Microvascular decompression for hemifacial spasm due to four offending vessels: a case report.

A 65-year-old woman presented with left facial involuntary movement and facial palsy for eight years. Brain magnetic resonance image (MRI) and magnetic resonance angiography (MRA) revealed multiple vascular compression of facial nerve root exit zone (REZ). Standard retromastoid suboccipital craniectomy and arachnoid dissection were performed. Right vertebral artery (VA), left VA, left anterior inferior cerebellar artery (AICA), and left posterior inferior cerebellar artery (PICA) compressed the facial nerve in that order. The offending vessels were dissected away from the facial nerve and transposed sequentially. Teflon was interposed between the arteries and the nerve. Electrophysiological monitoring showed disappearance of the abnormal hemifacial spasm response during the operation. The offending vessels were right VA, left VA, left AICA, and left PICA. Postoperatively, the patient's involuntary movement was completely resolved. We report a rare case of hemifacial spasm caused by four offending vessels that was treated by microvascular decompression (MVD) with wide arachnoid dissection.