A Surgical Case of Hemifacial Spasm Due to Tentorial Meningioma -peritorcular type- in Posterior Fossa

Abstract

Hemifacial spasm is commonly caused by compression of the facial nerve due to overlying vessels, and also due to various types of tumor or aneurysm, and other factors. It occurs, although rarely, as a secondary effect of cerebellar or brainstem shift resulting from a tumor. In such a case, the presence of a large tumor often leads to additional neurological deficits. We present a case of hemifacial spasm caused by a peritorcular type of large tentorial meningioma in the posterior fossa. A 68-year-old woman presented with right facial numbness 4 months ago and right hemifacial spasm 2 weeks ago. Upon visiting our hospital, she displayed no neurological deficits other than the right hemifacial spasm. MRI revealed a peritorcular type of large tentorial meningioma in the posterior fossa with perifocal edema. The right cerebellopontine cistern was narrowed, and the cerebellar tonsil was herniated. The right facial nerve ran adjacent to the anterior inferior cerebellar artery (AICA). Angiography showed that only the left posterior meningeal artery (PMA) flowed to the tumor. The loop of the right AICA extended into the right cerebellopontine cistern. After embolization of the PMA, the tumor was surgically removed, leading to an improvement in the patient's hemifacial spasm. Postoperative MRI confirmed complete removal of the tentorial meningioma without any contact with the right facial nerve. The hemifacial spasm was caused secondarily by the cerebellar or brainstem shift due to the large tentorial meningioma in the posterior fossa. This large tumor had not produced any other neurological deficits before the hemifacial spasm appeared. We report this case because it is extremely rare.