Predicting Depressor Anguli Oris Excision Outcomes Using Local Muscle Block

Introduction: Although depressor anguli oris (DAO) muscle block is a useful tool to help predict which patients will respond positively to myectomy, DAO excision outcomes have not been correlated with smile changes after muscle block. Objective: To compare changes in smile symmetry after DAO muscle block with changes after DAO myectomy. Methods: Nonflaccid facial paralysis patients undergoing DAO excision at a tertiary care facial nerve center were prospectively studied from August 2021 to June 2022. Dental show, oral commissure excursion, and smile angle at baseline, after DAO muscle block, and after myectomy, were quantified. Results: Twenty-three patients underwent DAO muscle block followed by myectomy. DAO excision produced improved dental show (p = 0.006) and oral commissure excursion (p = 0.024) symmetry compared with muscle block. A strong correlation exists between changes in oral commissure excursion symmetry after muscle block and after myectomy. Moderate correlations exist for changes in smile angle and dental show symmetry. Conclusion: Although DAO muscle block is a good predictor of smile symmetry after muscle excision, typically excision results in improved dental show and oral commissure symmetry compared with block.