Depressor anguli oris (DAO) excision
The depressor anguli oris (DAO) muscle attaches to the corner of the mouth and the bottom of the mandible (lower jaw), just to the side of the chin. It is one of the muscles which helps make a frown. Often, patients with chronic facial palsy from recovered Bells Palsy, Ramsay Hunt syndrome, Lyme disease, acoustic neuroma surgery, or trauma, have too much activity in this muscle on the affected side of the face. This decreases the ability of the corner of the mouth to turn up in a smile, creating asymmetry with smiling. One option is to treat this muscle an injection of Botox to weaken it in order to improve a patient’s smile.
Sometimes, resection of the DAO muscle will provide patients with a better smile than that which is achieved with Botox. Additionally, resection of the muscle is permanent unlike Botox which has to be re-administered every 3-4 months. Resection of this muscle is very straightforward, and there is almost no downside.
The procedure itself is performed in the office, and takes 15-30 minutes. Numbing medication is injected inside the mouth and a little bit over the chin as well. An incision is made inside the corner of the mouth, and fibers of the muscle are identified and removed. We then place a few dissolving stitches to close the incision, and patients are given a few days of an antibiotic. Patients can eat and drink normally after the numbing medication wears off (about an hour). As patients heal, they may develop a small amount of swelling on the inside of the mouth over the area where the muscle was removed. This phenomenon is completely normal, and resolves with time; one may massage the area to expedite this process.