Controversies in building a management algorithm for vestibular schwannomas

Cochlear Implantation in Sporadic Vestibular Schwannoma and Neurofibromatosis Type II

Cochlear implantation offers significantly better hearing outcomes than auditory brainstem implantation in patients with vestibular schwannoma. Neither the primary treatment modality nor the cause of the tumor (neurofibromatosis type 2 related or sporadic) seems to have a significant effect on hearing outcome with cochlear implantation. Some uncertainty remains regarding long-term hearing outcomes; however, cochlear implantation in vestibular schwannoma serves to offer patients, with a functioning cochlear nerve, the probability of open set speech discrimination with a consequent positive impact on quality of life.

Twelve-Month Outcomes of Simultaneous Translabyrinthine Resection and Cochlear Implantation

OBJECTIVE

Audiometric outcomes at 12 months following simultaneous translabyrinthine (TL) resection of vestibular schwannoma (VS) and cochlear implantation (CI).

STUDY DESIGN

Prospective cohort study.

SETTING

Tertiary referral center.

METHODS

Adult patients undergoing TL resection of sporadic, unilateral VS ≤ 2 cm were prospectively enrolled. Preoperative testing included binaural AZBio in noise and quiet and unilateral Consonant-Nucleus-Consonant (CNC). Tinnitus Handicap Index (THI) and Speech, Spatial, and Qualities of Hearing (SSQ) questionnaires were also completed. Patients underwent TL resection with simultaneous CI. The preoperative test battery was repeated at 1, 3, 6, and 12 months after activation. Statistical analysis was performed to characterize short-term outcomes (preoperative to 3 months), longer-term outcomes (3-12 months), and overall changes during the preoperative to 12-month period.

RESULTS

AZBio, CNC, and THI improved at 3 months with no significant changes thereafter and showed durable improvement at 12 months compared to preoperative testing. While SSQ did not improve at 12 months, a subset of patients showed either recovery or improvement of SSQ-spatial subscores. Patients with cerebellopontine angle tumors had poorer performance, although the impact of tumor size and location could not be deduced based on the small sample size.

CONCLUSION

Patients undergoing simultaneous CI and TL resection of VS had durable improvements in speech perception and tinnitus severity 12 months following surgery. Subjective improvements in localization were not observed. Additional studies are needed to determine which VS patients are optimal candidates for CI.

Simultaneous Cochlear Implantation After Translabyrinthine Vestibular Schwannoma Resection: A Report of 41 Cases

OBJECTIVE

To study the auditory outcome of simultaneous translabyrinthine vestibular schwannoma (VS) resection and cochlear implantation (CI) after successful cochlear nerve preservation.

STUDY DESIGN

A retrospective case series and patient questionnaire.

SETTING

Quaternary referral center for skull base pathologies.

PATIENTS

Patients with small (<2 cm) sporadic or neurofibromatosis 2 related tumors were included in this study.

INTERVENTION

Vestibular schwannoma resection + simultaneous cochlear implantation.

MAIN OUTCOME MEASURE

Audiological performance postimplantation and perceived patients' benefits.

RESULTS

Forty-one patients were included. Thirty-three were sporadic VS and eight were neurofibromatosis 2. Auditory perception postimplantation was achieved in 33 patients (80.5%). At the last follow-up, 20 patients (48.8%) were users and 21 (51.2%) were nonusers. In the users' group, and after 1 year of implant activation, vowel identification was 75.3%, disyllabic word recognition 54%, sentence recognition 60.7%, and common phrase comprehension 61%, whereas in the nonusers' group and after 1 year of implant activation, vowel identification was 22.9%, disyllabic word recognition 14.8%, sentence recognition 15.3%, and common phrase comprehension 14%. Sixteen users were classified into 10 high performers, three intermediate performers, and three poor performers. In the user' group, the mean postimplantation pure tone average was 63.4 dB and the mean speech discrimination score was 63.7%.

CONCLUSIONS

Simultaneous CI and VS resection is a viable option with many patients achieving auditory perception and nearly half the patients are CI users at long follow-up.

Clinical Predictors of Facial Nerve Outcomes After Surgical Resection of Vestibular Schwannoma

OBJECTIVE

To identify clinical predictors of facial nerve (FN) outcomes after microsurgical resection of vestibular schwannoma (VS).

STUDY DESIGN

Prospective cohort study.

SETTING

Academic medical center.

METHODS

Consecutive patients undergoing VS resection from November 2017 to October 2019 were included. FN function was evaluated with the House-Brackmann (HB) scale and stratified into good (HB I-II) and poor (HB III-VI) function. Analyses included descriptive statistics, correlation, and logistic regression.

RESULTS

Of 256 patients who met criteria (mean age, 47.7 years; 62.5% female), 227 (88.7%) achieved good FN function postoperatively and 238 (93.0%) at latest follow-up (mean, 154.8 days). Operative approaches consisted of translabyrinthine (50.8%), retrosigmoid (25.0%), and middle fossa craniotomies (24.2%). Extent of resection was decided intraoperatively, and gross or near total resection was accomplished in 237 (92.6%) cases. Postoperative HB grade correlated with latest HB grade (0.615, P < .001). Factors associated with good postoperative FN function included small tumor size (≤15 mm; odds ratio [OR], 2.425; P = .042), gross or near total resection (OR, 3.170; P = .041), and ≥100-µV intraoperative FN electromyographic response to a 0.05-mA stimulus (OR, 22.242; P < .001). Factors associated with good FN function at latest follow-up included gross total resection (OR, 7.764; P = .003) and ≥100-µV FN electromyographic response (OR, 8.518; P < .001), accounting for surgical approach and tumor size.

CONCLUSION

Microsurgical resection of VS can be accomplished with excellent FN outcomes. Gross total resection and ≥100-µV intraoperative FN electromyographic response predicted excellent FN outcomes. Immediate postoperative FN function is a prognosticator of long-term FN function.

Effect of Gamma Knife Radiosurgery on Vestibular Schwannoma with Serviceable Hearing: A Single-Center Indian Study

OBJECTIVE

Gamma Knife radiosurgery (GKRS) is an established treatment modality for vestibular schwannomas (VSs). The tumor control and hearing preservation rates suggest that GKRS is a good alternative treatment for small- and medium-size VS. Data are lacking from India regarding GKRS for VSs. Our aim was to find the hearing preservation and tumor control rates and the factors contributing to these.

METHODS

In a retrospective 9-year study period, 87 patients had undergone GKRS for unilateral VS with Gardner-Robertson (GR) class I or II serviceable hearing. All 87 had been evaluated with magnetic resonance imaging and audiometry before GKRS and during follow-up to assess for the factors influencing tumor control and hearing preservation.

RESULTS

Of the 87 patients, 77 with a minimum follow-up of 2 years and magnetic resonance imaging and audiometry evaluations available were included in the present study. The median follow-up period was 30 months. The tumor control rate and hearing preservation rate was 96.1% and 79.2%, respectively. Hearing preservation was not affected by the tumor volume. However, age >40 years, pre-GKRS pure tone average <30 decibels, speech discrimination score >85%, pre-GKRS Gardner-Robertson grade I hearing, mean cochlear dose <4 Gy, and pre-GKRS Ohata class of laterality C, D, E were significant on univariate analysis. The multivariate analysis revealed that age >40 years (P = 0.017), pre-GKRS pure tone average <30 decibels (P = 0.002), and Gardner-Robertson class I (P = 0.001) were significant factors. No patient developed cranial nerve dysfunction, hydrocephalus, or malignant degeneration.

CONCLUSION

For most patients with small VSs, GKRS will be an effective alternative treatment to microsurgery with retained serviceable hearing and good tumor control.

Cochlear Implantation in Sporadic Vestibular Schwannoma: A Systematic Literature Review

Objective  This study was aimed to perform a systematic literature review by examining outcomes in patients with sporadic vestibular schwannoma (VS) undergoing ipsilateral cochlear implant (CI). Data Sources  PubMed-NCBI (National Center for Biotechnology Information) and Scopus databases were searched through October 2017. Study Selection  Studies reporting auditory outcomes for each patient when a CI was placed with an ipsilateral sporadic VS were included. Main Outcome Measures  Demographic variables, VS characteristics, preoperative hearing metrics, duration of deafness, CI type, approach to tumor resection, postoperative auditory outcomes, and postoperative tinnitus outcomes were reported for each eligible patient within studies. Each study was evaluated for quality and bias. Results  Fifteen studies and 45 patients met inclusion criteria. Mean speech discrimination score (SDS) improved from 30.0 to 56.4% after CI placement. The majority when reported had an improvement in tinnitus. Preoperative ipsilateral SDS was a negative predictor of postoperative SDS, while neither tumor resection status, tumor location, duration of deafness, ipsilateral pure tone average, nor timing of CI placement had a significant effect on patient outcome. Conclusions  Notwithstanding the challenges inherent with surveillance magnetic resonance imaging (MRI) in the setting of a cochlear implant magnet, select sporadic vestibular schwannoma patients can be considered for cochlear implantation.

A Systematic Review of Radiosurgery Versus Surgery for Neurofibromatosis Type 2 Vestibular Schwannomas

OBJECTIVE

Neurofibromatosis type 2 (NF2) is an autosomal dominant disease characterized by bilateral vestibular schwannomas (VSs). NF2-associated VSs (NF2-VSs) are routinely treated with microsurgery; however, stereotactic radiosurgery (SRS) has emerged as an effective alternative in recent decades. To elucidate the role of SRS in NF2-VSs, a systematic review of the literature was conducted to compare outcomes of SRS versus surgery.

METHODS

PubMed, Web of Science, Scopus, Embase, and Cochrane databases were queried using relevant search terms. Retrospective studies investigating outcomes of NF2-VS patients treated with either SRS or surgery were included. Single-patient case reports were excluded. Outcome measures between the SRS and surgery groups were compared using χ² 2-sample tests for equality of proportions on the pooled patient data.

RESULTS

A total of 974 patients (485 SRS, 489 surgery) were identified. The mean 5-year local control rate for SRS was 75.1%, and the mean recurrence rate for surgery was 8.1%. The mean hearing and facial nerve preservation rates were 40.1% and 92.3%, respectively, for SRS and 52.0% and 75.7%, respectively, for surgery. Rates of hearing preservation were higher after surgery than after SRS (P = 0.006), whereas rates of facial nerve preservation were higher after SRS than after surgery (P < 0.001).

CONCLUSIONS

SRS appears to be a safe and effective alternative to surgery for NF2-VS. Although rates of hearing preservation were higher in the surgery cohorts, SRS demonstrated high rates of local control and significantly lower facial nerve complications. Certain patients may therefore benefit more from SRS than surgery.

Near total extirpation of vestibular schwannoma with salvage radiosurgery

OBJECTIVES/HYPOTHESIS

The management of a sporadic vestibular schwannoma (VS) has changed with the introduction of stereotactic radiosurgery (SRS). Because functional outcome is important, particularly regarding the facial nerve, a policy of near-total surgical resection of a large-size VS has emerged, minimizing damage to the facial nerve. The debate remains whether the surgical remnant should be treated immediately or after established growth.

STUDY DESIGN

Retrospective case series.

METHODS

A consecutive cohort of 55 patients underwent a retrosigmoid craniotomy and near-total removal of a large-size VS at our university medical center between 2005 and 2011 and had a follow-up of a least 3 years. Documented growth of the VS remnant after surgery necessitating adjuvant SRS was the primary outcome measure using analysis of variance.

RESULTS

In 45 patients (81.8%), a small tumor remnant was left during surgery. The mean preoperative tumor volume was 12.2 cm(3) (range, 1.13-50.16 cm(3)); the mean volume of the remnant was 0.22 cm(3) (range, 0-1.52 cm(3)). The mean postoperative follow-up time was 35.4 months (range, 3-76 months). Salvage SRS was deemed necessary in seven patients (13.0%). The size of the postoperative tumor remnant was a significant predictor for the necessity of postoperative adjuvant SRS. Normal facial nerve function (House-Brackmann [HB] I) was preserved in 30 patients (57.7%), 17 patients (32.7%) experienced a permanent mild facial nerve deficit (HB II, III), and five patients (9.6%) experienced a severe facial nerve deficit (HB grade IV-VI).

CONCLUSIONS

Initial observation after near total surgical removal of VS is a feasible strategy, with only a minority requiring salvage radiosurgery during follow-up.

The impact of comorbidities, regional trends, and hospital factors on discharge dispositions and hospital costs after acoustic neuroma microsurgery: a United States nationwide inpatient data sample study (2005-2009)

OBJECT

Hospitalization cost and patient outcome after acoustic neuroma surgery depend on several factors. There is a paucity of data regarding the relationship between demographic features such as age, sex, race, insurance status, and patient outcome. Apart from demographic factors, there are several hospital-related factors and regional issues that can affect outcomes and hospital costs. To the authors' knowledge, no study has investigated the issue of regional disparity across the country in terms of cost of hospitalization and discharge disposition.

METHODS

The authors analyzed the Nationwide Inpatient Sample (NIS) database over the years 2005-2009. Several variables were analyzed from the database, including patient demographics, comorbidities, and surgical complications. Hospital variables, such as bedsize, rural/urban location, teaching status, federal or private ownership, and the region, were also examined. Patient outcome and increased hospitalization costs were the dependent variables studied.

RESULTS

A total of 2589 admissions from 242 hospitals were analyzed from the NIS data over the years 2005-2009. The mean age was 48.99 ± 13.861 years (± SD), and 304 (11.7%) of the patients were older than 65 years. The cumulative cost incurred by the hospitals from 2005 to 2009 was $948.77 million. The mean expenditure per admission was $76,365.09 ± $58,039.93. The mean total charges per admission rose from $59,633.00 in 2005 to $97,370.00 in 2009. The factors that predicted most significantly with other than routine (OTR) disposition outcome were age older than 65 years (OR 2.22, 95% CI 1.411-3.518; p < 0.001), aspiration pneumonia (OR 16.085, 95% CI 4.974-52.016; p < 0.001), and meningitis (OR 11.299, 95% CI 3.126-40.840; p < 0.001). When compared with patients with Medicare and Medicaid, patients with private insurance had a protective effect against OTR disposition outcome. Higher comorbidities predicted independently for OTR disposition outcome (OR 1.409, 95% CI 1.072-1.852; p = 0.014). The West region predicted negatively for OTR disposition outcome. Large hospitals were independently associated with higher hospital charges (OR 4.269, 95% CI 3.106-5.867; p < 0.001). The West region had significantly higher (p < 0.001) mean hospital charges than the other regions. Patient factors such as meningitis and aspiration pneumonia were strong independent predictors of increased hospital charges (p < 0.001). Higher comorbidities (OR 1.297, 95% CI 1.036-1.624; p = 0.023) and presence of neurofibromatosis Type 2 (OR 2.341, 95% CI 1.479-3.707; p < 0.001) were associated with higher hospital charges.

CONCLUSIONS

The authors' study shows that several factors can affect patient outcome and hospital charges for patients who have undergone acoustic neuroma surgery. Factors such as younger age, higher ZIP code income, less comorbidity, private insurance, elective surgery, and the West region predicted for better disposition outcome. However, the West region, higher comorbidities, and weekend admissions were associated with higher hospitalization costs.

Nonvestibulocochlear cranial nerve schwannomas

OPINION STATEMENT

Nonvestibulocochlear cranial nerve schwannomas traditionally have been managed by surgical excision. Although debulking surgery is still considered the first treatment option for larger tumors, stereotactic radiosurgery is now preferred for smaller tumors because of its high tumor control rate and low treatment-related morbidity. Furthermore, an initial period of radiologic and clinical observation following the diagnosis should be strongly considered for smaller tumors because some may not grow or may grow at a slow rate. Medical management of tumor-associated symptoms (when present) should not be ignored. Most importantly, the time has come to embark on the first randomized controlled trials comparing clinical and radiologic observation, surgery, and radiosurgery in the management of cranial nerve schwannomas.

Management of patients with acoustic neuromas: a Markov decision analysis

OBJECTIVES/HYPOTHESIS

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

STUDY DESIGN

Markov decision analysis; societal perspective.

METHODS

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

RESULTS

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

CONCLUSIONS

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

Merlin knockdown in human Schwann cells: clues to vestibular schwannoma tumorigenesis

HYPOTHESIS

To investigate the early events in molecular progression toward schwannoma tumorigenesis, we developed an in vitro model of human Schwann cell tumorigenesis by merlin knockdown.

BACKGROUND

Neurofibromatosis 2 (NF2)-related and sporadic vestibular schwannoma (VS) exhibit loss of functional merlin (schwannomin). After loss of merlin expression in the Schwann cell, the initial steps toward VS tumorigenesis are unknown. Merlin, a putative tumor suppressor protein, interacts with many cellular proteins, regulating their function. Among these are receptor tyrosine kinases, including the epidermal growth factor receptor family B (ErbB) family receptors epidermal growth factor receptor and ErbB2. Functional merlin interacts with and internalizes these growth factor receptors, silencing their proliferation and survival signaling. Deregulation of CD44, the cell adhesion/signaling molecule and cancer stem cell marker, has also been implicated in VS tumorigenesis.

METHODS

Merlin knockdown was performed using small interfering RNA transfection into human Schwann cell primary cultures. Knockdown was confirmed by real-time quantitative PCR, immunofluorescence, and Western analysis. Expression profiles of ErbB, merlin, and the stem cell markers nestin and CD44 were examined in knockdowns. Proliferation rate was assessed with bromodeoxyuridine incorporation, and radiation sensitivity was assessed using the Annexin assay in knockdowns versus controls.

RESULTS

Merlin knockdowns demonstrated increased proliferation rate, upregulation of epidermal growth factor receptor, ErbB2, and ErbB3, CD44, and nestin. Short-term merlin depletion had no effect on gamma irradiation sensitivity compared with controls.

CONCLUSION

Merlin depletion results in deregulation of ErbB receptor signaling, promotes a dedifferentiated state, and increases Schwann cell proliferation, suggesting critical steps toward schwannoma tumorigenesis.

A comprehensive analysis of hearing preservation after radiosurgery for vestibular schwannoma

Object

Gamma Knife surgery (GKS) has evolved into a practical alternative to open microsurgical resection in the treatment of patients with vestibular schwannoma (VS). Hearing preservation rates in GKS series suggest very favorable outcomes without the possible acute morbidity associated with open microsurgery. To mitigate institutional and practitioner bias, the authors performed an analytical review of the published literature on the GKS treatment of vestibular schwannoma patients. Their aim was to objectively characterize the prognostic factors that contribute to hearing preservation after GKS, as well as methodically summarize the reported literature describing hearing preservation after GKS for VS.

Methods

A comprehensive search of the English-language literature revealed a total of 254 published studies reporting assessable and quantifiable outcome data obtained in patients who underwent radiosurgery for VSs. Inclusion criteria for articles were 4-fold: 1) hearing preservation rates reported specifically for VS; 2) hearing status reported using the American Association of Otolaryngology–Head and Neck Surgery (AAO-HNS) or Gardner-Robertson classification; 3) documentation of initial tumor size; and 4) GKS was the only radiosurgical modality in the treatment. In the analysis only patients with AAO-HNS Class A or B or Gardner-Robertson Grade I or II status at the last follow-up visit were defined as having preserved hearing. Hearing preservation and outcome data were then aggregated and analyzed based on the radiation dose, tumor volume, and patient age.

Results

The 45 articles that met the authors' inclusion criteria represented 4234 patients in whom an overall hearing preservation rate was 51%, irrespective of radiation dose, patient age, or tumor volume. Practitioners who delivered an average ≤ 13-Gy dose of radiation reported a higher hearing preservation rate (60.5% at ≤ 13 Gy vs 50.4% at > 13 Gy; p = 0.0005). Patients with smaller tumors (average tumor volume ≤ 1.5 cm3) had a hearing preservation rate (62%) comparable with patients harboring larger tumors (61%) (p = 0.8968). Age was not a significant prognostic factor for hearing preservation rates as in older patients there was a trend toward improved hearing preservation rates (56% at < 65 years vs 71% at ≥ 65 years of age; p < 0.1134). The average overall follow-up in the studies reviewed was 44.4 ± 32 months (median 35 months).

Conclusions

These data provide a methodical overview of the literature regarding hearing preservation with GKS for VS and a less biased assessment of outcomes than single-institution studies. This objective analysis provides insight into advising patients of hearing preservation rates for GKS treatment of VSs that have been reported, as aggregated in the published literature. Analysis of the data suggests that an overall hearing preservation rate of ~ 51% can be expected approaching 3–4 years after radiosurgical treatment, and the analysis reveals that patients treated with ≤ 13 Gy were more likely to have preserved hearing than patients receiving larger doses of radiation. Furthermore, larger tumors and older patients do not appear to be at any increased risk for hearing loss after GKS for VS than younger patients or patients with smaller tumors.

Spontaneous regression of vestibular schwannomas after resection of contralateral tumor in neurofibromatosis Type 2

The authors report on 2 patients with bilateral vestibular schwannomas (VSs) who underwent unilateral surgical tumor removal. One patient was followed up for 4 years, the other for 9; in both cases, the contralateral VS regressed markedly without any additional treatment during the follow-up period. Serial MR imaging was performed to monitor the untreated tumor, which in both cases involved the only hearing ear. The tumors were assessed volumetrically. The contralateral tumors appeared to enlarge mildly at initial follow-up and then, with no treatment, regressed (to 23% of the original maximum volume in Case 1 and to 15% of the original maximum in Case 2). The largest posterior fossa diameter decreased from 30.1 mm to 18.6 mm in Case 1 over 4 years and from 27 mm to 16 mm over 8 years in Case 2. Hearing declined only mildly during follow-up in both patients.

These cases demonstrate the first well-documented, long-term, spontaneous VS regressions in patients with neurofibromatosis Type 2. They underline the importance of careful observation of VS involving the only hearing ear in the management of bilateral VS to determine the natural growth pattern of the tumors. The mechanism of the dramatic spontaneous tumor regression is uncertain.

Follow-up assessment of vestibular schwannomas: volume quantification versus two-dimensional measurements

Introduction

A conservative treatment strategy is often proposed as a primary treatment option in the management of vestibular schwannomas (VS). In this “wait and scan” policy, audiovestibular symptoms are monitored regularly, and VS growth is measured on consecutive magnetic resonance images (MRI). The aim of this study is validation of two-dimensional versus volume MRI assessment in the longitudinal follow-up of VS and to define tumor growth beyond measurement error.

Methods

MRI scans of 68 consecutive patients with VS were analyzed retrospectively. Two-dimensional and volume measurements on contrast enhanced (CE) T1- and T2-weighted images were performed independently by two readers. Smallest detectable differences (SDD) were calculated, and intraclass correlation coefficients (ICCs) were determined for both assessment methods.

Results

Two-dimensional and volume measurements both showed best reproducibility on CE T1-weighted images. SDD for differences relative to baseline MRI [SDD (%)] for two-dimensional measurements had a higher interobserver error compared to volume measurements (40% versus 19.7%), which decreases when tumor size increases. The ICC for two-dimensional measurements in three directions was 0.947, 0.974, and 0.978 and for volume measurements 0.999.

Conclusion

Volume measurements are more accurate compared to two-dimensional measurements for the evaluation of VS growth. These measurements are assessed preferably on CE T1-weighted images. SDD (%) strongly depends on VS size. SDD between consecutive scans exceeds the common clinical applied criterion of 1 or 2 mm growth to define growth.

Cranial base approaches to inaccessible intracranial tumors

PURPOSE OF REVIEW

Craniotomy created through the base of the skull has improved exposure of many types of extraaxial tumors and thus enhanced both tumor control and preservation of neural function. The purpose of this article is to review recent advances in this emerging field.

RECENT FINDINGS

Use of microscopes and endoscopes has allowed these procedures to become progressively less invasive. Electrophysiological monitoring has enhanced neural identification and preservation. The increasingly documented efficacy of stereotactic radiation for certain tumor types (e.g. meningioma, schwannoma) has permitted nonoperative therapy for some individuals. In large tumors, selective use of less-than-complete microsurgical resection is establishing an increasing role, at times combined with focused radiotherapy of the surgical remnant. The role for transbasal craniotomy is well established in both benign tumors and vascular lesions, but has only limited applicability for high-grade malignant lesions. Today, the vast majority of procedures can be conducted in a single stage by a multidisciplinary team.

SUMMARY

Operative trajectories created through the cranial base, although technically demanding, have led to substantially improved outcomes for a wide variety of inaccessible intracranial lesions.