Commentary on: Three-Dimensional Evaluation of the Depressor Anguli Oris and Depressor Labii Inferioris for Botulinum Toxin Injections

I read with interest this article on a simple way to precisely identify the depressor anguli oris (DAO) and the nearby depressor labii inferioris (DLI) muscles, based on the authors’ 3-dimensional (3D) evaluations of cadaver specimens.1 Next, I did some drawings with an eyeliner on one of my staff to verify anatomic landmarks and distances before performing an off-label injection of neurotoxin into the DAO (Figure 1). The inherent simplicity of the authors’ approach for defining the DAO was impressive. Clinical applications of cosmetic neurotoxins in the face have continued to expand far beyond the corrugator, frontalis, orbicularis oculi, and platysma to now include advanced locations in the masseter, mentalis, and DAO. A precise knowledge of anatomy is needed to avoid inadvertent collateral paralysis of the zygomaticus when injecting the masseter and of the DLI when injecting the DAO. The authors are to be congratulated on combining...