Clinical features and response to botulinum toxin in primary and secondary hemifacial spasm

Background: Hemifacial spasm (HFS) is a hyperkinetic movement disorder of adults. The condition is usually primary, but may be secondary to facial nerve damage, and responds well to botulinum toxin therapy. Aim: To study the demographic and clinical features of primary and secondary HFS and assess its response to botulinum toxin therapy. Materials and Methods: A retrospective study of 40 patients of primary (33) and secondary (7) HFS, who attended our botulinum toxin clinic over the last 18 months, was conducted. We collected the data including the demographic profile, clinical features of primary and secondary HFS, severity measured by Likert scale, etiology, details of magnetic resonance imaging (MRI) of the brain, and a detailed account of the botulinum toxin injection. Results: Thirty-three out of the 40 patients had primary HFS. The mean age at presentation was 48.4 +/- 12.6 years whereas the mean duration of symptoms was 57.4 +/- 39.3 (6-144) months. The onset of spasm on the upper part of face was seen in 31 patients (77.5%). An ipsilateral ear click was found in 17 (42.5%) patients. Mild spasms were seen in 18 patients, whereas 12 patients had severe spasms. The severity of spasm was lower in patients with secondary HFS. Five out of 22 magnetic resonance imaging (MRI) results showed an abnormality. The mean dosage of botulinum toxin was 21.86 +/- 4.19 units in primary spasm and 17 +/- 4.16 units in secondary spasm (P = 0.018). The mean duration of response was 112.6 +/- 55.7 days (median: 90 days; range: 30-240 days) in primary spasm and 135 +/- 63.6 days (median: 135 days; range: 90-180 days) in secondary spasm (P = 0.29). Conclusion: Ipsilateral auditory clicks are fairly common in primary and secondary HFS. The patients with secondary HFS have a milder intensity of disease and they may have the onset of spasm from the upper part of face. Both primary as well as secondary HFS patients respond well to botulinum toxin injection; however, the adverse effects are more likely to occur in secondary HFS, and therefore, these patients require lower dosages of toxin.