Evolution from Platysma Myectomy to Myotomy: Preserving Lower Lip Function in Facial Synkinesis

BACKGROUND: Platysma hypertonicity, a sequela of facial synkinesis (FS), is treated with platysma myectomy. However, its close relationship to the facial nerve's cervical branch raises concern for postoperative lower lip dysfunction. This study compares lower lip outcomes following platysma myectomy, platysma myotomy at the thyroid cartilage level, and no platysma intervention. METHODS: Included were FS patients who underwent selective neurectomies and ipsilateral depressor anguli oris myectomy (NDAO) between 2019 and 2025. Mean follow-up was 12 months. Patient groups included NDAO (n=27), NDAO with platysma myectomy (n=19), and NDAO with platysma myotomy (n=10). Pre and postoperative commissure position, lower lip height, lower lip inclination angle, and lower quadrant dental show were measured using Emotrics and ImageJ. RESULTS: Patients were on average 52 years old. The NDAO group improved significantly across all outcomes (p ≤ 0.004); the myotomy group improved in inclination and dental show (p ≤ 0.014); the myectomy group showed no significant improvement. The myotomy group outperformed the myectomy group across all measures (p ≤ 0.006) and had better commissure position and dental show than the NDAO group (p ≤ 0.045). The NDAO group had significantly better lower lip height, inclination, and dental show than the myectomy group (p ≤ 0.018). CONCLUSIONS: Selective neurectomies with DAO myectomy alone and with platysma myotomy were associated with improved lower lip outcomes. Platysma myectomy was associated with postoperative lower lip elevation, consistent with possible cervical branch injury. Both platysmal approaches target cervical symptoms while the platysma myotomy also preserves lower lip position.