Magnetic Resonance Imaging Study on Patients With Hemifacial Spasm

Up to now, multiplanar reconstruction (MPR) has been widely used to detect the neurovascular compressions (NVC) on the patients with hemifacial spasm (HFS). However, due to lack of stereoscopic vision, this traditional method sometimes can not meet the requirement on identifying the details of NVC, especially when the aberrant vessels turn out to be veins not arteries. The three dimensional analytic techniques, such as curved planar reconstruction (CPR) and magnetic resonance virtual endoscopy (MRVE), may be helpful to improve the sensitivity and specificity on the demonstration of NVC with stereo and dynamic views, so as to assist the design of the surgical plan.

Furthermore, the frequent finding of NVC on MRI studies of asymptomatic patients incited the creation of several strict criteria for the imaging diagnosis of NVC: the vessel must cross perpendicular to the long axis of the nerve, the nerve must be deviated or indented at the root entry zoon (REZ) by the vessel. Alternatively, morphological measurement of the nerve may correlate with the severity of facial spasm due to atrophy of the nerve in most cases of HFS, and is likely secondary to the micro-structural abnormalities, such as axonal loss, demyelination, collagen deposition, etc. In this study, cross-sectional area (CSA) and volume (V) of the cisternal facial nerve will be assessed to determine whether it can be a useful biomarker for predicting the degree of HFS.