ABSTRACT
With the increased demand for facial rejuvenation done by non-invasive techniques, many experienced injectors of BOTOX® now are venturing below the upper face with their treatments1. As with any other part of the face, one must be completely knowledgeable of the levator and depressor action of the mimetic musculature. In the mid and lower face the reciprocating action of opposing mimetic muscles can prove to be a bit more complicated and challenging than in the upper face. Specifically, the muscles of the upper face are easily distinguishable from one another because of various topographic landmarks, making it easy to inject them with BOTOX®. However, in the mid and lower face, there is an interdependence of the superficial and deep muscles of facial expression, which also are adjacent to some of the muscles surrounding the mouth that function in the articulation of sounds or in mastication and deglutition. These muscles of facial expression are interlaced with and even help form the superficial muscular aponeurotic system (SMAS) and many of them perform complementary and, at times, unrelated functions. Nevertheless, the mimetic muscles of the mid and lower face have very specific functions, mostly centered around the mouth, sometimes acting as agonists, sometimes as antagonists, but always in a complex, synergistic manner. This allows a person to smile and laugh, grimace, or pucker the lips, or to make any other overt or subtle gesture with the mouth, or even to hold solids, liquid, and air within the mouth without loss of contents or to release at will the contents slowly or forcibly out of the mouth. These muscles allow for the fine motor movements necessary to produce subtle whispering sounds or thunderous clammer. They also facilitate the actions of chewing and swallowing and a myriad of other simple and complex movements that either explicitly or implicitly function in voluntary and involuntary motor movements that are so particular of an individual’s mannerisms. In addition, many of these superficial and deep muscles overlie a thicker mass of soft tissue as well as each other, creating an anatomy that is quite different from the forehead and brow (Figure 4.1). Consequently, in the mid and lower face, it then is understandable why, if injected BOTOX® migrates beyond the targeted muscles, unintended results and complications can occur more readily. Therefore, when treating anyone with BOTOX® in the mid and lower face, a little bit of BOTOX® may be good, but a little bit more usually is not necessarily better.
