Coil Embolization of VA-PICA Aneurysm Presenting with Hemifacial Spasm with Assistance of Abnormal Muscle Response Monitoring

OBJECTIVE: We report a rare case of symptomatic vertebral and posterior inferior cerebellar arteries (VA-PICA) aneurysm-caused ipsilateral hemifacial spasm (HFS) for which coil embolization of the aneurysm with the assistance of abnormal muscle response (AMR) monitoring was effective. CASE PRESENTATION: A 62-year-old woman presented with left HFS. Magnetic resonance imaging showed a saccular aneurysm of the left VA-PICA which compressed the seventh cranial nerve at its root exit zone (REZ). Stent-assisted coil embolization resulted in intraoperative disappearance of AMR in the intraoperative electrophysiological study and HFS was relieved temporally. One month after endovascular surgery, HFS slightly occurred again with the re-appearance of the AMR, although there was no recurrence of aneurysm. Thereafter, the frequency of her HFS markedly decreased to once per several days 1 year after the coiling. CONCLUSION: Although complete disappearance of symptoms was not obtained, it was suggested that coil embolization is one of the therapeutic options for HFS which is caused by aneurysmal compression of REZ and intraoperative AMR is useful for identification of responsible lesions and determination of therapeutic effects.