Perforating branches from oVending arteries in hemifacial spasm: anatomical correlation with vertebrobasilar configuration

Objective—In microvascular decompression for hemifacial spasm, the perforating branches around the facial nerve root exit zone occasionally complicate facial nerve decompression. In this context, the vertebrobasilar configuration was retrospectively correlated with the perforating branches. Methods—Based on vertebral angiography, magnetic resonance angiography, and three dimensional computed tomographic angiography, 69 patients were divided into three groups, according to the anatomy of the vertebrobasilar system. In patients with the type I configuration, the vertebral artery on the aVected side was dominant and had a sigmoidal course. The type II patients had the basilar artery curving mainly towards the aVected side. The type III patients showed the basilar artery either running straight or curving toward the unaVected side. The relation of the anatomical configuration of these vessels with the perforating branches around the facial nerve exit zone was investigated. Results—The posterior inferior cerebellar artery in type I patients (n=33) and the anterior inferior cerebellar artery in type II (n=5) and type III (n=31) patients were the most common oVending arteries. More than half of the type I patients (n=20) showed no perforating branches around the facial nerve exit zone. However, the type II (n=3) and III patients (n=23) often showed one or more perforating branches around that region. Conclusions—The configuration of the vertebrobasilar system has a significant correlation with the presence of perforating branches near the site of microvascular decompression. These perforating vessels are often responsible for the diYculty encountered in mobilising the offending artery during the procedure. (J Neurol Neurosurg Psychiatry 1999;67:73–77)