Preoperative detection of the facial nerve by high-field magnetic resonance imaging in patients with vestibular schwannoma.

INTRODUCTION: Preoperative knowledge of the position of the facial nerve relative to a vestibular schwannoma would be very helpful to decide for an adapted therapeutic strategy. The aim of this study is to assess the feasibility of predicting the course of the facial nerve in vestibular schwannoma patients using 3 T high-resolution magnetic resonance cisternography in a large consecutive series.
METHODS: The study was prospectively conducted in 82 patients operated for vestibular schwannoma. All patients underwent preoperative gadolinium (Gd)-enhanced, balanced fast-field echo (bFFE) imaging. The course of the facial nerve was estimated preoperatively and the results were verified with the intraoperative findings.
RESULTS: The facial nerve could be identified by preoperative MRI in 38 cases (46.3 %). In 28 cases (34.1 % of total patients, 73.7 % of identified patients), the course of the MRI-identified facial nerve was completely congruent with the intraoperative findings. In the patient group with MRI-identified facial nerves, tumor size was smaller and the number of solid type was larger. There were 23 cases where the tumor was solid and smaller than 20 mm. Nineteen (82.6 %) of those cases could estimate the facial nerve preoperatively and 16 cases (69.6 %) have complete congruency.
CONCLUSION: Gd-enhanced bFFE at 3 T is capable of demonstrating the location of the facial nerve in vestibular schwannoma patients prior to surgery. Slices that were perpendicular to the internal auditory canal were useful besides axial images. In small, solid-type tumors, facial nerve was more easily identified than other types of tumors.