Hemifacial spasm resulting from facial nerve compression near the internal acoustic meatus--case report.

A 61-year-old female presented with a rare case of hemifacial spasm (HFS) resulting from facial nerve compression near the internal acoustic meatus. She underwent a first surgery for microvascular decompression at the root entry zone of the facial nerve, but this did not achieve resolution of the HFS. During the second surgery, the meatal loop of the anterior inferior cerebellar artery (AICA) was found to be the offending artery near the internal acoustic meatus. When the AICA was dissected and separated from the facial nerve, abnormal muscle responses of the mentalis muscle due to electrical stimulation of the zygomatic branch of the facial nerve were abolished. Following surgery the patient was completely free of the HFS.