A Retrospective and Anatomical Study Describing the Injection of Botulinum Neurotoxins in the Depressor Anguli Oris

Abstract

SUMMARY: The depressor anguli oris acts to lower the lateral corners of the mouth and can cause an individual to appear sad or angry and contribute to the development of the labiomental folds. Many patients can benefit from the injection of small amounts of botulinum neurotoxin into the depressor anguli oris to enable the lip elevators to reposition the corners of the mouth. Although effective, the procedure is off-label, and the proximity of the depressor anguli oris to the depressor labii inferioris, particularly inferiorly, can lead to inadvertent treatment of the latter, resulting in lip asymmetry. The authors have taken a threefold approach to establish a depressor anguli oris injection technique that provides optimal aesthetic outcomes with a low incidence of adverse events. This involved, first, reviewing the limited existing literature for studies discussing depressor anguli oris anatomy and botulinum neurotoxin treatment technique; second, supplementing information from the published literature with information from cadaver dissections to demonstrate the relationship between the depressor anguli oris and surrounding anatomical structures; and third, performing a retrospective chart review of 275 patients treated with the authors' three-point injection technique. Combining data from published studies, cadaver dissections, and clinical experience, the authors demonstrate that a three-point technique performed in the upper half of the depressor anguli oris is associated with good clinical outcome and avoids common side effects related to injection or spread of neurotoxin to adjacent muscles. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.