Background: The treatment of post-paretic facial synkinesis is based on a combination of nonsurgical and surgical strategies. Even if improvements towards the restoration of a natural smile have been obtained with selective neurectomies (SN) and depressor anguli oris (DAO) myectomy, the lower lip frequently remains asymmetric and cranially displaced. The aim of this study was to evaluate the effect of the mentalis muscle on the position and symmetry of the lower lip in patients with synkinesis and to assess the added benefit of neurectomies of nerves innervating the mentalis muscle in improving the lower lip configuration and mandibular teeth show.
Methods: A retrospective cohort study on all patients affected by post-paretic synkinesis at our Institution was performed. A Non-mentalis Neurectomy Group including twelve patients treated with SN without targeting the branches to mentalis muscle was compared to a Mentalis Neurectomy Group, including sixteen patients who underwent additional specific mentalis branches neurectomies. All patients underwent DAO myectomy. Analyses of standardized images were performed with ImageJ software.
Results: Post-operative comparisons between the two groups showed superior and significant improvements in the Mentalis Neurectomy Group across all measures, including lower and upper border deviation (p=0.035 and p=.004, respectively), inclination of the lower lip (p=.019), and lower quadrant dental show (p=.004).
Conclusions: The addition of targeted selective neurectomies to the branches innervating mentalis muscle significantly improved dental show and caudal position and symmetry of the lower lip during open mouth smile.
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