Botulinum toxin A (BoNT-A) injection is one of the most widely used methods for hemifacial spasm (HFS) with high efficacy in controlling spasm. However, it is still unknown if esthetic symmetry could be desired as the spasm was controlled by BoNT-A therapy. The purpose of this study is to clarify the facial asymmetric characteristics of HFS patients and if the asymmetry could be amended by BoNT-A injection in the abnormal side. In this prospective analysis, HFS patients were enrolled, who received hemifacial BoNT-A injection and completed follow-up at weeks 2-4. Self-reported improvement and negative influence of facial asymmetry in social life were documented. Facial asymmetry was assessed by the Sunnybrook facial grading system (SFGS) and a new scale created by our clinic-the Symmetry Scale for Hemifacial Spasm (SSHS). Thirty-eight patients were eligible for analysis. Among them, 34 patients (89 %) had marked improvement in spasm after BoNT-A injection. After BoNT-A injection, SFGS showed an improvement of synkinesis (p = 0.01). And SSHS showed an amelioration of resting symmetry in lower face after treatment (p < 0.05). However, SFGS showed a deterioration of voluntary movement in lower face after treatment (p < 0.01). In addition, a deterioration of voluntary movement in upper face and lower face was found in SSHS after treatment (p < 0.01). SSHS composite score showed a deterioration after BoNT-A injection (p = 0.01). In conclusions, BoNT-A was effective in controlling spasm and synkinesis of HFS and improved resting symmetry in lower face, but facial symmetry of voluntary movement deteriorated after hemifacial BoNT-A injection.
Keywords: Botulinum toxin A; Facial asymmetry; Hemifacial spasm.