Automatic Segmentation of Vestibular Schwannomas: A Systematic Review

BACKGROUND

Vestibular schwannomas (VSs) are benign tumors often monitored over time, with measurement techniques for assessing growth rates subject to significant interobserver variability. Automatic segmentation of these tumors could provide a more reliable and efficient for tracking their progression, especially given the irregular shape and growth patterns of VS.

METHODS

Various studies and segmentation techniques employing different Convolutional Neural Network architectures and models, such as U-Net and convolutional-attention transformer segmentation, were analyzed. Models were evaluated based on their performance across diverse datasets, and challenges, including domain shift and data sharing, were scrutinized.

RESULTS

Automatic segmentation methods offer a promising alternative to conventional measurement techniques, offering potential benefits in precision and efficiency. However, these methods are not without challenges, notably the "domain shift" that occurs when models trained on specific datasets underperform when applied to different datasets. Techniques such as domain adaptation, domain generalization, and data diversity were discussed as potential solutions.

CONCLUSIONS

Accurate measurement of VS growth is a complex process, with volumetric analysis currently appearing more reliable than linear measurements. Automatic segmentation, despite its challenges, offers a promising avenue for future investigation. Robust well-generalized models could potentially improve the efficiency of tracking tumor growth, thereby augmenting clinical decision-making. Further work needs to be done to develop more robust models, address the domain shift, and enable secure data sharing for wider applicability.

Refining the predictive value of preoperative apparent diffusion coefficient (ADC) by whole-tumor analysis for facial nerve outcomes in vestibular schwannomas

BACKGROUND

Apparent diffusion coefficient (ADC) in MRI has been shown to correlate with postoperative House-Brackmann (HB) scores in patients with vestibular schwannoma despite limited methodology. To rectify limitations of single region of interest (ROI) sampling, we hypothesize that whole-tumor ADC histogram analysis will refine the predictive value of this preoperative biomarker related to postoperative facial nerve function.

METHODS

Of 155 patients who underwent resection of vestibular schwannoma (2014-2020), 125 patients were included with requisite clinical and radiographic data. After volumetric analysis and whole-tumor ADC histogram, regression tree analysis identified ADC cutoff for significant differences in HB grade. Outcomes were extent of resection, facial nerve function, hospital length of stay (LOS), and complications.

RESULTS

Regression tree analysis defined three quantitative ADC groups (× 10-6 mm2/s) as high (> 2248.77; HB 1.7), mid (1468.44-2248.77; HB 3.1), and low (< 1468.44; HB 2.3) range (p 0.04). The mid-range ADC group had significantly worse postoperative HB scores and longer hospital LOS. Large tumor volume was independently predictive of lower rates of gross total resection (p <0.0001), higher postoperative HB score (p 0.002), higher rate of complications (p 0.04), and longer LOS (p 0.003).

CONCLUSIONS

Whole-tumor histogram yielded a robust regression tree analysis that defined three ADC groups with significantly different facial nerve outcomes. This likely reflects tumor heterogeneity better than solid-tumor ROI sampling. Whole-tumor ADC warrants further study as a useful radiographic biomarker in patients with vestibular schwannoma who are considering surgical resection.

Management of sporadic intracanalicular vestibular schwannomas: A critical review and International Stereotactic Radiosurgery Society (ISRS) practice guidelines

BACKGROUND

The choice of an appropriate strategy for intracanalicular vestibular schwannoma (ICVS) is still debated. We conducted a systematic review and meta-analysis with the aim to compare treatment outcomes amongst management strategies (conservative surveillance (CS), microsurgical resection (MR), or stereotactic radiosurgery (SRS)) aiming to inform guideline recommendations on behalf of the International Stereotactic Radiosurgery Society (ISRS).

METHODS

Using PRISMA guidelines, we reviewed manuscripts published between January 1990 and October 2021 referenced in PubMed or Embase. Inclusion criteria were peer-reviewed clinical studies or case series reporting a cohort of ICVS managed with CS, MR, or SRS. Primary outcome measures included tumor control, the need for additional treatment, hearing outcomes, and posttreatment neurological deficits. These were pooled using meta-analytical techniques and compared using meta-regression with random effect.

RESULTS

Forty studies were included (2371 patients). The weighted pooled estimates for tumor control were 96% and 65% in SRS and CS series, respectively (P < .001). Need for further treatment was reported in 1%, 2%, and 25% for SRS, MR, and CS, respectively (P = .001). Hearing preservation was reported in 67%, 68%, and 55% for SRS, MR, and CS, respectively (P = .21). Persistent facial nerve deficit was reported in 0.1% and 10% for SRS and MR series, respectively (P = .01).

CONCLUSIONS

SRS is a noninvasive treatment with at least equivalent rates of tumor control and hearing preservation as compared to MR, with the caveat of better facial nerve preservation. As compared to CS, upfront SRS is an effective treatment in achieving tumor control with similar rates of hearing preservation.

Socioeconomic Disparities in the Pursuit of Care at a High-Volume Institution for Surgical Resection of Vestibular Schwannomas

OBJECTIVE

Increased institutional surgical resection case volume for vestibular schwannomas (VSs) has been associated with improved patient outcomes, including reduced risk of prolonged hospital stay and readmission. Socioeconomic disparities in the pursuit of care at these high-volume institutions remain unknown.

STUDY DESIGN

Retrospective cohort epidemiological study.

SETTING

National Cancer Database, a hospital-based registry of over 1,500 facilities in the United States.

PATIENTS

Adult VS patients (age, >18 years) treated surgically.

INTERVENTIONS

High- versus low-volume facilities, defined using a facility case volume threshold of 25 cases per year. A risk-adjusted restricted cubic spline model was previously used to identify this risk threshold beyond which the incremental benefit of increasing case volume began to plateau.

MAIN OUTCOME MEASURES

Sociodemographic factors, including race, ethnicity, income, insurance status, and rurality. Multivariable analyses were adjusted for patient and tumor characteristics, including age, sex, Charlson-Deyo score, and tumor size.

RESULTS

A totoal of 10,048 patients were identified (median [interquartile range] age = 51 [41-60] years, 54% female, 87% Caucasian). Patients with Spanish/Hispanic ethnicity (OR = 0.71, 95% confidence interval [CI] = 0.52-0.96), income below median (OR = 0.63, 95% CI = 0.55-0.73]), and Medicare, Medicaid, or other government insurance versus private insurance (OR = 0.63, 95% CI = 0.53-0.74) had reduced odds of treatment at a high-volume facility. Further sensitivity analyses in which facility volume was operationalized continuously reinforced direction and significance of these associations.

CONCLUSIONS

Socioeconomic disparities exist in the propensity for VS patients to be treated at a high-volume facility. Further work is needed to understand the nature of these associations and whether interventions can be designed to mitigate them.

Association Between Facility Surgical Volume and Excess Time in the Hospital After Surgical Resection of Vestibular Schwannomas

Importance

High surgical vestibular schwannoma case volume in a medical institution may decrease the risk of adverse outcomes among patients undergoing vestibular schwannoma surgery.

Objective

To study the association between surgical vestibular schwannoma case volume and excess time in the hospital after vestibular schwannoma surgery.

Design, Setting, and Participants

This cohort study evaluated data from the National Cancer Database from January 1, 2004, through December 31, 2019, on Commission on Cancer-accredited facilities in the US. The hospital-based sample comprised adult patients aged 18 years or older with a vestibular schwannoma treated with surgery.

Exposures

Facility case volume, defined as the mean number of surgical vestibular schwannoma cases per year in the 2 years preceding the index case.

Main Outcomes and Measures

The primary outcome was a composite of prolonged hospital stay (>90th percentile) or 30-day readmission. Risk-adjusted restricted cubic splines were used to model the probability of the outcome according to facility volume. The inflection point (in cases per year) when the declining risk of excess time in the hospital began to plateau was selected as the threshold to define high- and low-volume facilities. Outcomes were compared among patients treated at high- and low-volume facilities, with mixed-effects logistic regression models adjusting for patient sociodemographic characteristics, comorbidities, tumor size, and clustering within facilities. Collected data were analyzed between June 24 and August 31, 2022.

Results

Among 11 524 eligible patients (mean [SD] age, 50.2 [12.8] years; 53.5% female; 46.5% male) who underwent surgical resection of vestibular schwannoma at 66 reporting facilities, the median length of stay was 4 (IQR, 3-5) days, and 655 patients (5.7%) were readmitted within 30 days. The median case volume was 16 (IQR, 9-26) cases per year. An adjusted restricted cubic spline model identified a downtrending probability of excess time in the hospital with increasing volume. The declining risk of excess time in the hospital began to plateau at a facility volume of 25 cases per year. Surgery at a facility with an annual case volume at or above this threshold was independently associated with a 42% reduction in the odds of excess time in the hospital compared with surgery at a low-volume center (odds ratio, 0.58; 95% CI, 0.44-0.77).

Conclusions and Relevance

This cohort study found that among adults undergoing vestibular schwannoma surgery, a higher facility case volume was associated with a reduced risk of prolonged hospital stay or 30-day readmission. A facility case volume of 25 cases per year may represent a risk-defining threshold.

Subclassification of the Koos grade 2 vestibular schwannoma into 2a and 2b for individualized patient care: a validity and reliability study

OBJECTIVE

Vestibular schwannoma (VS) growth of ≥2 mm during serial MRI observation, irrespective of size, is the benchmark for treatment initiation in almost all centers. Although the probability of less optimal outcomes significantly increases in VS closer to the brainstem, early intervention does not improve long-term quality of life. Moving beyond the recommendation of definitive treatment for all VS after detected growth, we subclassified Koos 2 tumors based on extrameatal extension and relation to the brainstem. The aim of the current study was to evaluate the Koos 2 subclassification's validity and the inter-and intra-rater reliability of the entire Koos classification.

METHODS

Six experts, including neurosurgeons, otorhinolaryngologists and radiologists from two tertiary referral centers, classified 43 VS MRI scans. Validity of the Koos 2 subclassification was evaluated by the percentage agreement against the multidisciplinary skull base tumor board management advice. Inter- and intra-rater reliability were calculated using the intraclass correlation coefficient (ICC).

RESULTS

Validity was almost perfect in Koos 2a VSs with a 100% agreement and 87.5% agreement for Koos 2b. Inter-rater reliability for all Koos grades was significantly excellent (ICC 0.91; 95%CI 0.866 to 0.944, p= <0.001). Five raters had an excellent intra-rater reliability (ICC > 0.90; p= <0.01) and one rater had a good intra-rater reliability (ICC 0.88; 95% CI 0.742 to 0.949).

CONCLUSIONS

Although multiple factors influence decision-making, the classification of Koos 2a and 2b with excellent inter- and intra-rater reliability, can aid in recommending treatment initiation, moving beyond detected tumor growth, aiming to optimize patient centered care.

How to position the patient? A meta-analysis of positioning in vestibular schwannoma surgery via the retrosigmoid approach

Objective

Patient positioning is a matter of ongoing debate in the surgical treatment of vestibular schwannoma (VS). Main endpoints of this discussion are preservation of facial nerve functioning, extent of resection, and complications. In this meta-analysis, we aim to investigate the impact of patient positioning on VS surgery via the retrosigmoid approach.

Methods

We searched for eligible comparative trials on PubMed, Cochrane library, and Web of Science. Positioning groups were compared regarding facial nerve outcome, extent of resection, postoperative hydrocephalus, postoperative CSF leaks, perioperative venous air embolism, and perioperative mortality. Two groups of positions were defined, and the following positions were allocated to those groups: (1) Semi-sitting and Sitting-position; (2) Lateral position, supine position with extensive head rotation, lateral oblique (=Fukushima/Three-quarter prone), and park-bench position.

Results

From 374 full-text screenings, 7 studies met the criteria and were included in our meta-analysis comprising 1640 patients. Our results demonstrate a significantly better long-term (≥6 months) outcome of the facial nerve after VS surgery in the semi-sitting positioning (OR: 1.49, 95%CI: 1.03-2.15, p = 0.03). Positioning did not influence the extent of resection, rate of postoperative CSF leaks, and the presence of a postoperative hydrocephalus. Overall incidence of venous air embolisms was significantly associated with VS surgery in sitting positioning (OR: 6.77, 95% CI: 3.66-12.54, p < 0.00001). Perioperative mortality was equal among both positioning groups.

Conclusion

Semi-sitting positioning seems to be associated with an improved facial nerve outcome after VS surgery via the retrosigmoid approach. Venous air embolisms are significantly more often observed among VS patients who underwent surgery in the sitting position, but the perioperative mortality is equal in both positioning groups. Both positioning groups are a safe procedure. Multicentric prospective randomized trials are needed to evaluate the risk-benefit ratio of each positioning in VS surgery via the retrosigmoid approach.

A comparative study of microsurgery and gamma knife radiosurgery in vestibular schwannoma evaluating tumor control and functional outcome

Background

Both stereotactic radiosurgery (SRS) and microsurgical resection (SURGERY) are available as treatment options for sporadic vestibular schwannoma (VS). There are very few direct comparative studies comparing both treatment modalities in large cohorts allowing detailed subgroup analysis. This present study aimed to compare the nuances in the treatment of VS by SURGERY and SRS in 2 highly specialized neurosurgical centers.

Methods

This is a retrospective bicentric cohort study. Data from patients treated between 2005 and 2011 were collected retrospectively. Recurrence-free survival (RFS) was assessed radiographically by contrast-enhanced magnetic resonance imaging.

Results

The study population included N = 901 patients with a mean follow-up of 7 years. Overall, the incidence of recurrence was 7% after SURGERY, and 11% after SRS with superior tumor control in SURGERY in the Kaplan-Meier-analysis (P = 0.031). In small tumors (Koos I and II), tumor control was equivalent in both treatment arms. In large VS (Koos III and IV), however, RFS was superior in SURGERY. The extent of resection correlated with RFS (P < .001). Facial and hearing deterioration was similar in both treatment arms in small VS, but more pronounced in SURGERY of large VS. Tinnitus, vertigo, imbalance, and trigeminal symptoms were more often improved by SURGERY than SRS.

Conclusions

SRS can achieve similar tumor control compared to SURGERY in smaller VS (Koos I and II)-with similar postinterventional morbidities. In large VS (Koos III and IV), long-term tumor control of SRS is inferior to SURGERY. Based on these results, we suggest that if combination therapy is chosen, the residual tumor should not exceed the size of Koos II.

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.

Impact of Social Determinants of Health on Stereotactic Radiotherapy for Vestibular Schwannoma

OBJECTIVES/HYPOTHESIS

Linear accelerator (LINAC) and Gamma Knife (GK) are common stereotactic radiation therapies for treating vestibular schwannoma (VS). There is currently limited literature examining specific demographic and socioeconomic factors, which influence the type of stereotactic radiation therapy a patient with VS receives.

STUDY DESIGN

Retrospective database review.

METHODS

The National Cancer Database was queried for cases of VS between 2004 and 2016. Patient demographic characteristics were compared using chi-squared and t-tests between GK and LINAC treated groups. Multivariate regression analysis was performed to assess predictors of stereotactic radiation therapy received.

RESULTS

Of the 6,208 included patients, 5,306 (85.5%) received GK and 902 (14.5%) received LINAC. The mean age of GK patients was significantly lower than that of LINAC patients (58.0 vs. 59.7, P < .001). Individuals treated with GK had greater proportions of private insurance (P < .001) and incomes greater than $63,332 (P = .003). A greater proportion of GK patients were treated in academic centers (P < .001), in high-volume facilities (P < .001), in metropolitan areas (P < .001), and in the Northeastern United States (P < .001). On multivariate logistic regression analysis, region, metropolitan area, facility type, tumor size, and distance traveled by patients independently predict receipt of GK versus LINAC.

CONCLUSION

Differences in patient demographics and other social determinants of health influence choice of GK versus LINAC therapy for VS patients. Future studies focused on addressing barriers to care, which may influence postprocedural quality of life and clinical outcomes associated with these two treatments are necessary to better understand the impact of these social differences.

LEVEL OF EVIDENCE

4 Laryngoscope, 2022.

Assessing the long-term safety and efficacy of gamma knife and linear accelerator radiosurgery for vestibular schwannoma: A systematic review and meta-analysis

Background

Differences in long-term outcomes of single-fraction stereotactic radiosurgery (SRS) between gamma knife (GK) and linear accelerator (LINAC) systems for vestibular schwannoma (VS) management remain unclear. To investigate differences in safety and efficacy between modalities, we conducted a meta-analysis of studies over the past decade.

Methods

MEDLINE, EMBASE, and Cochrane databases were queried for studies with the following inclusion criteria: English language, published between January 2010 and April 2020, cohort size ≥30, and mean/median follow-up ≥5 years. Odds ratios (OR) compared rates of tumor control, hearing preservation, and cranial nerve toxicities before and after SRS.

Results

Thirty-nine studies were included (29 GK, 10 LINAC) with 6516 total patients. Tumor control rates were 93% (95% CI 91-94%) and 94% (95% CI 91-97%) for GK and LINAC, respectively. Both GK (OR 0.06, 95% CI 0.02-0.13) and LINAC (OR 0.47, 95% CI 0.29-0.76) reduced odds of serviceable hearing. Neither GK (OR 0.71, 95% CI 0.41-1.22) nor LINAC (OR 1.13, 95% CI 0.64-2.00) impacted facial nerve function. GK decreased odds of trigeminal nerve (TN) impairment (OR 0.55, 95% CI 0.32-0.94) while LINAC did not impact TN function (OR 1.45, 95% CI 0.81-2.61). Lastly, LINAC offered decreased odds of tinnitus (OR 0.15, 95% CI 0.03-0.87) not observed with GK (OR 0.70, 95% CI 0.48-1.01).

Conclusions

VS tumor control and hearing preservation rates are comparable between GK and LINAC SRS. GK may better preserve TN function, while LINAC decreases tinnitus rates. Future studies are warranted to investigate the efficacy of GK and LINAC SRS more directly.

Association of Metformin With Volumetric Tumor Growth of Sporadic Vestibular Schwannomas

OBJECTIVE

Recent research demonstrates a potential association between metformin use and reduced sporadic vestibular schwannoma (VS) growth in patients undergoing conservative observation. The current study was designed to elucidate the effect of metformin on tumor growth in sporadic VS using volumetric analyses.

STUDY DESIGN

Retrospective cohort.

SETTING

Tertiary referral center.

PATIENTS

Patients with sporadic VS who elected initial conservative treatment with at least two serial magnetic resonance imaging (MRI) scans were included.

INTERVENTIONS

Metformin use among patients with observed sporadic VS.

MAIN OUTCOME MEASURES

Tumor growth, defined as an increase in volume of at least 20% from the initial MRI.

RESULTS

A total of 361 patients were evaluated. Thirty-four patients (9%) had a diagnosis of diabetes at baseline. Nineteen patients (5%) were taking metformin at the time of the initial MRI. Metformin use was not significantly associated with a reduced risk of volumetric tumor growth in a univariable analysis in all patients undergoing observation for VS (hazard ratio [HR] 0.75; 95% confidence intervals [CI] 0.40-1.42; p = 0.38) or within the diabetic subset (HR 0.79; 95% CI 0.34-1.83; p = 0.58). Additionally, diabetes status, insulin dependence, hemoglobin A1c value, and metformin dose were not significantly associated with volumetric tumor growth.

CONCLUSION

Despite promising initial results in several previous studies, our data suggest that metformin use does not significantly reduce the risk of volumetric tumor growth in sporadic VS.

Long-term clinical outcomes of stereotactic radiosurgery and hypofractionated stereotactic radiotherapy using the CyberKnife® robotic radiosurgery system for vestibular schwannoma

AIM

The study aimed to evaluate the long-term clinical outcomes of patients with vestibular schwannoma (VS) treated with stereotactic radiosurgery (SRS) and hypofractionated stereotactic radiotherapy (HSRT) with frameless robotic whole-body radiosurgery system (CyberKnife^® ).

METHODS

This retrospective analysis of prospectively collected data included 123 consecutive patients with VS treated at the Radiosurgery center, Ramathibodi Hospital, Bangkok, Thailand. SRS was recommended for patients with unserviceable hearing and Koos grade I-III tumors, and HSRT for patients with serviceable hearing or Koos grade III-IV tumors. Between March 2009 and December 2015, 23 patients (19%) were treated with SRS, whereas 100 (81%) received HSRT. The commonly used regimen was 12 Gy in one fraction for SRS and 18 Gy in three fractions for HSRT.

RESULTS

After a median follow-up of 72 months (range: 12-123 months), the 5-year and 8-year progression-free survival (PFS) rates for the whole cohort were 96% and 92%, respectively. The PFS was not significantly different between the SRS and HSRT groups (p = 0.23). Among 28 patients with serviceable hearing in the HSRT group, the 5-year and 8-year hearing preservation rates were 87% and 65%, respectively. The rate of nonauditory complications was 14%. Koos grade III/IV was a predictor of disease progression and was associated with nonauditory complications.

CONCLUSION

SRS and HSRT with the CyberKnife^® system provided excellent long-term tumor control with a low rate of nonauditory complications. HSRT may result in acceptable hearing preservation rates.

Tumor-Related and Patient-Related Variables Affecting Length of Hospital Stay Following Vestibular Schwannoma Microsurgery

OBJECTIVE

Review a single institution's vestibular schwannoma (VS) microsurgery experience to determine (1) correlations between demographics, comorbidities, and/or surgical approach on hospital length of stay (LOS) and discharge disposition and (2) trends in surgical approach over time.

METHODS

Retrospective case series from a multidisciplinary skull base program at a tertiary care, academic hospital. All adult (>18 years) patients undergoing primary microsurgery for VS between 2008 and 2018 were included.

RESULTS

A total of 147 subjects were identified. Surgical approach was split between middle fossa (MF) (16%), retrosigmoid (RS) (35%), and translabyrinthine (TL) (49%) craniotomies. For the 8% of patients had other than routine (OTR) discharge. Mean LOS was significantly longer for patients undergoing RS than either MF or TL. Brainstem compression by the tumor was associated with longer LOS as were diagnoses of chronic obstructive pulmonary disease (COPD) and peripheral vascular disease (PVD). For all discharges, the 40 to 50- and 50 to 60-year-old subgroups had significantly shorter LOS than the 70-years-and-older patients. For the 92% of patients routinely discharged, there was a significantly shorter LOS in the 40 to 50-year-olds compared to the 70-years-and-older patients. There was a significant shift in surgical approach from RS to TL over the study period.

CONCLUSION

Over 90% of VS microsurgery patients were routinely discharged with a median hospital LOS of 3.2 days, both of which are consistent with published data. There is an inverse relationship between age and LOS with patients older than 70 years having significantly longer LOS. Brainstem compression, COPD, PVD, and the RS approach negatively affect LOS.

LEVEL OF EVIDENCE

4.

Underreporting of Vestibular Schwannoma Incidence Within National Brain Tumor and Cancer Registries in the United States

OBJECTIVE

Reports using large brain tumor and cancer registries suggest that the incidence of vestibular schwannoma is considerably lower in the United States compared with other countries. The current study compares the incidence and disease characteristics of vestibular schwannoma within a large tertiary referral center's brain tumor and cancer registry using nationally mandated reporting protocols to disease incidence in the same population using an externally validated population-based consortium.

STUDY DESIGN

Population-based study spanning 1,945,007 person-years.

SETTING

Large tertiary referral center.

PATIENTS

Adults with sporadic vestibular schwannoma.

MAIN OUTCOME MEASURE

Disease incidence rates from 2004 to 2016.

RESULTS

From 2004 to 2016, the incidence of vestibular schwannoma in the tumor registry was 1.3 per 100,000 person-years whereas the population-based cohort had an incidence of 4.4 per 100,000 person-years. From 2012 to 2016, the incidence in the tumor registry was 1.4 per 100,000 person-years compared with 5.2 in the population-based cohort. Patients within the population-based cohort were significantly more likely to have smaller tumors at diagnosis (78% intracanalicular versus 45%; p = 0.004) and consequently more likely to undergo management consisting of observation with serial imaging as opposed to treatment with either microsurgery or radiosurgery (71% versus 28%; p = 0.001).

CONCLUSIONS

The reliance on pathology specimens and cancer-related treatment data for the national registration of new cancer and brain tumor diagnoses may introduce selection bias and underreporting of benign brain tumors that frequently involve observation as a primary treatment modality. This selection bias likely accounts for the discrepant incidence rates of vestibular schwannoma reported between the United States and other countries.

Differential Impact of Advanced Age on Clinical Outcomes After Vestibular Schwannoma Resection in the Very Elderly: Cohort Study

BACKGROUND

Vestibular schwannomas (VS) have a peak incidence in the sixth and seventh decades of life. Stereotactic radiosurgery is often the preferred treatment for VS among patients of advanced age. The fraction of elderly patients potentially requiring consideration for surgical treatment is anticipated to expand, mandating an update to management paradigms in this population.

OBJECTIVE

To describe our experience with surgical management of VS in patients aged 75 yr and older.

METHODS

Cohort study of all patients aged ≥75 yr with sporadic VS requiring surgical treatment at our institution between 1999 and 2020. Data included preoperative baseline characteristics and outcome data including extent of resection, facial nerve and hearing status, functional outcome, length of stay, and complications.

RESULTS

A total of 24 patients were included, spanning an age range of 75 to 90 yr. Average tumor size was 2.76 ± 1.04 cm, and average baseline Modified 5-item Frailty Index (mFI-5) score was 1.08 ± 0.93. Extent of resection was gross total in 5 (20.8%), near total in 3 (12.5%), and sub-total resection in the remaining 16 (66.7%). One patient died in the postoperative period because of an acute sub-dural hematoma. Favorable facial nerve function (HB1-2) was preserved in 12 patients (75%) between 75 and 79 yr and 2 patients (28.6%) aged ≥ 80 yr. No cerebrospinal fluid leak or surgical site infection was observed; 3 patients developed hydrocephalus requiring ventriculo-peritoneal shunt placement. Nine patients required out-of-home disposition; all patients eventually returned to independent living.

CONCLUSION

Microsurgical resection of VS can be safely undertaken in patients greater than 75 y/o but may carry an increased risk of poor facial function.

Treatment Analysis and Overall Survival Outcomes of Patients With Bilateral Vestibular Schwannoma

OBJECTIVES

To investigate the clinical presentation, treatment breakdown, and overall survival (OS) outcomes of patients with neurofibromatosis type 2 (NF2)-associated bilateral vestibular schwannoma (NVS).

METHODS

The 2004 to 2016 National Cancer Database was queried for patients with a diagnosis of VS. The "Laterality" code was used to stratify patients into sporadic unilateral vestibular schwannoma (UVS) and NVS.

RESULTS

Of the 33,839 patients with VS, 155 (0.46%) were coded for NVS with an average age and tumor size of 37.4 ± 20.5 years and 23.5 ± 18.2 mm. Patients underwent observation (45.3%), surgery (29.3%), and radiotherapy (20.0%), and had a 5.8% 5-year mortality rate. Compared with UVS, NVS was negatively associated with receiving surgery (40.2% versus 29.3%, p = 0.02) while watchful observation was more prevalent (30.1% versus 45.3%, p = 0.001). In NVS, undergoing surgery was associated with larger tumor size (34.5 ± 21.2 versus 17.8 ± 13.3 mm, p = 0.001) and shorter diagnosis-to-treatment time (49.1 ± 60.6 versus 87.0 ± 78.5 d, p = 0.02), radiotherapy was associated with older age (44.4 ± 18.9 versus 35.2 ± 20.6 yr, p = 0.02) and longer diagnosis-to-treatment time (85.9 ± 77.9 versus 53.9 ± 65.5 d, p = 0.04), and observation was associated with smaller tumor size (17.8 ± 15.9 versus 28.0 ± 19.2 mm, p = 0.01). Kaplan-Meier log-rank analysis demonstrated similar 10-year OS between NVS and UVS patients (p = 0.58) without factoring the earlier age of presentation. Furthermore, there were no temporal changes in presentation/management of NVS, and OS was not dependent on the received treatment (p = 0.30).

CONCLUSIONS

With younger age, larger tumors, and more conservative management, NVS's OS was not treatment-dependent and was similar to sporadic UVS, though the latter should not be interpreted as similar life expectancies due to the much earlier presentation.

Vestibular Schwannoma Surgery: Outcome and Complications in Lateral Decubitus Position versus Semi-sitting Position-A Personal Learning Curve in a Series of 544 Cases over 3 Decades

OBJECTIVE

To retrospectively evaluate influence of intraoperative positioning (semisitting vs. lateral decubitus) and surgeon's learning curve with regard to functional outcome of patients with vestibular schwannoma.

METHODS

This study included 544 patients (median age 57 years) and spanned 3 decades: 1991-1999 (n = 103), 2000-2009 (n = 210), and 2010-2019 (n = 231). Surgery was performed in the lateral decubitus position in 318 patients and the semisitting position in 163 patients. Large T3 and T4 tumors were present in 77% of patients.

RESULTS

Complete tumor removal was achieved in 94.3% of patients. A significant reduction in surgery duration and blood loss was observed over 3 decades for T3 (from 325 to 261 minutes, P < 0.001) and T4 (from 440 to 330 minutes, P < 0.001), but not for T1 and T2, tumors. The semisitting position diminished surgical time in T3 and T4 tumors by 1 more hour (P < 0.001). Over 3 decades, facial nerve outcome improved significantly from 59.8% House-Brackmann grade 1-2 in the first decade to 81.7% in the last decade (P < 0.001). Furthermore, hearing was preserved in 45.3%: 23.3% of patients in the first decade and 50.5% in the last decade (P = 0.03). However, neither facial nerve outcome nor hearing preservation significantly differed in patients operated on in the lateral decubitus versus the semisitting position. The most common complication was cerebrospinal fluid leak (6.1%) followed by hemorrhage (3.5%) and pulmonary embolism (2.2%).

CONCLUSIONS

Follow-up over 3 decades illustrates a learning curve with significantly improved results. While the semisitting position accelerates the procedure and is associated with reduced blood loss, it does not significantly influence functional outcome.

Epidemiology of vestibular schwannoma in the United States, 2004-2016

Background

Vestibular schwannomas (VS) are nonmalignant tumors of the eighth cranial nerve and are the most common nonmalignant nerve sheath tumor. This study provides the most comprehensive and current analysis of VS epidemiology in the United States.

Methods

Incidence data were obtained from the Central Brain Tumor Registry of the United States, from 2004 to 2016 for VS. Age-adjusted incidence rates (AAIRs), rate ratios (AAIRRs), and prevalence ratios (AAPRs) per 100 000 were analyzed by age, sex, race and ethnicity, and laterality. Additional analyses were performed to assess differences in treatment, laterality, and diagnostic confirmation.

Results

Incidence of VS was highest among adults (aged 65–74 years, AAIR: 3.18, 95% confidence interval [CI]: 3.15–3.25). However, there was a much higher distribution of bilateral tumors compared to unilateral in children aged 0–19 years (28.5% vs 1.0%, P < .001). VS incidence was highest among white non-Hispanics (AAIR:1.30, 95% CI: 1.29–1. 31) and lowest among black non-Hispanics. Incidence of radiographically confirmed VS increased from 2004 to 2016 (annual percent change: 1.64, 95% CI: 0.15–3.16, P = .03). For treatment, 40.1% received surgery, while only 23.7% received radiation. There were an estimated 44 762 prevalent cases of VS in 2016 (AAPR: 12.17, 95% CI: 12.06–12.29).

Conclusions

VS incidence and prevalence are highest among adults and white non-Hispanics. Bilateral VS was more common among children. There was an increase of radiographically confirmed VS over time. A higher proportion of patients received surgical treatment than radiotherapy. Population-based statistics provide healthcare professionals with vital information regarding disease burden and help improve patient care.

National Trends in Surgical Resection of Vestibular Schwannomas

OBJECTIVE

To characterize the national trend for surgical resection of vestibular schwannoma (VS) and to assess changes in demographics, length of stay (LOS), discharge patterns, and hospital charges.

STUDY DESIGN

Population-based inpatient registry analysis.

SETTING

National Inpatient Sample and SEER database (Surveillance, Epidemiology, and End Results).

PATIENTS AND METHODS

Retrospective review of the US National Inpatient Sample and the SEER database from 2001 to 2014 of all patients who underwent resection of VS.

RESULTS

A total of 24,380 VS resections were performed. While the annual incidence of VS remained stable at 1.38 per 100,000, surgical volume declined by 36.1%, from 2807 in 2001 to 1795 in 2014 (R² = 0.58). Total hospital charges more than doubled, from $52,475 in 2001 to $115,164 in 2014 ($4478 per year, R² = 0.96). While most procedures were performed at large-sized hospitals, this decreased from 89% in 2002 to 75.8% in 2014. Average LOS remained stable at 5.2 days during the study period. The number of discharges to a nursing facility increased from 113 (5.5%) in 2002 to 245 (13.6%) in 2014 (P = .0002).

CONCLUSION

VS resection has evolved in the United States. While the incidence remained stable, surgical volume decreased by 36%, and hospital charges more than doubled. More cases are being performed at smaller hospitals. Although LOS did not vary significantly, there is an increase in nonroutine discharges. These data may guide future research in resource utilization in neurotology.

The Clinical Implications of Spontaneous Hemorrhage in Vestibular Schwannomas

Background  Spontaneous hemorrhage into vestibular schwannomas (VSs) is rare and can render more rapid symptom onset and a seemingly poorer prognosis for an otherwise benign pathology. We describe our series of hemorrhagic VS (HVSs) and systematically reviewed the literature to better understand relevant clinical factors and outcomes. Methods  Retrospective case review series and systematic review of the literature using PRISMA guidelines. Results  Fifty-three patients with HVS met inclusion criteria. Compared with historical data for all VS, patients with HVS had relatively higher rates of perioperative mortality, significant preoperative facial weakness, and harbored relatively larger tumors. Regardless of the extent of resection (EOR), surgery for HVS resulted in significant improvement of facial weakness ( p  = 0.041), facial numbness ( p  < 0.001), vertigo ( p  < 0.001), and headache ( p  < 0.001). Patients with facial weakness tended to have larger tumors ( p  = 0.058) on average and demonstrated significant improvement after surgery, irrespective of EOR ( p  < 0.01). The use of blood-thinning medications did not affect patient health outcome. Histopathology of HVS samples showed an increased number of dilated/ectatic thin-walled vascular channels, reflective of potentially increased vascular permeability and hypervascularity. Conclusion  HVS may be an aggressive subgroup of VS, associated with a surprisingly high mortality rate. When features of HVS are identified on imaging, these patients should be treated expeditiously, especially given that facial nerve dysfunction, which is identified in more than half of patients with HVS, appears to be reversible. Overall, this study has significant implications in the management of VS, raising awareness of a small, but highly morbid subgroup.