Methods of Secondary Smile Salvation After a Failed Primary Salvation Procedure for Facial Nerve Palsy: A Systematic Review.

The smile is a fundamental facial expression that is important for emotional wellbeing. Long-term facial nerve palsy leads to an inability to smile, which can have profound effects on mental health. Although numerous techniques exist for facial reanimation, evidence on secondary interventions following a failed primary procedure remains scarce. This systematic review, conducted in accordance with PRISMA guidelines, aimed to identify techniques for secondary smile restoration. A systematic search of PubMed, Scopus, and MEDLINE identified 41 studies; after independent screening using PICOT-based inclusion and exclusion criteria, and a subsequent quality assessment, 4 studies (12 patients) were included. Eight distinct secondary techniques were reported, all of which were associated with improvement in smile-related outcomes and/or facial symmetry, alongside reduced House-Brackmann scores. However, these findings are limited by the small sample size, methodological shortcomings, and incomplete reporting, precluding an indication of the optimal technique. Future high-quality studies, particularly long-term randomised controlled trials with larger cohorts, and comprehensive reporting of patient characteristics and clinical outcomes, are required to establish the most effective method of secondary smile restoration.