Efficacy of isolated periocular botulinum toxin A injections versus periocular and adjunctive lower facial injections in hemifacial spasm: a randomized, controlled, noninferiority, crossover trial

PURPOSE: To evaluate the necessity of botulinum toxin A (BoNT-A) administration in the lower face of patients with hemifacial spasm (HFS). METHODS: A randomized controlled non-inferiority crossover trial was conducted with 46 HFS patients (non-inferiority margin = 1). Patients were randomized (1:1) to receive either isolated periocular BoNT-A injections followed by conventional injections (periocular and lower face area) or the reverse sequence, with a 16-week washout. Primary outcomes were visual analog scale (VAS) for periocular and lower face regions at 4 weeks post injection. Secondary outcomes included the Hemifacial Spasm Grading Scale (HSGS), Samsung Medical Center grading system (SMC), HFS questionnaire (HFS-30), and adverse events. Trial registration: TCTR20220916002. RESULTS: Data from 43 patients were analyzed. Isolated periocular injections demonstrated non-inferiority to conventional injections. Periocular VAS was 0.488 ± 0.140 (isolated injections) and 0.279 ± 0.085 (conventional) , mean difference 0.209 (95% CI: 0.064, 0.354, p<0.01). Lower face VAS was 0.878 ± 0.167 and 0.582 ± 0.113, mean difference 0.295 (95% CI: 0.039, 0.552, p<0.01). No significant differences were noted in HSGS, SMC, or HFS-30 scores. Minor adverse events were observed in both techniques, while mouth drooping occured only with conventional injections. CONCLUSION: Isolated periocular injections resulted in slightly poorer symptom relief but did not exceed the non-inferiority margin, providing comparable efficacy to conventional injections in controlling HFS while using a lower total toxin dose and minimizing adverse effects.