Electrophysiologic Change and Facial Contour following Botulinum Toxin A Injection in Square Faces

Abstract

In this study, there was a 2-month interval between the lowest value of the maximal amplitude of the surface electromyography and the maximal clinical effects following botulinum toxin A injection, and there was similarity between the recovery of the masseter function and the diminution of the clinical effect. The clinical effect of botulinum toxin A persisted for 12 months after treatment on physical measurements, and the authors felt that this long-lasting effect of botulinum toxin A beyond expectation could be explained by incomplete recovery of muscle function.