Depressor Anguli Oris Resection for Postparalysis Facial Synkinesis: Who Stands to Benefit?

BACKGROUND: Several studies report smile improvements after depressor anguli oris (DAO) resection for patients with postparalysis facial synkinesis. However, outcomes postprocedure are variable, and it is difficult to predict which patients will derive the greatest benefit. METHODS: The medical records of all patients who underwent DAO resection from January of 2021 to June of 2022 were retrospectively reviewed. Preprocedure and postprocedure photographs were analyzed using the automated Emotrics software program, and a blinded clinician-graded assessment using the Electronic Facial Paralysis Assessment instrument (eFACE) was performed. A subgroup analysis was conducted to compare outcomes by baseline synkinesis severity. RESULTS: Eighty-four patients were included. DAO resection resulted in a statistically significant improvement in all Emotrics smile measures, including a 1.3-mm improvement in oral commissure excursion ( P < 0.0001), 0.8-mm improvement in dental display ( P < 0.0001), and 1.6-degree improvement in upper-lip slope ( P < 0.001). Significant improvements in smile symmetry were observed for all measures ( P < 0.001). A median 10-point (10%) improvement in oral commissure excursion by eFACE was similarly observed ( P < 0.001). When a subgroup analysis was conducted based on mild, moderate, or severe baseline synkinesis, all subgroups demonstrated significant improvements in smile measures; however, patients in the mild group derived the greatest smile improvement. The severe group demonstrated the next-greatest improvement, and the moderate group experienced the most modest improvement. CONCLUSIONS: DAO resection results in significant improvements in automated and clinician-graded assessments of facial function. Patients with mild synkinesis derived the greatest absolute benefit as well as the greatest improvement in smile symmetry. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, II.