Botulinum toxin application to the buccinator muscle in the treatment of facial synkinesis: a prospective cohort study

Abstract

**Background**: Synkinesis may develop following facial nerve palsy, impacting quality of life. Botulinum toxin treatment for synkinesis is commonly used, but buccinator muscle injection is less common. We aim to investigate buccinator botulinum toxin for management of synkinesis. **Methods**: Patients received botulinum toxin to synkinetic areas (standard botulinum toxin) with physiotherapy. Four months later they were re-treated at the same sites, with addition of buccinator injections. After both treatments, outcomes were measured using the Facial Disability Index and Synkinesis Assessment Questionnaire at baseline and five weeks later (four assessments in total). **Results**: Twenty-seven patients were recruited, 25 completing standard botulinum toxin treatment and 20 completing standard and buccinator botulinum toxin. Standard botulinum toxin showed improvements in the Synkinesis Assessment Questionnaire (63.5 v 50.3, _p_ < 0.001) and Facial Disability Index–Social (59.2 v 73.8, _p_ < 0.001). Further benefits were noted with buccinator botulinum toxin in the Synkinesis Assessment Questionnaire (52.2 to 44.4, _p_ = 0.017) and Facial Disability Index–Social (72.6 to 77.4, _p_ = 0.049). Synkinesis Assessment Questionnaire subset analysis showed improvement in ocular synkinesis with buccinator botulinum toxin (9.3 to 7.8, _p_ = 0.04). **Conclusion**: Botulinum toxin treatment with physiotherapy is effective for synkinesis and reducing social impact. Addition of buccinator botulinum toxin resulted in further improvements.