RESUMEN
INTRODUCTION: Hemifacial spasm (HFS) is an involuntary contracture of the facial muscles innervated by the ipsilateral facial nerve. We studied the etiology of these HFS. MATERIALS AND METHODS: This retrospective study included 233 patients with HFS who came to the ophthalmologist for quarterly botulinum neurotoxin A injection. Of these, we analyzed the 198 patients for whom MRI scans were performed. We recorded patient clinical data and clarified the etiology of their HFS. RESULTS: The 198 patients (62.6% women) had a mean age of 55.7±14years. An etiology was found in 52.5% of cases. In 34.5% of HFS, MRI revealed vascular compression where the facial nerve emerged from the brainstem. We specify the arteries involved. Brain tumors accounted for 1.5% of cases. MRI was normal in 64.5% of cases. In these secondary cases of HFS, we found 8.5% peripheral facial palsy, 4% post-traumatic HFS and 4% secondary to an eye injury. Stress was found in 17% of patients. DISCUSSION AND CONCLUSION: This study illustrates the need for MRI with attention to the posterior fossa in the work-up of HFS in order to identify primary HFS associated with vascular compression of the facial nerve and to rule out a rare but serious posterior fossa tumor. The treatment of HFS is based on quarterly injections of botulinum neurotoxin/A (NTBo/A), the three brands of which have market approval. The injection pattern and frequency is customized according to the results. In cases of insufficient response to injections of NTBo/A, neurosurgical microvascular decompression may be considered for cases of primary HFS.