Vascular compression of the facial nerve is a well recognized cause of hemifacial spasm (HFS). In this study, we described the magnetic resonance imaging (MRI) and three-dimensional magnetic resonance angiography (MRA) techniques used and findings in 34 patients with hemifacial spasm. A vascular abnormality, defined as a vessel seen in close proximity, touching or compressing the facial nerve, was identified in 22 of the 25 patients (88%) who had both MRI and MRA studies. Vessels identified were anterior inferior cerebellar artery (59.2%), posterior inferior cerebellar artery (13.6%), vertebral artery (18.2%) and basilar artery (4.5%). All vascular abnormalities were ipsilateral to the side of the HFS. Only 3 of the 12 controls (25%) had a vascular abnormality in both MRI and MRA studies. One of the 9 HFS patients (11.1%) who had MRI only had an ipsilateral vascular abnormality. There is a role for combined MRI and MRA studies in the non-invasive evaluation of patients with HFS.
Hemifacial spasm (HFS), characterized by intermittent twitching of muscles supplied by one facial nerve is commonly due to compression of the facial nerve by blood vessel(s) adjacent to its root exit zone (REZ). The facial nerve REZ refers to the part where facial nerve exits from the pons.
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