Kelly, Patrick D.

Objective: To survey critical areas of variation in published research methodology with a primary aim of highlighting fundamental aspects that contribute to ongoing controversy surrounding optimal management of patients with sporadic vestibular schwannoma. Interventions: Observation, stereotactic radiosurgery (SRS), and microsurgery. Main outcome measures: Variation in reported outcomes surrounding facial function, useful hearing, tumor pseudoprogression following SRS, and tumor growth/natural history. Results: Published research defines “good” post-treatment facial function as anything ranging from HB I, ≤HB II, to ≤HB III. While most studies define serviceable hearing as AAO Class A/B, others include Class C in published post-treatment hearing preservation results; meanwhile, patients report their greatest decrement in quality-of-life at a threshold around 75% in word recognition scores. Heterogeneously defined as post-SRS tumor growth 6 months after SRS to 5 years after SRS, the reported incidence of tumor pseudoprogression ranges from 7% to 77% within the published literature. Natural history studies that employ linear tumor measurements consistently suggest most tumors do not grow following diagnosis, whereas volumetric studies of natural history suggest the exact opposite is true. Limited follow-up and absent time-to-event analyses undermine many outcomes surrounding vestibular schwannoma that are inherently time-dependent. Conclusions: Disparate definitions used in vestibular schwannoma research beget variable outcome reporting and confuse interpretation of optimal management, particularly for the increasingly common scenario of a small tumor in a minimally symptomatic patient. Progress towards optimizing management requires re-evaluation and alignment on key outcome measures to improve consistency in reporting with renewed emphasis on clinically significant, patient-driven outcomes that often exceed the thresholds most frequently studied to date.

Objective: To evaluate the ethical implications, clinical benefits, and challenges associated with centralizing the surgical care of vestibular schwannoma (VS) care. Databases reviewed: PubMed, Embase, CINAHL, Web of Science, Cochrane, Scopus. Methods: A scoping review was conducted per the PRISMA-ScR (Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews) guidelines. A comprehensive search of 6 electronic databases yielded 1,231 articles using keywords related to vestibular schwannoma, centralization of care, centers of excellence, and ethical considerations. After removing duplicates (n=344) and screening titles and abstracts (n=887), 17 full-text articles were reviewed. Two additional articles were identified through manual screening. A total of 15 studies were included in the final analysis. Results: Hospitals were categorized by surgical case volume (high, medium, low) to compare patient demographics and clinical outcomes. Patients seen at low-volume hospitals (LVHs) were generally older and more racially diverse, and more likely to have public insurance (Medicare or Medicaid), whereas high-volume hospitals (HVHs) served a younger, predominantly White, and privately insured population. Of the 14 studies evaluating outcomes, 12 demonstrated a positive association between higher surgical volume and improved outcomes, including reduced complications, lower mortality, shorter length of stay, and decreased hospitalization costs. High-volume hospitals also had significantly higher rates of routine discharge. Conclusion: Centralization of vestibular schwannoma care to high-volume centers is associated with improved clinical outcomes and reduced health care costs. However, these benefits must be carefully weighed against potential ethical concerns, including disparities in access related to socioeconomic status, insurance coverage, and geographic location.

ABSTRACTSurgical biopsy of brainstem tumors carries a risk of neurological injury. We performed magnetic resonance spectroscopy (MRS) of 2‐hydroxyglutarate (2HG) and glycine in patients with brainstem tumors to assess the feasibility of detecting and quantifying 2HG in the brainstem to obviate the need for a diagnostic biopsy and to establish the clinical significance of glycine MRS in brainstem tumors in vivo. Twenty adult patients with radiographically identified presumed brainstem gliomas were prospectively enrolled in the study. Proton MRS was obtained at 3T with a protocol tailored for detection of 2HG and glycine (TE 97‐ms PRESS). Spectra were fit using LCModel software and in‐house basis signals of metabolites and lipids. The metabolite concentrations were quantified with reference to water and examined with respect to clinical outcomes, including postgadolinium MRI and overall survival time. MRS data from 19 patients were included in subsequent analysis, excluding suboptimal data from one patient. Tumors with elevated 2HG (> 1.9 mM, N = 8) and undetectable 2HG (< 0.3 mM, N = 11) were clearly distinguishable. Tumors with elevated glycine (> 1.5 mM, N = 4) showed rapid progression. Kaplan–Meier survival analyses with metabolite measures demonstrated that tumors with 2HG higher than 1.0 mM were significantly associated with a favorable prognosis (p = 0.01). In contrast, tumors with glycine higher than 2.5 mM showed a strong association with poor survival (p = 0.0005). The data confirm detection of 2HG in brainstem tumors at a concentration that is consistent with an IDH mutation and expected good prognosis, whereas elevated glycine in brainstem tumors portends rapid tumor progression and a worse prognosis.