Objective:To evaluate unusual possible causes and clinical presentations of hemifacial spasm (HFS).Methods:The authors reviewed 1642 cases of HFS.Assessments were based on clinical features,3-dimensionaltime-of-flight magnetic resonance angiography,and surgical fmdings.Causes other than neurovascularcompression at the root exit zone of the facial nerve were investigated and unusual clinical presentations werenoted.Results:Nine (0.5%) patients had a secondary causative structural lesion,7 patients had a tumor,and theremaining 2 had a vascular malformation.Direct compression by dolichoectatic vertebrobasilar artery was noted in Objective: To evaluate unusual possible causes and clinical presentations of hemifacial spasm (HFS). Methods: The authors reviewed 1642 cases of HFS. Assessments based on clinical features, 3-dimensional time-of-flight magnetic resonance angiography, and surgical fmdings. Causes other than neurovascularcompression at the root exit zone of the facial nerve were investigated and unusual clinical presentations werenoted. Results: Nine (0.5%) patients had a secondary causative structural lesion, 7 patients had a tumor, and theremaining 2 had a vascular malformation. Direct compression by dolichoectatic vertebrobasilar artery was noted in