[Hemifacial spasm due to a compression of the facial nerve by a fusiform aneurysm of the vertebral artery: case report].

We report a rare case of symptomatic hemifacial spasm caused by a fusiform vertebral artery aneurysm and by a branch of the anterior inferior cerebellar artery compressing the facial nerve at the root exit zone (REZ). A 71-year-old female had an 11-year history of right hemifacial spasm. MRIs demonstrated an aneurysm compressing the facial nerve at the REZ. Angiography disclosed a fusiform aneurysm of the right vertebral artery at the origin of the posterior inferior cerebellar artery. After the vertebral aneurysm was clipped distal to the origin of the posterior inferior cerebellar artery, a branch of the right anterior inferior cerebellar artery was also observed compressing the facial nerve at the REZ. Both the clipped aneurysm and the branch of the anterior inferior cerebellar artery were mobilized away from the REZ of the facial nerve, and a prosthesis was inserted between the branch of the anterior inferior cerebellar artery and the brain stem to keep the aneurysm away from its original position. The patient's hemifacial spasm immediately disappeared without any neurological deficits just after the surgery. Hemifacial spasm, especially caused by an aneurysm, is quite rare. In a review of the literature, we found only 4 cases of symptomatic hemifacial spasm caused by an aneurysm of the vertebral artery. This case is the first reported case of hemifacial spasm caused by both a fusiform vertebral artery aneurysm and a branch of the anterior inferior cerebellar artery compressing the facial nerve at the REZ.