LAUSR

Dear editor, There is a growing stream of demands for lower face contouring treatments for ovaland almond-shaped jaws among Asian populations.1 Among various treatment options, botulinum toxin type A (BoNT-A) injection for masseter muscle hypertrophy (MMH) is an increasingly soughtafter noninvasive and easy treatment option for lower face contouring.2 Despite the popularity of BoNT-A in the clinical field and excellent results in clinical studies, currently, no validated esthetic scale exists for measuring MMH. In previous studies evaluating BoNT-A injection for MMH, objective measurements such as ultrasonography and twoor three-dimensional computed tomography were used to assess masseter muscle volume changes.2 These measuring methods are very useful for evaluating muscle changes as they can quantify the volume or thickness of muscles. However, the requirement for significant equipment and their inability to reflect clinical changes in facial contour limit their utility in clinical practice. Furthermore, structural and anatomical features specific to the Asian face necessitate a distinct esthetic scale for the Asian population; Asians tend to have a wider, square-shaped face due to broader, well-developed zygomas and a square jawline.2,3 Asians also have more developed masseter muscles than most Caucasians.4 Therefore, this study aimed to develop and validate the first MMH scale specifically for Asian patients. This novel masseter muscle hypertrophy scale (MMHS) evaluates the overall MMH degree, with grades ranging from 1 (minimal) to 5 (very marked) (Table 1). The MMHS assesses MMH during rest (with mouth closed and no clenching) and during maximum contraction (clenched teeth with full force) by separately evaluating the right and left sides of the subject's face. In this assessment, the MMH is ascertained by visual inspection and palpation of the masseter muscle. When the grades rated at rest and at maximum contraction do not concur, the latter is used. We validated the MMHS by using it to evaluate MMH among Asian subjects and created a supplemental photo guideline. The validation study included 110 Asian subjects assessed by four experienced board-certified dermatologists. Each dermatologist independently evaluated the subjects using MMHS in two independent validation sessions performed 4 weeks apart to evaluate intra-rater reliability. To create the photograph guideline, standardized photographs were taken of subjects who provided consent under standard conditions at rest. A photograph was selected as a candidate for the photograph guideline when all four evaluators reached consensus. Among the candidate photographs, one photograph of each grade was selected to create the photograph guideline (Figure 1).