Facial synkinesis outcome measures: A systematic review of the available grading systems and a Delphi study to identify the steps towards a consensus

Introduction: Facial synkinesis is characterised by abnormal and unintentional co-contractions of facial muscles caused by aberrant facial nerve healing, usually as a sequalae of facial palsy. The aim of this project is to propose a consensus for reporting this condition in the literature to facilitate the conduction of primary and secondary evidence studies, considering that no previous research has inquired in to this matter. Methods: A systematic literature search was performed in MEDLINE and EMBASE databases, considering all the published articles on facial synkinesis. Studies that used a particular measuring system for this condition were included. Two authors independently assessed these articles focusing on the grading instruments utilised. The most commonly used instruments were analysed, and their basic components were incorporated in a modified Delphi survey, which was sent to a panel of experts. Results: The systematic literature search retrieved 502 articles, of which 159 met the inclusion criteria. The two most commonly mentioned instruments were the House–Brackmann Scale and the Sunnybrook Facial Grading System. These were then followed by the Yanagihara scale, the Synkinesis Assessment Questionnaire, the eFace system and the Facial Clinimetric Evaluation. The modified Delphi study concluded that an ideal grading system for facial synkinesis should not only include a clinician-based evaluation of symmetry and signs of synkinesis, but also patient-reported symptoms. Conclusions: Considering the characteristics of the studies found in the literature, the Sunnybrook Facial Grading System fits best with the ideal synkinesis measuring instrument described by the panel of experts. However, in order to satisfy the need to include patient-reported outcomes, the use of the Facial Clinimetric Evaluation as an adjunct to the Sunnybrook Facial Grading System is proposed.