Gamma Knife radiosurgery following subtotal resection of vestibular schwannoma

[Vestibular Schwannoma: Factors in Therapy Decision-Making]

The treatment of vestibular schwannomas (VS) has always posed a challenge for physicians. Three essential treatment principles are available: wait-and-scan, surgery, and stereotactic radiotherapy. In addition to the type of treatment, decisions must be made regarding the optimal timing of therapy, the combination of different treatment modalities, the potential surgical approach, and the type and intensity of radiation. Factors influencing the therapy decision include tumor location and size or stage, patient age, comorbidities, symptoms, postoperative hearing rehabilitation options, patient preferences, and, not least, the experience of the surgeons and the personnel and technical capabilities of the clinical site. This article begins with a brief overview of vestibular schwannomas, then outlines the fundamental interdisciplinary treatment options, and finally discusses the ENT (ear, nose, and throat)-relevant factors in the therapy decision.

Growth potential of small residual tumors after vestibular schwannoma surgery: comparison between remnants and the natural history of small tumors

OBJECTIVE

Due to the heterogeneous definitions of tumor regrowth and various tumor volume distributions, the nature of small remnants after vestibular schwannoma (VS) surgery and the appropriate timing of adjuvant stereotactic radiosurgery for these remnants remain unclear. In this study, the growth potential of small remnants (< 1 cm3) after VS surgery was compared with that of treatment-naïve (TN) small VSs.

METHODS

This retrospective single-center study included 44 patients with VS remnants following subtotal resection (STR) of a large VS (remnant group) and 75 patients with TN VS (< 1 cm3; TN group). A 20% change in tumor volume over the imaging interval indicated radiographic progression or regression. Tumor progression-free survival (TPFS) rates were estimated using the Kaplan-Meier method.

RESULTS

In the remnant group, the mean preoperative tumor volume was 13.8 ± 9.0 cm3 and the mean tumor resection rate was 95% ± 5%. The mean tumor volume at the start of the observation period did not differ significantly between the two groups (remnant vs TN: 0.41 ± 0.29 vs 0.34 ± 0.28 cm3, p = 0.171). The median periods until tumor progression was detected were 15.1 (range 4.9-76.2) months and 44.7 (range 12.6-93.2) months in the TN and remnant groups, respectively. In the remnant group, the TPFS rates were 74% and 70% at 3 and 5 years after the surgery, respectively, compared with 59% and 47% in the TN group. The log-rank test demonstrated a significant difference (p = 0.008) in the TPFS rates between the two groups. Furthermore, 42 patients each from the remnant and TN groups were matched based on tumor volume. TPFS was significantly longer in the remnant group than in the TN group (3-year rates, 77% vs 62%; 5-year rates, 73% vs 51%; p = 0.02). In the remnant group, 18% of the tumor remnants demonstrated regression during follow-up, compared with 9% in the TN group, but this intergroup difference was not significant (p = 0.25).

CONCLUSIONS

This study demonstrated that the growth potential of small VS remnants was lower than that of TN tumors. Observing for small remnants may be appropriate after STR of a large VS. Given the risk of tumor regrowth, careful observation using MRI should be mandatory during follow-up.

Clinical outcomes and safety of large or giant vestibular schwannoma in older patients undergoing microsurgery: a matched cohort study

OBJECTIVE

To compare the clinical outcomes of large or giant vestibular schwannomas (VSs) between older patients and younger patients who underwent microsurgery and to explore whether the incidence of postoperative complications increased and whether the postoperative hospital stay was prolonged.

METHODS

We conducted a retrospective matched cohort study based on the surgical approach, maximum tumor diameter and extent of resection. Older patients (≥ 60 years) and a matched group (<60 years) who had undergone microsurgery for VSs between January 2015 and December 2021 were included. Clinical data, surgical outcomes and postoperative complications were analyzed statistically.

RESULTS

Forty-two older patients (≥ 60 years, 66.0 ± 3.8 years) were identified and matched to younger patients (<60 years, 43.9 ± 11.2 years), and they all underwent microsurgery through a retrosigmoid approach. There were twenty-nine patients with 3-4 cm VSs and thirteen patients with > 4 cm VSs in both groups. The older patients had a higher proportion of imbalance (P = 0.016) and lower American Society of Anesthesiology scores (P = 0.003) before surgery than the younger patients. There was no significant difference in facial nerve function one week (p = 0.851) and one year (p = 0.756) after surgery and no difference in the postoperative complication incidence (40.5% vs. 23.8%, p = 0.102) between the older patients and controls. Furthermore, the older patients had longer postoperative hospital stays than the younger patients (p = 0.043). In the older group, six patients with near total resection and five with subtotal resection were administered stereotactic radiotherapy, and one had recurrence three years after surgery and received conservative treatment. The postoperative follow-up time ranged from 1 to 83 months, with an average of 33.5 ± 21.1 months.

CONCLUSIONS

For older patients (≥ 60 years) with symptomatic, large or giant -VSs, microsurgery is the only effective method to prolong lifespan, alleviate clinical symptoms and cure the tumor. However, radical resection of VSs may result in a decreased preservation rate of facial-acoustic nerve function and an increased postoperative complication incidence. Therefore, subtotal resection followed by stereotactic radiotherapy should be recommended.

Salvage Management of Vestibular Schwannoma

The current management of vestibular schwannomas (VS) includes observation, microsurgery (MS), and stereotactic radiosurgery (SRS) or radiotherapy, and treatment failures may occur with any primary modality. SRS is most often used for microsurgical failures, as it carries a low risk of adverse events. Salvage MS following previous MS is reserved for specific cases and can present certain surgical challenges. Irradiation failures can be managed with both salvage MS and repeat SRS. This article is intended to review an approach to the failure of primary interventions for VS, with a focus on the time interval between modalities, rates of tumor control, functional outcomes, and possible complications.

Impact of Demographics and Clinical Features on Initial Treatment Pathway for Vestibular Schwannoma

OBJECTIVE

To identify demographic and clinical features impacting initial treatment pathway for vestibular schwannoma.

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary care academic medical center.

PATIENTS

Patients diagnosed with vestibular schwannoma between 2009 and 2019.

INTERVENTIONS

Observation, stereotactic radiosurgery, or microsurgical resection.

MAIN OUTCOME MEASURES

χ 2 Test, one-way analysis of variance, and multivariate logistic regression were used to correlate demographic and clinical factors with initial treatment pathway for 197 newly diagnosed vestibular schwannoma patients.

RESULTS

Among 197 patients, 93 (47%) were initially treated with observation, 60 (30%) with stereotactic radiation (Gamma Knife) and 44 (22%) with surgical resection. Age univariately had no statistically significant impact on initial pathway, but those undergoing surgery trended toward a younger demographic (49.1 yr [surgery] versus 57.2 yr [observation] versus 59.0 yr [Gamma Knife]). Men were more likely to be initially observed than women ( p = 0.04). Patients initially observed were more likely to have a lower Koos classification ( p < 0.001) and have better tumor-ear hearing ( p = 0.03). Only 34.4% of patients living outside the local geographic region were initially observed compared with 53.0% living locally ( p = 0.055). Surgeon correlated with initial treatment ( p = 0.04) but did not maintain significance when adjusting for hearing level or tumor size. A multiple linear regression model found age, maximum tumor diameter, and Koos class to correlate with initial treatment pathway ( p < 0.0001, r2 = 0.42).

CONCLUSION

Initial treatment pathway for newly diagnosed vestibular schwannoma is impacted by demographic factors such as age, sex, and geographic proximity to the medical center. Clinical features including hearing level and tumor size also correlated with initial treatment modality.

Factors Influencing Personalized Management of Vestibular Schwannoma: A Systematic Review

Management of vestibular schwannoma (VS) is a complex process aimed at identifying a clinical indication for fractionated stereotactic radiotherapy (sRT) or microsurgical resection or wait and scan (WS). The aim of the review was to clarify which patient and tumor parameters may lead to different therapeutic choices, with a view to a personalized VS approach. A systematic review according to Preferred Reporting Items for Systematic Review and Meta-Analysis criteria was conducted between February and March 2022. The authors defined six parameters that seemed to influence decision-making in VS management: 1-incidental VS; 2-tumor size; 3-tumor regrowth after sRT; 4-subtotal resection; 5-patients' age; 6-symptoms. The initial search yielded 3532 articles, and finally, 812 articles were included. Through a qualitative synthesis of the included studies, management strategies were evaluated and discussed. An individualized proposal of procedures is preferable as compared to a single gold-standard approach in VS decision-making. The most significant factors that need to be considered when dealing with a VS diagnosis are age, tumor size and hearing preservation issues.

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

OBJECTIVE

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

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary referral center.

METHODS

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

RESULTS

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

CONCLUSIONS

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

Optimal Volume of the Residual Tumor to Predict Long-term Tumor Control Using Stereotactic Radiosurgery after Facial Nerve-preserving Surgery for Vestibular Schwannomas

BACKGROUND

Intended subtotal resection (STR) followed by adjuvant gamma knife radiosurgery (GKRS) has emerged as an effective treatment option for facial nerve (FN) preservation in vestibular schwannomas (VSs). This study aimed to identify the optimal cut-off volume of residual VS to predict favorable outcomes in terms of both tumor control and FN preservation.

METHODS

This retrospective study assessed the patients who underwent adjuvant GKRS for residual VS after microsurgery. A total of 68 patients who had been followed up for ≥ 24 months after GKRS were included. Tumor progression was defined as an increase in tumor volume (TV) of ≥ 20%. House-Brackmann grades I and II were considered to indicate good FN function.

RESULTS

The median residual TV was 2.5 cm³ (range: 0.3-27.4). The median follow-up period after the first adjuvant GKRS was 64 months (range: 25.7-152.4). Eight (12%) patients showed tumor progression. In multivariate analyses, residual TV was associated with tumor progression (P = 0.003; hazard ratio [HR], 1.229; 95% confidence interval [CI], 1.075-1.405). A residual TV of 6.4 cm³ was identified as the cut-off volume for showing the greatest difference in progression-free survival (PFS). The 5-year PFS rates in the group with residual TVs of < 6.4 cm³ (54 patients) and that with residual TVs of ≥ 6.4 cm³ (14 patients) were 93.3% and 69.3%, respectively (P = 0.014). A good FN outcome was achieved in 57 (84%) patients. Residual TV was not associated with good FN function during the immediate postoperative period (P = 0.695; odds ratio [OR], 1.024; 95% CI, 0.908-1.156) or at the last follow-up (P = 0.755; OR, 0.980; 95% CI, 0.866-1.110).

CONCLUSION

In this study, residual TV was associated with tumor progression in VS after adjuvant GKRS following STR. As preservation of FN function is not correlated with the extent of resection, optimal volume reduction is imperative to achieve long-term tumor control. Our findings will help surgeons predict the prognosis of residual VS after FN-preserving surgery.

EANO guideline on the diagnosis and treatment of vestibular schwannoma

The level of evidence to provide treatment recommendations for vestibular schwannoma is low compared with other intracranial neoplasms. Therefore, the vestibular schwannoma task force of the European Association of Neuro-Oncology assessed the data available in the literature and composed a set of recommendations for health care professionals. The radiological diagnosis of vestibular schwannoma is made by magnetic resonance imaging. Histological verification of the diagnosis is not always required. Current treatment options include observation, surgical resection, fractionated radiotherapy, and radiosurgery. The choice of treatment depends on clinical presentation, tumor size, and expertise of the treating center. In small tumors, observation has to be weighed against radiosurgery, in large tumors surgical decompression is mandatory, potentially followed by fractionated radiotherapy or radiosurgery. Except for bevacizumab in neurofibromatosis type 2, there is no role for pharmacotherapy.

Progressive Vestibular Schwannoma following Subtotal or Near-Total Resection: Dose-Escalated versus Standard-Dose Salvage Stereotactic Radiosurgery

Objective  Local failure of incompletely resected vestibular schwannoma (VS) following salvage stereotactic radiosurgery (SRS) using standard doses of 12 to 13 Gy is common. We hypothesized that dose-escalated SRS, corrected for biologically effective dose, would have superior local control of high-grade VS progressing after subtotal or near-total resection compared with standard-dose SRS. Design  Retrospective cohort study. Setting  Tertiary academic referral center. Participants  Adult patients treated with linear accelerator-based SRS for progressive VS following subtotal or near-total resection. Main Outcome Measures  Dose-escalated SRS was defined by a biologically effective dose exceeding a single-fraction 13-Gy regimen. Study outcomes were local control and neurologic sequelae of SRS. Binary logistic regression was used to evaluate predictors of study outcomes. Results  A total of 18 patients with progressive disease following subtotal (71%) and near-total (39%) resection of Koos grade IV disease (94%) were enrolled. Of the 18 patients, 7 were treated with dose-escalated SRS and 11 with standard-dose SRS. Over a median follow-up of 32 months after SRS, local control was 100% in the dose-escalated cohort and 91% in the standard-dose cohort ( p  = 0.95). Neurologic sequelae occurred in 28% of patients, including 60% of dose-escalated cohort and 40% of the standard-dose cohort ( p  = 0.12), although permanent neurologic sequelae were low at 6%. Conclusions  Dose-escalated SRS has similar local control of recurrent VS following progression after subtotal or near-total resection and does not appear to have higher neurologic sequalae. Larger studies are needed.

Therapy of Sporadic and NF2-Related Vestibular Schwannoma

Vestibular schwannoma (VS) is a benign primary brain tumor that occurs sporadic or as part of a genetic syndrome. The most common cause is the mutation of the NF2 tumor suppressor gene that is involved in the production of the protein merlin. Merlin plays a role in cell growth and cell adhesion. In patients with NF2, the VSs arise bilaterally and coincide with other brain tumors. In sporadic VS, the tumor is typically unilateral and does not coincide in combination with other tumors. MRI is the standard imaging technique and can be used to assess the size and aspect of the tumor as well as the progression of disease. The preferred management of large VS in both VS types is surgery with or without adjuvant radiation. The management for the medium- or small-sized VS includes wait and scan, radiotherapy and/or surgery. This choice depends on the preference of the patient and institutional protocols. The outcomes of surgical and radiotherapy treatments are improving due to progress in surgical equipment/approaches, advances in radiation delivery techniques and dose optimizations protocols. The main purpose of the management of VS is preserving function as long as possible in combination with tumor control.

Adaptive hybrid surgery analysis (AHSA) for adjuvant gamma knife radiosurgery treatment of vestibular schwannoma residuals

OBJECTIVES

Adaptive Hybrid Surgery Analysis (AHSA, Brainlab, Munich, Germany) is a software application generating in real-time conceptual dose plans for tumor residuals but has so far not been assessed for usability in a Gamma Knife (Elekta, Stockholm, Sweden) radiosurgery practice. We aimed to compare AHSA stereotactic radiosurgery dose plans with Leksell Gamma Plan (LGP, Elekta, Stockholm, Sweden) plans for adjuvant radiosurgical treatment of Vestibular Schwannoma (VS) residuals.

PATIENTS AND METHODS

In this retrospective comparative study, we compared the automatically calculated AHSA dose plans with clinical LGP treatment plans in 13 patients radiosurgically treated for VS residuals. We first created an LGP template based on our specific constraints to organs at risk (OAR), and a tumor prescription volume coverage of minimum 98%. As most proximal anatomy at risk is not manually contoured in our practice, OARs (i.e. brainstem, optic apparatus and cochlea) in the planning images were automatically segmented in Elements Anatomical Mapping and imported into the AHSA software for re-planning and comparison with the LGP dose plans.

RESULTS

There was no significant difference in tumor coverage and conformity index between the LGP and AHSA dose planning data, with the mean and maximal dose to the brainstem slightly higher in the latter.

CONCLUSION

The AHSA dose plans for adjuvant radiosurgical treatment of VS residuals were comparable to those of LGP used in our Gamma Knife practice, confirming the usability of AHSA in the management of Vestibular Schwannoma in a Gamma Knife practice.

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

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

Local Tumor Control and Clinical Symptoms After Gamma Knife Radiosurgery for Residual and Recurrent Vestibular Schwannomas

BACKGROUND

The use of Gamma Knife radiosurgery (GKRS) for recurrent or residual vestibular schwannoma (VS) after microsurgery (MS) has been investigated in several retrospective studies. The purpose of this study was to identify potential risk factors for both neurologic deterioration and tumor progression after GKRS for previously operated VSs in a prospective setting.

METHODS

Patients who underwent GKRS for previously operated and histopathologically confirmed VS between 1998 and 2015 were prospectively followed-up. Risk factors for therapy side effects and predictors for tumor control were investigated in uni- and multivariate analyses.

RESULTS

A total of 160 individuals with a median age of 55 years were included. Median tumor volume prior to GKRS was 1.40 cm³ (range, 0.06-35.80 cm³). After a median follow-up of 36 months, hearing and facial nerve function were serviceable (modified Gardner-Robertson and House-Brackmann grades I and II) in 7 (5%) and 82 (55%) patients, respectively. Deterioration to a nonserviceable facial nerve function after GKRS was found in 3% (3/89) and tended to increase with rising tumor volume (odds ratio, 1.65 per cm³; 95% confidence interval, 1.00-2.71; P = 0.051). Median tumor volume prior to GKRS was higher in patients with radiologic (P = 0.020) or clinical tumor progression (P < 0.001). Critical tumor volume prior to GKRS to predict clinical and radiologic tumor progression was 1.30 cm³ (P < 0.001) and 3.30 cm³ (P = 0.019), respectively. However, in multivariate analyses, none of the analyzed variables were found to independently predict tumor progression.

CONCLUSIONS

Intended submaximal resection followed by GKRS is a viable treatment for VS. Because tumor remnant size after MS is an important predictor for recurrence after adjuvant GKRS, both brainstem and cerebellar decompression and maximal safely achievable resection should remain major goals of microsurgery.

Adaptive Hybrid Surgery: Paradigm Shift for Patient-centered Neurosurgery

The surgical management of cerebral and skull base lesions has evolved greatly in the last few decades. Still, a complete resection of lesions abutting critical neurovascular structures carries significant morbidity. Stereotactic radiosurgery (SRS) has emerged as an increasingly accepted treatment option. Minimally invasive, SRS results in excellent tumor control and low complication rates in patients with moderate-size tumors. The management of large cerebral and skull base tumors remains a formidable challenge. In such large tumors, radical surgical extirpation offers a significantly higher risk of neurological deficit, and SRS alone cannot be used because of the elevated incidence of radiation-induced complications known to be associated with large-volume tumors. With increasing treatment volumes, SRS-associated tumor control rates decrease and complication rates increase. Planned subtotal resection (STR) with adjuvant SRS (adaptive hybrid surgery [AHS]) has gained increasing interest in recent years as a multimodal approach. In AHS, a planned STR (aimed at decreasing surgical morbidity) followed by SRS to a preplanned residual tumor aids in harnessing advantages offered by both approaches. Although intuitive and reasonable, this paradigm shift from maximal resection at all cost has not been adopted widely. Combining open microsurgery with SRS requires a good understanding of both surgical and SRS modalities and their respective safety-efficacy features. We present a review and discussion on AHS as a modern, multidisciplinary treatment approach. Available data and views are discussed for vestibular schwannoma (VS) as a sample tumor. Other indications for AHS are mentioned in brief.

[Facial nerve injury in neurosurgery: a rehabilitation potential of botulinum therapy]

Surgical treatment of posterior cranial fossa and cerebellopontine angle tumors is associated with a risk of facial nerve dysfunction. The causes for facial muscle paresis include nerve compression by the tumor, destruction of the nerve structure by the tumor growing from nerve fibers, nerve injury during surgical removal of the tumor, etc. The first 3 months after facial nerve injury are a potential therapeutic window for the use of botulinum toxin type A (BTA). During this period, the drug is introduced both in the healthy side to improve the facial symmetry at rest and during mimetic movements and in the affected side to induce drug-induced ptosis. Post-paralytic syndrome develops 4-6 months after facial nerve injury. At this stage, administration of BTA is also an effective procedure; in this case, drug injections are performed on the affected side at small doses and symmetrically on the healthy side at doses doubling those for the affected side. BTA injections are mandatory in complex treatment of facial muscle paralysis.

Systematic review and meta-analysis of the technique of subtotal resection and stereotactic radiosurgery for large vestibular schwannomas: a “nerve-centered” approach

OBJECTIVE

During the last decade, the primary objective for large vestibular schwannoma (VS) management has progressively shifted, from tumor excision to nerve preservation by using a combined microsurgical and radiosurgical approach. The aim of this study was to provide a systematic review and meta-analysis of the available literature regarding the combined strategy of subtotal resection (STR) followed by stereotactic radiosurgery (SRS) for large VSs.

METHODS

The authors performed a systematic review and meta-analysis in compliance with the PRISMA guidelines for article identification and inclusion using the PubMed, Embase, and Cochrane databases. Established inclusion criteria were used to screen all identified relevant articles published before September 2017 without backward date limit.

RESULTS

The authors included 9 studies (248 patients). With a weighted mean follow-up of 46 months (range 28–68.8 months), the pooled rate of overall tumor control was 93.9% (95% CI 91.0%–96.8%). Salvage treatment (second STR and/or SRS) was necessary in only 13 (5.24%) of 18 patients who experienced initial treatment failure. According to the House-Brackmann (HB) grading scale, functional facial nerve preservation (HB grade I–II) was achieved in 96.1% of patients (95% CI 93.7%–98.5%). Serviceable hearing after the combined approach was preserved in 59.9% (95% CI 36.5%–83.2%).

CONCLUSIONS

A combined approach of STR followed by SRS was shown to have excellent clinical and functional outcomes while still achieving a tumor control rate comparable to that obtained with a total resection. Longer-term follow-up and larger patient cohorts are necessary to fully evaluate the rate of tumor control achieved with this approach.

Preserving normal facial nerve function and improving hearing outcome in large vestibular schwannomas with a combined approach: planned subtotal resection followed by gamma knife radiosurgery

Objective

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.

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.

Multivariate Analysis of Factors Influencing Facial Nerve Outcome following Microsurgical Resection of Vestibular Schwannoma

Objective To assess through multivariate analysis the clinical pre- and intraoperative factors of facial nerve outcomes at day 8 and 1-year recovery of facial palsy, as compared with day 8 status among patients who underwent total resection of unilateral vestibular schwannoma. Study Design Case series with chart review. Setting Tertiary referral center. Subjects and Methods This study included 229 patients with preoperative normal facial function and anatomic preservation of the facial nerve. Clinical, radiologic, and intraoperative factors were assessed according to facial nerve function at day 8 and 1 year. Results We observed that 74% and 84% of patients had good facial function (House-Brackmann [HB] I-II) at day 8 and 1 year, respectively. Of 60 patients, 26 (43%) who had impaired facial function (HB III-VI) at day 8 recovered good facial function (HB I-II) 1 year after surgery. A structured equation model showed that advanced tumor stage and strong facial nerve adhesion were independently associated with facial nerve conduction block at day 8. No predictive factor of impaired facial function recovery was seen at 1 year. In terms of the extracanalicular diameter of the tumor, the cutoff point to minimize the risk of impaired facial function was 16 mm. Conclusion At day 8 after vestibular schwannoma resection, facial function was impaired in the case of large tumors or strong facial nerve adhesion to the tumor. After 1 year, less than half of the patients recovered good facial function, and no predictive factor was found to be associated with this possible recovery.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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