Botulinum toxin a for lower facial contouring: a prospective study

A prominent mandibular angle is a common reason for aesthetic treatment among Asian women. Such women usually present with hypertrophic masseteric muscles, and one treatment for this uses botulinum toxin A (BoNTA). Detailed effectiveness and physiologic influences of this therapy are still under investigation.

The authors report a prospective study of 10 female volunteers with hypertrophic masseteric muscles who received a single treatment comprising intramuscular injection of BoNTA. The facial change and the discomfort of the injection were self-rated using a visual analog scale, and the patients were regularly inspected up to 1 year. Bite forces also were measured for chronological documentation. Volume changes of masticating muscles were evaluated by three-dimensional computed tomography (CT) scans before and 3 months after injection of BoNTA.

The serial photographs and patient subjective evaluation showed an obvious facial change 3 to 6 months after injection. Bite forces decreased from the first day after injection, but started to recover during week 3 and were normal 3 months after injection. Three-dimensional CT evaluation showed a statistically significant mean masseter reduction of about 30%, but no change in the volume of other masticating muscles. There were no serious complications during this study.

Injection of BoNTA is an effective alternative for contouring of the lower facial profile by reducing the bulkiness of masseteric muscles. Its effectiveness was noticed as early as 2 weeks after injection and reached a peak effect in month 3. The facial contour gradually returned 6 months after injection. The reduction in bite force was temporary and caused no daily life interference.