2026 Poster Presentations
P502: TUMOR NERVE OF ORIGIN AND HEARING PRESERVATION OUTCOMES FOR PATIENTS WITH SMALL VESTIBULAR SCHWANNOMAS UNDERGOING MIDDLE FOSSA CRANIOTOMY
Pawina Jiramongkolchai1; Tamara Wahlin2; Alexandra Vacaru2; Marc Schwartz2; Rick Friedman2; 1Washington University in St. Louis; 2University of California, San Diego
Objective: To evaluate hearing preservation (HP) outcomes based on tumor nerve origin for patients with small sporadic vestibular schwannomas (VS) undergoing microsurgical resection using the middle cranial fossa (MCF) approach.
Methods: Retrospective single-institution study of individuals 18 years or older with small sporadic VS (≤ 15 mm) undergoing microsurgical resection between November 2017 to December 2023. The primary outcome measure was HP, defined as word recognition score ≥ 50%.
Results: Of the 189 consecutive patients who underwent surgery, 164 (89%) of patients had intraoperative identification of tumor nerve of origin. Of those 164 patients, 88 (54%) patients had tumors originating from the inferior vestibular nerve (IVN), and 76 (46%) patients had tumors originating from the superior vestibular nerve (SVN). The mean size (SD) of SVN tumors was 8.7 (3.8 mm) compared to 9.8 (3.5) mm for IVN tumors; however, this difference in size was not statistically significant (p=0.06). Hearing was preserved in 83% of patients with SVN tumors compared to 49% of patients with IVN tumors. For patients with SVN tumors in whom hearing was preserved, the mean (SD) PTA and WRS scores were 26.6 (13.4) and 93.7 (9.3), respectively. For patients with IVN tumors with hearing preservation, the mean (SD) PTA and WRS scores were 25.9 (13.8) and 91.3 (11.3), respectively. When stratified by size, the rate of hearing preservation was highest (91%) for tumors of SVN origin ≤5 mm in size. On multivariate analysis, patients with SVN tumors ≤5 mm in size had an 8-fold increase in hearing preservation compared to patients with SVN tumors larger than 10 mm in size. Tumors of SVN origin were also associated with statistically significant reduction in operating time compared to tumors of IVN origin (mean difference 15.1 minutes, 95% CI 1.91 to 28.26). There was no significant difference in facial nerve function with HB 1/2 in 70 (92%) patients with SVN tumors and 83 (94%) patients with IVN tumors, respectively (p=0.06).
Conclusion: Patients with small SVN tumors have a significantly higher likelihood of hearing preservation as well as shorter operative time compared to IVN tumors with the MCF approach, suggesting that in appropriate candidates, early surgical intervention may be beneficial.