NIMG-09. PREDICTION OF FACIAL NERVE POSITION IN LARGE VESTIBULAR SCHWANNOMA USING DIFFUSION TENSOR IMAGING TRACTOGRAPHY AND ITS INTRA-OPERATIVE CORRELATION

Abstract

Resection of large vestibular schwannomas (VS), can be associated with postoperative facial nerve injury. Diffusion-based tractography has emerged as a powerful tool for three- dimensional imaging and reconstruction of white matter fibers; however, tractography of the cranial nerves has not been well studied. In this prospective study, we aim to predict the position of facial nerve in large vestibular schwannomas (> 3cm) using Diffusion Tensor Imaging (DTI) tractography and correlate it with intra-operative finding of the position of facial nerve. Twenty patients with large vestibular schwannomas (>3cm) undergoing surgery were subjected to preoperative DTI imaging to predict the position of facial nerve in relation to the tumor. The surgeon was blinded to the results of the preoperative DTI tractography. A comparative analysis was then made during operation. The location of the facial nerve in relation to the tumor was recorded during surgery using facial nerve stimulator. Out of the twenty patients who underwent DTI tractography, it was not possible to preoperatively identify facial nerve in one patient. In another patient, although DTI tractography predicted the position of facial nerve, it was not identified intraoperatively. Out of the remaining 18 patients, DTI tractography predicted facial nerve position was in sync with intraoperative facial nerve position in 16 patients (89 % concordance). It was discordant in two patients (11%), but this was not found to be statistically significant (p value -0.3679). This study validates the reliability of facial nerve diffusion tensor (DT) imaging–based fiber tracking for prediction of facial nerve position in patients with large vestibular schwannomas. The reliable preoperative visualization of facial nerve location in relation to VS would allow surgeons to plan tumor removal accordingly and may increase the safety of surgery.