The functional anatomy of the lower face as it applies to rejuvenation via chemodenervation.

Botulinum toxin type A (Botox) injections have revolutionized nonsurgical rejuvenation of the upper face since their introduction in the early 1990s. Their use in the lower face has not become nearly as popular. The key to using Botox to improve the appearance of the lower face lies in understanding the functional anatomy of the lower face musculature. Although the facial plastic surgeon should be familiar with the muscles of the lower face and anatomic variations, the functional anatomy of the lower face varies widely from patient to patient and even more from one side of the face to the other. Understanding how the lower face moves is the key to using Botox to improve nasolabial folds, perioral rhytids, chin dimpling, marionette's lines, and downturned oral commissures. This is not an area for the novice injector, as a few stray units are not tolerated nearly so well as they are in the upper face.