KeywordsNeurotoxinNeuromodulatorBotoxPharmacologyDysportXeominBotox cosmeticMuscle memoryNeurotoxin effectsBoNT/AIndicationsFacial linesLower faceDimpled chinPlatysmaJeuveau
13.1 Patient Selection and Expectations
It is important to understand that some patients with lower face concerns are candidates for additional treatment that can include dermal filler, laser resurfacing, or surgical intervention (Carruthers and Carruthers 2005; Carruthers et al. 1996). Volume loss resulting in deep nasolabial folds, flattened cheeks, sunken oral commissures, and thin lips requires additional treatment with dermal filler to create the overall desired outcome of a smooth, younger looking appearance, whereas photo-aged, sagging skin may require laser or surgery (Carruthers and Carruthers 2013). Static fine lines of the upper lip and dimpling of the chin are areas frequently treated with neurotoxin, but drooping at the corners of the mouth, “gummy smile,” “bunny lines,” and neck bands are also appropriate areas for treatment and frequently sought out by patients for improvement (Carruthers and Carruthers 2005, 2003).
As with any cosmetic dermatology treatment, the expectations of the patient are crucial to the outcome and the patient’s satisfaction with treatment. Direct communication that outlines the side effects, risks, and benefits of treatment must be relayed to the patient, and assurance of patient understanding is critical. The effects of using BoNT/A on the lower face are mostly tied to the softening of structures through muscle relaxation rather than “freezing” certain areas (Carruthers and Carruthers 2005). Also, the potential for the addition of dermal filler in combination to BoNT/A to more effectively rejuvenate the lower face is an essential component of the consultation and should be clear to the patient prior to treatment.
When using BoNT/A on the lower face, there is potential for unexpected outcomes from the effects of the neurotoxin related to the weakening of the function of the lip such as the patient’s inability to enunciate words, play musical instruments, or smile normally (Carruthers and Carruthers 2004). The muscles of the lower face appear to be more responsive to the effects of BoNT/A and for this reason, lower doses are used in these muscles vs. the muscles of the upper face (Carruthers and Carruthers 2005, 2003). Exaggerated muscle weakness and/or dysfunction in the lower face can be avoided by having a keen knowledge of lower facial anatomy and muscle function, using small doses, and taking a conservative approach (Carruthers and Carruthers 2004). As of publication, there are no available studies on prabotulinumtoxinA (Jeuveau), however, the dosing is the same as onabotulinumtoxinA (Botox) and incobotulinumtoxinA (Xeomin). All lower face areas are off-label indications for BoNT/A treatment.
13.2 Gummy Smile
Gummy smile is described as a smile where a large portion of the upper gum line is visible. It is caused by the contraction of the levator labii superioris alaeque nasi (LLSAN) muscle. BoNT/A treatment of this muscle results in the lengthening of the upper lip and decreased contraction and travel of the upper lip when smiling (Carruthers and Carruthers 2005; Mazzuco and Hexsel 2010). On occasion, a patient may complain about a naturally occurring asymmetric smile and want only one side treated; treatment on one side is quite acceptable (Carruthers and Carruthers 2005).
Dimpling in the chin is a result of an active mentalis muscle and is most apparent during speaking or expression (Trevidic et al. 2015). This bunching up and dimpling of the chin can be an unwelcome feature in the overall facial appearance. Patients may not complain about the dimpling specifically, but might report they do not like how the chin looks. It is part of the practitioner’s responsibility to educate the patient on the treatment effect of BoNT/A on the chin and the potential improvement in appearance. Chin treatment is relatively easy and is usually one injection site, although two sites may be required for certain patients (Carruthers and Carruthers 2005; Trevidic et al. 2015).
In some cases, the unique composition and strength of the patient’s facial musculature, along with advancing age, create a deep groove or cleft in the chin that intensifies the appearance of age (Carruthers and Carruthers 2005). In addition the chin softening of the BoNT/A treatment, these deep grooves may require a small amount of dermal filler to be placed into the cleft to soften the appearance of the chin (Moradi et al. 2019).