Beyond the smile: a systematic review of diagnostic tools for peripheral facial paralysis

Background: Effective rehabilitation of peripheral facial paralysis (PFP) requires reliable assessment tools. This systematic review aimed to identify and validate instruments used in PFP rehabilitation, categorizing them according to the ICF framework. Methods: A comprehensive search was conducted across PubMed, Cinahl, Web of Science, and Scopus up to April 2024. Observational analytical studies and one non-randomized controlled trial that validated tools for assessing PFP were included. Results: Thirty-three studies were included, covering twenty different tools. Seventeen tools were related to the "Structure and Function" domain, while three addressed "Activity and Participation." The Sunnybrook and House-Brackmann scales were the most extensively studied. The Sunnybrook scale exhibited excellent intra- and inter-rater reproducibility and internal validity, making it suitable for clinical use. The House-Brackmann scale was user-friendly but had limitations in reproducibility and sensitivity to subtle differences, which newer versions like the FNGS 2.0 aimed to address. The FAME scale showed promise by reducing subjective scoring. Computerized tools, such as eFACE and A-FPG, and instruments for lip asymmetry and ocular involvement demonstrated potential but require further validation. The Facial Disability Index and the FaCE Scale were validated for assessing disability and participation restrictions. Conclusion: This review identified several validated tools for PFP assessment, with the Sunnybrook and House-Brackmann scales being the most reliable. While emerging tools and computerized programs show promise, they need further validation for routine clinical use. Integrating validated tools into clinical practice is essential for comprehensive assessment and effective rehabilitation of PFP.