Hemifacial spasm associated with posterior inferior cerebellar artery aneurysm: illustrative case

BACKGROUND: Hemifacial spasms (HFSs) complicated by intracranial aneurysms are rare. Recently, endovascular treatment has been widely used for this disease entity and can allow the cessation of intracranial aneurysm arterial pulsation, leading to recovery from the HFS. Here, the authors present a case of HFS associated with an ipsilateral posterior inferior cerebellar artery (PICA) aneurysm successfully treated with open surgery. OBSERVATIONS: A 68-year-old woman was annually followed-up for an incidentally found right PICA aneurysm. Over 3 years, the PICA aneurysm gradually increased in size, which eventually led to right HFS. An axial fast spoiled gradient-recalled echo sequence with gadolinium enhancement showed the PICA aneurysm compressing the root exit zone (REZ), which was attributed as the cause of the HFS. However, a fusion image of the three-dimensional T1-weighted fast spin-echo sequence and magnetic resonance angiogram clearly showed a direct contact between the REZ and the anterior inferior cerebellar artery (AICA), which was located at the apex of the PICA aneurysm. Intraoperatively, the AICA was found compressing the REZ; hence, microvascular decompression with aneurysmal clipping was performed. The HFS resolved immediately after surgery. LESSONS: In cases of HFS associated with an ipsilateral intracranial aneurysm, a detailed neuroradiological assessment to identify the responsible lesion is important to use the most optimal treatment of choice.