Identification of the facial nerve in the operation of vestibular schwannoma using diffusion tensor tractography

Abstract

Objective To explore the method and accuracy of diffuse tensor tractography of facial nerve in the operation of vestibular schwannoma (VS). Methods We prospectively collected data of 19 patients with vestibular schwannoma who underwent diffuse tensor tractography (DTT) to identify the location and running course of the facial nerve. The seed of ROI was set in the internal auditory meatus and brainstem. The value of FA was set to 0.15. The fibers were considered to represent the facial nerve which connected the internal auditory meatus and brainstem. We intraoperatively evaluated the consistency between tractography and surgerical findings using navigation system、intraoperative facial nerve monitoring and visual inspections byneurosurgeons. Facial nerve function was evaluated at different time postoperatively according to the House-Brackmann (H-B) facial nerve grading system. Results The facial nerve of all patients were preserved, most of which were displaced anteroinferiorly.We successfully reconstructed the fibers that represent the facial nerve in 18 cases. In 16 of 18 cases, location of the tractography was entirely consistent with intraoperative findings. In the other two cases of vestibular schwannoma with cyst, the tractography image did not match intraoperative findings. No patient had severe facial paralysis 6 months post surgery. Seventeen patients were graded Ⅰ-Ⅲ according to H-B grade 6 months after the operation. Conclusions DTT with intraoperative neuronavigation seems to be a useful tool to identifyfacial nerve in the VS resection and could helpfacilitate facial nerve preservation. Key words: Neuroma, acoustic; Facial nerve; Diffusion tensor tractography; Neurosur-gical procedures