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

Objective-In microvascular decompression for hemifacial spasm, the perforat ing branches around the facial nerve root exit zone occasionally complicate facial nerve decompression. In this context, the vertebrobasilar configura tion was retrospectively correlated with the perforating branches. Methods-Based on vertebral angiography, magnetic resonance angiography, and three dimensional computed tomographic angiography, 69 patients were divid ed into three groups, according to the anatomy of the vertebrobasilar syste m. In patients with the type I configuration, the vertebral artery on the a ffected side was dominant and had a sigmoidal course. The type If patients had the basilar artery curving mainly towards the affected side. The type I II patients showed the basilar artery either running straight or curving to ward the unaffected side. The relation of the anatomical configuration of t hese vessels with the perforating branches around the facial nerve exit zon e 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 offending arteries. More than half of t he 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 s howed one or more perforating branches around that region. Conclusions-The configuration of the vertebrobasilar system has a significa nt correlation with the presence of perforating branches near the site of m icrovascular decompression. These perforating vessels are often responsible for the difficulty encountered in mobilising the offending artery during t he procedure.