Deciphering Depressor Anguli Oris for Lower Face Rejuvenation: A Prospective Ultrasound-based Investigation.

This work established an informative ultrasound portrait of the DAO and structures in the perioral region, which suggested the LMF as a convenient landmark for locating the DAO. Injection at the middle and lower thirds of the LMF at a 4- to 5-mm depth is recommended.