Unusual causes of hemifacial spasm.

Hemifacial spasm (HFS) has been defined as consisting of brief clonic jerking movements of the facial musculature, beginning in the orbicularis oculi with downward spreading to other facial muscles. HFS, perhaps the most common of the abnormal involuntary facial movements, has been classically ascribed to vascular loop compression at the root exit zone of the facial nerve. Causes other than such vascular loops are rare in the medical literature. Here we present three case studies in which the phenomenology of the HFS was atypical in onset and evolution. Using these three patients as introduction to the topic, we reviewed the literature of all cases of HFS with causes other than the vascular loop. In these three cases, HFS was caused by (1) a parotid gland tumor, (2) a cerebellopontine angle meningioma, and (3) an acoustic schwannoma. We also discuss the radiological findings as well as possible differences in the genesis of HFS and phenomenology in such cases and present recommendations on how to evaluate these patients.