Objective Assessment of the Repeated Botox Treatment to the Synkinesis of Facial Paralysis by the Integrated Electromyography

Background: The widely used botox type A (BTX-A) is effective against synkinesis in facial palsy sequelae. Repeated injections are necessary and permanent improvements have been reported. We objectively evaluated the changes in synkinesis at >6 months after BTX-A injection, including changes over time with the number of administrations. Methods: In 48 patients who received multiple BTX-A injections, evaluation by the Sunnybrook Facial Grading System (FGS) and integrated electromyography (iEMG) was performed before treatment and at least 6 months after the first, second, and third BTX-A injection. The iEMG ratio on the affected and healthy sides was calculated for each mimetic muscle and mimic motion. Results: There was no significant difference in the FGS synkinesis score before treatment and after the third injection, although an improvement was observed. The iEMG ratio was significantly improved in the orbicularis oculi with open-mouth smile and lip pucker after the third dose compared to before treatment. The orbicularis oris showed a significant improvement when the eyelids were closed, while the platysma showed a significant improvement when the eyelids were closed and when the lip was pursed. Multiple regression analysis revealed that the orbicularis oculi and platysma had a greater effect on the iEMG ratio for the number of treatments than other factors. Conclusions: Repeated BTX-A injections showed improvements in synkinesis for the orbicularis oculi, orbicularis oris, and platysma, even after >6 months, compared to before treatment.