Hemifacial spasms triggered by compression of tortuous anterior inferior cerebellar artery loop on the facial nerve in the internal auditory canal: A case report.

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Hemifacial spasm (HFS) is triggered by neurovascular compression mostly at the root entry/exit zone of the facial nerve. HFS with the responsible blood vessel located in the internal auditory canal (IAC) is a very rare occurrence. In our case, the HFS was triggered by compression of the anterior inferior cerebellar artery (AICA) loop on the facial nerve in the IAC. A 27-year-old female presented with a 5-year history of right-sided facial twitching with no obvious course. The frequency and severity of the attacks increases when the patient was anxious or agitated which severely affected her quality of life. Preoperative 3D-TOF magnetic resonance imaging (MRI) evaluation of cranial nerves showed that the right AICA loop had a tortuous course within the IAC and compressed the facial nerve. Microvascular decompression (MVD) surgery was carried out to separate the tortuous AICA loop and facial nerve in the IAC using a Teflon pad. The abnormal muscle response disappeared intraoperatively and 2-years follow-up revealed no recurrence of her symptomatology. She is current well and go about her daily activities with no neurological deficits. The attachment of the facial nerve to the tortuous AICA loop coupled with the pulsatile impulse of tortuous AICA loop may have resulted in the entrapment and compression of the CN VII in the IAC.