EVOLVING USE OF BoNT-A THROUGHOUT THE FACE
The use of BoNT-As is a very important component of nonsurgical rejuvenation. The science behind the agents injected and the facial anatomy are important factors in the final result. The panelists were in general agreement regarding the number of injection points and dosing in the upper and midface (Table 2) and the lower face and neck (Table 3) but there was some disagreement on the extremes, resulting in wide ranges. These values reflect differences in agent reconstitution, injection technique, and patient presentation. The most important variables, however, are the skill, experience, and artistic eye of the injector.17 The wide range of opinions reflects the variety of strategies that can be used to achieve safe, successful results in the hands of experienced aesthetic physicians.
The first FDA-approved aesthetic use of BoNT-A was for treatment of glabellar rhytides. With frowning, the paired corrugator and depressor supercilii muscles contract primarily horizontally, contributing to vertical rhytides. Together, with occasional contribution from the medial orbicularis oculi and frontalis, these muscles form the glabellar complex.29 The typical targets of injection are the procerus, corrugators, and depressor supercilii muscles, the latter of which are highly variable in angle of insertion and length. Injection points are best determined by observing muscle contraction, although muscle palpation and reference to surface landmarks can sometimes be useful, as can bony landmarks and anatomic diagrams, to a lesser extent.27
BoNT-A injections into the glabellar complex can have significant impact on brow height and position. The brows are critical to the unspoken messages that humans send to others, as low medial brows can signal hostility and anger and lower lateral brows can signal uncertainty, concern, or distress.17 Product labeling recommends 20 units of onabotulinumtoxinA, prabotulinumtoxinA-xvfs, or incobotulinumtoxinA, divided into 5 equal injection points (2 in each corrugator and 1 in the procerus) of 4 units each.20-22 For abobotulinumtoxinA, the recommended dosage is 50 units divided into 5 equal injection points (2 in each corrugator and 1 in the procerus) of 10 units each.23 The range of units and injection points recommended by the panel, reflecting real world BoNT-A experience, are listed in Table 2. Lower values reflect patients who may need only a medial corrugator injection, 1 or 2 procerus injections, or perhaps both medial corrugator and procerus variations.
To minimize risk of eyelid and/or brow ptosis, it is important to inject more superficially at the tail of the corrugator or at the