Culprit vascular patterns and surgical outcomes of hemifacial spasm caused by an AICA segment passing between cranial nerve VII and VIII: A series of 25 cases.

OBJECTIVE: To report the vascular anatomic characteristics and surgical outcomes of hemifacial spasm (HFS) caused by an anterior inferior cerebellar artery (AICA) segment passing between cranial nerve VII (CN VII) and cranial nerve VIII (CN VIII).

PATIENTS AND METHODS: This case series study retrospectively reviewed records of 1040 consecutive patients treated with MVD for HFS in our hospital in 10 years. 25 patients had the culprit vessel recorded as an AICA segment passing between CN VII and CN VIII. Vascular anatomic characteristics were reviewed from intraoperative microscopic videos. The clinical outcomes were followed up at 3-month and 1-year time points.

RESULTS: The culprit AICA segments feature 3 discrete anatomic patterns. The patterns denoted as pattern A, B, and C were identified in 19(76%), 3(12%), and 3 (12%) of the 25 patients respectively. Postoperative spasm relief were achieved in 19(76%), 22(88%), and 23 (92%) of the patients at immediately after surgery, 3-month, and 1-year follow-up respectively. 3(12%) of them have permanent postoperative cranial nerve deficits, including one patient with hearing loss and 2 patients with vocal cord palsy.

CONCLUSIONS: Though an AICA segment passing between CN VII and CN VIII is common, very rarely it was deemed the culprit for HFS in our patients. We used fREZ centered definition and operation. We found the culprit AICA segments feature 3 discrete anatomic patterns. We observed good spasm relief outcome and relatively fewer complications with CN VII and CN VIII. Identifying the 3 anatomic patterns may help with a smooth decision-making when vascular compression by an AICA segment passing between CN VII and CN VIII is suspected.