Facial Asymmetry Index: Validation and Applications in Various Smile Restoration Techniques

Abstract

Consistent and objective evaluation of the paralyzed face is imperative for documenting preoperative findings and assessing postoperative outcomes of reanimation techniques. Static and dynamic facial asymmetry are the key features of the paralyzed face. To date, there is no consensus among surgeons on how best to document facial asymmetry. The authors propose a Facial Asymmetry Index (FAI) as an objective measure of facial asymmetry and validate its use and reliability across numerous reanimation techniques. Frontal photographs of patients with unilateral facial nerve paralysis were analyzed. The length from the medial canthus to the ipsilateral oral commissure was compared between affected and nonaffected sides. The FAI is the difference between the two values, with a higher value reflecting poorer facial symmetry. Validation and reliability testing was then performed. There was a consistent decrease in the FAI with procedural intervention (FAI pre = 10.1, FAI post = 3.17; p < 0.0001). Furthermore, there was excellent inter- and intrarater reliability among independent judges. The FAI is a powerful and accessible tool to quantify operative outcomes for many lower facial nerve reanimation techniques.

Keywords

facial paralysis - facial reanimation - outcome assessment

• References

• 1 Fattah AY, Gurusinghe ADR, Gavilan J. , et al; Sir Charles Bell Society. Facial nerve grading instruments: Systematic review of the literature and suggestion for uniformity. Plast Reconstr Surg 2015; 135 (02) 569-579
• 2 Wang TT, Wessels L, Hussain G, Merten S. Discriminative thresholds in facial asymmetry: A review of the literature. Aesthet Surg J 2017; 37 (04) 375-385
• 3 Kochhar A, Albathi M, Sharon JD, Ishii LE, Byrne P, Boahene KD. Transposition of the intratemporal facial to hypoglossal nerve for reanimation of the paralyzed face: The VII to XII transposition technique. JAMA Facial Plast Surg 2016; 18 (05) 370-378
• 4 Albathi M, Oyer S, Ishii LE, Byrne P, Ishii M, Boahene KO. Early nerve grafting for facial paralysis after cerebellopontine angle tumor resection with preserved facial nerve continuity. JAMA Facial Plast Surg 2016; 18 (01) 54-60
• 5 Rüfer F, Schröder A, Erb C. White-to-white corneal diameter: Normal values in healthy humans obtained with the Orbscan II topography system. Cornea 2005; 24 (03) 259-261
• 6 Chu EA, Farrag TY, Ishii LE, Byrne PJ. Threshold of visual perception of facial asymmetry in a facial paralysis model. Arch Facial Plast Surg 2011; 13 (01) 14-19
• 7 Hohman MH, Kim SW, Heller ES, Frigerio A, Heaton JT, Hadlock TA. Determining the threshold for asymmetry detection in facial expressions. Laryngoscope 2014; 124 (04) 860-865