Preoperative Identification of the Facial Nerve in Patients with Large CPA Tumors Using Advanced MRI Tractographic Techniques

In patients with large cerebellopontine angle (CPA) tumors and intact facial nerve function preoperatively, the most common and potentially devastating complication is loss of facial nerve function. This can result in dysphagia, dysphonia, keratitis, and can be quite disfiguring. Intraoperatively, a great amount of time is spent to identify and preserve the facial nerve. This can be quite difficult as the nerve can be displaced in any number of directions, which may not be evident on routine standard preoperative imaging. Preoperative identification of the facial nerve can be done in a rapid noninvasive manner using advanced diffusion tensor imaging in a reliable manner. Previous studies have undertaken mapping of the cranial nerves using tractography, but none have taken advantage of the newer methods of tractography, which function more reliably in areas of tissue non-uniformity (such as the tumor-brain interface and the CPA where brain/CSF/mastoid air cells are present).