Hemifacial spasm due to tumor, aneurysm, or arteriovenous malformation.

The authors report eight cases of so-called symptomatic hemifacial spasm. They had gross pathological lesions such as a tumor (one epidermoid, one neurinoma, and two meningiomas), vascular malformation (one medullary venous malformation and two arteriovenous malformations), and aneurysm. In all four cases with a tumor, no artery compressed the facial nerve at the root exit zone. In three of the four cases, the hemifacial spasm disappeared after removal of the tumor in contact with the facial nerve. Compression or encasement of the facial nerve by the tumor was the pathogenesis of the hemifacial spasm in these three cases. The remaining case with tumor (tentorial meningioma) did not have a mass or vessel that directly compressed the facial nerve at the root exit zone. However, the hemifacial spasm disappeared after the removal of the tumor. In a case with a medullary venous malformation with arterial component, an engorged draining vein compressed the root exit zone of the facial nerve. In the remaining three vascular cases--two cases of arteriovenous malformation and a case of saccular aneurysm--enlarged feeding arteries and an aneurysm directly compressed the root exit zone of the facial nerve. Not only arterial or venous but also mass compression can cause hemifacial spasm in some symptomatic cases. Surgical decompression of the facial nerve from the causative organic lesion is the primary choice of treatment.