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open access eISSN 2093-3673

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Review Article

Anat Cell Biol 2023; 56(2): 161-165

Published online June 30, 2023


Copyright © Korean Association of ANATOMISTS.

Novel anatomical proposal for botulinum neurotoxin injection targeting depressor anguli oris for treating drooping mouth corner

Kyu-Ho Yi1,2,* , Ji-Hyun Lee3,* , Hye-Won Hu2 , You-Jin Choi4 , Kangwoo Lee2 , Hyung-Jin Lee5 , Hee-Jin Kim2

1Wonju Public Health Center, Wonju, 2Division in Anatomy and Developmental Biology, Department of Oral Biology, Human Identification Research Institute, BK21 PLUS Project, Yonsei University College of Dentistry, Seoul, 3Department of Anatomy and Acupoint, College of Korean Medicine, Gachon University, Seongnam, 4Department of Anatomy, Research Institute of Medical Science, Konkuk University School of Medicine, Seoul, 5Department of Anatomy, Catholic Institute for Applied Anatomy, College of Medicine, The Catholic University of Korea, Seoul, Korea

Correspondence to:Hee-Jin Kim
Division in Anatomy and Developmental Biology, Department of Oral Biology, Yonsei University College of Dentistry, Seoul 03722, Korea
E-mail: hjk776@yuhs.ac

*These two authors contributed equally to this work.

Received: December 14, 2022; Revised: January 10, 2023; Accepted: January 25, 2023

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.


The depressor anguli oris (DAO) muscle is a thin, superficial muscle located below the corner of the mouth. It is the target for botulinum neurotoxin (BoNT) injection therapy, aimed at treating drooping mouth corners. Hyperactivity of the DAO muscle can lead to a sad, tired, or angry appearance in some patients. However, it is difficult to inject BoNT into the DAO muscle because its medial border overlaps with the depressor labii inferioris and its lateral border is adjacent to the risorius, zygomaticus major, and platysma muscles. Moreover, a lack of knowledge of the anatomy of the DAO muscle and the properties of BoNT can lead to side effects, such as asymmetrical smiles. Anatomical-based injection sites were provided for the DAO muscle, and the proper injection technique was reviewed. We proposed optimal injection sites based on the external anatomical landmarks of the face. The aim of these guidelines is to standardize the procedure and maximize the effects of BoNT injections while minimizing adverse events, all by reducing the dose unit and injection points.

Keywords: Botulinum toxins, Depressor anguli oris, Drooping mouth corner, Dermotoxin, Anatomy

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