Vestibular schwannoma management. Part II. Failed radiosurgery and the role of delayed microsurgery

Clinical Outcomes of Salvage Microsurgical Resection after Radiation Therapy for Sporadic Vestibular Schwannomas

Background  The purpose of this study was to evaluate clinical outcomes after salvage microsurgery for vestibular schwannoma (VS) treated initially with modern radiotherapy techniques as compared to those treated with primary microsurgical resection. Methods  Patients who underwent microsurgical resection of sporadic VS undergoing a translabyrinthine approach at a single academic skull base tertiary referral center were included. Baseline and postoperative dynamic gait index, functional gait assessment, House-Brackmann facial nerve grading, and completeness of resection were prospectively recorded. Results  Of the 265 patients reviewed, 21 (7.9%) patients underwent prior radiation. Median age of the cohort was 55 years (interquartile range: 51-63). The likelihood of achieving a gross total resection was significantly lower for radiated as compared to nonradiated patients (odds ratio: 0.18, 95% confidence interval: 0.05-0.53, p  = 0.004) when controlling for tumor size. Radiated patients had better postoperative facial nerve function on the first postoperative day, but this difference was not significant at long-term follow-up. Radiated patients had lower preoperative postural stability scores than nonradiated patients on FGA (26 vs. 23, p  = 0.035). Postoperatively, radiated patients had comparable outcomes compared to nonradiated patients when controlling for age and tumor size. Conclusion  Compared to patients with VS treated with surgery alone, previously radiated patients are less likely to achieve gross total resection in the salvage setting. Radiated patients scored better on facial nerve outcomes compared to nonradiated patients in the initial postoperative period but demonstrated similar long-term outcomes.

Simultaneous Cochlear Implantation and Salvage Translabyrinthine Resection of Vestibular Schwannoma after Radiotherapy

OBJECTIVE

To report on the novel use of simultaneous cochlear implantation (CI) during salvage translabyrinthine resection of vestibular schwannoma (VS) after failed stereotactic radiosurgery (SRS).

PATIENT

A 52-year-old woman presented with a medium-sized right VS. She experienced continued tumor growth despite previous SRS, resulting in medial extension beyond the internal auditory canal into the cerebellopontine angle. Associated symptoms included asymmetrical right moderate to severe sensorineural hearing loss, poor word recognition, tinnitus, and dizziness.

INTERVENTION

Simultaneous CI with translabyrinthine VS resection.

MAIN OUTCOME MEASURE

CI-aided pure-tone averages.

RESULTS

After 4 months of device use, CI-aided speech audiometry revealed hearing thresholds in the normal range, with a four-tone pure-tone, average of 16.3 dB. Speech perception with consonant-nucleus-consonant testing in the CI-only condition was 46%, representing a 12% improvement compared with preoperatively. Tinnitus and dizziness burden were subjectively reduced.

CONCLUSIONS

Despite challenges inherent to second procedures after radiotherapy failure, successful CI outcomes can be achieved. The current study demonstrates the feasibility of simultaneous CI during salvage VS resection after SRS. A larger study should be undertaken to further substantiate these preliminary findings.

Pseudoprogression of Vestibular Schwannoma after Stereotactic Radiosurgery with Cyberknife®: Proposal for New Response Criteria

(1) Background: Transient increase in volume of vestibular schwannomas (VS) after stereotactic radiosurgery (SRS) is common and complicates differentiation between treatment-related changes (pseudoprogression, PP) and tumor recurrence (progressive disease, PD). (2) Methods: Patients with unilateral VS (n = 63) underwent single fraction robotic-guided SRS. Volume changes were classified according to existing RANO criteria. A new response type, PP, with a >20% transient increase in volume was defined and divided into early (within the first 12 months) and late (>12 months) occurrence. (3) Results: The median age was 56 (range: 20-82) years, the median initial tumor volume was 1.5 (range: 0.1-8.6) cm³. The median radiological and clinical follow-up time was 66 (range: 24-103) months. Partial response was observed in 36% (n = 23), stable disease in 35% (n = 22) and PP in 29% (n = 18) of patients. The latter occurred early (16%, n = 10) or late (13%, n = 8). Using these criteria, no case of PD was observed. (4) Conclusion: Any volume increase after SRS for vs. assumed to be PD turned out to be early or late PP. Therefore, we propose modifying RANO criteria for SRS of VS, which may affect the management of vs. during follow-up in favor of further observation.

Salvage radiosurgery following subtotal resection of vestibular schwannomas: does timing influence tumor control?

OBJECTIVE

The goal of microsurgical resection of vestibular schwannoma (VS) is gross-total resection (GTR) to provide oncological cure. However, a popular strategy is to halt the resection if the surgical team feels the risk of cranial nerve injury is imminent, achieving a maximally safe subtotal resection (STR) instead. The tumor remnant can then be treated with stereotactic radiosurgery (SRS) once the patient has recovered from the immediate postoperative period, or it can be followed with serial imaging and treated with SRS in a delayed fashion if residual tumor growth is seen. In this study, the authors evaluated the efficacy of this multimodality approach, particularly the influence of timing and dose of SRS on radiological tumor control, need for salvage treatment, and cranial nerve function.

METHODS

VS patients treated with initial microsurgery and subsequent radiosurgery were retrospectively included from two tertiary treatment centers and dichotomized depending on whether SRS was given upfront (defined as before 12 months) or later. Radiological tumor control was defined as less than 20% tumor volume expansion and oncological tumor control as an absence of salvage treatment. Facial and cochlear nerve functions were assessed after surgery, at the time of SRS, and at last follow-up. Finally, a systematic literature review was conducted according to PRISMA guidelines.

RESULTS

A total of 110 VS patients underwent SRS following microsurgical resection, with a mean preradiosurgical tumor volume of 2.2 cm3 (SD 2.5 cm3) and mean post-SRS follow-up time of 5.8 years (SD 4.1 years). The overall radiological tumor control and oncological tumor control were 77.3% and 90.9%, respectively. Thirty-five patients (31.8%) received upfront SRS, while 75 patients (68.2%) were observed for a minimum of 12 months prior to SRS. The timing of SRS did not influence the radiological tumor control (p = 0.869), the oncological tumor control (p = 0.560), or facial nerve (p = 0.413) or cochlear nerve (p = 0.954) function. An escalated marginal dose (> 12 Gy) was associated with greater tumor shrinkage (p = 0.020) and superior radiological tumor control (p = 0.020), but it did not influence the risk of salvage treatment (p = 0.904) or facial (p = 0.351) or cochlear (p = 0.601) nerve deterioration.

CONCLUSIONS

Delayed SRS after close observation of residuals following STR is a safe alternative to upfront SRS regarding tumor control and cranial nerve preservation in selected patients.

Malignant peripheral nerve sheath tumour transformation of histological benign vestibular schwannoma after stereotactic radiosurgery in patients without neurofibromatosis

Stereotactic radiosurgery (SRS) poses a minimal but important risk for tumour transformation, typically occurring 8-10 years after the treatment. Malignant peripheral nerve sheath tumour (MPNST) is the most common tumour arising from a vestibular schwannoma treated with SRS, with only 14 cases previously reported. We present the fifteenth case and describe its evolution and clinical course. A 56-year-old man without a history of neurofibromatosis was diagnosed 9 years prior with a vestibular schwannoma. SRS to the residual tumour was given 3 months later. During the current hospitalisation, he was reoperated where histology confirmed a MPNST. All 15 MPNST cases were analysed, showing a 77% female predominance presenting a malignant transformation at a mean age of 51. The diagnosis was made at a mean time of 74 months after SRS. The mean survival time after diagnosis was 16 months. MPNST arising from benign vestibular schwannoma after SRS treatment is an uncommon but devastating complication.

Outcomes of Salvage Resection and Radiosurgery Following Failed Primary Treatment of Vestibular Schwannomas

OBJECTIVE

To evaluate outcomes following salvage microsurgery (MS) and salvage stereotactic radiosurgery (SRS) after failure of primary treatment for vestibular schwannomas (VS).

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary referral center.

METHODS

Patients with more than 1 intervention for their VS were divided into 4 groups: MS followed by SRS (n = 61), MS followed by MS (n = 9), SRS followed by MS (n = 7), and SRS followed by SRS (n = 7), and outcomes were evaluated.

RESULTS

A total of 77 patients were included (84 procedures). In group 1 (MS then SRS), 3% developed a decline in facial function, 3% developed trigeminal sensory loss, and 13% patients had gradual improvement of facial nerve function following SRS. Group 2 (MS then MS) had the highest rates of facial nerve deterioration, although all but 1 patient achieved a House-Brackmann score of II or III. Gross-total resection (GTR) was achieved in 56% of patients. When a different approach was used for salvage resection, GTR occurred more commonly, and facial nerve outcomes were similar. In group 3 (SRS then MS), GTR occurred in 43% of cases, and 2 of 7 patients developed worsened facial function. In group 4 (SRS then SRS), no patient developed facial weakness after reirradiation, and 1 developed a trigeminal nerve deficit.

CONCLUSIONS

For MS recurrences/residuals, SRS is the mainstay of treatment and does not preclude facial function recovery. If salvage microsurgery is required, an alternate approach should be considered. For SRS failures, when MS is required, less-than GTR may be preferable, and reirradiation is a potential safe alternative.

Resection of vestibular schwannomas after stereotactic radiosurgery: a systematic review

OBJECTIVE

Multiple short series have evaluated the efficacy of salvage microsurgery (MS) after stereotactic radiosurgery (SRS) for treatment of vestibular schwannomas (VSs); however, there is a lack of a large volume of patient data available for interpretation and clinical adaptation. The goal of this study was to provide a comprehensive review of tumor characteristics, management, and surgical outcomes of salvage of MS after SRS for VS.

METHODS

The Medline/PubMed, Scopus, CINAHL, Cochrane Library, and Google Scholar databases were queried according to PRISMA guidelines. All English-language and translated publications were included. Studies lacking adequate study characteristics and outcomes were excluded. Cases involving neurofibromatosis type 2, previous MS, or malignant transformation were excluded when possible.

RESULTS

Twenty studies containing 297 cases met inclusion criteria. Three additional cases from Rush University Medical Center were added for 300 total cases. Tumor growth with or without symptoms was the primary indication for salvage surgery (92.3% of cases), followed by worsening of symptoms without growth (4.6%) and cystic enlargement (3.1%). The average time to MS after SRS was 39.4 months. The average size and volume of tumor at surgery were 2.44 cm and 5.92 cm3, respectively. The surgical approach was retrosigmoid (42.8%) and translabyrinthine (57.2%); 59.5% of patients had a House-Brackmann (HB) grade of I or II. The facial nerve was preserved in 91.5% of cases. Facial nerve preservation and HB grades were lower for the translabyrinthine versus retrosigmoid approach (p = 0.31 and p = 0.18, respectively); however, fewer complications were noted in the translabyrinthine approach (p = 0.29). Gross-total resection (GTR) was completed in 55.7% of surgeries. Studies that predominantly used subtotal resection (STR) were associated with a lower rate of facial nerve injury (5.3% vs 11.3%, p = 0.07) and higher rate of HB grade I or II (72.9% vs 48.0%, p = 0.00003) versus those using predominantly GTR. However, majority STR was associated with a recurrence rate of 3.6% as compared to 1.4% for majority GTR (p = 0.29).

CONCLUSIONS

This study showed that the leading cause of MS after SRS was tumor growth at an average of 39.4 months after radiation. There were no significant differences in outcomes of facial nerve preservation, postoperative HB grade, or complication rate based on surgical approach. Patients who underwent STR showed statistically significant better HB outcomes compared with GTR. MS after SRS was considered by most authors to be more difficult than primary MS. These data support the notion that the surgical goals of salvage surgery are debulking of tumor mass, decreasing compression of the brainstem, and not necessarily pursuing GTR.

Hypervascular vestibular schwannoma: A case report and review of the literature

Vestibular schwannomas, also known as acoustic neuromas, are benign tumors that arise from Schwann cells near the transition from glial cells to Schwann cells. While most vestibular schwannomas are hypovascular tumors, a small percentage constitute the hemorrhagic and/or hypervascular vestibular schwannomas (HVS) subtype. We describe a case of a 36-year-old female who presented with nausea, vomiting, and an acute decrease in vision in her right eye. Computed tomography of the head demonstrated a hemorrhagic lesion in the right hemisphere with evidence of ventricular effacement. Follow-up magnetic resonance imaging revealed a mass in the right cerebellopontine angle that was hypointense on T1-weighted imaging and mild hyperintense heterogeneous signal on T2-weighted imaging, suggestive of a hemorrhagic vestibular schwannoma. It is important for radiologists to recognize the unique clinical and radiological features of HVS in the initial diagnostic assessment of cerebellopontine angle tumors and to distinguish it from common (hypovascular) vestibular schwannomas and other related pathologies. A preoperative diagnosis of HVS allows clinicians to become familiar with the unique characteristics of the tumor and to devise a feasible operative strategy prior to surgical resection.

Is salvage surgery for large vestibular schwannomas after failed gamma knife radiosurgery more challenging?

In order to verify whether a previous gamma knife surgery (GKS) treatment could influence the oncological and functional outcome in large vestibular schwannoma (VS) surgery, we have compared group of patients operated on for large VS after failed GKS to a group of genuine VS that underwent the same functional nerve-sparing resection technique regimen in the same period. Single center retrospective cohort study of 23 consecutive GKS failure and 170 genuine VS patients operated on between April 2003 and March 2019. After resection, patients were allocated to a Wait-&-rescan or an upfront GKS policy. At last follow-up examination, the facial nerve function was good (House-Brackmann grades I or II) in 95% of the GKS failure and 84% of the genuine VS patients (p = .25). The median volume of tumor residue was .56 cc in the GKS failure group and .62 cc in the genuine VS group (p = .70). Tumor control was achieved in 91% and 83% of cases with a mean follow-up of 74 and 63 months in the GKS failure and the genuine VS populations, respectively. The 1-, 5-, and 7-year progression-free survival were 100%, 95%, and 85% respectively in the GKS failure group and 97%, 80%, and 81% in the genuine VS group (p = .27). Despite significant modifications of the microsurgical environment associated to salvage surgery after GKS failure, a functional nerve-sparing resection is an effective strategy to optimize the results on facial nerve function, with similar long-term tumor control to those observed in the genuine VS population.

Near-complete regression 19 years after Gamma Knife radiosurgery of vestibular schwannoma with massive pseudoprogression: case report

Gamma Knife radiosurgery (GKRS) is a frequent treatment choice for patients with small- to moderate-sized vestibular schwannoma (VS). However, pseudoprogression after GKRS is commonly observed, with a reported incidence ranging from 7% to 77%. The wide range of the reported incidence of pseudoprogression reflects the fact that there is no consensus on how it should be diagnosed. The authors present the case of a 66-year-old woman who had a 2.5-cm right-sided VS treated with GKRS in 1997. The first posttreatment MRI obtained 5 months later showed that the tumor volume had increased to 9.7 cm3. The tumor volume increased further and reached its peak 24 months after treatment at 20.9 cm3, which was a 161% increase from pretreatment volume. Thereafter, the tumor shrank gradually and mass effect on the brainstem reduced over time. By 229 months after treatment, the tumor volume was 1.0 cm3, equaling 12.5% of pretreatment tumor volume, or 4.8% of peak tumor volume after treatment. This case demonstrates that if a patient remains asymptomatic despite a dramatic increase in tumor volume after GKRS, observation remains an option, because even a very sizable tumor can shrink with near-complete resolution. Patients undergoing GKRS for VS should be counseled regarding the possibility of pseudoprogression, and followed carefully over time while avoiding premature decisions for surgical removal after treatment.

Preplanned Partial Surgical Removal Followed by Low-Dose Gamma Knife Radiosurgery for Large Vestibular Schwannomas

OBJECTIVE

The present study evaluated outcomes after preplanned partial surgical removal of a large vestibular schwannoma (VS) followed by low-dose Gamma Knife surgery (GKS).

METHODS

Between January 2000 and May 2015, 47 patients with a unilateral VS (median maximum diameter 32 mm) underwent preplanned partial tumor removal at our clinic. GKS for a residual lesion was done within a median time interval of 3 months. The median prescription dose was 12 Gy. The median length of subsequent follow-up was 74 months.

RESULTS

The actuarial tumor growth control rates without a need for additional management at 3, 5, and 15 years after GKS were 92%, 86%, and 86%, respectively. At the time of the last follow-up, the function of the ipsilateral facial nerve corresponded to House-Brackmann grade I in 92% of patients. Significant improvement of ipsilateral hearing was noted in two patients after partial tumor removal and in one after GKS. Among 16 patients who presented with ipsilateral serviceable hearing, it was preserved immediately after surgery in 81% of cases and at the time of the last follow-up in 44%. Salvage surgical treatment was required in 9% of patients.

CONCLUSION

Preplanned partial surgical removal followed by low-dose GKS provides a high level of functional preservation in patients with a large VS.

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

BACKGROUND AND OBJECTIVE

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

MATERIAL AND METHODS

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

RESULTS

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

CONCLUSION

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

Outcomes of Gamma Knife Surgery retreatment for growing vestibular schwannoma and review of the literature

OBJECTIVE

Gamma Knife surgery has become an accepted treatment for small to medium‑size vestibular schwannoma with a high rate of tumor control and good clinical outcome. When GKS treatment fails to stop tumor growth, GKS retreatment can be proposed in selected cases. This retrospective study examines the clinical and tumor control outcome after the second GKS retreatment for the same vestibular schwannomas.

METHODS

A total of 14 consecutive vestibular schwannomas patients retreated with 2nd GKS were included: The median time interval between GKS treatments was 44 months, and the median follow‑up duration after last GKS retreatment was 60 months. The median marginal dose used for the first and second treatments was 12 Gy. The median tumor volume at the initial GKS was 2.4cc (range 0.27-3.8) and was 3.8cc (range 1.21-7.6) at the GKS retreatment.

RESULTS

At the last follow‑up, 93% (13 patients) had tumor growth control, decreased in 4, remained unchanged in 9, and increased tumor size in one patient. New facial or severe trigeminal palsy did not occur after the second GKS retreatment. The hearing was not preserved except in one patient post-GKS retreatment.

CONCLUSIONS

GKS retreatment after the failure of initial GKS to control vestibular schwannomas growth appears to be an effective strategy and can be proposed as an alternative to microsurgery when the tumor volume remains within the usual radiosurgical range.

Is There a Need for a 6-Month Postradiosurgery Magnetic Resonance Imaging in the Treatment of Vestibular Schwannoma?

BACKGROUND

Stereotactic radiosurgery (SRS) is a common treatment modality for vestibular schwannoma (VS), with a role in primary and recurrent/progressive algorithms. At our institution, routine magnetic resonance imaging (MRI) is obtained at 6 and 12 mo following SRS for VS.

OBJECTIVE

To analyze the safety and financial impact of eliminating the 6-mo post-SRS MRI in asymptomatic VS patients.

METHODS

A prospectively maintained SRS database was retrospectively reviewed for VS patients with 1 yr of post-treatment follow-up, 2005 to 2015. Decisions at 6-mo MRI were binarily categorized as routine follow-up vs clinical action-defined as a clinical visit, additional imaging, or an operation as a direct result of the 6-mo study.

RESULTS

A total of 296 patients met screening criteria, of whom 53 were excluded for incomplete follow-up and 8 for NF-2. Nine were reimaged prior to 6 mo due to clinical symptoms. Routine 6-mo post-SRS MRI was completed by 226 patients (76% of screened cohort), following from which zero instances of clinical action occurred. When scaled using national insurance database-derived financials-which estimated the mean per-study charge for MRI of the brain with and without contrast at $1767-the potential annualized national charge reduction was approximated as $1 611 504.

CONCLUSION

For clinically stable VS, 6-mo post-SRS MRI does not contribute significantly to management. We recommend omitting routine MRI before 12 mo, in patients without new or progressive neurological symptoms. If extrapolated nationally to the more than 100 active SRS centers, thousands of patients would be spared an inconvenient, nonindicated study, and national savings in health care dollars would be on the order of millions annually.

Arterial spin labeling imaging correlates with the angiographic and clinical vascularity of vestibular schwannomas

PURPOSE

Hypervascular vestibular schwannomas (HVSs) are a type of the vestibular schwannomas (VSs) that are extremely difficult to remove. We examined whether HVSs can be predicted by using arterial spin labeling (ASL) imaging.

METHODS

A total of 103 patients with VSs underwent ASL imaging and digital subtraction angiography (DSA) before surgery. Regional cerebral blood flow (CBF) of gray matter and regional tumor blood flow (TBF) were calculated from ASL imaging, and we defined the ratio of TBF to CBF as the relative TBF (rTBF = TBF/CBF). Angiographic vascularity was evaluated by DSA, and clinical vascularity was evaluated by the degree of intraoperative tumor bleeding. Based on the angiographic and clinical vascularity, the VSs were divided into two categories: HVS and non-HVS. We compared rTBF with angiographic and clinical vascularities, retrospectively.

RESULTS

The mean rTBFs of angiographic non-HVSs and HVSs were 1.29 and 2.58, respectively (p < 0.0001). At a cutoff value of 1.55, the sensitivity and specificity were 93.9% and 72.9%, respectively. The mean rTBFs of clinical non-HVS and HVSs were 1.45 and 2.22, respectively (p = 0.0002). At a cutoff value of 1.55, the sensitivity and specificity were 79.4% and 66.7%, respectively.

CONCLUSION

The rTBF calculated from ASL imaging correlates well with tumor vascularity and may be useful for predicting HVSs before surgery.

How to radiologically identify a spontaneous regression of sporadic vestibular schwannoma?

Background

The natural history of sporadic vestibular schwannoma is unpredictable, with tumors growing, non-growing and even showing spontaneous regression in some rare cases.

Objective

This retrospective study aims to describe the radiologic signs characterizing and identifying the shrinking vestibular schwannoma.

Methods

Involution was considered to have occurred if tumor size had decreased by 2 mm or more on its largest diameter. All magnetic resonance imaging scans were reviewed for tumor size, internal auditory meatus size, and tumor characteristics. Volumetric measurements were performed on the first and last scan. Audiometric data were collected at the first and last visit.

Results

Fourteen patients with a confirmed spontaneous regression were included, with a mean follow-up of 5 ± 2.6 years. The mean shrinkage rate was 0.9 ± 0.59 mm/year on 2D measurements, and 0.2 ± 0.17 cm³/year on volumetric measurements, with a relative shrinkage of 40 ± 16.9%. Two remarkable radiologic features were observed: First, a festooned aspect, defined by multiple curves in the tumor outline, noticed in 12 cases (86%); second, the appearance of cerebrospinal fluid filling the internal auditory meatus, associated with an enlargement of the internal auditory meatus compared to the contralateral side, and observed in 10 out of 13 cases with internal auditory meatus invasion (77%). Those two aspects were associated in 64% of cases.

Conclusion

These two newly reported radiologic features could help neurosurgeons, oto-neurosurgeons and neuroradiologists to identify a spontaneous vestibular schwannoma involution at first visit. This could allow any treatment to be postponed, monitoring to be more widely spaced, and patients to be reassured.

Impact of pretreatment growth on Tumor control for vestibular schwannomas following gamma knife

OBJECTIVES/HYPOTHESIS

To determine if volumetric growth prior to gamma knife (GK) radiosurgery predicts long-term tumor control.

STUDY DESIGN

Retrospective cohort study.

METHODS

Sporadic vestibular schwannomas (VS) treated with GK between 2002 and 2014 at a single tertiary care center were identified. Patients were included if they had over 6 months of pretreatment observation and over 1.5 years of posttreatment follow-up. Volumetric tumor analysis was performed on T1 postcontrast imaging. Pretreatment and posttreatment volume change was calculated. Tumors with over 20% volume increase were classified as growing.

RESULTS

There were 62 patients included in this study; 48 had pretreatment growth and 14 had no pretreatment growth. Median tumor volume was 0.58 ± 1.8 cm³ and median follow-up was 3.3 ± 2.0 years. For tumors with and without pretreatment growth, salvage treatment rates were 2% and 7% (P = .35), and posttreatment radiologic stability rates were 73% and 86%, respectively (P = .33). Median pretreatment growth was 27 ± 33% per year for tumors with posttreatment radiographic growth and 18 ± 26% per year for tumors without posttreatment radiographic growth (P = .99).

CONCLUSIONS

Pretreatment growth was not associated with increased salvage treatment or posttreatment radiographic progression rates in VS following GK.

LEVEL OF EVIDENCE

4 Laryngoscope, 129:743-747, 2019.

Comparing Outcomes Following Salvage Microsurgery in Vestibular Schwannoma Patients Failing Gamma-knife Radiosurgery or Microsurgery

OBJECTIVE

The increasing use of primary gamma-knife radiosurgery (GKS) for the treatment of vestibular schwannoma (VS) has led to a concomitant increase in the number of patients requiring salvage surgery for GKS failure. When patients underwent GKS as the primary treatment, it is known that dissecting tumor from adjacent nerves during salvage surgery is more difficult. In this report, we share our clinical experience with such patients and analyze the clinical findings of patients with tumor regrowth/recurrence.

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary center.

PATIENTS

Nine patients who underwent salvage surgery for VS regrowth/recurrence after GKS or microsurgery were enrolled.

MAIN OUTCOME MEASURES

Symptom progression, radiological changes, intraoperative findings, and surgical outcomes were evaluated and compared.

RESULTS

Six patients with previous GKS and three with previous microsurgery underwent salvage microsurgery. The most obvious symptom of tumor regrowth was aggravation of hearing loss. Salvage surgery in all patients was limited to subtotal or near-total resection via a translabyrinthine/transotic approach. Severe adhesion, thickening, and fibrosis were more prominent findings in the GKS than in the previous microsurgery group. Dissection of the tumor from the facial nerve was more difficult in the GKS than in the microsurgery patients. Despite anatomical preservation of the facial nerve in all the six patients, three in the GKS group, but none in the revision microsurgery group, had worsening of facial nerve function.

CONCLUSION

Salvage microsurgery of VS after failed GKS is more difficult than revision microsurgery, and the facial nerve outcomes are relatively poor. Therefore, the primary method of VS treatment should be carefully chosen. Additional imaging studies are recommended in patients with a sudden change in hearing loss who underwent GKS.

Management of Vestibular Schwannomas with Linear Accelerator-Based Stereotactic Radiosurgery: A Single Center Experience

Aims and background

The primary goal of treatment for vestibular schwannoma is to achieve local control without comprimising regional cranial nerve function. Stereotactic radiosurgery has emerged as a viable therapeutic option for vestibular schwannoma. The aim of the study is to report our 15-year single center experience using linear accelerator-based stereotactic radiosurgery in the management of patients with vestibular schwannoma.

Methods and study design

Between July 1998 and January 2013, 68 patients with unilateral vestibular schwannoma were treated using stereotactic radiosurgery at the Department of Radiation Oncology, Gulhane Military Medical Academy. All patients underwent high-precision stereotactic radiosurgery using a linear accelerator with 6-MV photons.

Results

Median follow-up time was 51 months (range, 9–107). Median age was 45 years (range, 20–77). Median dose was 12 Gy (range, 10–13) prescribed to the 85%-95% isodose line encompassing the target volume. Local tumor control in patients with periodic follow-up imaging was 96.1%. Overall hearing preservation rate was 76.5%.

Conclusions

Linear accelerator-based stereotactic radiosurgery offers a safe and effective treatment for patients with vestibular schwannoma by providing high local control rates along with improved quality of life through well-preserved hearing function.

Stereotactic Radiosurgery for Cystic Vestibular Schwannomas

BACKGROUND

The optimum treatment for cystic vestibular schwannoma (VS) remains controversial. Anecdotally, many treating physicians feel that cystic VSs do not respond to stereotactic radiosurgery (SRS) as well as noncystic tumors.

OBJECTIVE

To present outcomes after treatment of predominantly cystic VS with SRS.

METHODS

A prospectively maintained clinical database of patients undergoing Gamma Knife (Elekta Instruments, Stockholm, Sweden) radiosurgery (GKRS) for VS at a single tertiary academic referral center was retrospectively reviewed. Patients diagnosed with cystic VS who were treated with GKRS between 1997 and 2014 were analyzed. Size-matched solid tumors treated with GKRS during this period were selected as controls.

RESULTS

Twenty patients (12 women; median age at treatment, 56 years; range, 36-85 years) with cystic VS met inclusion criteria. The median radiologic follow-up within the cystic group was 63 months (range, 17-201 months), and the median change in tumor size was -4.9 mm (range, -10.4 to 9.3 mm). Sixteen tumors (80%) shrank, 2 (10%) remained stable, and 2 (10%) enlarged, accounting for a tumor control rate of 90%. The median radiologic follow-up in the noncystic control group was 67 months (range, 6-141 months), and the median change in size was -2.0 mm (range, -10.4 to 2.5 mm). Tumor control in the solid group was 90%. Comparing only those tumors that decreased in size showed that there was a trend toward a greater reduction within the cystic group ( P = .05).

CONCLUSION

The present study demonstrates that tumor control after SRS for cystic VS may not differ from that of noncystic VS in selected cases.

Pretreatment ADC Values Predict Response to Radiosurgery in Vestibular Schwannomas

BACKGROUND AND PURPOSE

The response rate of vestibular schwannomas to radiation therapy is variable, and there are surgical options available in the event of treatment failure. The aim of this study was to determine whether pre- and posttreatment ADC values can predict the tumor response to radiation therapy.

MATERIALS AND METHODS

From a data base of 162 patients with vestibular schwannomas who underwent radiation therapy with gamma knife, CyberKnife, or fractionated stereotactic radiation therapy as the first-line therapy between January 2003 and December 2013, we found 20 patients who had pretreatment ADC values. There were 108 patients (including these 20) had serial MR images that included DWI allowing calculated ADC values from 2-132 months after radiation therapy. Two reviewers measured the mean, minimum, and maximum ADC values from elliptical ROIs that included tumor tissue only. Treatment responders were defined as those with a tumor total volume shrinkage of 20% or more after radiation therapy.

RESULTS

The pretreatment mean minimum ADC for nonresponders was 986.7 × 10^-6 mm²/s (range, 844-1230 × 10^-6 mm²/s) and it was 669.2 × 10^-6 mm²/s (range, 345-883 × 10^-6 mm²/s) for responders. This difference was statistically significant (P < .001). Using a minimum ADC value of 800 × 10^-6 mm²/s led to the correct classification of 18/20 patients based on pretreatment ADC values. The intraclass correlation between reviewers was 0.61. No posttreatment ADC values predicted response.

CONCLUSIONS

Pretreatment ADC values of vestibular schwannomas are lower in responders than nonresponders. Using a minimum ADC value of 800 × 10^-6 mm²/s correctly classified 90% of cases.

Surgery After Primary Radiation Treatment for Sporadic Vestibular Schwannomas: Case Series

BACKGROUND: As radiation has become an increasingly popular primary treatment option for sporadic vestibular schwannomas, there is a minority of tumors that do not respond favorably to radiation. Data on repeat radiosurgery are emerging, and salvage surgery has been associated with increased technical difficulty and poor facial nerve outcomes.

OBJECTIVE: To review the current literature and report our results with surgical resection of sporadic vestibular schwannomas that have failed primary radiation treatment.

METHODS: This is a retrospective, single-surgeon case series of patients with sporadic vestibular schwannomas who failed primary radiation treatment and underwent subsequent surgical resection. We analyze demographics, clinical information, and intraoperative findings, focusing on facial nerve functional outcomes and extent of resection.

RESULTS: Between 2006 and 2015, 10 patients with sporadic vestibular schwannomas whose only prior treatment was radiation underwent microsurgical resection. Eight of 10 patients had a postoperative House-Brackmann score of 1 at a median follow-up of 14 months, while 2 patients had House-Brackmann score of 4. Gross total resection was achieved in 7 of 10 cases. Near total resection was achieved in 2 cases, and only subtotal resection was achieved in 1 case.

CONCLUSION: Salvage surgery is a safe and effective option after failure of primary radiation and may offer benefits over repeat radiosurgery.

Outcomes in Patients with Vestibular Schwannoma after Subtotal Resection and Adjuvant Radiosurgery

BACKGROUND

The debate continues with a limited number of publications describing outcomes in patients with vestibular schwannoma (VS) treated with planned subtotal resection (STR) plus stereotactic radiosurgery (SRS). Here we present our experience.

METHODS

This is a retrospective review of 22 patients with VS Koos grade III and IV who were treated with STR followed by SRS. Tumor volumes, facial nerve function, hearing preservation, and the presence of trigeminal neuropathy were noted. Spearman's rank test was used to correlate facial nerve grade with postoperative tumor residual tumor volume.

RESULTS

Tumor control was achieved in all patients with a mean follow-up of 28 months. No patient required other treatment beyond the original surgery and adjuvant SRS during this period. After a mean postoperative period of 28 months, 19/22 patients had excellent (House-Brackmann I or II) facial nerve function grading. Improved facial nerve function was positively correlated with larger residual tumor volume (rs = 0.63). Kaplan-Meier curve showed around 80% probability for regaining facial nerve function after initial deterioration. Four patients reported postoperative facial numbness at the side of surgery, with 3 cases showing improvement within a month. Temporary postoperative caudal cranial nerve dysfunction was observed in 2 patients.

CONCLUSION

Hybrid strategy of STR and adjuvant SRS provides patients with large VS excellent tumor control and a good clinical outcome.

Microsurgical management of vestibular schwannoma after failed previous surgery

OBJECTIVE Microsurgical treatment of recurrent vestibular schwannoma (VS) is difficult and poses specific challenges. The authors report their experience with 53 cases of surgically treated recurrent VS. Outcome of these tumors was compared to that of primarily operated on VS. Special attention was given to the facial nerve functional outcome. METHODS A retrospective analysis was performed of the patients who underwent surgery for recurrent VS at one institution from 2000 to 2013. The preoperative data, intraoperative findings, and outcome in terms of facial nerve function and improvement of the preoperative symptoms were analyzed and compared with those in a control group of 30 randomly selected patients with primarily operated on VS. A multivariate regression analysis was performed to test the factors that could affect the facial nerve outcome in each group. RESULTS Fifty-three consecutive patients underwent surgery for recurrent VS. Seventeen patients were previously operated on and received postoperative radiosurgery (Group A). Thirty-six patients were previously operated on but did not receive postoperative radiosurgery (Group B). The overall postoperative facial nerve function was significantly worse in Groups A and B in comparison with the control group (Group C). Interestingly, there was no significant difference in the facial nerve outcome among the 3 groups in patients who had good preoperative facial nerve function. The tumor size and the preoperative facial nerve function are variables that significantly affect the facial nerve outcome. Most of the patients showed improvement of the preoperative symptoms, such as trigeminal hypesthesia, gait disturbance, and headache. CONCLUSIONS Complete microsurgical tumor removal is the optimal management for patients with recurrent or regrowing VS. The procedure is safe, associated with favorable facial nerve outcome, and may also improve existing neurological symptoms.

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

OBJECT

Resection of vestibular schwannoma (VS) after Gamma Knife surgery (GKS) is infrequently performed. The goals of this study were to analyze and discuss the neurological outcomes and technical challenges of VS resection and to explore strategies for treating tumors that progress after GKS.

METHODS

In total, 708 patients with VS underwent GKS between 1993 and 2012 at Taipei Veterans General Hospital. The post-GKS clinical courses, neurological presentations, and radiological changes in these patients were analyzed. Six hundred patients with imaging follow-up of at least 1 year after GKS treatment were included in this study.

RESULTS

Thirteen patients (2.2%) underwent microsurgery on average 36.8 months (range 3-107 months) after GKS. The indications for the surgery included symptomatic adverse radiation effects (in 4 patients), tumor progression (in 6), and cyst development (in 3). No morbidity or death as a result of the surgery was observed. At the last follow-up evaluation, all patients, except 1 patient with a malignant tumor, had stable or near-normal facial function.

CONCLUSIONS

For the few VS cases that require resection after radiosurgery, maximal tumor resection can be achieved with modern skull-based techniques and refined neuromonitoring without affecting facial nerve function.

Malignant transformation in vestibular schwannoma: report of a single case, literature search, and debate

OBJECT

The significance of radiation in the induction of malignancy in vestibular schwannomas (VSs) after radiosurgery is unclear despite an increasing number of case reports. The authors describe a new case of verified malignant transformation in a vestibular schwannoma (MTVS) and provide a new evaluation of such cases previously reported in the literature.

METHODS

A 46-year-old woman underwent subtotal resection of a right-sided VS in 2004. The histological characteristics of the lesion were typical and benign. In early 2007 Gamma Knife surgery (GKS) was performed to treat a residual enlarging remnant. The radiosurgery parameters included the following: target volume 3.5 cm(3), prescription dose 12 Gy, prescription isodose 45%, maximum dose 26.7 Gy, and coverage 97%. At 2 years' follow-up the lesion was enlarged to 5.2 cm(3), but by 5 years it had decreased to 2.3 cm(3). Six months later the lesion was 8.4 cm(3). Repeated surgery was performed, and a histological analysis revealed a malignant peripheral nerve sheath tumor. The case was further managed with repeated GKS performed in the spring of 2013. At that time, the radiosurgery parameters included the following: target volume 3.5 cm(3), prescription dose 16 Gy, prescription isodose 45%, maximum dose 35.6 Gy, and coverage 91%. This Gamma Knife Department has treated a total of 205 patients with VS (local incidence of MTVS 0.49%). A search of the literature published up to and including 2013 was performed using PubMed as well as more informal search methods.

RESULTS

This patient is the 29th reported case of MTVS after radiation therapy. Of these cases, 40.7% were patients with neurofibromatosis (NF). In those cases in which histology showed tumors with previously benign characteristics, totally conforming to the criteria for MTVS, the mean delay to malignant expression was 68 months (median delay 72 months). The authors also retrieved papers reporting 30 cases of malignant VS in patients who had not undergone radiation treatment. Five of those cases were malignant transformation of a benign entity, and in 4 of them histology had verified that the initial disease was benign. In those 4 cases, there was a mean delay to malignant expression of 7.2 months (median delay 8 months).

CONCLUSIONS

Despite more frequent reports of MTVS after radiation treatment recently, there has been no accurate quantification of the risk, except in patients with NF, in whom the incidence of malignancy is high in relation to the numbers treated. The present analysis indicates that the risk of malignancy over 20 years in cases in which no radiation treatment has occurred is 1.32-2.08 per 100,000, and this risk decreases to 1.09-1.74 per 100,000 if cases of NF are excluded. After radiation treatment, the overall risk over 20 years is 25.1 per 100,000, and this risk decreases to 15.6 per 100,000 if cases of NF are excluded. Radiation treatment increases the risk by approximately 10 times in non-NF cases.

Gamma Knife radiosurgery for vestibular schwannoma: clinical results at long-term follow-up in a series of 379 patients

Object

Since the 1990s, Gamma Knife radiosurgery (GKRS) has become the first-line treatment option for small- to medium-size vestibular schwannomas (VSs), especially in patients without mass effect–related symptoms and with functional hearing. The aim of this study was to assess the safety and efficacy of GKRS, in terms of tumor control, hearing preservation, and complications, in a series of 379 consecutive patients treated for VS.

Methods

Of 523 patients treated at the authors' institution for VS between 2001 and 2010, the authors included 379 who underwent GKRS as the primary treatment. These patients were not affected by Type 2 neurofibromatosis and had clinical follow-up of at least 36 months. Clinical follow-up (mean and median 75.7 and 69.5 months, respectively) was performed for all patients, whereas audiometric and quantitative radiological follow-up examinations were obtained for only 153 and 219 patients, respectively. The patients' ages ranged from 23 to 85 years (mean 59 years). The mean tumor volume was 1.94 ± 2.2 cm3 (median 1.2 cm3, range 0.013–14.3 cm3), and the median margin dose was 13 Gy (range 11–15 Gy). Parameters considered as determinants of the clinical outcome were long-term tumor control, hearing preservation, and complications. A statistical analysis was performed to correlate clinical outcomes with the radiological features of the tumor, dose-planning parameters, and patient characteristics.

Results

Control of the tumor with GKRS was achieved in 97.1% of the patients. In 82.7% of the patients, the tumor volume had decreased at the last follow-up, with a mean relative reduction of 34.1%. The rate of complications was very low, with most consisting of a transient worsening of preexisting symptoms. Patients who had vertigo, balance disorders, or facial or trigeminal impairment usually experienced a complete or at least significant symptom relief after treatment. However, no significant improvement was observed in patients previously reporting tinnitus. The overall rate of preservation of functional hearing at the long-term follow-up was 49%; in patients with hearing classified as Gardner-Robertson (GR) Class I, this value was 71% and reached 93% among cases of GR Class I hearing in patients younger than 55 years.

Conclusions

Gamma Knife radiosurgery is a safe and effective treatment for VS, achieving tumor control in 97.1% of cases and resulting in a very low morbidity rate. Younger GR Class I patients had a significantly higher probability of retaining functional hearing even at the 10-year follow-up; for this reason, the time between symptom onset, diagnosis, and treatment should be shortened to achieve better outcomes in functional hearing preservation.

Role of stereotactic radiosurgery in meningiomas and vestibular schwannomas

OPINION STATEMENT

Intracranial meningiomas and vestibular schwannomas (VS, aka acoustic neuromas) are typically benign, slow-growing, non-invasive neoplasms. The imaging and radiobiologic characteristics of these tumors make them good candidates for stereotactic radiosurgery (SRS), a technique that has been in use for over three decades. Patient selection is critical for successful SRS: small- to moderate-sized tumors can be effectively treated with SRS if the patient does not have symptoms related to mass effect. Factors related to tumor control in meningioma SRS include histology, history of prior surgery, and volume. Tumor control rates after SRS is significantly lower for patients with WHO grade II or III meningiomas compared to patients with WHO grade I meningiomas. The risk of radiation-related complications is higher for patients with larger tumors and tumors located over the convexities or along the falx. Patients with small-volume non-operated skull base or tentorial WHO grade I meningiomas typically have the best outcomes after SRS. Radiosurgery of sporadic VS provides a high tumor control rate (92-95 %), with less than a 5 % risk of facial weakness. Hearing preservation progressively declines for 10 years or more after SRS, and the primary factors related to long-term preservation of useful hearing are tumor size and pre-SRS hearing class. Radiosurgery remains an important option for patients with neurofibromatosis type 2, but tumor control is lower and the risk of cranial nerve deficits is greater when compared to patients with sporadic VS.

Fractionated radiation therapy for vestibular schwannoma

Vestibular schwannomas are the most common tumors of the cerebellopontine angle. Multiple management paradigms exist for patients with these benign tumors, including observation, microsurgery, stereotactic radiosurgery, and fractionated radiation therapy, or some combination of these. While the proper course of management is controversial, the goals of therapy are to achieve excellent local tumor control and optimize functional outcomes with as little treatment-related morbidity as possible. Decision-making is tailored to patient-specific factors such as tumor size, clinical presentation, patient age, and goals of hearing preservation. We review the literature in order to summarize the application of fractionated radiation therapy to this tumor entity, where it is used as a primary treatment or, more commonly, as an adjunct therapy. We also provide an overview of the use of fractionated radiation therapy for the preservation of hearing and facial function, and dosing and other technical considerations, in light of the indolent natural history of vestibular schwannomas. We also discuss potential risks associated with this treatment modality, including its effects on temporal bone structures and cranial nerves among other possible complications. Lastly, we outline future directions in this rapidly evolving segment of vestibular schwannoma therapy, which has benefited from the advent of intensity-modulated radiation therapy coupled with stereotactic localization.

Salvage surgery of vestibular schwannoma after failed radiotherapy: the Gruppo Otologico experience and review of the literature

OBJECTIVES

The use of radiation therapy has largely widespread and becomes in many centers the preference modality of treatment for symptomatic patients who are old, medically unfit for surgical therapy, those who refuse surgery and in some recurrent or residual growing tumors. The risk of radiotherapy failure in the treatment of vestibular schwannoma might be underestimated in the literature. The purpose of this study is to show the Gruppo Otologico experience with salvage surgery to better understand the surgical outcomes and difficulties in treating vestibular schwannoma after failed radiotherapy.

STUDY DESIGN

Retrospective chart review of patients who required salvage surgery of vestibular schwannoma after failed radiotherapy.

SETTINGS

Quaternary referral otology and skull base center.

RESULTS

Between 1987 and 2010, 2500 cases of VS underwent surgical treatment at the Gruppo Otologico. Nineteen patients had received stereotactic radiation therapy before the surgical treatment. The interval time between radiotherapy and surgical salvage ranged from 1 to 10 years. In all the cases decision of surgery was taken following an increase in tumor size with or without new onset of symptoms. Complete tumor removal was achieved in 86.6% of the cases through a transotic, transcochlear or enlarged translabyrinthine approach with trans-apical extension. Difficult dissection of the tumor was encountered in 93.3% the cases. The facial nerve was anatomically preserved in 93.3% but its function was worsened in 73.3% of patients after at least 6 months of follow up. Malignant transformation of the vestibular schwannoma was encountered in one patient.

CONCLUSION

Complete surgical resection of VS is more difficult after radiotherapy with relatively poor facial nerve outcomes and nearly impossible hearing preservation. Patients who receive radiation therapy for the treatment of vestibular schwannoma should be made aware of its potential complications and risk of failure, especially in young patients and NF2 cases.

Facial nerve outcome after vestibular schwannoma surgery: our experience

In this study we evaluate the postoperative facial nerve function after vestibular schwannoma (VS) surgery and analyze the factors that cause it. We included 97 consecutive patients undergoing surgical excision of sporadic unilateral VS. Patient and tumor characteristics, surgical approaches, facial nerve function, extent of tumor removal, perioperative complications are all analyzed through standardized systems. Four different surgical approaches are used: translabyrinthine, retrolabyrinthine, retrosigmoid, and middle cranial fossa. Anatomic preservation of the facial nerve is achieved in 97% of patients. The incidence of postoperative facial palsy is found to be statistically correlated to tumor size, but not to the surgical approach used and to extent of tumor penetration in the internal auditory canal. A significant improvement of the short-term facial nerve outcome is detected in patients undergone simultaneous intraoperative electromyography (EMG) and pneumatic facial nerve monitoring. Complete tumor excision is achieved in 94% of cases. Complication rates are excellent and no deaths are reported. Short- and long-term facial nerve outcome is good and comparable with those of other series reported in literature. In VS surgery both EMG and pneumatic facial nerve monitors should be simultaneously used. Further investigations are desirable to improve the facial outcome respecting the oncological radicality.

Whether gamma knife radiosurgery is really necessary for treatment of patients with vestibular schwannomas

The present study was directed at establishing the role of Gamma Knife radiosurgery (GKS) in the management of vestibular schwannomas (VSs), particularly those that are large. We analyzed a consecutive series of 222 tumors operated on by a single neurosurgeon (T. Hori) at Tottori University (1981-1998) and Tokyo Women's Medical University (1998-2011). The surgical strategy for sporadic unilateral VSs was typically total or nearly total tumor removal with facial nerve preservation, whereas in some cases of neurofibromatosis type 2 intentional subtotal resection was performed. In all, 15 patients (8.6 %) in the series underwent GKS before (4 cases), after (9 cases), or before and after (2 cases) tumor removal. Overall, 211 patients (95 %) were cured by microsurgery alone. Of note, six patients underwent primary radiosurgery but were operated later on for regrowth of the neoplasm, and in four of them near-total resection led to good long-term tumor control. GKS was required in only 5 % of cases for management of residual VS or, more frequently, its regrowth. Radiosurgery resulted in volume reduction in one-third of these tumors. In other cases it stabilized the lesion, preventing further progression. Thus, GKS is considered a reasonable management option for residual or regrowing small VSs to obtain maximum tumor growth control after initially attempting complete surgical removal.

Neurofibromatosis type 2 (NF2): diagnosis and management

Neurofibromatosis type 2 (NF2) is an autosomal dominant inherited tumor predisposition syndrome caused by mutations in the NF2 gene on chromosome 22. Affected individuals develop schwannomas typically involving both vestibular nerves leading to hearing loss and eventual deafness. Rehabilitation with brainstem implants and in some cases cochlear implants is improving this outcome. Schwannomas also occur on other cranial nerves, on spinal nerve roots and peripheral nerves, and intracutaneously as plaques. Cranial and spinal meningiomas and spinal ependymomas are other common tumors. Fifty to sixty percent of patients represent de novo mutations and as many as 33% of these are mosaic for the underlying disease causing mutation. Truncating mutations (nonsense, frameshift insertions/deletions) are the most frequent germline events and cause the most severe disease, whilst single and multiple exon deletions are common and are usually associated with milder NF2. Neurological deficits are a major feature of the condition and neurologists have a pivotal role in assigning symptoms to lesions and in managing neuropathies. NF2 represents a difficult management problem with most patients facing substantial morbidity and reduced life expectancy. Surgery remains the focus of current management although watchful waiting and occasionally radiation treatment have a role. We are seeing the advent of tailored drug therapies aimed at the genetic level and these are likely to provide huge improvements for this devastating, life-limiting condition.

Management of radiation/radiosurgical complications and failures

To describe the incidence and the course of complications after the radiosurgical treatment of vestibular schwannomas, the authors reviewed their own experience and reviewed the literature. Failure is described in less than 3% of cases, and this had to be distinguished from transient enlargement of tumor volume. In case of failure, microsurgical resection or another radiosurgical procedure should be discussed. The risk of radio-induced tumorigenesis is not clearly established with single-dose radiosurgical technique. Incidence and management of potential complications should be explained at the time of decision making in the management of vestibular schwannomas.

Multisession stereotactic radiosurgery for vestibular schwannomas: single-institution experience with 383 cases

BACKGROUND

Single-session stereotactic radiosurgery (SRS) treatment of vestibular schwannomas results in excellent tumor control. It is not known whether functional outcomes can be improved by fractionating the treatment over multiple sessions.

OBJECTIVE

To examine tumor control and complication rates after multisession SRS.

METHODS

Three hundred eighty-three patients treated with SRS from 1999 to 2007 at Stanford University Medical Center were retrospectively reviewed. Ninety percent were treated with 18 Gy in 3 sessions, targeting a median tumor volume of 1.1 cm3 (range, 0.02-19.8 cm3).

RESULTS

During a median follow-up duration of 3.6 years (range, 1-10 years), 10 tumors required additional treatment, resulting in 3- and 5-year Kaplan-Meier tumor control rates of 99% and 96%, respectively. Five-year tumor control rate was 98% for tumors < 3.4 cm3. Neurofibromatosis type 2-associated tumors were associated with worse tumor control (P = .02). Of the 200 evaluable patients with pre-SRS serviceable hearing (Gardner-Robertson grade 1 and 2), the crude rate of serviceable hearing preservation was 76%. Smaller tumor volume was associated with hearing preservation (P = .001). There was no case of post-SRS facial weakness. Eight patients (2%) developed trigeminal dysfunction, half of which was transient.

CONCLUSION

Multisession SRS treatment of vestibular schwannomas results in an excellent rate of tumor control. The hearing, trigeminal nerve, and facial nerve function preservation rates reported here are promising.

Different responses of benign and atypical meningiomas to gamma-knife radiosurgery: report of two cases with immunohistochemical analysis

Recent reports have shown that gamma-knife radiosurgery provides a safe and effective strategy for the management of brain tumors. To evaluate the role of stereotactic radiosurgery in the management of meningiomas, we investigated the histopathology of two patients. The patients, a 37-year-old man and a 54-year-old woman, presented with visual field disturbance or headache. Imaging studies demonstrated intracranial meningiomas--tentorial and sphenoid ridge, respectively. Each patient undewent subtotal surgical resection (more than 90% in both patients), followed by gamma-knife radiosurgery of the remnant tumor marginal doses of 15 Gy. Pathological examination of the original tumors revealed a meningothelial meningioma and an atypical meningioma, respectively. Enlargement of the remnant tumors 4 months after radiosurgery resulted in total surgical resection in both patients. Thirteen months later, the patient with the atypical meningioma underwent a third operation for early recurrence of the tumor. Histopathology was investigated, and MIB-1, p53, and bcl-2 labeling indexes (LI) were analyzed immunohistochemically. Histopathologically, the specimens showed necrosis and intratumoral vessel obliteration after radiosurgery in both cases. However, more remnant tumor cells survived in the atypical meningioma. Immunohistochemically, increased wild-type p53, decreased bcl-2 expression, and decreased MIB-1 LI were observed in the benign meningioma. In the atypical meningioma, on the contrary, MIB-1 LI was decreased and mutant-type p53 and bcl-2 expression were unchanged. The specimen from the third operation revealed an anaplastic meningioma, and MIB-1 LI was markedly increased. These findings suggest that the efficacy of radiosurgery may differ between benign and atypical meningiomas.

Long-term tumor control and cranial nerve outcomes following Gamma Knife surgery for larger-volume vestibular schwannomas

Object

Gamma Knife surgery (GKS) for vestibular schwannoma (VS) is an accepted treatment for small- to medium-sized tumors, generally smaller than 2.5 cm in the maximum posterior fossa dimension. The purpose of this study was to evaluate the efficacy and toxicity of GKS for larger tumors.

Methods

Prospectively collected data were analyzed for 22 patients who had undergone GKS for VSs larger than 2.5 cm in the posterior fossa diameter between 1997 and 2006. No patient had symptomatic brainstem compression at the time of GKS. The median treated tumor volume was 9.4 cm3 (range 5.3–19.1 cm3). The median maximum posterior fossa diameter was 2.8 cm (range 2.5–3.8 cm). The median tumor margin dose was 12 Gy (range 12–14 Gy). Serial imaging, audiometry (10 patients with serviceable hearing pre-GKS), and clinical follow-up were available for a median of 66 months (range 26–121 months). Tumor control failure was defined as either a progressive increase in tumor diameter of at least 2 mm in any dimension or a later resection.

Results

Four patients met the criteria for GKS failure, including 1 patient who demonstrated sarcomatous degeneration more than 7 years after GKS and died 3 months after microsurgical debulking. An enlarging cystic component was the surgical indication in 1 of the 2 patients who required resection, although 27% of tumors (6 lesions) were cystic before GKS. The 3-year actuarial rate of tumor control, freedom from new facial neuropathy, and preservation of functional hearing were 86%, 92%, and 47%, respectively. At 5 years post-GKS, these rates decreased to 82%, 85%, and 28%, respectively. At the most recent follow-up, 91% of tumors were smaller than at the time of GKS and the median maximum posterior fossa diameter reduction was 26%. On multivariate analysis, none of the following factors was associated with GKS failure, new facial weakness, new trigeminal neuropathy, or loss of serviceable hearing: patient age, tumor volume, tumor margin dose, and preoperative cranial nerve dysfunction.

Conclusions

Single-session radiosurgery is a successful treatment for the majority of patients with larger VSs. Although tumor control rates are lower than those for smaller VSs managed with GKS, the cranial nerve morbidity of GKS is significantly lower than that typically achieved via resection of larger VSs.

Surgical treatment of patients with vestibular schwannomas after failed previous radiosurgery

OBJECT

An increasing number of patients with vestibular schwannomas (VSs) are being treated with radiosurgery. Treatment failure or secondary regrowth after radiosurgery, however, has been observed in 2%-9% of patients. In large tumors that compress the brainstem and in patients who experience rapid neurological deterioration, surgical removal is the only reasonable management option.

METHODS

The authors evaluated the relevance of previous radiosurgery for the outcome of surgery in a series of 28 patients with VS. The cohort was further subdivided into Group A (radiosurgery prior to surgery) and Group B (partial tumor removal followed by radiosurgery prior to current surgery). The functional and general outcomes in these 2 groups were compared with those in a control group (no previous treatment, matched characteristics). RESULTS There were 15 patients in Group A, 13 in Group B, and 30 in the control group. The indications for surgery were sustained tumor enlargement and progression of neurological symptoms in 12 patients, sustained tumor enlargement in 15 patients, and worsening of neurological symptoms without evidence of tumor growth in 1 patient. Total tumor removal was achieved in all patients in Groups A and B and in 96.7% of those in the control group. There were no deaths in any group. Although no significant differences in the neurological morbidity or complication rates after surgery were noted, the risk of new cranial nerve deficits and CSF leakage was highest in patients in Group B. Patients who underwent previous radiosurgical treatment (Groups A and B) tended to be at higher risk of developing postoperative hematomas in the tumor bed or cerebellum. The rate of facial nerve anatomical preservation was highest in those patients who were not treated previously (93.3%) and decreased to 86.7% in the patients in Group A and to 61.5% in those in Group B. Facial nerve function at follow-up was found to correlate to the previous treatment; excellent or good function was seen in 87% of the patients from the control group, 78% of those in Group A, and 68% of those in Group B.

CONCLUSIONS

Complete microsurgical removal of VSs after failed radiosurgery is possible with an acceptable morbidity rate. The functional outcome, however, tends to be worse than in nontreated patients. Surgery after previous partial tumor removal and radiosurgery is most challenging and related to worse outcome.

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.