An Evidence-Based Vestibular Schwannoma Surgical Outcome Grading Scale for Large-to-Giant Vestibular Schwannomas

Abstract Objectives: The objective of this study was to determine the relationship between facial nerve function and extent of resection (EOR) as outcomes in the surgical management of large vestibular schwannoma (VS) (≥ 2.5 cm maximal) and evaluate use of a new grading system that incorporates both outcomes.Methods: We conducted a systematic review of the electronic databases using different MeSH terms from 1990 to 2021. 5,623 patients from 56 studies were found appropriate for inclusion in the study. Surgical approach was reported in 5,144 patients, including translabyrinthine approach (TL) in 43.3% (n=2,225), retrosigmoid (RS) approach in 56.3% (n=2,899), retrolabyrinthine (RL) approach in 0.3% (n=16), and extended translabyrinthine (EX) approach in 0.1% (n=4). The proposed VS Grading System defines outcomes of gross total resection (GTR), near total resection (NTR) and subtotal resection (STR) with good facial nerve function [House-Brackmann (HB) Grade I-II] as Classes A, B and C respectively. Those with poor facial nerve outcome (HB III-VI) are graded as Classes D, E and F, respectively. Results:. As expected, patients with STR had a higher likelihood of better facial nerve outcomes (HB I-II) compared to NTR [Odds Ratio (OR): 7.30, 95%CI: 2.45-12.1, p=0.004] and GTR (OR: 9.61, 95%CI: 3.61-15.6, p=0.002), while NTR had better facial nerve outcome than GTR (OR: 1.5, 95%CI: 1.14-4.6, p<0.0001). A Class A result, representing the best possible outcome, was obtained in 55.8% of TL vs. 49.4% undergoing RS approach. Conclusion: Complete surgical resection with preservation of facial nerve function is the gold standard for large VS.