Clinical aspects and pathophysiology

The twenty-first century has seen an explosion in the numbers of individuals seeking out ways to look younger and more beautiful. As the demand for procedures increases, so does the desire for less invasive therapy with shortened downtimes. Botulinum toxin (BoNT) has become the most common aesthetic procedure performed in the USA with more than three million such procedures performed in 2005 (The American Society for Aesthetic Plastic Surgery, 2007).

For cosmetic uses, the target of BoNT is primarily the muscles of facial expression. These muscles generally have soft tissue attachments and when contracted, move the overlying skin. With age, there is atrophy of the underlying facial support, including the muscles (Spencer, 2006). The skin thins and with repeated muscle contraction there is folding and pleating of the skin, which becomes permanent creases over time. Botulinum toxin will temporarily weaken hyperfunctional muscles, thereby improving or eliminating the overlying skin creases. The position and interplay of opposing muscle actions contribute to the appearance of facial aging, and, again, BoNT can be used to alter such relationships. In fact, patients report a change in appearance within 2 weeks of receiving botulinum toxin type A (BoNT-A) and by 4 weeks after therapy to the upper face, report looking 3 years younger than baseline (Carruthers & Carruthers, 2007).