Application of 3D MR Neurogram for Intraparotid Facial Nerves Evaluation

Parotid neoplasm consists of a wide range of benign and malignant lesions, and parotidectomy has been the mainstay for management of these neoplasms. Within the parotid gland there are branches of the intra-parotid facial nerves, which are tiny in calibre and are prone to injury to injury during operation. It has been reported in recent retrospective view that the incidence of temporary and permanent facial nerve injury were 9.2% and 5.2% respectively, the risk of which increased with old age, malignant tumour and revision surgery. Traditional the incidental of facial nerve injury is reduced by intra-operative facial nerve monitoring and surgical magnification, while imaging has limited role in aiding this purpose. However with advancement in MRI technique high resolution three-dimensional sequences (i.e. neurogram sequences) are available for better visualization of branches of facial nerves. The investigators would therefore aim to demonstrate additional efficacy of these techniques and also to compare with conventional 3D post-contrast anatomical imaging studies in the localization and visualization of the facial nerve branches in patients with tumour. With better pre-operative imaging, the investigators hope to reduce the chance of facial nerve injury in these patients.