Efficacy and Short-term Durability of Combined Botulinum Toxin Type A and Rehabilitation for Chronic Facial Asymmetry After Facial Nerve Palsy

Background: Although the benefits of botulinum toxin last for 3–4 months, the durability has not been quantitatively evaluated. Recent studies have suggested that combining botulinum toxin injections with neuromuscular retraining can enhance both functional and aesthetic results. This study aims to assess the efficacy and short-term durability up to 4 months of this combined approach in patients with chronic facial asymmetry after facial nerve palsy. Methods: We retrospectively evaluated patients with facial asymmetry due to facial palsy treated with botulinum toxin type A injections followed by neuromuscular retraining between January 2019 and December 2024. Patients were evaluated before treatment, at 2 weeks posttreatment, and at 4 months posttreatment using the Sunnybrook Facial Grading System (SFGS). Synkinesis was assessed using the palpebral fissure height ratio (PFHR). Results: A total of 28 patients (age range: 17–79 y; median age 49.0; interquartile range , 38.0–59.2 y) were included. Patients showed improved facial symmetry. The median SFGS score increased by 17.4 points at 2 weeks and remained 12.0 points above the baseline at 4.7 months (both P < 0.001). The PFHR improved from 0.76 pretreatment to 0.96 at 2 weeks ( P < 0.001) and remained improved at 0.77 at 4 months ( P < 0.05). Conclusions: A combination of botulinum toxin type A injections and rehabilitation was effective in patients with chronic facial nerve palsy. Improvements in SFGS score and PFHR indicate a sustained therapeutic effect beyond the expected 3–4 months.