MR imaging of vascular compression in hemifacial spasm

Hemifacial spasm is related to vascular compression of the root entry zone of the facial nerve at the brainstem by elongated tortuous vessels of the vertebrobasilar arterial system. In this study, we performed MR imaging in 16 patients with hemifacial spasm and investigated the vascular structures in bilateral-cerebellopontine angles and the relationship of each vessel to the root entry zone of the facial nerve. MR examination was performed with a 0.5 tesla MRI system, and MR angiography (3D time-of-flight) was obtained. Of 15 patients in whom both the nerve and vessels were clearly visible and could be observed to contact each other at the root entry zone, in 11 the tortuous artery could be identified by name. In only 1 patient was the contact between the nerve and vessel indeterminate, due to nonvisualization of the vessel around the facial nerve at its root entry zone. These findings suggest that MRI is a useful screening method in the preoperative assessment of hemifacial spasm.