Tag: Vestibular schwannoma

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Stereotactic radiosurgery as the first-line treatment for intracanalicular vestibular schwannomas

J Neurosurg February 5, 2021: 1-7

This report evaluates the outcomes of stereotactic radiosurgery (SRS) as the first-line treatment of intracanalicular vestibular schwannomas (VSs).

METHODS Between 1987 and 2017, the authors identified 209 patients who underwent SRS as the primary intervention for a unilateral intracanalicular VS. The median patient age was 54 years (range 22–85 years); 94 patients were male and 115 were female. Three patients had facial neuropathy at the time of SRS. One hundred fifty-five patients (74%) had serviceable hearing (Gardner-Robertson [GR] grades I and II) at the time of SRS. The median tumor volume was 0.17 cm3 (range 0.015–0.63 cm3). The median margin dose was 12.5 Gy (range 11.0–25.0 Gy). The median maximum dose was 24.0 Gy (range 15.7–50.0 Gy).

RESULTS The progression-free survival rates of all patients with intracanalicular VS were 97.5% at 3 years, 95.6% at 5 years, and 92.1% at 10 years. The rates of freedom from the need for any additional intervention were 99.4% at 3 years, 98.3% at 5 years, and 98.3% at 10 years. The serviceable hearing preservation rates in GR grade I and II patients at the time of SRS were 76.6% at 3 years, 63.5% at 5 years, and 27.3% at 10 years. In univariate analysis, younger age (< 55 years, p = 0.011), better initial hearing (GR grade I, p < 0.001), and smaller tumor volumes (< 0.14 cm3, p = 0.016) were significantly associated with improved hearing preservation. In multivariate analysis, better hearing (GR grade I, p = 0.001, HR 2.869, 95% CI 1.569–5.248) and smaller tumor volumes (< 0.14 cm3, p = 0.033, HR 2.071, 95% CI 1.059–4.047) at the time of SRS were significantly associated with improved hearing preservation. The hearing preservation rates of patients with GR grade I VS were 88.1% at 3 years, 77.9% at 5 years, and 38.1% at 10 years. The hearing preservation rates of patients with VSs smaller than 0.14 cm3 were 85.5% at 3 years, 77.7% at 5 years, and 42.6% at 10 years. Facial neuropathy developed in 1.4% from 6 to 156 months after SRS.

CONCLUSIONS SRS provided sustained tumor control in more than 90% of patients with intracanalicular VS at 10 years and freedom from the need for additional intervention in more than 98% at 10 years. Patients with initially better hearing and smaller VSs had enhanced serviceable hearing preservation during an observation interval up to 10 years after SRS.

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A critical comparison between the semisitting and the supine positioning in vestibular schwannoma surgery: subgroup analysis of a randomized, multicenter trial

J Neurosurg 133:249–256, 2020

Patient positioning in vestibular schwannoma (VS) surgery is a matter of ongoing discussion. Factors to consider include preservation of cranial nerve functions, extent of tumor resection, and complications. The objective of this study was to determine the optimal patient positioning in VS surgery.

METHODS A subgroup analysis of a randomized, multicenter trial that investigated the efficacy of prophylactic nimodipine in VS surgery was performed to investigate the impact of positioning (semisitting or supine) on extent of resection, functional outcomes, and complications. The data of 97 patients were collected prospectively. All procedures were performed via a retrosigmoid approach. The semisitting position was chosen in 56 patients, whereas 41 patients were treated while supine.

RESULTS Complete resection was obtained at a higher percentage in the semisitting as compared to the supine position (93% vs 73%, p = 0.002). Logistic regression analysis revealed significantly better facial nerve function in the early postoperative course in the semisitting group (p = 0.004), particularly concerning severe facial nerve paresis (House- Brackmann grade IV or worse; p = 0.002). One year after surgery, facial nerve function recovered. However, there was still a tendency for better facial nerve function in the semisitting group (p = 0.091). There were no significant differences between groups regarding hearing preservation rates. Venous air embolism with the necessity to terminate surgery occurred in 2 patients in the semisitting position (3.6%). Supplementary analysis with a 2-tailed permutation randomization with 10,000 permutations of treatment choice and a propensity score matching showed either a tendency or significant results for better facial nerve outcomes in the early postoperative course and extent of resection in the semisitting group.

CONCLUSIONS Although the results of the various statistical analyses are not uniform, the data indicate better results concerning both a higher rate of complete removal (according to the intraoperative impression of the surgeon) and facial nerve function after a semisitting as compared to the supine position. These advantages may justify the potential higher risk for severe complications of the semisitting position in VS surgery. The choice of positioning has to consider all individual patient parameters and risks carefully.

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Postoperative Hearing Preservation in Patients Undergoing Retrosigmoid Craniotomy for Resection of Vestibular Schwannomas: A Systematic Review of 2034 Patients

Neurosurgery 2019 DOI:10.1093/neuros/nyz147

Vestibular schwannomas (VS) are benign tumors derived from Schwann cells ensheathing the vestibulocochlear nerve. The retrosigmoid (RS) surgical approach is useful to resect tumors of multiple sizes while affording the possibility of preserving postoperative hearing.

OBJECTIVE: To conduct a systematic review of published literature investigating hearing preservation rates in patients who underwent the RS approach for VS treatment.

METHODS: The PubMed, Scopus, and Embase databases were surveyed for studies that reported preoperative and postoperative hearing grades on VS patients who underwent RS treatment. Hearing preservation rates were calculated, and additional patient demographic data were extracted. Tumor size data were stratified to compare hearing preservation rates after surgery for intracanalicular, small (0-20 mm), and large (>20 mm) tumors.

RESULTS: Of 383 deduplicated articles, 26 studies (6.8%) met eligibility criteria for a total of 2034 patients with serviceable preoperative hearing, for whom postoperative hearing status was evaluated. Aggregate hearing preservation was 31% and 35% under a fixed and random effects model, respectively. A mixed effects model was used to determine hearing preservation rates depending on tumor size, which were determined to be 57%, 37%, and 12% for intracanalicular, small, and large tumors, respectively. Significant crossstudy heterogeneity was found (I2 = 93%, τ 2 = .964, P < .01; Q = 287.80, P = < .001), with rates of hearing preservation ranging from 0% to 100%.

CONCLUSION: Tumor size may have an effect on hearing preservation rates, but multiple factors should be considered. Discussion of a patient’s expectations for hearing preservation is critical when deciding on VS treatment plans.

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

Neurosurgery, Volume 86, Issue 2, February 2020, Pages 250–256

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 dollarswouldbe on the order ofmillions annually.

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Face-to-face four hand technique in vestibular schwannoma surgery: results from 256 Danish patients with larger tumors

Acta Neurochirurgica (2020) 162:61–69

The objective of this study was to investigate the clinical outcome after microsurgical treatment of vestibular schwannomas using face-to-face four hand technique in 256 Danish patients treated in the Department of Neurosurgery at the Copenhagen University Hospital from 2009 to 2018.

Methods Data were retrospectively collected from patient records.

Results The mean tumor size was 30.6 mm and approximately 46% of the patients had tumors >30 mm. In around 1/3 of the patients a retrosigmoid approach was used and in 2/3 a translabyrinthine. In 50% of the patients, the tumor was completely removed, and in 38%, only smaller remnants were left to preserve facial function. The median operative time was approximately 2.5 h for retrosigmoid approach, and for translabyrinthine approach, it was around 3.5 h. One year after surgery, 84% of the patients had a good facial nerve function (House-Brackmann grade 1–2). In tumors ≤ 30 mm approximately 89%preserved good facial function, whereas this was only the case for around 78% of the patients with tumors > 30 mm. In 60% of the patients who had poor facial nerve function at hospital discharge, the function improved to good facial function within the 1 year follow-up period. Four patients died within 30 days after surgery, and 6% underwent reoperation for cerebrospinal fluid leakage.

Conclusion Surgery for vestibular schwannomas using face-to-face four hand technique may reduce operative time and can be performed with lower risk and excellent facial nerve outcome. The risk of surgery increases with increasing tumor size.

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Treatment Outcomes and Dose Rate Effects Following Gamma Knife Stereotactic Radiosurgery for Vestibular Schwannomas

Neurosurgery 85:E1084–E1094, 2019

Gamma Knife radiosurgery (GKRS; Elekta AB) remains a well-established treatment modality for vestibular schwannomas. Despite highly effective tumor control, further research is needed toward optimizing long-term functional outcomes. Whereas dose-rate effects may impact post-treatment toxicities given tissue dose-response relationships, potential effects remain largely unexplored.

OBJECTIVE: To evaluate treatment outcomes and potential dose-rate effects following definitive GKRS for vestibular schwannomas.

METHODS: We retrospectively reviewed 419 patients treated at our institution between 1998 and 2015, characterizing baseline demographics, pretreatment symptoms, and GKRS parameters. The cohort was divided into 2 dose-rate groups based on the median value (2.675 Gy/min). Outcomes included clinical tumor control, radiographic progression-free survival, serviceable hearing preservation, hearing loss, and facial nerve dysfunction (FND). Prognostic factors were assessed using Cox regression.

RESULTS: The study cohort included 227 patientswith available follow-up. Following GKRS 2-yr and 4-yr clinical tumor control rates were 98% (95% CI: 95.6%-100%) and 96% (95% CI: 91.4%-99.6%), respectively. Among 177 patients with available radiographic follow-up, 2-yr and 4-yr radiographic progression-free survival rateswere 97% (95% CI: 94.0%-100.0%) and 88% (95% CI: 81.2%-95.0%). The serviceable hearing preservation rate was 72.2% among patients with baseline Gardner-Robertson class I/II hearing and post-treatment audiological evaluations. Most patients experienced effective relief from prior headaches (94.7%), tinnitus (83.7%), balance issues (62.7%), FND (90.0%), and trigeminal nerve dysfunction (79.2%), but not hearing loss (1.0%). Whereas GKRS provided effective tumor control independently of dose rate, GKRS patients exposed to lower dose rates experienced significantly better freedom from post-treatment hearing loss and FND (P = .044).

CONCLUSION:Whereas GKRS provides excellent tumor control and effective symptomatic relief for vestibular schwannomas, dose-rate effectsmay impact post-treatment functional outcomes. Further research remains warranted.

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Comparing costs of microsurgical resection and stereotactic radiosurgery for vestibular schwannoma

J Neurosurg 131:1395–1404, 2019

Given rising scrutiny of healthcare expenditures, understanding intervention costs is increasingly important. This study aimed to compare and characterize costs for vestibular schwannoma (VS) management with microsurgery and radiosurgery to inform practice decisions and appraise cost reduction strategies.

METHODS In conjunction with medical records, internal hospital financial data were used to evaluate costs. Total cost was divided into index costs (costs from arrival through discharge for initial intervention) and follow-up costs (through 36 months) for 317 patients with unilateral VSs undergoing initial management between June 2011 and December 2015. A retrospective matched cohort based on tumor size with 176 patients (88 undergoing each intervention) was created to objectively compare costs between microsurgery and radiosurgery. The full sample of 203 patients treated with resection and 114 patients who underwent radiosurgery was used to evaluate a broad range of outcomes and identify cost contributors within each intervention group.

RESULTS Within the matched cohort, average index costs were significantly higher for microsurgery (100% by definition, because costs are presented as a percentage of the average index cost for the matched microsurgery group; 95% CI 93–107) compared to radiosurgery (38%, 95% CI 38–39). Microsurgery had higher average follow-up costs (1.6% per month, 95% CI 0.8%–2.4%) compared to radiosurgery (0.5% per month, 95% CI 0.4%–0.7%), largely due to costs incurred in the initial months after resection. A major contributor to total cost and cost variability for both resection and radiosurgery was the need for additional interventions in the follow-up period, which were necessary due to complications or persistent functional deficits. Although tumor size was not associated with increased total costs for radiosurgery, linear regression analysis demonstrated that, for patients who underwent microsurgery, each centimeter increase in tumor maximum diameter resulted in an estimated increase in total cost of 50.2% of the average index cost of microsurgery (95% CI 34.6%–65.7%) (p < 0.001, R 2 = 0.17). There were no cost differences associated with the proportion of inpatient days in the ICU or with specific surgical approach for patients who underwent resection.

CONCLUSIONS This study is the largest assessment to date based on internal cost data comparing VS management with microsurgery and radiosurgery. Both index and follow-up costs are significantly higher when tumors were managed with resection compared to radiosurgery. Larger tumors were associated with increased resection costs, highlighting the incremental costs associated with observation as the initial management.

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Long-Term Hearing Outcomes Following Stereotactic Radiosurgery in Vestibular Schwannoma Patients

Neurosurgery, Volume 85, (4), October 2019, 550–559

An understanding of the hearing outcomes is needed for treatment counseling for patients with vestibular schwannomas (VS).

OBJECTIVE: To determine long-term hearing results following stereotactic radiosurgery (SRS) for VS and identify any influential variables.

METHODS: Tertiary hospital retrospective cohort.

RESULTS: There were 579 tumors (576 patients) treated with SRS. Eighty-two percent (473) of tumors had ≥1 yr and 59% (344 ≥3 yr follow-up. In the 244 tumor ears, with measurable hearing before SRS who were followed ≥1 yr, 14% (31) had improved hearing, 13% (29) unchanged hearing, and 74% (158) had worsened hearing. In 175 patients with ≥3 yr followup and who had measurable hearing pretreatment, 6% (11 ears) improved hearing, 31% (54 ears) unchanged hearing, and 63% (110 ears) had worsened hearing. Patients with tumors with larger target volumes (P = 0.040) and with neurofibromatosis type 2 (NF2; P = 0.017) were associated with poorer hearing (P = 0.040). Patients with word recognition scores (WRS) of 50% or poorer had tumors with a larger volume (P = 0.0002), larger linear size (P=0.032),andNF2(P=0.045).TraditionallyreportedhearingoutcomesusingtheGardner RobertsonmaintenanceofPTA ≤50dborWRS≥50%were48%at3yr,whichoverestimates hearing outcomes compared to the above reporting standards.

CONCLUSION: Hearing declines over time in VS treated with SRS in a high proportion of cases. The frequency and magnitude of long-term hearing decline following SRS argues against prophylactic radiation for small tumors in hearing ears with undetermined growth behavior.

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Koos Classification of Vestibular Schwannomas: A Reliability Study

Neurosurgery, Volume 85, Issue 3, September 2019, 409–414

The Koos classification of vestibular schwannomas is designed to stratify tumors based on extrameatal extension and compression of the brainstem. While this classification system is widely reported in the literature, to date no study has assessed its reliability.

OBJECTIVE: To assess the intra- and inter-rater reliability of the Koos classification system.

METHODS: After institutional review board approval was obtained, a cross-sectional group of the Magnetic Resonance imagings of 40 patients with vestibular schwannomas varying in size comprised the study sample. Four raters were selected to assign a Koos grade to 50 total scans. Inter- and intrarater reliability were calculated and reported using Fleiss’ kappa, Kendall’s W, and Intraclass correlation coefficient (ICC).

RESULTS: Inter-rater reliability was found to be substantial when measured using Fleiss’ kappa (.71), extremely strong using Kendall’sW(.92), and excellent as calculated by ICC (.88). Intrarater reliability was perfect for 3 out of 4 raters as assessed using weighted kappa, Kendall’s W and ICC, with the intrarater agreement for the fourth rater measured as extremely high.

CONCLUSION: We have demonstrated that the Koos classification system for vestibular schwannoma is a reliable method for tumor classification. This study lends further support to the results of current literature using Koos grading system. Further studies are required to evaluate its validity and utility in counseling patients with regard to outcomes.

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Surgical outcome in smaller symptomatic vestibular schwannomas. Is there a role for surgery?

Acta Neurochirurgica (2018) 160:2263–2275

Currently, there is no consensus in the initial management of small vestibular schwannomas (VSs). They are routinely watched and/or referred for radiosurgical treatment, although surgical removal is also an option. We hereby evaluate clinical outcomes of patients who have undergone surgical removal of smaller symptomatic VSs.

Methods Patients with vestibular schwannomas (grade T1–T3b according to Hannover classification) were reviewed. Patients with symptomatic tumors who underwent surgery were evaluated. Their preoperative hearing status was based on the guideline of the committee on hearing and equilibriumof the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) foundation. Their postoperative facial nerve function, hearing status, vestibular symptoms, and degree of tumor resection were assessed.

Results Thirty patients were selected for surgery via a retrosigmoid approach based on their age, symptoms, and their own decision-making after discussion of management options. Most patients presented with hearing loss. Seventeen patients had useful hearing preoperatively. Among them, 10 patients (59%) preserved useful hearing (class A or B) postoperatively. MRI at 1-year follow-up confirmed complete resection in 26/29 patients. Also, 29 patients (97%) had HB grade I–II, and 1 patient had HB III at 1-year follow-up. Except for 1 patient with CSF leak, 1 patient with delayed facial nerve palsy, and 2 patients with asymptomatic sigmoid sinus occlusion, there were no other new morbidities.

Conclusion Although both observation and radiosurgery are valid options in the management of smaller size vestibular schwannomas, surgical treatment seems to offer a high rate of facial nerve preservation, a reasonable rate of hearing sparing, and a high total resection rate. Clinicians should consider surgical treatment as a valid option in the initial management of symptomatic small vestibular schwannomas in younger patients.

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Gamma Knife radiosurgery for large vestibular schwannomas greater than 3 cm in diameter

J Neurosurg 128:1380–1387, 2018

Stereotactic radiosurgery (SRS) is an important alternative management option for patients with small and medium-sized vestibular schwannomas (VSs). Its use in the treatment of large tumors, however, is still being debated. The authors reviewed their recent experience to assess the potential role of SRS in larger-sized VSs.

METHODS Between 2000 and 2014, 35 patients with large VSs, defined as having both a single dimension > 3 cm and a volume > 10 cm3, underwent Gamma Knife radiosurgery (GKRS). Nine patients (25.7%) had previously undergone resection. The median total volume covered in this group of patients was 14.8 cm3 (range 10.3–24.5 cm3). The median tumor margin dose was 11 Gy (range 10–12 Gy).

RESULTS The median follow-up duration was 48 months (range 6–156 months). All 35 patients had regular MRI followup examinations. Twenty tumors (57.1%) had a volume reduction of greater than 50%, 5 (14.3%) had a volume reduction of 15%–50%, 5 (14.3%) were stable in size (volume change < 15%), and 5 (14.3%) had larger volumes (all of these lesions were eventually resected). Four patients (11.4%) underwent resection within 9 months to 6 years because of progressive symptoms. One patient (2.9%) had open surgery for new-onset intractable trigeminal neuralgia at 48 months after GKRS. Two patients (5.7%) who developed a symptomatic cyst underwent placement of a cystoperitoneal shunt. Eight (66%) of 12 patients with pre-GKRS trigeminal sensory dysfunction had hypoesthesia relief. One hemifacial spasm completely resolved 3 years after treatment. Seven patients with facial weakness experienced no deterioration after GKRS. Two of 3 patients with serviceable hearing before GKRS deteriorated while 1 patient retained the same level of hearing. Two patients improved from severe hearing loss to pure tone audiometry less than 50 dB. The authors found borderline statistical significance for post-GKRS tumor enlargement for later resection (p = 0.05, HR 9.97, CI 0.99–100.00). A tumor volume ≥ 15 cm3 was a significant factor predictive of GKRS failure (p = 0.005). No difference in outcome was observed based on indication for GKRS (p = 0.0761).

CONCLUSIONS Although microsurgical resection remains the primary management choice in patients with VSs, most VSs that are defined as having both a single dimension > 3 cm and a volume > 10 cm3 and tolerable mass effect can be managed satisfactorily with GKRS. Tumor volume ≥ 15 cm3 is a significant factor predicting poor tumor control following GKRS.

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Risk Factors for Readmission with Cerebrospinal Fluid Leakage Within 30 Days of Vestibular Schwannoma Surgery

Neurosurgery 82:630–637, 2018

Cerebrospinal fluid (CSF) leak is a well-recognized complication after surgical resection of vestibular schwannomas and is associated with a number of secondary complications, including readmission and meningitis. OBJECTIVE: To identify risk factors for and timing of 30-d readmission with CSF leak.

METHODS: Patients who had undergone surgical resection of a vestibular schwannoma from 1995 to 2010 were identified in the California Office of Statewide Health Planning and Development database. The most common admission diagnoses were identified by International Classification of Disease, ninth Revision, diagnosis codes, and predictors of readmission with CSF leak were determined using logistic regression.

RESULTS: A total of 6820 patients were identified. CSF leak, though a relatively uncommon cause of admission after discharge (3.52% of all patients), was implicated in nearly half of 490 readmissions (48.98%). Significant independent predictors of readmission with CSF leak were male sex (odds ratio [OR] 1.72, 95% confidence interval [CI] 1.32-2.25), first admission at a teaching hospital (OR 3.32, 95% CI 1.06-10.39), CSF leak during first admission (OR 1.84, 95% CI 1.33-2.55), obesity during first admission (OR 2.10, 95% CI 1.20-3.66), and case volume of first admission hospital (OR of log case volume 0.82, 95% CI 0.70-0.95). Median time to readmission was 6 d from hospital discharge.

CONCLUSION: This study has quantified CSF leak as an important contributor to nearly half of all readmissions following vestibular schwannoma surgery. We propose that surgeons should focus on technical factors that may reduce CSF leakage and take advantage of potential screening strategies for the detection of CSF leakage prior to first admission discharge.

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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?

Neurosurgery 82:541–547, 2018

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 NeuromaQuality 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.

 

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

J Neurosurg 128:903–910, 2018

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.

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Intended Near-Total Removal of Koos Grade IV Vestibular Schwannomas

Neurosurgery 82:202–210, 2018

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 resectionwas 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.

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Magnetic resonance imaging characteristics and the prediction of outcome of vestibular schwannomas following Gamma Knife radiosurgery

J Neurosurg 127:1384–1391, 2017

Gamma Knife surgery (GKS) is a promising treatment modality for patients with vestibular schwannomas (VSs), but a small percentage of patients have persistent postradiosurgical tumor growth. The aim of this study was to determine the clinical and quantitative MRI features of VS as predictors of long-term tumor control after GKS.

METHODS The authors performed a retrospective study of all patients with VS treated with GKS using the Leksell Gamma Knife Unit between 2005 and 2013 at their institution. A total of 187 patients who had a minimum of 24 months of clinical and radiological assessment after radiosurgery were included in this study. Those who underwent a craniotomy with tumor removal before and after GKS were excluded. Study patients comprised 85 (45.5%) males and 102 (54.5%) females, with a median age of 52.2 years (range 20.4–82.3 years). Tumor volumes, enhancing patterns, and apparent diffusion coefficient (ADC) values were measured by region of interest (ROI) analysis of the whole tumor by serial MRI before and after GKS.

RESULTS The median follow-up period was 60.8 months (range 24–128.9 months), and the median treated tumor volume was 3.54 cm3 (0.1–16.2 cm3). At last follow-up, imaging studies indicated that 150 tumors (80.2%) showed decreased tumor volume, 20 (10.7%) had stabilized, and 17 (9.1%) continued to grow following radiosurgery. The postradiosurgical outcome was not significantly correlated with pretreatment volumes or postradiosurgical enhancing patterns. Tumors that showed regression within the initial 12 months following radiosurgery were more likely to have a larger volume reduction ratio at last follow-up than those that did not (volume reduction ratio 55% vs 23.6%, respectively; p < 0.001). Compared with solid VSs, cystic VSs were more likely to regress or stabilize in the initial postradiosurgical 6–12-month period and during extended follow-up. Cystic VSs exhibited a greater volume reduction ratio at last follow-up (cystic vs solid: 67.6% ± 24.1% vs 31.8% ± 51.9%; p < 0.001). The mean preradiosurgical maximum ADC (ADCmax) values of all VSs were significantly higher for those with tumor regression or stabilization at last follow-up compared with those with progression (2.391 vs 1.826 × 10-3 mm2/sec; p = 0.010).

CONCLUSIONS Loss of central enhancement after radiosurgery was a common phenomenon, but it did not correlate with tumor volume outcome. Preradiosurgical MRI features including cystic components and ADCmax values can be helpful as predictors of treatment outcome.

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Cystic Vestibular Schwannomas Respond Best to Radiosurgery

Neurosurgery 81:490–497, 2017

Vestibular schwannomas (VS) have a well-documented response to Gamma Knife R  (Elekta AB, Stockholm, Sweden) Stereotactic radiosurgery (SRS). However, there are limited data available regarding the volumetric response of cystic tumors.

OBJECTIVE: This report correlates the radiographic appearance of VS before radiosurgery with the delayed volumetric response.

METHODS: This study reviewed our SRS experience with 219 VS patients between 2003 and 2013. Patients were treatment naïve and had a significant extracanalicular tumor volume. Magnetic resonance imaging at the time of SRS identified 42 contrast-enhancing macrocystic tumors, 45 contrast-enhancing microcystic tumors, and 132 homogeneously enhancing tumors with no intratumoral cyst formation. The median follow-up was 49.1 months. The median tumor volume was 2.6 cm3 (0.70-16.1 cm3) and the median dose was 12.5 Gy (11-13 Gy).

RESULTS: The actuarial tumor control rate was 99.4% at 2 years and 96.4% at 5 years. A volumetric reduction of >20% occurred in 85.4% of macrocystic tumors, 76.1% of microcystic tumors, and 62.8% of homogeneously enhancing VS. The median volume decrease per year for macrocystic, microcystic, and homogenous tumors was 17.2%, 7.5%, and 7.9% per year respectively (P < .001). A 2:1 blinded volumetric case match showed a significant size reduction in macrocystic tumors compared to noncystic tumors (P = .007). Serviceable hearing was maintained in 61.5% of patients that had Gardner-Robertson grade I-II hearing before treatment. Surgical resection or repeat radiosurgery was performed in 8 patients (3.6%) who had sustained tumor progression.

CONCLUSION: SRS provided VS tumor control in >95% of patients, regardless of radiographic characteristics. Tumor volume regression was most evident in patients with cystic tumors.

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Preserving normal facial nerve function and improving hearing outcome in large vestibular schwannomas with a combined approach

Acta Neurochir (2017) 159:1197–1211

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

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

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

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

 

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Control of vestibular schwannomas treated with Gamma Knife

vestibular-schwannoma

J Neurosurg 124:1619–1626, 2016

The authors of this study sought to assess tumor control and complication rates in a large cohort of patients who underwent Gamma Knife radiosurgery (GKRS) for vestibular schwannoma (VS) and to identify predictors of tumor control. Methods The records of 420 patients treated with GKRS for VS with a median marginal dose of 11 Gy were retrospectively analyzed. Patients with neurofibromatosis Type 2 or who had undergone treatment for VS previously were excluded. The authors assessed tumor control and complication rates with chart review and used the Cox proportional hazards model to identify predictors of tumor control. Preservation of serviceable hearing, defined as Gardner-Robertson Class I–II, was evaluated in a subgroup of 71 patients with serviceable hearing at baseline and with available followup audiograms.

Results The median VS tumor volume was 1.4 cm3, and the median length of follow-up was 5.1 years. Actuarial 5- and 10-year tumor control rates were 91.3% and 84.8%, respectively. Only tumor volume was a statistically significant predictor of tumor control rate. The tumor control rate decreased from 94.1% for tumors smaller than 0.5 cm3 to 80.7% for tumors larger than 6 cm3. Thirteen patients (3.1%) had new or increased permanent trigeminal nerve neuropathy, 4 (1.0%) had new or increased permanent facial weakness, and 5 (1.2%) exhibited new or increased hydrocephalus requiring a shunting procedure. Actuarial 3-year and 5-year hearing preservation rates were 65% and 42%, respectively.

Conclusions The 5-year actuarial tumor control rate of 91.3% in this cohort of patients with VS compared slightly unfavorably with the rates reported in other large studies, but the complication and hearing preservation rates in this study were similar to those reported previously. Various factors may contribute to the observed differences in reported outcomes. These factors include variations in treatment indication and in the definition of treatment failure, as well as a lack of standardization of terminology and of evaluation of complications. Last, differences in dosimetric variables may also be an explanatory factor.

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Delayed Facial Palsy After Vestibular Schwannoma Resection

vestibular-schwannoma

Neurosurgery 78:251–255, 2016

Preservation of facial nerve function following vestibular schwannoma surgery is a high priority. Even those patients with normal to near-normal function in the early postoperative period remain at risk for delayed facial palsy (DFP).

OBJECTIVE: To evaluate the incidence and prognosis of DFP and to identify risk factors for its occurrence.

METHODS: A retrospective cohort study of 489 patients who underwent vestibular schwannoma resection at our institution between 2000 and 2014. Delayed facial palsy was defined as deterioration in facial function of at least 2 House-Brackmann (HB) grades between postoperative days 5 to 30. Only patients with a HB grade of I to III by postoperative day 5 were eligible for study inclusion.

RESULTS: One hundred twenty-one patients with HB grade IV to VI facial weakness at postoperative day 5 were excluded from analysis. Of the remaining 368, 60 (16%) patients developed DFP (mean 12 days postoperatively, range: 5-25 days). All patients recovered function to HB grade I to II by a mean of 33 days (range: 7-86 days). Patients that developed DFP had higher rates of gross total resections (83% vs 71%, P = .05) and retrosigmoid approaches (72% vs 52%, P, .01). There was no difference in recovery time between patients who received treatment with steroids, steroids with antivirals, or no treatment at all (P = .530).

CONCLUSION: Patients with a gross total tumor resection or undergoing a retrosigmoid approach may be at higher risk of DFP. The prognosis is favorable, with patients likely recovering to normal or near-normal facial function within 1 month of onset.

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