) is that any significant VS growth may impact treatment strategy. A conservative treatment strategy is often proposed as a primary treatment option in the management of VS. Several authors have demonstrated that a significant proportion of VSs do not grow, and those that do, usually grow slowly. Surgical and/or radiosurgical treatment options may be offered to the patient according to the VS growth. Therefore, defining the VS growth is a determinant in managing treatment strategies. A comprehensive literature search was performed to examine the definition of tumor growth for VS. The literature review was conducted using PubMed and Embase databases dated back to 20 years (1995-2015) and was updated until February 2015. VS growth should be measured on contrast-enhanced T1-weighted images. Although there the overall quality of the present studies is low, all highlight a significant VS growth of > 2 mm, and/or 1.2 cm3, and/or 20% change in volume, and/or the square of the product of the 2 orthogonal diameters. We suggest that VS growth should instead change management strategies when a 3-mm increase in diameter on two consecutive MRI scans are performed 1 year apart.

What is the Required Frequency of MRI Scanning in the Wait and Scan Management?

The wait and scan policy is being increasingly used as the first measure after the diagnosis of a vestibular schwannoma (VS) using magnetic resonance imaging (MRI). As part of the European Academy of Otology and Neuro-Otology (EAONO) position statement on VS, the frequency of imaging has been studied in the literature. Among 163 studies, 29 fulfilled the inclusion criteria and were scored using the Grading of Recommendations, Assessment, Development, and Evaluation system. Because tumor growth rate during the first 5 years of follow-up is predictive of further growth during the upcoming years, a protocol for wait and scan is useful for centers dealing with this condition. The EAONO proposal is that after the initial diagnosis by MRI, a first new MRI would take place after 6 months, annually for 5 years, and then every other year for 4 years, followed by a lifelong MRI follow-up every 5 years. The first early MRI is to screen for fast-growing tumors, and the lifelong follow-up with tapered intervals is to detect late repeated growth.

Surgery of the lateral skull base: a 50-year endeavour

Disregarding the widely used division of skull base into anterior and lateral, since the skull base should be conceived as a single anatomic structure, it was to our convenience to group all those approaches that run from the antero-lateral, pure lateral and postero-lateral side of the skull base as “Surgery of the lateral skull base”. “50 years of endeavour” points to the great effort which has been made over the last decades, when more and more difficult surgeries were performed by reducing morbidity. The principle of lateral skull base surgery, “remove skull base bone to approach the base itself and the adjacent sites of the endo-esocranium”, was then combined with function preservation and with tailoring surgery to the pathology. The concept that histology dictates the extent of resection, balancing the intrinsic morbidity of each approach was the object of the first section of the present report. The main surgical approaches were described in the second section and were conceived not as a step-by-step description of technique, but as the highlighthening of the surgical principles. The third section was centered on open issues related to the tumor and its treatment. The topic of vestibular schwannoma was investigated with the current debate on observation, hearing preservation surgery, hearing rehabilitation, radiotherapy and the recent efforts to detect biological markers able to predict tumor growth. Jugular foramen paragangliomas were treated in the frame of radical or partial surgery, radiotherapy, partial “tailored” surgery and observation. Surgery on meningioma was debated from the point of view of the neurosurgeon and of the otologist. Endolymphatic sac tumors and malignant tumors of the external auditory canal were also treated, as well as chordomas, chondrosarcomas and petrous bone cholesteatomas. Finally, the fourth section focused on free-choice topics which were assigned to aknowledged experts. The aim of this work was attempting to report the state of the art of the lateral skull base surgery after 50 years of hard work and, above all, to raise questions on those issues which still need an answer, as to allow progress in knowledge through sharing of various experiences. At the end of the reading, if more doubts remain rather than certainties, the aim of this work will probably be achieved.

The Role of Particle Therapy for the Treatment of Skull Base Tumors and Tumors of the Central Nervous System (CNS)

Radiation therapy (RT) is a mainstay in the interdisciplinary treatment of brain tumors of the skull base and brain. Technical innovations during the past 2 decades have allowed for increasingly precise treatment with better sparing of adjacent healthy tissues to prevent treatment-related side effects that influence patients' quality of life. Particle therapy with protons and charged ions offer favorable kinetics with sharp dose deposition in a well-defined depth (Bragg-Peak) and a steep radiation fall-off beyond that maximum. This review highlights the role of particle therapy in the management of primary brain tumors and tumors of the skull base.

Should we be moving to a national standardized non-gadolinium MR imaging protocol for the surveillance of vestibular schwannomas?

OBJECTIVES:

To examine whether the model of Getting It Right First Time (GIRFT) could be relevant to the surveillance of non-operated vestibular schwannomas (vs) by testing the following hypotheses: (1) in the UK there is a great variation in the imaging protocol for the follow-up of vs; (2) high-resolution, T ₂ weighted MRI (HRT ₂W-MRI) has an equivalent accuracy to gadolinium-enhanced T ₁ weighted MRI (Gd-MRI) in the assessment of vs size and; (3) imaging with HRT ₂W-MRI rather than Gd-MRI could offer financial savings.

METHODS:

Two neuroradiologists independently performed measurements of 50 vs imaged with HRT ₂W-MRI and Gd-MRI. Differences in mean tumour measurements between HRT ₂W-MRI and Gd-MRI were determined, as were intra- and interobserver concordance. Level of agreement was measured using Bland-Altman plots. Consultant neuroradiologists within 30 adult neurosurgical units in the UK were contacted via email and asked to provide the MRI protocol used for the surveillance of non-operated vs in their institution. The financial difference between scanning with HRT ₂W-MRI and Gd-MRI was determined within Leeds Teaching Hospitals NHS Trust.

RESULTS:

There was no statistically significant difference in the mean diameter of vs size, measured on HRT ₂W-MRI and Gd-MRI (p = 0.28 & p = 0.74 for observers 1 and 2 respectively). Inter- and intraobserver concordance were excellent (Interclass correlation coefficient = 0.99, Interclass correlation coefficient ≥ 0.98 respectively). Differences between the two sequences were within limits of agreement. 26 of 30 UK neuroscience centres (87 % response rate) provided imaging protocols. 16 of the 26 (62%) centres use Gd-MRI for the surveillance of vs. HRT ₂-MRI is £36.91 cheaper per patient than Gd-MRI.

CONCLUSION:

Variation exits across UK centres in the imaging surveillance of non-operated vs. HRT ₂W-MRI and Gd-MRI have equivalent accuracy when measuring vs. Imaging with HRT ₂W-MRI rather than Gd-MRI offers potential financial savings.

ADVANCES IN KNOWLEDGE:

This study highlights the potential health and economic benefits of a national standardized imaging protocol for the surveillance of non-operated vs.

Middle Fossa Approach for Resection of Vestibular Schwannomas: A Decade of Experience

BACKGROUND

The middle cranial fossa (MCF) approach is a challenging surgical technique for the resection of small and intermediate sized, primarily intracanalicular, vestibular schwannomas (VS), with the goal of hearing preservation (HP).

OBJECTIVE

To describe a decade-long, single institutional experience with the MCF approach for resection of VS.

METHODS

This is a retrospective cohort study of 63 patients who underwent the MCF approach for resection of VS from 2006 to 2016. Audiometric data included pure-tone average (PTA), low-tone pure-tone average (LtPTA), word recognition score, and American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) hearing classification at presentation and follow-up. Patients with postoperative serviceable (AAO-HNS class A-B) and/or useful (AAO-HNS class A-C) hearing were compared to those without HP. Facial nerve function was assessed using the House–Brackmann scale.

RESULTS

The mean age and duration of follow-up were 50 ± 13 yr and 21 ± 21 mo, respectively. The mean tumor size was 10 ± 4 mm. The serviceable and usable HP rates were 54% and 50%, respectively. Some residual hearing was preserved in 71% of patients. Large tumor size (P = .05), volume (P = .03), and extrameatal tumor extension (P = .03) were associated with poor audiometric outcomes. The presence of a fundal fluid cap (P = .01) was a favorable finding. At definitive testing, LtPTA was significantly better preserved than traditional PTA (P = .01). Facial nerve outcomes, tumor control rates, and durability of audiometric outcomes were excellent. 47% of patients pursued aural rehabilitation.

CONCLUSION

In our series, the MCF approach for VS provided excellent rates of tumor and facial nerve function, with durable serviceable HP.

Growth Patterns of Residual Tumor in Preoperatively Growing Vestibular Schwannomas

Objectives  To analyze growth of residual vestibular schwannoma (VS) following incomplete tumor resection and determine the influence of residual location and size. Design  Retrospective case note and scan review. Setting  Tertiary skull base unit. Participants  Patients with residual tumor following primary surgery for medium and large unilateral growing vestibular schwanomas between 2006 and 2009. Main Outcome Measures  Location of residual VS and post-operative growth, comparing those with more (>5%) or less than 5% of tumor residual (<5%). Results  Fifty-two patients had visible residual tumor left behind at surgery. Twenty had < 5% and 32 had > 5% residual. The residual growth rates were 38% overall, 20% in < 5%, and 50% in > 5% residuals. There was no significant difference in growth rates at different residual locations. Median follow-up was 6.4 years. Conclusions  There is a greater risk of regrowth of residuals > 5%. All positions of residual tumor can regrow, and the preoperative tumor size plays a role in this. Further data is needed to confirm if residual tumor in the fundus is less likely to grow.

Outcome of hearing preservation related to tumor morphologic analysis in acoustic neuromas treated by gamma knife radiosurgery

Background

Gamma Knife radiosurgery (GKRS) is an important part of the neurosurgical armamentarium in the treatment of acoustic neuromas. However, the treatment outcome related to the morphology of the tumor has not been rigorously studied. In this cohort, we evaluated the morphological features of the tumor in the tumor response and neurological outcomes after GKRS.

Material and methods

From July 2003 to December 2008, there were 93 cases of acoustic neuromas treated upfront with GKRS with 64 cases with serviceable hearing and 29 cases without serviceable hearing to fulfill the margin dose of 12Gy with at least follow up 5 years.

Results

The duration of symptom before GKRS in serviceable /no serviceable hearing was 7.9 ± 1.2 and 15.3 ± 3.1 months (p < 0.001) and associated no-hearing symptom was 70% and 35%, respectively (p < 0.001). There was 81.2% of hearing preservation after GKRS in serviceable hearing group including 27 cases of pear type (84%), 14 of linear type (70%), and 9 cases of sphere type (90%) (p < 0.01); however, there was no case of hearing improvement in the no-serviceable hearing group (0 of 29). There were 85% of patients with decreased tinnitus in serviceable hearing groups as compared to 61.5% of patients in no serviceable hearing group (p < 0.05). In multivariate analysis, the tumor morphology was highly correlated to hearing preservation rate (p < 0.01).

Conclusion

In the limited case of this cohort, we found that the tumor morphology and timing of treatment was highly correlated to the rate of hearing preservation. The sphere type of tumor morphology was associated with the best chance of hearing preservation.

Pretreatment growth rate as a predictor of tumor control following Gamma Knife radiosurgery for sporadic vestibular schwannoma

OBJECTIVE

Over the last 30 years, stereotactic radiosurgery (SRS) has become an established noninvasive treatment alternative for small- to medium-sized vestibular schwannoma (VS). This study aims to further define long-term SRS tumor control in patients with documented pretreatment tumor growth for whom conservative observation failed.

METHODS

A prospective clinical database was queried, and patients with sporadic VS who elected initial observation and subsequently underwent SRS after documented tumor growth between 2004 and 2014 were identified. Posttreatment tumor growth or shrinkage was determined by a ≥ 2-mm increase or decrease in maximum linear dimension, respectively.

RESULTS

Sixty-eight patients met study inclusion criteria. The median pre- and posttreatment observation periods were 16 and 43.5 months, respectively. The median dose to the tumor margin was 13 Gy (range 12–14 Gy), and the median maximum dose was 26 Gy (range 24–28 Gy). At the time of treatment, 59 tumors exhibited extracanalicular (EC) extension, and 9 were intracanalicular (IC). Of the 59 EC VSs, 50 (85%) remained stable or decreased in size following treatment, and 9 (15%) enlarged by > 2 mm. Among EC tumors, the median pretreatment tumor growth rate was 2.08 mm/year for tumors that decreased or were stable, compared with 3.26 mm/year for tumors that grew following SRS (p = 0.009). Patients who demonstrated a pretreatment growth rate of < 2.5 mm/year exhibited a 97% tumor control rate, compared with 69% for those demonstrating ≥ 2.5 mm/year of growth prior to SRS (p = 0.007). No other analyzed variables were found to predict tumor growth following SRS.

CONCLUSIONS

Overall, SRS administered using a marginal dose between 12–14 Gy is highly effective in treating VSs in which initial observation fails. Tumor control is achieved in 97% of VSs that exhibit slow (< 2.5 mm/year) pretreatment growth; however, SRS is less successful in treating tumors exhibiting rapid growth (≥ 2.5 mm/year).

The behaviour of residual tumour after the intentional incomplete excision of a vestibular schwannoma: is it such a bad thing to leave some behind?

OBJECTIVES

To evaluate the biological behaviour of tumour remnants intentionally left in the surgical bed following the incomplete excision of vestibular schwannomas (VS) and to review the relation between extent of resection and preservation of facial nerve function.

METHODS

A retrospective chart review of 450 patients who underwent surgery for resection of VS over 23 years (1992-2014). Of these, 50 (11%) patients had residual tumour intentionally left on/around the facial nerve (near-total or subtotal excision) to preserve facial nerve function intra-operatively. The growth of residual tumour was evaluated using serial magnetic resonance imaging scanning; pre- and postoperative facial nerve function was assessed using the House-Brackmann grading scale.

SETTING

Tertiary referral neurotology unit.

RESULTS

Of the 42 non-NF2 cases where the tumour was intentionally incompletely excised, 28 (67%) patients underwent subtotal resection (mean follow-up 68.5 ± 39.0 months) and 14 (33%) underwent near-total resection (mean follow-up 72.9 ± 48.3 months). Three patients (all in subtotal resection group) showed regrowth. This was not statistically different from the near-total resection group (χ² = 0.92, P = 0.31). The mean overall growth for these cases was 0.68 mm ± 0.32 mm/year. 5 (one near total, four subtotal) of the eight NF2 patients (62.5%) were excluded from our analysis. In the non-NF2 group, poor facial nerve outcomes (House-Brackmann scores of III-IV) were seen in 2/14 and V-VI in 3/14 of the near total compared with 7/25 and 4/25 respectively in the subtotal group.

CONCLUSIONS

Given that the primary surgery for the VS was only for tumours that were relatively large or grew during conservative treatment, the low rate of tumour remnant growth (7%) is reassuring. It may be appropriate to have a lower threshold for leaving tumour on the facial nerve in non-NF2 patients where complete resection may jeopardise facial nerve function.

Early Radiosurgery Improves Hearing Preservation in Vestibular Schwannoma Patients With Normal Hearing at the Time of Diagnosis

PURPOSE

Vestibular schwannomas (VS) are increasingly diagnosed in patients with normal hearing because of advances in magnetic resonance imaging. We sought to evaluate whether stereotactic radiosurgery (SRS) performed earlier after diagnosis improved long-term hearing preservation in this population.

METHODS AND MATERIALS

We queried our quality assessment registry and found the records of 1134 acoustic neuroma patients who underwent SRS during a 15-year period (1997-2011). We identified 88 patients who had VS but normal hearing with no subjective hearing loss at the time of diagnosis. All patients were Gardner-Robertson (GR) class I at the time of SRS. Fifty-seven patients underwent early (≤2 years from diagnosis) SRS and 31 patients underwent late (>2 years after diagnosis) SRS. At a median follow-up time of 75 months, we evaluated patient outcomes.

RESULTS

Tumor control rates (decreased or stable in size) were similar in the early (95%) and late (90%) treatment groups (P=.73). Patients in the early treatment group retained serviceable (GR class I/II) hearing and normal (GR class I) hearing longer than did patients in the late treatment group (serviceable hearing, P=.006; normal hearing, P<.0001, respectively). At 5 years after SRS, an estimated 88% of the early treatment group retained serviceable hearing and 77% retained normal hearing, compared with 55% with serviceable hearing and 33% with normal hearing in the late treatment group.

CONCLUSIONS

SRS within 2 years after diagnosis of VS in normal hearing patients resulted in improved retention of all hearing measures compared with later SRS.

Hearing subclassification may predict long-term auditory outcomes after radiosurgery for vestibular schwannoma patients with good hearing

OBJECTIVE In the era of MRI, vestibular schwannomas are often recognized when patients still have excellent hearing. Besides success in tumor control rate, hearing preservation is a main goal in any procedure for management of this population. The authors evaluated whether modified auditory subclassification prior to radiosurgery could predict long-term hearing outcome in this population. METHODS The authors reviewed a quality assessment registry that included the records of 1134 vestibular schwannoma patients who had undergone stereotactic radiosurgery during a 15-year period (1997-2011). The authors identified 166 patients who had Gardner-Robertson Class I hearing prior to stereotactic radiosurgery. Fifty-three patients were classified as having Class I-A (no subjective hearing loss) and 113 patients as Class I-B (subjective hearing loss). Class I-B patients were further stratified into Class I-B1 (pure tone average ≤ 10 dB in comparison with the contralateral ear; 56 patients), and I-B2 (> 10 dB compared with the normal ear; 57 patients). At a median follow-up of 65 months, the authors evaluated patients' hearing outcomes and tumor control. RESULTS The median pure tone average elevations after stereotactic radiosurgery were 5 dB, 13.5 dB, and 28 dB in Classes I-A, I-B1, and I-B2, respectively. The median declines in speech discrimination scores after stereotactic radiosurgery were 0% for Class I-A (p = 0.33), 8% for Class I-B1 (p < 0.0001), and 40% for Class I-B2 (p < 0.0001). Serviceable hearing preservation rates were 98%, 73%, and 33% for Classes I-A, I-B1, and I-B2, respectively. Gardner-Robertson Class I hearing was preserved in 87%, 43%, and 5% of patients in Classes I-A, I-B1, and I-B2, respectively. CONCLUSIONS Long-term hearing preservation was significantly better if radiosurgery was performed prior to subjective hearing loss. In patients with subjective hearing loss, the difference in pure tone average between the affected ear and the unaffected ear was an important factor in long-term hearing preservation.

Hearing Outcomes After Stereotactic Radiosurgery for Vestibular Schwannomas : Mechanism of Hearing Loss and How to Preserve Hearing

The use of stereotactic radiosurgery (SRS) expanded to include the treatment of vestibular schwannomas (VSs) in 1969; since then, efforts to increase tumour control and to reduce cranial neuropathy have continued. Using the currently recommended marginal dose of 12-13 Gy, long-term reported outcomes after SRS include not only excellent tumour control rates of 92-100 % but also outstanding functional preservation of the trigeminal and facial nerves, with values of 92-100 % and 94-100 %, respectively. Nonetheless, hearing preservation remains in the range of 32-81 %. Previous studies have suggested possible prognostic factors of hearing preservation such as the Gardner-Robertson grade, radiation dose to the cochlea, transient volume expansion (TVE) after SRS, length of irradiated cochlear nerve, marginal dose to the tumour, and age. However, we still do not clearly understand why patients lose their hearing after SRS for VS.Relevant to these considerations, one study recently reported that the auditory brainstem response (ABR) wave V latency and waves I and V interval (IL_I-V) correlated well with intracanalicular pressure values and even with hearing level. The demonstration that ABR values, especially wave V latency and IL_I-V, correlate well with intracanalicular pressure suggests that patients with previously elevated intracanalicular pressure might have an increased chance of hearing loss on development of TVE, which has been recognised as a common phenomenon after SRS or stereotactic radiotherapy (SRT) for intracranial schwannomas.In our experience, the ABR IL_I-V increased during the first 12 months after SRS for VSs in patients who lost their serviceable hearing. The effect of increased ABR IL_I-V on hearing outcome also became significant over time, especially at 12 months after SRS, and was more prominent in patients with poor initial pure-tone average (PTA) and/or ABR values. We hypothesise that patients with considerable intracanalicular pressure at the time of SRS are prone to lose their serviceable hearing due to the added intracanalicular pressure induced by TVE, which usually occurs within the first 12 months after SRS for VSs. Using these findings, we suggested a classification system for the prediction of hearing outcomes after SRS for VSs. This classification system could be useful in the proper selection of management modalities for hearing preservation, especially in patients with only hearing ear schwannoma or neurofibromatosis type 2.Advances in diagnostic tools, treatment modalities, and optimisation of radiosurgical dose have improved clinical outcomes, including tumour control and cranial neuropathies, in patients with VSs. However, the preservation of hearing function still falls short of our expectation. A prediction model for hearing preservation after each treatment modality will guide the proper selection of treatment modalities and permit the appropriate timing of active treatment, which will lead to the preservation of hearing function in patients with VSs.

Conservative management of vestibular schwannomas of 15 to 31 mm intracranial diameter

Objective:

To study the natural course of vestibular schwannomas 15 to 31 mm in diameter.

Methods:

A retrospective study of 45 patients conservatively managed with interval scanning was performed. Outcome measures were: changes in tumour size, clinical features and hearing. A tumour was considered to be growing if it increased in size by more than 2 mm.

Results:

Initial tumour sizes ranged from 15 to 31 mm, with a mean (± standard deviation) diameter of 20.1 ± 4.3 mm. The duration of follow up ranged from 6 months to 14 years (median, 3 years). Tumours grew in 11 cases (24.4 per cent), remained stable in 30 cases (66.7 per cent) and regressed in 4 cases (8.9 per cent). The overall mean tumour growth rate was 0.9 ± 2.2 mm per year; in growing tumours, it was 3.6 ± 2.9 mm per year.

Conclusion:

Outcomes were similar to those reported for smaller tumours. These findings suggest that patients with medium or moderately large tumours can be safely offered an initial period of conservative management before intervention is considered.

[Clinical and radiological evolution of a group of untreated acoustic neuromas]

INTRODUCTION

The acoustic neuroma is a benign tumour that originates in the vestibular branch of the eighth cranial nerve. The main treatment is surgery, but many authors suggest that with elderly patients or in small neuromas we can opt for watchful waiting.

METHODS

This was a retrospective study from 2007 to 2013 that included 27 patients diagnosed of acoustic neuroma that had not been treated due to the size of the tumour, age and comorbidities, or by patient choice. We evaluated overall condition, hearing thresholds, degree of canal paresis and central disorders.

RESULTS

After 6 years of follow up, clinical manifestations of 18 patients remained unchanged, 5 patients underwent hearing loss and developed tinnitus, 2 cases had more intense tinnitus and 2 cases had dizziness. The radiological controls by magnetic resonance imaging showed that the initial maximum diameters (5-16mm) increased by 1.7mm on average, with annual growth rates below 0.5mm.

CONCLUSION

In selected cases, such as for small neuromas and in elderly patients, the conservative option of close monitoring with magnetic resonance imaging is an important alternative given that, in our cases, clinical features and radiological image did not suffer major changes. If there were any such changes, therapeutic options could be proposed.

Hypofractionated stereotactic radiotherapy of acoustic neuroma: volume changes and hearing results after 89-month median follow-up

PURPOSE

The goal of this work was to evaluate toxicity and local control following hypofractionated stereotactic radiation treatment with special focus on changes in tumor volume and hearing capacity.

PATIENTS AND METHODS

In all, 29 patients with unilateral acoustic neuroma were treated between 2001 and 2007 within a prospective radiation protocol (7 × 4 Gy ICRU dose). Median tumor volume was 0.9 ml. Follow-up started at 6 months and was repeated annually with MRI volumetry and audiometry. Hearing preservation was defined as preservation of Class A/B hearing according to the guidelines of the American Academy of Otolaryngology (1995).

RESULTS

No patient had any intervention after a median imaging follow-up of 89.5 months, one patient showed radiological progression. Transient increase of tumor volume developed in 17/29 patients, whereas 22/29 patients (75.9%) presented with a volume reduction at last follow-up. A total of 21 patients were eligible for hearing evaluation. Mean pure tone average (PTA) deteriorated from 39.3 to 65.9 dB and mean speech discrimination score (SDS) dropped from 74.3 to 38.1%. The 5-year actuarial Class A/B hearing preservation rate was 50.0 ± 14.4%.

CONCLUSION

Radiation increases only minimally, if at all, the hearing deterioration which emerges by observation alone. Presbyacusis is not responsible for this deterioration. Transient tumor enlargement is common. Today radiation of small- and medium-sized acoustic neuroma can be performed with different highly conformal techniques as fractionated treatment or single low-dose radiosurgery with equal results regarding tumor control, hearing preservation, and side effects. Hypofractionation is more comfortable for the patient than conventional regimens and represents a serious alternative to frameless radiosurgery.

Determining benchmarks in hearing preservation surgery for vestibular schwannoma

Objectives The objectives of this study were to determine minimal benchmarks of success in vestibular schwannoma hearing preservation surgery, wherein the likelihood of having preserved hearing in a single patient is at least as likely as having created a poor facial nerve outcome for a single patient. Design This is a statistical analysis of published literature. Setting Academic Tertiary Medical Center. Main Outcome Measures Based on published natural history data, the number needed to treat (NNT) equation was used to calculate the minimally acceptable hearing preservation rates within various hearing classification schemes. Results Given good facial nerve outcome rates of 85, 90, and 95%, the corresponding hearing preservation rates at 4.7 years that are likely to preserve classes A and B hearing (American Academy of Otolaryngology-Head and Neck Surgery classification) in a single patient as to cause a poor facial nerve outcome are 70, 65, and 60%, respectively. If surgery is limited exclusively to intracanalicular tumors, these rates drop to 62, 57, and 52%, respectively. If the word recognition scoring classification is used, required hearing preservation rates are higher. Conclusion It is possible to use the NNT equation alongside projected facial nerve outcomes to estimate benchmarks of minimally acceptable hearing preservation rates.

The newly diagnosed vestibular schwannoma: radiosurgery, resection, or observation?

OBJECT

Management recommendations for patients with smaller-volume or newly diagnosed vestibular schwannomas (< 4 cm(3)) need to be based on an understanding of the anticipated natural history of the tumor and the side effects it produces. The natural history can then be compared with the risks and benefits of therapeutic intervention using a minimally invasive strategy such as stereotactic radiosurgery (SRS).

METHODS

The authors reviewed the emerging literature stemming from recent recommendations to "wait and scan" (observation) and compared this strategy with published outcomes after early intervention using SRS or results from matched cohort studies of resection and SRS.

RESULTS

Various retrospective studies indicate that vestibular schwannomas grow at a rate of 0-3.9 mm per year and double in volume between 1.65 and 4.4 years. Stereotactic radiosurgery arrests growth in up to 98% of patients when studied at intervals of 10-15 years. Most patients who select "wait and scan" note gradually decreasing hearing function leading to the loss of useful hearing by 5 years. In contrast, current studies indicate that 3-5 years after Gamma Knife surgery, 61%-80% of patients maintain useful hearing (speech discrimination score > 50%, pure tone average < 50).

CONCLUSIONS

Based on published data on both volume and hearing preservation for both strategies, the authors devised a management recommendation for patients with small vestibular schwannomas. When resection is not chosen by the patient, the authors believe that early SRS intervention, in contrast to observation, results in long-term tumor control and improved rates of hearing preservation.

An update on unilateral sporadic small vestibular schwannoma

Advances in neuroimaging have increased the detection rate of small vestibular schwannomas (VSs, maximum diameter < 25 mm). Current management modalities include observation with serial imaging, stereotactic radiosurgery, and microsurgical resection. Selecting one approach over another invites speculation, and no standard management consensus has been established. Moreover, there is a distinct clinical heterogeneity among patients harboring small VSs, making standardization of management difficult. The aim of this article is to guide treating physicians toward the most plausible therapeutic option based on etiopathogenesis and the highest level of existing evidence specific to the different cohorts of hypothetical case scenarios. Hypothetical cases were created to represent 5 commonly encountered scenarios involving patients with sporadic unilateral small VSs, and the literature was reviewed with a focus on small VS. The authors extrapolated from the data to the hypothetical case scenarios, and based on the level of evidence, they discuss the most suitable patient-specific treatment strategies. They conclude that observation and imaging, stereotactic radiosurgery, and microsurgery are all important components of the management strategy. Each has unique advantages and disadvantages best suited to certain clinical scenarios. The treatment of small VS should always be tailored to the clinical, personal, and social requirements of an individual patient, and a rigid treatment protocol is not practical.

Paradoxical trends in the management of vestibular schwannoma in the United States

Object

Recent natural history studies of vestibular schwannomas (VSs) suggest that most of these tumors do not grow. The impact of these new data on management trends in the US is currently unknown. The aim in the present study was to evaluate current trends in the treatment of VS in the US by analyzing a national cancer database.

Methods

The Surveillance, Epidemiology, and End Results Program is a national database maintained by the National Cancer Institute representing 26% of the US population. Data from the database were downloaded using provided software. Cases were isolated based on histology codes and the site code. Data from 2004 to 2007 were included in the analysis. The number of patients undergoing resection was compared with the number treated with beam radiation and observation, based on tumor size.

Results

Three thousand six hundred fifty cases were identified in the database. Over the study period, management choices for VSs showed a significant change only for tumors with a diameter < 2 cm. In this tumor category, a decrease in resection and an increase in radiation were observed, with observation showing a modest increase but remaining low at an average of 25%.

Conclusions

Study data demonstrated a shift in the management of small VSs in the US between 2004 and 2007, with microsurgical removal giving way to radiation treatment and the overall rate for observation remaining low and stable. With recent literature suggesting that the majority of small tumors do not grow, the authors assert that VSs are being overtreated in the US.

Vestibular schwannoma of oscillating size: A case report and review of literature

Background:

Vestibular schwannomas are benign brain tumors arising from the 8th cranial nerve with a varying natural history. Various reports have described discernable growth patterns for these tumors. However, growth predictability remains low because of slow and indeterminate changes over time with follow-up reports not usually exceeding 3 years. Our report describes the long-term follow-up of an unusual cystic schwannoma with growth patterns prior to and following treatment, adding valuable information to the variable natural history and outcome of these infrequent tumors.

Case Description:

A 68-year-old gentleman presented with a left-sided cystic vestibular schwannoma, initially managed conservatively. Imaging revealed wide variations in the size of his tumor over a period of 3 years. He was finally treated with Gamma Knife radiosurgery, and at 1 year following treatment shows tumor shrinkage with a change in tumor morphology.

Conclusion:

To our knowledge, the present case represents the first instance of a schwannoma showing wide fluctuations in tumor size and morphology over a period of time, with a good response to radiosurgery. We emphasize in this report that there is no “one size fits all” treatment paradigm for these tumors and each patient requires individualized care and intervention, taking into account their differing natural histories.

Conservative Management of Vestibular Schwannoma—A Prospective Cohort Study: Treatment, Symptoms, and Quality of Life

BACKGROUND:

One hundred ninety-three patients with sporadic unilateral vestibular schwannoma given conservative management were enrolled in a prospective study.

OBJECTIVE:

To evaluate the efficacy of conservative management and to determine the effect of an initial conservative management on the quality of life (QOL) and severity of audio vestibular symptoms.

METHODS:

The patients underwent magnetic resonance imaging scans, clinical examination, and QOL assessment by 2 validated questionnaires, the Short Form-36 (SF-36) and Glasgow Benefit Inventory (GBI). Using regression analysis of clustered data, we analyzed possible associations between tumor growth and symptoms and tested whether our earlier finding that vertigo is associated with reduced QOL could be verified.

RESULTS:

The median follow-up time was 43 months (range, 9–115 months; SD, 21.48 months). Results are based on 703 clinical controls and 642 (SF-36) and 638 (GBI) questionnaires. Seven patients were lost to follow-up. Approximately 40% of patients were in need of treatment during follow-up. We found a statistically significant association between tinnitus and vertigo and tumor growth. Vertigo was found to significantly reduce QOL. There was a significant drop in the Social Function subscales of both SF-36 and GBI, possibly attributable to progressive hearing loss. Otherwise, there was no overall trend toward any change in QOL during the observation period. In addition, QOL seemed to be little affected by treatment.

CONCLUSION:

There was a small but statistically significant improvement in vestibular complaints and no change in the occurrence of tinnitus. Except for hearing loss caused by surgery, treatment did not affect symptoms or QOL significantly. Growth was associated with the occurrence of tinnitus and balance problems.

Morbidity and mortality following acoustic neuroma excision in the United States: analysis of racial disparities during a decade in the radiosurgery era

Acoustic neuromas present a challenging problem, with the major treatment modalities involving operative excision, stereotactic radiosurgery, observation, and fractionated stereotactic radiotherapy. The morbidity/mortality following excision may differ by patient race. To address this concern, the morbidity of acoustic neuroma excision was assessed on a nationwide level. The Nationwide Inpatient Sample from 1994-2003 was used for analysis. Only patients admitted for acoustic neuroma excision were included (International Classification of Diseases, 9th edition, Clinical Modification = 225.1; primary procedure code = 04.01). Analysis was adjusted for several variables, including patient age, race, sex, primary payer for care, income in ZIP code of residence, surgeon caseload, and hospital caseload. Multivariate analyses revealed that postoperative mortality following acoustic neuroma excision was 0.5%, with adverse discharge disposition of 6.1%. The odds ratio for mortality in African Americans compared with Caucasians was 8.82 (95% confidence interval = 1.85-41.9, P = .006). Patients with high-caseload surgeons (more than 2 excisions/year), private insurance, and younger age had decreased mortality, better discharge disposition, and lower overall morbidity (P < .04). Neither hospital caseload nor median income were predictive factors. African Americans were 9 times more likely to die following surgery than Caucasians over a decade-long analysis. Given the relatively benign natural history of acoustic neuroma and the alarmingly increased mortality rate following surgical excision among older patients, African Americans, and patients receiving care from low-caseload surgeons, acoustic neuromas in these patient populations may be best managed by a more minimally invasive modality such as observation, fractionated stereotactic radiotherapy, or stereotactic radiosurgery.

Predictors of volumetric growth and auditory deterioration in vestibular schwannomas followed in a wait and scan policy

OBJECTIVE

The purpose of this study was to identify factors predicting growth and audiologic deterioration during follow-up (FU) in a wait and scan (W&S) policy of vestibular schwannomas (VSs) using a novel volumetric measuring tool. So far, only consecutive magnetic resonance imaging (MRI) is able to show growth objectively, and growth, combined with hearing function, generally dictates further intervention. Other factors predicting growth or hearing deterioration would be invaluable and might ease clinical decision making.

STUDY DESIGN

Retrospective case study.

SETTING

Tertiary referral center.

PATIENTS

Sixty-three patients diagnosed with VS at Maastricht University Medical Center between 2003 and 2008, with FU data available from 36 patients.

INTERVENTION(S)

A W&S policy for unilateral VS with sequential contrast-enhanced T1- and T2-weighted MRI and audiograms during FU.

MAIN OUTCOME MEASURE(S)

1. Patient and radiologic VS features potentially related to growth and auditory function during a W&S policy. 2. The correlation between increase in VS volume and audiologic deterioration during FU.

RESULTS

Labyrinthine hypointensity on T2-weighted magnetic resonance images and complaints of hearing loss at presentation are predictive of a faster deterioration of hearing (p < 0.05). Growth during the first FU year predicts further growth. Vestibular schwannoma volume does not correlate with audiologic deterioration significantly.

CONCLUSION

Hypointensity on T2-weighted image of the affected labyrinth will result in a significant faster deterioration of hearing. Hearing loss was more profound, and hearing will deteriorate significantly faster in patients presenting with complaints of hearing loss. Significant growth during the first year of FU predicts further growth during FU. Sequential MRI cannot be substituted by audiologic examinations solely because increase in VS volume does not correlate with audiologic deterioration significantly.

Decision analysis of treatment options for vestibular schwannoma

Object

Widespread use of MR imaging has contributed to the more frequent diagnosis of vestibular schwannomas (VSs). These tumors represent 10% of primary adult intracranial neoplasms, and if they are symptomatic, they usually present with hearing loss and tinnitus. Currently, there are 3 treatment options for quality of life (QOL): wait and scan, microsurgery, and radiosurgery. In this paper, the authors' purpose is to determine which treatment modality yields the highest QOL at 5- and 10-year follow-up, considering the likelihood of recurrence and various complications.

Methods

The MEDLINE, Embase, and Cochrane online databases were searched for English-language articles published between 1990 and June 2008, containing key words relating to VS. Data were pooled to calculate the prevalence of treatment complications, tumor recurrence, and QOL with various complications. For parameters in which incidence varied with time of follow-up, the authors used meta-regression to determine the mean prevalence rates at a specified length of follow-up. A decision-analytical model was constructed to compare 5- and 10-year outcomes for a patient with a unilateral tumor and partially intact hearing. The 3 treatment options, wait and scan, microsurgery, and radiosurgery, were compared.

Results

After screening more than 2500 abstracts, the authors ultimately included 113 articles in this analysis. Recurrence, complication rates, and onset of complication varied with the treatment chosen. The relative QOL at the 5-year follow-up was 0.898 of normal for wait and scan, 0.953 for microsurgery, and 0.97 for radiosurgery. These differences are significant (p < 0.0052). Data were too scarce at the 10-year follow-up to calculate significant differences between the microsurgery and radiosurgery strategies.

Conclusions

At 5 years, patients treated with radiosurgery have an overall better QOL than those treated with either microsurgery or those investigated further with serial imaging. The authors found that the complications associated with wait-and-scan and microsurgery treatment strategies negatively impacted patient lives more than the complications from radiosurgery. One limitation of this study is that the 10-year follow-up data were too limited to analyze, and more studies are needed to determine if the authors' results are still consistent at 10 years.

Long-term hearing preservation after microsurgical excision of vestibular schwannoma

OBJECTIVE

To examine long-term hearing outcomes after microsurgical excision of vestibular schwannoma (VS).

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral center.

PATIENTS

Forty-nine subjects at a single institution who had undergone microsurgical excision of a VS via middle cranial fossa (MCF) approach between 1994 and 2007 with immediate postoperative (PO) hearing preservation and for whom long-term audiograms were available.

INTERVENTION

Diagnostic.

MAIN OUTCOME MEASURES

Word Recognition Score (WRS) is defined by speech discrimination scores (SDS) greater than 70% (grade I), 50% to 70% (grade II), less than 50% (grade III), and 0% (grade IV).

RESULTS

For subjects with more than 2 years of follow-up, WRS I hearing was present PO in 42 of 49 patients and was preserved at the latest follow-up in 38 (90%) of 42 patients. No subjects fell beyond WRS II. WRS I hearing was maintained in 23 (88%) of 26 patients with more than 5 years of follow-up. Postoperative WRS I to II hearing was maintained in 28 (96%) of 29 patients with more than 5 years of follow-up. The patient who lost significant hearing in the ear operated on had sensorineural hearing loss that paralleled deterioration in her ear that was not operated on.

CONCLUSION

Most subjects maintain their initial PO SDS after microsurgical VS removal, and therefore, the initial PO WRS is predictive of long-term hearing. Postsurgical changes do not alter the natural rate or pattern of progressive bilateral sensorineural hearing loss in individual subjects.

Acoustic neuroma growth: a systematic review of the evidence

AIM

To undertake a systematic review of the literature on acoustic neuroma growth. Predictors of growth were also explored.

MATERIALS AND METHODS

A comprehensive search was conducted to identify the relevant literature. The search yielded 2,455 papers. All titles were reviewed by 2 of the authors, and finally, 41 papers were found reporting data pertinent to growth.

RESULTS

The percentage of acoustic neuromas exhibiting growth ranges widely from 18 to 73%. The percentage of tumors reported not to grow for some years after diagnosis ranges from 9 to 75%. Some (usually less than 10%, but up to 22%) may get smaller. No reliable predictors of growth have been identified. The mean growth rate for all tumors varies between 1 and 2 mm/yr, and for only those that grow, between 2 and 4 mm/yr. However, there are cases with significant regression or exceptional growth (exceeding 18 mm/yr). There are various patterns of growth, and a tumor that shows growth may stop doing so and vice versa. Finally, some tumors that have been stable for many years can exhibit tumor growth.

CONCLUSION

The growth pattern of acoustic neuromas is variable and incompletely understood. As much as 75% of tumors have been reported to show no growth, supporting a "wait and rescan" policy in many patients, although there are no reliable predictors of tumor behavior, and some tumors may grow rapidly. Primary longitudinal studies are needed to better define the natural history and limit unnecessary interventions.

Intratumoral hemorrhage and fibrosis in vestibular schwannoma: a possible mechanism for hearing loss

OBJECT

Vestibular schwannomas (VSs) are benign lesions with an unpredictable natural history. Perhaps the greatest barrier to predicting which patients need treatment is our poor understanding of how these tumors cause hearing loss in the first place. In this case-control study, the authors investigated the relationship between preoperative hearing loss and histological changes such as intratumoral microhemorrhage and extensive fibrosis.

METHODS

From a prospectively collected database, the authors selected all patients with VS who had undergone microsurgical resection as their initial treatment for histopathologically confirmed VS. Histological specimens obtained in 274 of these patients were systematically reviewed by a blinded neuropathologist who graded the extent of microhemorrhage and fibrosis in these tumors. The effect of these variables on preoperative hearing loss was studied using binary logistic regression.

RESULTS

On univariate analysis, patients with extensive intratumoral microhemorrhage or fibrosis (p < 0.0001), patients with larger tumors (p < 0.05), and patients 65 years of age or older (p < 0.05) were significantly more likely to have unserviceable hearing at the time of surgery. On multivariate analysis, only patients with extensive intratumoral microhemorrhage or fibrosis had an increased risk of having unserviceable hearing at the time of surgery (OR 3.72, 95% CI 1.3-10; p = 0.01). Older age and tumor size greater than 3 cm were not statistically significant risk factors for hearing loss, controlling for the effect of microhemorrhage and fibrosis.

CONCLUSIONS

In this study, the authors have demonstrated a correlation between the extent of nonneoplastic histological changes, such as microhemorrhage and fibrosis, and hearing loss. This alternate hypothesis has the potential to explain many of the exceptions to previously described mechanisms of hearing loss in patients with VS. The advent of high-resolution MR imaging technology to identify microhemorrhages may provide a method to screen for patients with VS at risk for hearing loss.

Management of patients with acoustic neuromas: a Markov decision analysis

OBJECTIVES/HYPOTHESIS

The management of patients with small (<1.5 cm) acoustic neuromas is controversial. Immediate treatment via microsurgical resection or radiosurgery is often advocated. A period of observation is sometimes advised followed by microsurgery or radiosurgery for tumors that demonstrate growth during the observation period. The purpose of this study is to calculate quality-adjusted life expectancy for the most commonly applied management strategies in hypothetical cohorts of patients of various ages.

STUDY DESIGN

Markov decision analysis; societal perspective.

METHODS

Assumptions used in creating this model and event probabilities were obtained from a thorough literature review. Key parameters were identified and defined by the best available evidence. The main outcome measure is the benefit derived from each management strategy in quality-adjusted life years (QALYs). Sensitivity analysis was used to define benchmark performance information for these parameters.

RESULTS

The benefit of a period of observation followed by radiosurgery, if needed, for significant tumor growth is greater then all other strategies for all age groups and both sexes. When compared to observation followed by microsurgery, the additional benefit is small. QALY totals for the two immediate treatment groups were significantly lower than that for the observation groups.

CONCLUSIONS

For patients of all ages, a period of observation during which tumor growth and hearing thresholds are closely monitored is the superior strategy. For tumors that grow substantially or when hearing deteriorates, definitive management via radiosurgery is recommended.