Dynamic three-dimensional facial topography in pediatric facial palsy: Understanding asymmetrical facial contours

Background: Objective assessment of facial movements remains pivotal for diagnosis, treatment, and long-term monitoring of patients with facial palsy (FP). This study aims to utilize curvature analysis in pediatric patients with and without FP to define facial contours and to quantify three-dimensional (3D) excursion during smile.

Methods: Pediatric patients with and without FP had 3D motion capture acquired from rest to maximum smile positions. 3D curvature analysis was performed with a custom MATLAB algorithm. A 40-vertex "smile curve" along the nasolabial fold-cheek-orbit contour was extracted from each patient-specific 3D mesh hemiface. This allowed the quantification of excursion and asymmetry for affected vs. unaffected sides in FP patients, and comparison with controls.

Results: Twelve FP (mean 12.5 yr, range 5-18) and 12 control (mean 12.1 yr, range 5-18) patients were analyzed. Differences in facial contour are intensified during animation, especially in the nasolabial fold, cheek, and periorbital regions of interest and the smile curve that links them. Mean excursion differed significantly between the FP and control groups in all regions of interest (p < 0.0001).

Conclusions: Curvature analysis provides insight into the unexplored relationship of the 3D morphological dynamics of the concavity and convexity of the face, to add to the understanding of this complex condition. The magnitude of asymmetry between an FP patient's affected vs. unaffected smile curve excursion, and comparison to the control group, could allow surgical treatment to be tailored to an individual patient's dynamic anatomy by identifying and quantifying facial region-specific asymmetry.