Facial Nerve Length Influence on Vestibular Schwannoma Microsurgery Outcomes

OBJECTIVE: Facial nerve (FN) function preservation is the primary goal during vestibular schwannoma (VS) resection. Many factors are linked to postoperative FN outcomes. In the present study, we evaluated the association between FN length and VS surgical outcomes. METHODS: We included 70 consecutive patients who had undergone VS microsurgery between October 2019 and November 2020. The clinical data were prospectively obtained from the patients. The relative FN (rFN) length was obtained by subtracting the contralateral FN length from the ipsilateral FN length as measured using DSI Studio software (available at: http://dsi-studio.labsolver. org/). RESULTS: The postoperative FN function was House-Brackmann grade I in 47 of the 70 patients (67.1%), grade II in 10 (14.3%), and grade III in 13 (18.6%). Gross total resection (GTR) was performed in 61 patients (87.1%). A residual tumor was retained to preserve FN function in 9 of the 70 patients (12.9%), and rFN length was measured (mean diameter, 20.8 mm; range, 2.5-51.5]). On multivariate analysis, the rFN length was significantly associated with the extent of tumor resection. The receiver operating characteristic curve indicated that the cutoff value for rFN length to predict for intraoperative near total resection versus GTR was 36.6 mm, with a specificity and sensitivity of 93.4% and 88.9%, respectively. CONCLUSIONS: The rFN length is important for predicting surgical outcomes. An rFN length >36.6 mm might indicate difficulty in achieving GTR with preservation of FN function. Therefore, the rFN length could become an objective indicator for neurosurgeons to predict the difficulty of GTR to preserve FN function.