Predictive Factors of Hearing Preservation After Surgical Resection of Small Vestibular Schwannomas

Objective: To identify factors predictive of hearing preservation in patients undergoing resection of small vestibular schwannoma. Study Design: A retrospective chart review. Setting: Tertiary care medical center. Patients: Forty patients with serviceable hearing preoperatively who underwent a potentially hearing sparing procedure for resection of small vestibular schwannoma (extending 1 cm or less into the cerebellopontine angle). Intervention: Resection of vestibular schwannoma via the middle fossa (subtemporal) or retrosigmoid (suboccipital) approach. Main Outcome Measures: Hearing was assessed preoperatively and postoperatively and classified according to the criteria of the American Academy of Otolaryngology-Head and Neck Surgery. Postoperatively, audiograms were unavailable for 5 patients without subjective hearing in the affected ear. These patients are included in the group without hearing preservation. Potential predictive factors of hearing preservation included patient demographics, tumor characteristics, audiometric data, and intraoperative brainstem auditory evoked response (BAER) monitoring. Results: Serviceable hearing was preserved in 23 patients (57.5%). Patient age, sex, preoperative hearing status, tumor size, laterality, extent of internal auditory canal involvement, surgical approach, wave V latency, and wave V amplitude were not predictive of hearing preservation. The presence of wave V on intraoperative BAER was the only significant predictor of hearing preservation (p < 0.019). Serviceable hearing was preserved in 14 patients (77.8%) with wave V present. Of note, serviceable hearing also was preserved in 9 patients (40.9%) without a measurable wave V. Conclusion: No preoperative factor was predictive of hearing preservation. The presence of wave V on intraoperative BAER is a significant predictor of hearing preservation. Additionally, absence of wave V does not preclude preservation of serviceable hearing.