Magnetic resonance imaging surveillance following vestibular schwannoma resection

Clinical practice guideline on the management of vestibular schwannoma

INTRODUCTION

Vestibular schwannoma (VS) is the most common tumour of the cerebellopontine angle. The greater accessibility to radiological tests has increased its diagnosis. Taking into account the characteristics of the tumour, the symptoms and the age of the patient, three therapeutic strategies have been proposed: observation, surgery or radiotherapy. Choosing the most appropriate for each patient is a frequent source of controversy.

MATERIAL AND METHODS

This paper includes an exhaustive literature review of issues related to VS that can serve as a clinical guide in the management of patients with these lesions. The presentation has been oriented in the form of questions that the clinician usually asks himself and the answers have been written and/or reviewed by a panel of national and international experts consulted by the Otology Commission of the SEORL-CCC.

RESULTS

A list has been compiled containing the 13 most controversial thematic blocks on the management of VS in the form of 50 questions, and answers to all of them have been sought through a systematic literature review (articles published on PubMed and Cochrane Library between 1992 and 2023 related to each thematic area). Thirty-three experts, led by the Otology Committee of SEORL-CCC, have analyzed and discussed all the answers. In Annex 1, 14 additional questions divided into 4 thematic areas can be found.

CONCLUSIONS

This clinical practice guideline on the management of VS offers agreed answers to the most common questions that are asked about this tumour. The absence of sufficient prospective studies means that the levels of evidence on the subject are generally medium or low. This fact increases the interest of this type of clinical practice guidelines prepared by experts.

Comparison of Surgeons' Assessment of the Extent of Vestibular Schwannoma Resection with Immediate Post Operative and Follow-Up Volumetric MRI Analysis

(1) Background: Incomplete excision of vestibular schwannomas (VSs) is sometimes preferable for facial nerve preservation. On the other hand, subtotal resection may be associated with higher tumor recurrence. We evaluated the correlation between intra-operative assessment of residual tumor and early and follow-up imaging. (2) Methods: The charts of all patients undergoing primary surgery for sporadic vestibular schwannoma during the study period were retrospectively reviewed. Data regarding surgeons' assessments of the extent of resection, and the residual size of the tumor on post-operative day (POD) one and follow-up MRI were extracted. (3) Results: Of 109 vestibular schwannomas meeting inclusion criteria, gross-total resection (GTR) was achieved in eighty-four, near-total (NTR) and sub-total resection (STR) in twenty-two and three patients, respectively. On follow up imaging, volumetric analysis revealed that of twenty-two NTRs, eight were radiographic GTR and nine were radiographic STR (mean volume ratio 11.9%), while five remained NTR (mean volume ratio 1.8%). Of the three STRs, two were radiographic GTR while one remained STR. Therefore, of eighteen patients with available later follow up MRIs, radiographic classification of the degree of resection changed in six. (4) Conclusions: An early MRI (POD#1) establishes a baseline for the residual tumor that may be more accurate than the surgeon's intraoperative assessment and may provide a beneficial point of comparison for long-term surveillance.

Recurrences and progression following microsurgery of vestibular schwannoma

Background

The treatment approach of vestibular schwannoma (VS) has seen a change in recent years, with a trend away from radical surgery towards preservation of cranial nerve function. A recent study reported recurrences as long as 20 years after complete removal of VS.

Objective

To report the risk of recurrence and progression in our patient population the authors retrospectively reviewed outcomes of patients.

Methods

Cases with unilateral VS who had undergone primary microsurgery via retrosigmoidal approach between 1995 and 2021 were investigated. Complete tumor removal was defined as gross total resection (GTR), a capsular remnant was categorized as near total resection (NTR) and residual tumor was designated as subtotal resection (STR). The primary endpoint was radiological recurrence-free survival.

Results

386 patients fulfilled the inclusion criteria of the study and were evaluated. GTR was achieved in 284 patients (73.6%), NTR was achieved in 63 patients (10.1%) and STR was present in 39 patients (16.3%). A total of 28 patients experienced recurrences with significant differences in the three subgroups. The strongest predictor of recurrence was the extent of resection, with patients who underwent STR having an almost 10-fold higher risk of recurrence and patients who had undergone NTR having an almost 3-fold higher risk than those treated with GTR. More than 20% of recurrences (6/28) occured after more than 5 years.

Conclusion

The degree of resection is an important guide to the interval of follow-up, but long-term follow-up should be considered also in the case of GTR. The majority of recurrences occurs after 3-5 years. Nevertheless, a follow-up of at least 10 years should be carried out.

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.

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

OBJECTIVE

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

STUDY DESIGN

Retrospective case series from 2018 to 2021.

SETTING

Tertiary academic medical center.

PATIENTS

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

INTERVENTIONS

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

MAIN OUTCOME MEASURES

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

RESULTS

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

CONCLUSIONS

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

Microsurgery for vestibular schwannoma: analysis of short-term clinical outcome

BACKGROUND

Total removal of the vestibular schwannoma when preserving the function of the facial nerve is difficult. The objective of the current study was to investigate the short-term clinical outcome of vestibular schwannoma removal via retro-sigmoid approach.

METHODS

One-hundred consecutive patients diagnosed with vestibular schwannoma were surgically treated between December 2018 and August 2019 in Xuanwu Hospital, Capital Medical University. The clinical classification, surgical position, gross total removal rate, the anatomical and functional preservation rates of facial nerve, and the postoperative complications were retrospectively analyzed.

RESULTS

All 100 patients including 34 males and 66 females were operated on via retro-sigmoid approach. According to Koos vestibular schwannoma grading system, 18 cases were grade 2, 34 cases were grade 3, and 48 cases were grade 4. According to Hannover vestibular schwannoma grading system, 5 cases were T2, 6 cases were T3a, 8 cases were T3b, 30 cases were T4a, and 51 cases were T4b. Seventy-three surgeries were performed under lateral position, and 27 cases were operated under semi-sitting position. The gross total removal rate was 90.0%; the anatomic reservation rate of the facial nerve was 96.0%. According to the House-Brackman system, the facial nerve function was grades 1-2 in 78.0% cases, grade 3 in 7.0% cases, and grades 4-5 in 15% cases. For patients with effective hearing before operation, the hearing reservation rate was 19.0%. Two patients (2.0%) developed intracranial hematoma after operation.

CONCLUSION

Most vestibular schwannoma could be completely removed with good postoperative facial nerve function. If total removal of tumor is difficult, we should give priority to the functional preservation of the nerve function.

Predicting Extent of Microsurgical Resection of Sporadic Vestibular Schwannoma

OBJECTIVE

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

STUDY DESIGN

Historical cohort.

SETTING

Tertiary referral center.

PATIENTS

Patients with sporadic VS.

INTERVENTIONS

Microsurgery with preoperative intent of gross total resection.

MAIN OUTCOME MEASURES

Patient and tumor characteristics that influence extent of resection.

RESULTS

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

CONCLUSION

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

Evaluating growth trends of residual sporadic vestibular schwannomas: a systematic review and meta-analysis

BACKGROUND

Gross total resection remains the gold-standard approach for vestibular schwannomas (VS) when surgery is indicated. In select cases, incomplete resection (IR) becomes a desired alternative to preserve the facial nerve function and the patient's quality of life. While a lot of earlier studies described incompletely resected sporadic VSs as dormant, more recent studies reported a higher growth rate following IR, therefore an evaluation of the residual VS growth rates could have important implications for the follow-up treatment protocols and provide relevant information for neurosurgeons, neuro-otologists, neuropathologists, and radiologists. Although prognostic factors predicting preoperative VS growth have been previously investigated, these factors have not been investigated following IR. Our review aims to examine the growth rate of residual sporadic VS following IR and to examine variables associated with the regrowth of residual VS.

METHODS

The review was conducted in accordance with the PRISMA guidelines. Six databases (MEDLINE (Ovid), Embase (Ovid), CINAHL Plus (EBSCO), Cochrane Central Register of Controlled Trials (CENTRAL), WHO International Clinical Trials Registry Platform and UK Clinical Trials Gateway (WHO ICTRP) were searched. Full-text articles analysing growth rates in at least ten patients who had residual VS after IR were assessed. We conducted a meta-analysis using a random-effects model via RevMan.

RESULTS

14 studies totalling 849 patients were included in the analysis. The mean planimetric growth rate was 1.57 mm/year (range 0.16-3.81 mm/year). The mean volumetric growth rate was 281.725 mm³/year (range 17.9-530.0 mm³/year). Age, sex, pre-operative tumour size/volume, cystic tumour sub-type, MIB-1 index, and intracanalicular tumour location were not associated with residual growth. Residual tumour size/volume was statistically significant to growth (OR = 0.65, 95% CI 0.47-0.90, p = 0.01). Radiological re-growth occurred in an average of 26.6% of cases (range 0-54.5%).

CONCLUSION

From our analysis, only the residual tumour volume/size was associated with residual VS growth. Therefore, close postoperative surveillance for the first year, followed by an annual MRI scan for at least 5 years, and subsequently extended interval surveillance remains of utmost importance to monitor disease progression and provide timely surgical and adjuvant interventions. Our study shows that future work should be aimed at molecular and histological characteristics of residual VSs to aid prognostic understanding of growth.

Defining clinically significant tumor size in vestibular schwannoma to inform timing of microsurgery during wait-and-scan management: moving beyond minimum detectable growth

OBJECTIVE

Detection of vestibular schwannoma (VS) growth during observation leads to definitive treatment at most centers globally. Although ≥ 2 mm represents an established benchmark of tumor growth on serial MRI studies, 2 mm of linear tumor growth is unlikely to significantly alter microsurgical outcomes. The objective of the current work was to ascertain where the magnitude of change in clinical outcome is the greatest based on size.

METHODS

A single-institution retrospective review of a consecutive series of patients with sporadic VS who underwent microsurgical resection between January 2000 and May 2020 was performed. Preoperative tumor size cutpoints were defined in 1-mm increments and used to identify optimal size thresholds for three primary outcomes: 1) the ability to achieve gross-total resection (GTR); 2) maintenance of normal House-Brackmann (HB) grade I facial nerve function; and 3) preservation of serviceable hearing (American Academy of Otolaryngology-Head and Neck Surgery class A/B). Optimal size thresholds were obtained by maximizing c-indices from logistic regression models.

RESULTS

Of 603 patients meeting inclusion criteria, 502 (83%) had tumors with cerebellopontine angle (CPA) extension. CPA tumor size was significantly associated with achieving GTR, postoperative HB grade I facial nerve function, and maintenance of serviceable hearing (all p < 0.001). The optimal tumor size threshold to distinguish between GTR and less than GTR was 17 mm of CPA extension (c-index 0.73). In the immediate postoperative period, the size threshold between HB grade I and HB grade > I was 17 mm of CPA extension (c-index 0.65). At the most recent evaluation, the size threshold between HB grade I and HB grade > I was 23 mm (c-index 0.68) and between class A/B and C/D hearing was 18 mm (c-index 0.68). Tumors within 3 mm of the 17-mm CPA threshold displayed similarly strong c-indices. Among purely intracanalicular tumors, linear size was not found to portend worse outcomes for all measures.

CONCLUSIONS

The probability of incurring less optimal microsurgical outcomes begins to significantly increase at 14-20 mm of CPA extension. Although many factors ultimately influence decision-making, when considering timing of microsurgical resection, using a size threshold range as depicted in this study offers an evidence-based approach that moves beyond reflexively recommending treatment for all tumors after detecting ≥ 2 mm of tumor growth on serial MRI studies.

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

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

A prediction model for recurrence after translabyrinthine surgery for vestibular schwannoma: toward personalized postoperative surveillance

Purpose

The aim of this study is to compute and validate a statistical predictive model for the risk of recurrence, defined as regrowth of tumor necessitating salvage treatment, after translabyrinthine removal of vestibular schwannomas to individualize postoperative surveillance.

Methods

The multivariable predictive model for risk of recurrence was based on retrospectively collected patient data between 1995 and 2017 at a tertiary referral center. To assess for internal validity of the prediction model tenfold cross-validation was performed. A ‘low’ calculated risk of recurrence in this study was set at < 1%, based on clinical criteria and expert opinion.

Results

A total of 596 patients with 33 recurrences (5.5%) were included for analysis. The final prediction model consisted of the predictors ‘age at time of surgery’, ‘preoperative tumor growth’ and ‘first postoperative MRI outcome’. The area under the receiver operating curve of the prediction model was 89%, with a C-index of 0.686 (95% CI 0.614–0.796) after cross-validation. The predicted probability for risk of recurrence was low (< 1%) in 373 patients (63%). The earliest recurrence in these low-risk patients was detected at 46 months after surgery.

Conclusion

This study presents a well-performing prediction model for the risk of recurrence after translabyrinthine surgery for vestibular schwannoma. The prediction model can be used to tailor the postoperative surveillance to the estimated risk of recurrence of individual patients. It seems that especially in patients with an estimated low risk of recurrence, the interval between the first and second postoperative MRI can be safely prolonged.

Risk Factors for Progression in Vestibular Schwannomas After Incomplete Resection: A Single Center Retrospective Study

Background and Purpose: The risk factors for progression in vestibular schwannomas (VSs) after incomplete resection (IR) remain to be elucidated. The purpose of this study was to investigate the risk factors for progression in remnant VSs after surgery.

Methods: From January 2009 to January 2018, 140 consecutive patients who underwent IR of VSs via suboccipital retrosigmoid approach in our institution were retrospectively analyzed. During follow-up, if progression was detected, the patient was classified into Progressive Group (PG); if the residual tumor was stable or shrank, the patient was classified into Stable Group (SG). Univariate analysis and multivariate analysis were used to evaluate the risk factors for progression after IR of VSs.

Results: After a mean follow-up of 80.4 months (range, 24–134 months), 35 (25.0%) patients (PG) had a progression, and no progression was detected in 105 (75.0%) patients (SG). The average tumor size was 36.5 ± 8.9 mm in PG and 31.0 ± 9.8 mm in SG, respectively. The residual tumor volume was 304.6 ± 443.3 mm³ in PG and 75.9 ± 60.0 mm³ in SG, respectively. Univariate analysis showed that preoperative tumor size, residual tumor volume, and irregular internal auditory canal (IAC) expansion were significantly different between the two groups, whereas gender, age, cystic component, or Ki-67 labeling index (LI) did not differ significantly between the two groups. Multivariate analysis showed residual tumor volume was the independent risk factor for progression.

Conclusions: VSs that underwent IR with larger preoperative size, greater residual tumor volume, or irregular IAC expansion may have a higher progression rate. Strict follow-up with shorter interval in these patients to detect early progression is necessary.

Imaging of the Vestibular Schwannoma: Diagnosis, Monitoring, and Treatment Planning

Appropriate imaging strategies for the detection, treatment planning, and posttreatment monitoring of vestibular schwannomas will be discussed. The typical and variant imaging appearances of vestibular schwannomas, as well as the imaging features that should prompt consideration of differential diagnoses, will be illustrated. Understanding the natural history of vestibular schwannomas, optimal measurement and definition of tumour growth helps the radiologist evaluate for the failure of conservative management and requirement for surgery or radiotherapy. In order to determine the success of conservative management, the radiologist is required to understand the natural history of vestibular schwannomas and how tumour growth is defined. Finally, the imaging features which help guide appropriate treatment with surgery or radiotherapy will be highlighted, and the expected posttreatment imaging changes will be described.

Lifetime Cost and Quality-Adjusted Life-Years Across Management Options for Small- and Medium-Sized Sporadic Vestibular Schwannoma

OBJECTIVE

Despite the growing emphasis on healthcare costs, limited data address this aspect of care within the vestibular schwannoma (VS) literature. We sought to determine which strategy confers the lowest lifetime cost and greatest quality-adjusted life-years (QALYs) for patients with small- to medium-sized sporadic VS tumors.

STUDY DESIGN

A Markov model was created to determine the most cost-effective management algorithm. Tumor characteristics, magnetic resonance imaging surveillance schedule, treatment outcomes, and health-related quality of life values were derived from previously published data. Cost estimates were based on CMS Fee Schedule reimbursement rates.

SETTING

Economic Evaluation Service within the Kern Center for the Science of Healthcare Delivery.

PATIENTS

Patients diagnosed with small- to medium-sized sporadic VS.

INTERVENTIONS

Upfront microsurgery following diagnosis, upfront radiosurgery following diagnosis, observation with microsurgery reserved for observed tumor growth, and observation with radiosurgery reserved for observed tumor growth.

RESULTS

Across patient ages at time of diagnosis ranging from 18 to 70 years, observation with subsequent radiosurgery used for tumor growth was the most cost-effective management algorithm while upfront microsurgery was the least. When presented with a hypothetical 50-year-old patient, the strategy with the lowest lifetime cost and highest QALYs was observation with subsequent radiosurgery reserved for tumor growth ($32,161, 14.11 QALY), followed by observation with microsurgery reserved for tumor growth ($34,503, 13.94 QALY), upfront radiosurgery ($43,456, 14.02 QALY), and lastly, upfront microsurgery ($47,252, 13.60 QALY). Sensitivity analyses varying mortality rates, estimated costs, health-related quality of life, and progression to nonserviceable hearing demonstrated consistent ranking among treatments.

CONCLUSIONS

When considering initial management of small- and medium-sized sporadic VSs, neither lifetime cost nor QALYs support upfront microsurgery or radiosurgery, even for younger patients. Initial observation with serial imaging, reserving radiosurgery or microsurgery for patients exhibiting tumor growth, confers the greatest potential for optimized lifetime healthcare cost and QALY outcomes.

Changing Enhancement Pattern and Tumor Volume of Vestibular Schwannomas After Subtotal Resection

BACKGROUND

Surgical strategy in vestibular schwannomas may require subtotal resection to preserve neurologic function. Residual tumor growth pattern and contrast enhancement in the immediate postresection period remain uncertain. We sought to evaluate changes in the enhancement pattern and volume of vestibular schwannomas after subtotal resection in the immediate postoperative period.

METHODS

Volumetric analysis of tumor size and enhancement patterns of vestibular schwannomas were measured on magnetic resonance imaging (MRI) scans obtained within 3 days of surgery, 3 months after surgery, and 1 year after surgery.

RESULTS

Nineteen patients were eligible for inclusion in the study (9 male and 10 female) with an average age of 47 years. Contrast enhancement was absent in 6 of 19 (32%) of cases on the immediate postresection MRI with return of expected enhancement on subsequent studies. Volumetric analysis identified that tumors decreased in size by an average of 35% in the first 3 months (P = 0.025) after resection and 46% in the first year after resection (P < 0.01).

CONCLUSIONS

Vestibular schwannomas that undergo subtotal resection tend to decrease in size over the first 3 months after resection. Residual tumor volume may fail to enhance on the immediate postresection MRI. Both of these findings could lead surgeons to misinterpret degree of resection after surgery and have implications for clinical decision making and research reporting in the scientific literature for vestibular schwannomas after subtotal resection.

The behavior of residual tumors following incomplete surgical resection for vestibular schwannomas

The management of vestibular schwannoma (VS) with residual tumor following incomplete resection remains controversial and little is known regarding postoperative tumor volume changes. The behavior of residual tumors was analyzed for 111 patients who underwent surgery for newly diagnosed VS between September 2006 and July 2017. The postoperative tumor volume changes were assessed during a mean follow-up of 69 months (range 36–147 months). Fifty-three patients underwent imaging surveillance following incomplete resection. There was no residual tumor growth in 44 patients (83%). A significant regression of residual tumor volume was noted in the no growth group at postoperative 1 year (p = 0.028), 2 years (p = 0.012), but not from 3 years onwards. Significant predictors of regrowth were immediate postoperative tumor volume ≥ 0.7 cm³ (HR 10.5, p = 0.020) and residual tumor location other than the internal auditory canal (IAC) (HR 6.2, p = 0.026). The mean time to regrowth was 33 months (range 5–127 months). The 2-, 5-, and 10-year regrowth-free survival rates were 90.6%, 86.8%, and 83%, respectively. In conclusion, significant residual tumor regression could occur within 2 years for a VS with an immediate postoperative tumor volume less than 0.7 cm³ or residual tumor in IAC.

Guidelines in the management of CNS tumors

INTRODUCTION

Evidence-based, clinical practice guidelines in the management of central nervous system tumors (CNS) continue to be developed and updated through the work of the Joint Section on Tumors of the Congress of Neurological Surgeons (CNS) and the American Association of Neurological Surgeons (AANS).

METHODS

The guidelines are created using the most current and clinically relevant evidence using systematic methodologies, which classify available data and provide recommendations for clinical practice.

CONCLUSION

This update summarizes the Tumor Section Guidelines developed over the last five years for non-functioning pituitary adenomas, low grade gliomas, vestibular schwannomas, and metastatic brain tumors.

Microsurgical Treatment and Follow-Up of KOOS Grade IV Vestibular Schwannoma: Therapeutic Concept and Future Perspective

Purpose

Surgery of KOOS IV vestibular schwannoma remains challenging regarding the balance of extent of tumor resection (EoR) and functional outcome. Our aim was to evaluate the outcome of surgical resection and define a cut-off value for safe resection with low risk for tumor regrowth of KOOS IV vestibular schwannoma.

Methods

All patients presenting at the authors’ institution between 2000 and 2019 with surgically treated KOOS IV vestibular schwannoma were included. Outcome measures included EoR, facial/hearing nerve function, surgical complications and progression of residual tumor during the median follow-up period of 28 months.

Results

In 58 patients, mean tumor volume was 17.1 ± 9.2 cm³, and mean EoR of 81.6 ± 16.8% could be achieved. Fifty-one patients were available for the follow-up analysis. Growth of residual tumor was observed in 11 patients (21.6%) followed by adjuvant treatment with stereotactic radiosurgery or repeat surgery in 15 patients (29.4%). Overall serviceable hearing preservation was achieved in 38 patients (74.5%) and good facial outcome at discharge was observed in 66.7% of patients, significantly increasing to 82.4% at follow-up. Independent predictors for residual tumor growth was EoR ≤ 87% (OR11.1) with a higher EoR being associated with a very low number of residual tumor progression amounting to 7.1% at follow-up (p=0.008).

Conclusions

Subtotal tumor resection is a good therapeutic concept in patients with KOOS IV vestibular schwannoma resulting in a high rate of good hearing and facial nerve function and a very low rate of subsequent tumor progression. The goal of surgery should be to achieve more than 87% of tumor resection to keep residual tumor progression low.

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.

MRI of the Internal Auditory Canal, Labyrinth, and Middle Ear: How We Do It

MRI is firmly established as an essential modality in the imaging of the temporal bone and lateral skull base. It is used to evaluate normal anatomic structures, evaluate for vestibular schwannomas, assess for inflammatory and/or infectious processes, and detect residual and/or recurrent cholesteatoma. It is also extensively used in pre- and postoperative evaluations, particularly in patients with vestibular schwannomas and candidates for cochlear implantation. Nevertheless, despite the widespread use of MRI for these purposes, many radiologists remain unfamiliar with the complex anatomy and expected imaging findings with such examinations. The purpose of this review is to provide an overview of the most useful MRI sequences for internal auditory canal and labyrinthine imaging, review the relevant anatomy, and discuss the expected appearances of the most commonly encountered pathologic entities. In addition, the features at pre- and postprocedural MRI will be discussed to help ensure that diagnostic radiologists may be of greatest use to the ordering physicians. © RSNA, 2020.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Residual Tumor Volume and Location Predict Progression After Primary Subtotal Resection of Sporadic Vestibular Schwannomas: A Retrospective Volumetric Study

BACKGROUND

Preservation of functional integrity during vestibular schwannoma surgery has become critical in the era of patient-centric medical decision-making. Subtotal tumor removal is often necessary when dense adhesions between the tumor and critical structures are present. However, it is unclear what the rate of tumor control is after subtotal resection (STR) and what factors are associated with recurrence.

OBJECTIVE

To determine the rate of residual tumor growth after STR and identify clinical and radiographic predictors of tumor progression.

METHODS

A single-institution retrospective study was performed on all sporadic vestibular schwannomas that underwent surgical resection between January 1, 2002 and December 31, 2015. Clinical charts, pathology, radiology, and operative reports were reviewed. Volumetric analysis was performed on all pre- and postoperative MR imaging. Univariate and multivariate logistic regression was performed to identify predictors of the primary endpoint of tumor progression. Kaplan-Meier analysis was performed to compare progression free survival between 2 groups of residual tumor volumes and location.

RESULTS

In this cohort of 66 patients who underwent primary STR, 30% had documented progression within a median follow up period of 3.1 yr. Greater residual tumor volume (OR 2.0 [1.1-4.0]) and residual disease within the internal auditory canal (OR 3.7 [1.0-13.4]) predicted progression on multivariate analysis.

CONCLUSION

These longitudinal data provide insight into the behavior of residual tumor, helping clinicians to determine if and when STR is an acceptable surgical strategy and to anchor expectations during shared medical decision-making consultation with patients.

MMP-14 (MT1-MMP) Is a Biomarker of Surgical Outcome and a Potential Mediator of Hearing Loss in Patients With Vestibular Schwannomas

Improved biomarkers are needed for vestibular schwannoma (VS), the most common tumor of the cerebellopontine angle, as existing clinical biomarkers have poor predictive value. Factors such as tumor size or growth rate do not shed light on the pathophysiology of associated sensorineural hearing loss (SNHL) and suffer from low specificity and sensitivity, whereas histological markers only sample a fraction of the tumor and are difficult to ascertain before tumor treatment or surgical intervention. Proteases play diverse and critical roles in tumorigenesis and could be leveraged as a new class of VS biomarkers. Using a combination of in silico, in vitro, and ex vivo approaches, we identified matrixmetalloprotease 14 (MMP-14; also known as MT1-MMP), from a panel of candidate proteases that were differentially expressed through the largest meta-analysis of human VS transcriptomes. The abundance and proteolytic activity of MMP-14 in the plasma and tumor secretions from VS patients correlated with clinical parameters and the degree of SNHL. Further, MMP-14 plasma levels correlated with surgical outcomes such as the extent of resection. Finally, the application of MMP-14 at physiologic concentrations to cochlear explant cultures led to damage to spiral ganglion neuronal fibers and synapses, thereby providing mechanistic insight into VS-associated SNHL. Taken together, MMP-14 represents a novel molecular biomarker that merits further validation in both diagnostic and prognostic applications for VS.

Management von Patienten mit Vestibularisschwannomen Typ IV

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

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

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

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

Magnetic Resonance Imaging Surveillance for Vestibular Schwannoma After Microsurgical Resection Using a Retrosigmoid Transmeatal Approach

BACKGROUND

Vestibular schwannoma (VS) is a benign, usually slow-growing tumor. The drawback of radical microsurgical VS resection is the increased likelihood of neurologic injury, forcing surgeons to leave a tumor remnant in some cases. We evaluated the prognostic value of magnetic resonance imaging (MRI) enhancement patterns to determine the risk of tumor regrowth.

METHODS

This clinical study included 30 patients (20 women and 10 men) with VS who underwent surgery via a retrosigmoid transmeatal approach. The extent of resection was assessed by MRI 6 months after surgery. Two subtypes of intracanalicular linear enhancement were defined: linear enhancement of the walls of the internal auditory canal (IAC) or in the cerebellopontine angle (CPA) and linear enhancement covering the end of the IAC. All patients included in the study underwent follow-up MRI every year for at least 6 years.

RESULTS

Intracanalicular nodular enhancement suggestive of a tumor remnant was seen in the IAC in 11 patients (36.7%). Volume of nodular enhancements was <0.5 cm³ when measurable. The enhancement remained stable throughout follow-up except in 2 cases that showed a slight decrease in size and in 1 case with an initial tumor remnant of 0.5 cm³ showing a slight increase over the years. Eighteen patients (60%) had linear enhancement in the IAC or in the CPA. No patients with linear enhancement showed nodular enhancement.

CONCLUSIONS

Although specific monitoring protocols can be designed based on MRI findings 6 months after microsurgical VS resection, follow-up should be maintained indefinitely given the slight possibility of very late regrowth.

Prediction of vestibular schwannoma recurrence using artificial neural network

OBJECTIVES

To compare two statistical models, namely logistic regression and artificial neural network (ANN), in prediction of vestibular schwannoma (VS) recurrence.

METHODS

Seven hundred eighty-nine patients with VS diagnosis completed an online survey. Potential predictors for recurrence were derived from univariate analysis by reaching the cut off P value of .05. Those nine potential predictors were years since treatment, surgeon's specialty, resection amount, and having incomplete eye closure, dry eye, double vision, facial pain, seizure, and voice/swallowing problem as a complication following treatment. Multivariate binary logistic regression model was compared with a four-layer 9-5-10-1 feedforward backpropagation ANN for prediction of recurrence.

RESULTS

The overall recurrence rate was 14.5%. Significant predictors of recurrence in the regression model were years since treatment and resection amount (both P < .001). The regression model did not show an acceptable performance (area under the curve [AUC] = 0.64; P = .27). The regression model's sensitivity and specificity were 44% and 69%, respectively and correctly classified 56% of cases. The ANN showed a superior performance compared to the regression model (AUC = 0.79; P = .001) with higher sensitivity (61%) and specificity (81%), and correctly classified 70% of cases.

CONCLUSION

The constructed ANN model was superior to logistic regression in predicting patient-answered VS recurrence in an anonymous survey with higher sensitivity and specificity. Since artificial intelligence tools such as neural networks can have higher predictive abilities compared to logistic regression models, continuous investigation into their utility as complementary clinical tools in predicting certain surgical outcomes is warranted.

Inner ear MRI: is it always useful to manage intravenous contrast?

OBJECTIVE

To evaluate the added value of administering intravenous contrast (IVC) routinely to the MRI of patients with audiovestibular symptoms in the assessment of a neuroradiologist and a resident.

MATERIALS AND METHODS

Retrospective study including patients who had an inner ear MRI for two months. Two radiologists reviewed independently and blinded the images. A first assessment was made analyzing just the sequences acquired without contrast and then a second evaluation of all the sequences, including post-contrast T1 sequences. The interobserver correlation and the correlation between MRI findings and the reason for requesting the study were calculated.

RESULTS

40 patients were included. The range age was 36-80 years. The most frequent reason for request the MRI was hearing loss (52.5%). Neuroradiologist without IVC found 82.5% of extraotic pathology and 17.5% of otic pathology, highlighting the neurinoma of the VIII pair (7.5%); ossifying labyrinthitis, retrofenestrated otosclerosis and cholesteatoma. After IVC administration, findings were similar. The resident identified otic pathology in 5% in baseline sequences and 20% using CIV. The interobserver correlation using IVC was excellent (0.97), but weak without IVC (0.52). There was a correlation between the reasons for request the MRI and the findings in the ears, both in protocols without IVC (p = 0.004) and in protocols with IVC (p = 0.002).

CONCLUSION

Inner ear MRI without contrast gives relevant information to assess audiovestibular symptoms. The use of IVC increases the degree of confidence in a novel radiologist, while in the expert its use is less relevant. A protocol should be proposed in which gadolinium is used in selected patients.

Quality of Life in Patients with Vestibular Schwannomas Following Gross Total or Less than Gross Total Microsurgical Resection: Should We be Taking the Entire Tumor Out?

BACKGROUND

The goal of microsurgical removal of a vestibular schwannoma is to completely remove the tumor, to provide long-term durable cure. In many cases, less than gross total resection (GTR) is performed to preserve neurological, and especially facial nerve function.

OBJECTIVE

To analyze long-term quality of life (QoL) in a cohort of patients who received either GTR or less than GTR.

METHODS

Patients operated for vestibular schwannoma less than 3.0 cm in posterior fossa diameter at 1 of 2 international tertiary care centers were surveyed using generic and disease-specific QoL instruments.

RESULTS

A total of 143 patients were analyzed. GTR was performed in 122, and 21 underwent less than GTR. QoL was assessed at a mean of 7.7 yr after surgery (interquartile range: 5.7-9.6). Patients who underwent GTR had smaller tumors; otherwise, there were no baseline differences between groups. Patients who underwent GTR, after multivariable adjustment for baseline features and facial nerve and hearing outcomes, reported statistically significantly better Short Form Health Survey-36 (SF-36) physical and mental scores, Patient-Reported Outcomes Measurement Information System (PROMIS-10) physical and mental scores, and Penn Acoustic Neuroma Quality of Life (PANQOL) facial, energy, general health, and total scores compared to patients receiving less than GTR.

CONCLUSION

GTR is associated with better QoL using the general QoL measures SF-36 and PROMIS-10 and the disease-specific PANQOL, even after controlling for baseline and outcome differences. This is especially significant in the assessment of mental health, indicating there may indeed be a psychological advantage to the patient that translates to overall well-being to have the entire tumor removed if microsurgical resection is undertaken.

Intended Near-Total Removal of Koos Grade IV Vestibular Schwannomas: Reconsidering the Treatment Paradigm

BACKGROUND

The goals of treating Koos grade IV vestibular schwannomas are to relieve brainstem compression, preserve or restore neurological function, and achieve long-term tumor control while minimizing tumor- and treatment-related morbidity.

OBJECTIVE

To propose a treatment paradigm involving the intentional near-total removal of Koos grade IV vestibular schwannomas, in which a small amount of residual tumor is not dissected off the cisternal portion of the facial nerve. Patients are then followed by a wait-and-scan approach. Any subsequent volumetric progression of the residual tumor is treated with radiosurgery.

METHODS

This is a case series of 44 consecutive unselected patients who underwent intended near-total resection of a Koos grade IV vestibular schwannoma through a retrosigmoid approach from January 2009 to December 2015. Pre- and postoperative volumetric analyses were performed on routine magnetic resonance imaging sequences (constructive interference in steady state and gadolinium-enhanced T1-weighted sequence).

RESULTS

The mean preoperative tumor volume was 10.9 cm3. The mean extent of resection was 89%. At the last clinical follow-up, facial nerve function was good [House and Brackmann (HB) I-II] in 89%, fair (HB III) in 9%, and poor (HB IV-VI) in 2% of the patients. At the last radiological follow-up, the residual tumor had become smaller or remained the same size in 84% of patients. Volumetric progression was negatively correlated with the original extent of resection and positively correlated with postoperative residual tumor volume (P = .01, P < .001, respectively).

CONCLUSION

Intended near-total removal results in excellent preservation of facial nerve function and has a low recurrence rate. Any progressive residual tumor may be treated by radiosurgery.

Reliability of clinical diagnosis of masses of the cerebellopontine angle: A retrospective multi-institutional study

OBJECTIVES

To assess the accuracy of pre-operative diagnosis of masses of the cerebellopontine angle (CPA) when compared to surgical pathology.

DESIGN

Retrospective chart review.

PARTICIPANTS

Patients who underwent surgery for CPA masses at two tertiary care institutions from 2007 to 2017.

MAIN OUTCOME MEASURES

Percent concordance between pre-operative and surgical pathologic diagnosis; sensitivity, specificity, positive predictive value, and negative predictive value for predicted diagnoses.

RESULTS

Concordance between pre-operative diagnosis and surgical pathology was 93.2% in 411 sampled patients. Concordance was 57.9% for masses other than vestibular schwannoma. Prediction of vestibular schwannoma and meningioma had high positive (0.95 and 0.97, respectively) and negative (0.76 and 0.99, respectively) predictive values. Prediction of facial neuroma had sensitivity of 0.13 and positive predictive value of 0.25. Headache (p = 0.001) and facial weakness (p = 0.003) were significantly associated with different pathologic profiles. Hearing loss was associated with differences in diagnostic prediction (p = 0.02) but not with differences in surgical pathology (p > 0.05).

CONCLUSIONS

Comparison between pre-operative predicted diagnosis and surgical pathology for cerebellopontine angle masses is presented. Vestibular schwannoma and meningioma were effectively identified while rarer CPA masses including facial neuroma were rarely identified correctly. Clinicians caring for patients with CPA masses should be mindful of diagnostic uncertainty which may lead to changes in treatment plan or prognosis.

Cross Sectional Imaging of the Ear and Temporal Bone

CT and MR imaging are essential cross-sectional imaging modalities for assessment of temporal bone anatomy and pathology. The choice of CT versus MR depends on the structures and the disease processes that require assessment, delineation, and characterization. A thorough knowledge of the two imaging modalities' capabilities and of temporal bone anatomy greatly facilitates imaging interpretation of pathologic conditions.

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.

Facial Nerve Outcome and Tumor Control Rate as a Function of Degree of Resection in Treatment of Large Acoustic Neuromas: Preliminary Report of the Acoustic Neuroma Subtotal Resection Study (ANSRS)

BACKGROUND

Patients with large vestibular schwannomas are at high risk of poor facial nerve (cranial nerve VII [CNVII]) function after surgery. Subtotal resection potentially offers better outcome, but may lead to higher tumor regrowth.

OBJECTIVE

To assess long-term CNVII function and tumor regrowth in patients with large vestibular schwannomas.

METHODS

Prospective multicenter nonrandomized cohort study of patients with vestibular schwannoma ≥2.5 cm who received gross total resection, near total resection, or subtotal resection. Patients received radiation if tumor remnant showed signs of regrowth.

RESULTS

Seventy-three patients had adequate follow-up with mean tumor diameter of 3.33 cm. Twelve received gross total resection, 22 near total resection, and 39 subtotal resection. Fourteen (21%) remnant tumors continued to grow, of which 11 received radiation, 1 had repeat surgery, and 2 no treatment. Four of the postradiation remnants (36%) required surgical salvage. Tumor regrowth was related to non-cystic nature, larger residual tumor, and subtotal resection. Regrowth was 3 times as likely with subtotal resection compared to gross total resection and near total resection. Good CNVII function was achieved in 67% immediately and 81% at 1-year. Better immediate nerve function was associated with smaller preoperative tumor size and percentage of tumor left behind on magnetic resonance image. Degree of resection defined by surgeon and preoperative tumor size showed weak trend toward better late CNVII function.

CONCLUSION

Likelihood of tumor regrowth was 3 times higher in subtotal resection compared to gross total resection and near total resection groups. Rate of radiation control of growing remnants was suboptimal. Better immediate but not late CNVII outcome was associated with smaller tumors and larger tumor remnants.

ABBREVIATIONS

CNVII, cranial nerve VIIGTR, gross total resectionHB, House-BrackmannMRI, magnetic resonance imageNTR, near total resectionSTR, subtotal resection.

Anterior Extension of Tumor is as Important as Tumor Size to Facial Nerve Outcome and Extent of Resection for Vestibular Schwannomas

Objectives  We examined vestibular schwannoma tumor dimension and direction of growth to determine whether these correlate with facial nerve outcome as well as extent of resection (EOR). Design  Retrospective review of prospectively maintained databases. Participants  206 patients were a part of this study. Main Outcome Measures  Tumor dimensions were measured using preoperative magnetic resonance imaging, and a series of ratios were then calculated to further characterize tumor dimension. Regression analyses were performed to investigate correlation with facial nerve outcome and EOR. Results  Patients with tumor extending >1.5 cm anterior to the internal auditory canal (IAC) (AB measurement) were three times more likely to have postoperative House-Brackman grades of 3 or worse. We also found that an EB/BF ratio (representing elongated growth parallel to the IAC axis) ≥1.1 was associated with half the risk of poor facial nerve outcome. Tumors with anterior-posterior diameter (AC measurement) >1.9 cm were five times less likely to undergo gross total resection (GTR). Furthermore, an increased degree of tumor extension into the IAC (DE measurement >2.4 cm) or an increased amount of brainstem compression (EB measurement >1.1 cm) were each associated with a nearly 3-fold decrease in the likelihood of GTR. Conclusion  Our study demonstrates that anterior extent of the tumor is as important as tumor size to facial nerve outcome and degree of resection for vestibular schwannomas.

Long-term risk of recurrence and regrowth after gross-total and subtotal resection of sporadic vestibular schwannoma

OBJECTIVE

The management of vestibular schwannoma (VS) remains controversial. One commonly cited advantage of microsurgery over other treatment modalities is that tumor removal provides the greatest chance of long-term cure. However, there are very few publications with long-term follow-up to support this assertion. The purpose of the current study is to report the very long-term risk of recurrence among a large historical cohort of patients who underwent microsurgical resection.

METHODS

The authors retrospectively reviewed the medical records of patients who had undergone primary microsurgical resection of unilateral VS via a retrosigmoid approach performed by a single neurosurgeon-neurotologist team between January 1980 and December 1999. Complete tumor removal was designated gross-total resection (GTR), and anything less than complete removal was designated subtotal resection (STR). The primary end point was radiological recurrence-free survival. Time-to-event analyses were performed to identify factors associated with recurrence.

RESULTS

Four hundred fourteen patients met the study inclusion criteria and were analyzed. Overall, 67 patients experienced recurrence at a median of 6.9 years following resection (IQR 3.9-12.1, range 1.2-22.5 years). Estimated recurrence-free survival rates at 5, 10, 15, and 20 years following resection were 93% (95% CI 91-96, 248 patients still at risk), 78% (72-85, 88), 68% (60-77, 47), and 51% (41-64, 22), respectively. The strongest predictor of recurrence was extent of resection, with patients who underwent STR having a nearly 11-fold greater risk of recurrence than the patients treated with GTR (HR 10.55, p < 0.001). Among the 18 patients treated with STR, 15 experienced recurrence at a median of 2.7 years following resection (IQR 1.9-8.9, range 1.2-18.7). Estimated recurrence-free survival rates at 5, 10, 15, and 20 years following GTR were 96% (95% CI 93-98, 241 patients still at risk), 82% (77-89, 86), 73% (65-81, 46), and 56% (45-70, 22), respectively. Estimated recurrence-free survival rates at 5, 10, and 15 years following STR were 47% (95% CI 28-78, 7 patients still at risk), 17% (5-55, 2), and 8% (1-52, 1), respectively.

CONCLUSIONS

Long-term surveillance is required following microsurgical resection of VS even after GTR. Subtotal resection alone should not be considered a definitive long-term cure. These data emphasize the importance of long-term follow-up when reporting tumor control outcomes for VS.

Subtotal resection of vestibular schwannoma: Evaluation with Ki-67 measurement, magnetic resonance imaging, and long-term observation

Purpose

The aim of this study was to compare the postoperative clinical and radiological data of patients with vestibular schwannomas who were initially managed by near total resection (NTR) or subtotal resection (STR). The Ki-67 analysis results were compared with tumor regrowth to determine the presence of a correlation between this proliferative index and postoperative tumor regrowth.

Study Design

Seventeen adult patients (7 male, 10 female) were retrospectively reviewed. Nine (52.9%) and eight (47.1%) patients underwent NTR and STR, respectively. Postoperative clinical and radiological data associated with vestibular schwannoma growth were compared with the Ki-67 immunohistochemical analysis results.

Results

Evidence of clinically significant regrowth was observed in four (23.5%) patients. Patients who underwent NTR had a lower rate/incidence of tumor regrowth than did patients who underwent STR. Patients with a higher Ki-67 index had the highest tumor regrowth rates.

Conclusions

Our study indicates that assessment of the Ki-67 index may be useful for determining the probability of regrowth of vestibular schwannomas when only partial removal is accomplished.

Role of electrophysiology in guiding near-total resection for preservation of facial nerve function in the surgical treatment of large vestibular schwannomas

OBJECTIVE In large vestibular schwannoma (VS) surgery, the facial nerve (FN) is at high risk of injury. Near-total resection has been advocated in the case of difficult facial nerve dissection, but the amount of residual tumor that should be left and when dissection should be stopped remain controversial factors. The objective of this study was to report FN outcome and radiological results in patients undergoing near-total VS resection guided by electromyographic supramaximal stimulation of the FN at the brainstem. METHODS This study was a retrospective analysis of a prospectively maintained database. Inclusion criteria were surgical treatment of a large VS during 2014, normal preoperative FN function, and an incomplete resection due to the strong adherence of the tumor to the FN and the loss of around 50% of the response of supramaximal stimulation of the proximal FN at 2 mA. Facial nerve function and the amount and evolution of the residual tumor were evaluated by clinical examination and by MRI at a mean of 5 days postoperatively and at 1 year postoperatively. RESULTS Twenty-five patients met the inclusion criteria and were included in the study. Good FN function (Grade I or II) was observed in 16 (64%) and 21 (84%) of the 25 patients at Day 8 and at 1 year postoperatively, respectively. At the 1-year follow-up evaluation (n = 23), 15 patients (65%) did not show growth of the residual tumor, 6 patients (26%) had regression of the residual tumor, and only 2 patients (9%) presented with tumor progression. CONCLUSIONS Near-total resection guided by electrophysiology represents a safe option in cases of difficult dissection of the facial nerve from the tumor. This seems to offer a good compromise between the goals of preserving facial nerve function and achieving maximum safe resection.

Clinical features, microsurgical treatment, and outcome of vestibular schwannoma with brainstem compression

Background:

Presenting symptoms, treatment considerations, and outcome are strongly related to the extension of vestibular schwannomas (VS). The aim of the current retrospective study was to analyze the clinical features, microsurgical treatment, and outcome of VS with brainstem compression.

Methods:

Forty-nine patients presented with VS (Hannover grading scale T4a or T4b) in our department. A subgroup analysis was performed among patients without (T4a) and with (T4b) compression and dislocation of the fourth ventricle.

Results:

Patients with type T4b VS presented significantly more often with long tract signs/ataxia (P < 0.05), tonsillar herniation (P < 0.001), and preoperative hydrocephalus (P < 0.01). No significant difference was found between the groups regarding hearing loss and facial nerve, trigeminal nerve, and lower cranial nerve function. Gross total resection was achieved in 83% of the cases, near total resection was achieved in 15% of the cases, and subtotal resection was performed in 2% of the cases. One patient died after massive postoperative bleeding caused by a coagulopathy. At last follow-up, 69% of the patients had excellent facial nerve function (Grade I–II) and the remaining 31% a fair outcome. Six patients (12%) required permanent ventriculoperitoneal shunting. Hearing was preserved in two patients. Forty-six patients (94%) were independent without occasional assistance (Karnofsky scale 70–100%).

Conclusions:

VS with brainstem compression is frequently associated with hydrocephalus, ataxia, long tract signs, multiple cranial nerve disorders, and occasionally, signs of intracranial hypertension. Primary microsurgical resection is an appropriate management option for large VS.

Improvement in imaging common temporal bone pathologies at 3 T MRI: small structures benefit from a small field of view

AIM

To compare image quality and evaluate its clinical importance in common temporal bone pathologies of a pTX-SPACE (parallel transmit [pTX] three-dimensional turbo spin-echo with variable flip angle [SPACE]) magnetic resonance imaging (MRI) sequence improved for spatial resolution to a standard-SPACE sequence exhibiting the same scan time at 3 T.

MATERIALS AND METHODS

Thirty-four patients were examined using a standard-SPACE and resolution improved pTX-SPACE sequence at 3 T MRI. The signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and image quality were assessed. Diseases investigated were vestibular schwannoma (VS), intralabyrinthine schwannoma (ILS), inner ear malformations, labyrinthitis, temporal bone fractures, and situation after VS resection.

RESULTS

Edge definition, intratumoural pattern, discrimination of VS from the modiolus and edge definition of ILS, separability from the spiral lamina, and detectability within cochlear turns were improved on the pTX-SPACE sequence. Detectability of malformations, post-traumatic changes, and discrimination of the cochlear and facial nerve after VS resection was improved on the pTX-SPACE sequence. In labyrinthitis, pTX-SPACE was not superior to standard-SPACE. The SNR and CNR were significantly reduced for pTX-SPACE.

CONCLUSIONS

pTX-SPACE significantly improves the detectability of temporal bone diseases, in particular, VS, ILS, and post-VS resection.

Summary and consensus in 7th International Conference on acoustic neuroma: An update for the management of sporadic acoustic neuromas

Sporadic vestibular schwannoma (acoustic neuroma) is a benign tumor arising from cochleovestibular nerve. Nowadays, various specialties and medical centers are treating this disease, and the multidisciplinary collaboration is the trend. In an effort to promote a uniform standard for reporting clinical results, even for treatment indications, the mainly controversies were posed and discussed during the 7th International Conference on acoustic neuroma, and the agreement was summarized by the Committee of this conference. The main symptoms grading and tumor stage should note its name of classification for making them comparable. The goal of the modern managements for vestibular schwannoma is to improve the quality of life with lower mortality, lower morbidity and better neurological function preservation. The experience of surgical team and their preference might be a major factor for the outcome. Because of lacking of long-term follow-up large data after radiotherapy, and with the development of microsurgery, radiotherapy is now less recommended except for recurrent cases or elderly patients.

Facial Nerve Schwannomas: Review of 80 Cases Over 25 Years at Mayo Clinic

OBJECTIVE

To elucidate the long-term clinical behavior, treatment, and outcomes of sporadic facial nerve schwannoma (FNS) in a large cohort of patients managed in the post-magnetic resonance imaging era.

PATIENTS AND METHODS

Retrospective review at a single tertiary health care system (January 1, 1990, through December 31, 2015), evaluating 80 consecutive patients with sporadic FNS.

RESULTS

Ninety-eight patients with FNS were identified; 10 with incomplete data and 8 with neurofibromatosis type 2 were excluded. The remaining 80 patients (median age, 47 years; 58% women) were analyzed. Forty-three (54%) patients presented with asymmetrical hearing loss, 33 (41%) reported facial paresis, and 21 (26%) reported facial spasm. Seventeen (21%) exhibited radiologic features mimicking vestibular schwannoma, 14 (18%) presented as a parotid mass, and 5 (6%) were discovered incidentally. Factors predictive of facial nerve paresis or spasm before treatment were female sex and tumor involvement of the labyrinthine/geniculate and tympanic facial nerve segments. The median growth rate among growing FNS was 2.0 mm/y. Details regarding clinical outcome according to treatment modality are described.

CONCLUSION

In patients with FNS, female sex and involvement of the labyrinthine/geniculate and tympanic segments of the facial nerve predict a higher probability of facial paresis or spasm. When isolated to the posterior fossa or parotid gland, establishing a preoperative diagnosis of FNS is challenging. Treatment should be tailored according to tumor location and size, existing facial nerve function, patient priorities, and age. A management algorithm is presented, prioritizing long-term facial nerve function.

Prevalence and Surgical Implications of Dural Enhancement at the Porus Acusticus in Vestibular Schwannomas

OBJECTIVE

Demonstrate the association of radiographic dural enhancement with increased tumor adherence at the porus acusticus, which may influence completeness of resection and facial nerve outcome.

STUDY DESIGN

Case series with chart review.

SETTING

Academic referral center.

SUBJECTS AND METHODS

A total of 205 consecutive patients with histopathologically confirmed vestibular schwannoma (VS) were evaluated. Patients with tumors exhibiting dural enhancement on postgadolinium T1-weighted magnetic resonance imaging were identified and compared with matched controls. Completeness of resection, intraoperative details, and facial nerve outcomes were analyzed.

RESULTS

Excluding strictly intracanalicular tumors (n = 32, 16%) and those with NF2 (n = 10, 4.9%), the presence of dural enhancement was radiographically confirmed in 16 (9.8%) cases. Paired analysis did not reveal significant baseline differences between cases and controls. Subtotal resection was performed in 5 (31%) of the 16 patients with tumors exhibiting dural enhancement, in contrast to 1 (3%) of the matched controls (P = .01). Four (25%) demonstrated increased tumor adherence at the porus acusticus intraoperatively, compared with 1 control (3%, P = .04). Long-term facial nerve function was similar between cases and controls (81% vs 84% House-Brackmann I-II function, P = 1.00).

CONCLUSION

Dural enhancement is present in approximately 10% of extracanalicular VS. Dural enhancement at the porus acusticus may represent hypervascularity, dural reaction, or infiltration, and portends increased tumor adherence and greater likelihood of subtotal resection to preserve facial nerve function. To our knowledge, this is the first series that reports the prevalence of this phenomenon in VS and the potential surgical implications. Recognition preoperatively may be valuable toward patient counseling.