Dynamic augmentation of lip levator function via depressor anguli oris transfer for post-facial paralysis synkinesis

Post-facial paralysis synkinesis (PFPS) is characterized by the restriction of natural smile due to antagonism between the lip levator muscles and depressor anguli oris (DAO) in the perioral area. Although treatment is often aimed at reducing the DAO alone, which pathologically co-contracts when the mouth corners are elevated, we report a case in which the DAO was turned over and shifted cephalad, thereby alleviating synkinesis and augmenting lip levator function. In a 64-year-old female patient with PFPS due to Hunt syndrome, the DAO flap was elevated from the mandibular origin while preserving the nerve and vascular supply and then inverted cranially to enhance the levator function of the oral commissure. Twelve months after surgery, perioral synkinesis was alleviated, and excursion of the mouth corners and dental show during voluntary and spontaneous smiling were significantly enhanced. This surgical procedure may provide a novel method that can simultaneously improve the dynamic lip levator function and reduce perioral synkinesis in patients with PFPS. Lay summary: This report describes a novel method that can simultaneously improve the dynamic function of the oral commissure and reduce perioral synkinesis during post-facial paralysis synkinesis.