Unusual causes and presentations of hemifacial spasm

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-dimensional time-of-flight magnetic resonance angiography, and surgical findings. Causes other than neurovascular compression at the root exit zone of the facial nerve were investigated and unusual clinical presentations were noted. RESULTS: Nine (0.5%) patients had a secondary causative structural lesion, 7 patients had a tumor, and the remaining 2 had a vascular malformation. Direct compression by dolichoectatic vertebrobasilar artery was noted in 12 (0.7%) patients. In 7 (0.4%) patients, only the distal portion of the facial nerve was compressed, and five (0.3%) had only venous compression. Bilateral HFS and tic convulsif were encountered in 7 (0.4%) and 6 (0.37%) patients, respectively. Fifty-six (3.4%) patients were younger than 30 years old at the time of microvascular decompression. CONCLUSION: HFS can result from tumor, vascular malformation, and dolichoectatic artery. Therefore, appropriate preoperative radiological investigations are crucial to achieve a correct diagnosis. The authors emphasize that distal compression or only venous compression can be responsible for persistent or recurrent symptoms postoperatively. In cases of bilateral HFS, a definite differential diagnosis is necessary for appropriate therapy. MVD is recommended as the treatment of choice in patients younger than 30 years old or patients with painful tic convulsif.