Synkinesis in primary and postparalytic hemifacial spasm: Clinical features and therapeutic outcomes of botulinum toxin A treatment

Abstract Facial synkinesis can be present in both primary and postparalytic hemifacial spasm (HFS). The present retrospective study aimed to summarize the clinical features of synkinesis and explore an appropriate botulinum toxin A (BoNT-A) injection strategy to manage the synkinesis accompanying HFS. Video recordings of 234 patients with primary and postparalytic HFSs were analyzed. Improvements in the severity of spasm and synkinesis owing to BoNT-A treatment were monitored and compared among 36 primary and 12 postparalytic HFS patients with synkinesis and completed follow-up records. BoNT-A was injected into the voluntary facial region (VFR), the synkinetic facial region (SFR), or both VFR and SFR, and the efficacy of these strategies was evaluated and analyzed. Oral–ocular synkinesis in the primary group (32.8%) and ocular–oral synkinesis in the postparalytic group (81.0%) showed the highest incidence. Patients in both the primary and postparalytic groups exhibited a tremendous alleviation of spasm (97.2% vs. 91.7%, P > 0.05) following BoNT-A treatment. In both groups, coinjection and SFR injection were commonly used and effective in treatment of ocular and oral synkinesis, while VFR was frequently used but ineffective for frontal synkinesis. In addition, the improper muscle selection surrounding the mouth corner resulted in pattern change and treatment failure of oral synkinesis. Synkinesis mostly affected the ocular and oral regions. BoNT-A, via treatment of SFR, is effective against synkinesis accompanying HFS.