Vascular loop compressing facial nerve in hemifacial spasm: demonstrated by 3D-phase contrast magnetic resonance angiography in 101 patients.

Background: Vascular compression of the facial nerve is deemed to be the common cause of hemifacial spasm producing emphatic transmission. Although facial nucleus supersensitivity is more accepted as the main cause of hemifacial spasm.

Purpose: To determine the vascular loop compression of the facial nerve in patients with hemifacial spasm by 3D-phase contrast (PC) magnatic resonance imaging (MRI).

Material And Method: A retrospective study of 101 patients with hemifacial spasm who went MRI and magnetic resonance angiography (MRA) of the brain was done. The magnitude images of the 3D-PC MRA was evaluated in axial and oblique coronal reconstruction planes blindly from symptomatic information.

Results: Among 101 patients, 53 affected the left side, 48 patients were right sided and none had bilateral involvement. Vascular loop compressing on the symptomatic side was found in 61 (60.4%) patients. For the asymptomatic side, there were 14 (13.86%) with vascular loop contact. Five patients (4.9%) had bilateral vascular compression. The proportion of vascular contact of the symptomatic and asymptomatic side was significantly different (with p < 0.001). The offending vessels were vertebral artery (32, 52.46%), posterior inferior cerebellar artery (7, 6.93%), anterior inferior cerebellar artery (6, 5.94%) and artery of uncertain origin (16, 26.23%).

Conclusion: The study implied the usefulness of this simple technique to demonstrate the neurovascular contact of the facial nerve.