Skeletal and Soft-tissue Facial Shape Changes in Facial Weakness Disorders

Objectives: Moebius syndrome and other facial weakness disorders are characterized by partial or complete facial paralysis resulting in a mask-like facies. The aim of this study is to examine and compare the skeletal and soft tissue morphology in patients with facial weakness disorders.
Methods: Patients were enrolled in an IRB-approved protocol at multiple sites. Bjork cephalometric analysis was performed on CBCT images (Planmeca ProMax 3D) using InVivo5 (Anatomage); 3D facial photos (Planmeca ProFace) were examined using geometric morphometric analysis. We used an age, gender and ethnicity matched control group for the 3D photos.
Results: Sixteen patients (mean age 39 years, range 17-64 years; 8 females) with Moebius Syndrome, isolated hereditary congenital facial paresis, Carey-Fineman-Ziter Syndrome, congenital fibrosis of the extraocular muscles, or other complex syndromes were included. In some cases associated molecular diagnoses were known. Patients with facial weakness disorders had significantly longer upper facial heights, long lower facial heights due to an open bite and mandibles were small and retrognathic. The anterior and posterior cranial base measured significantly below the norm.
The 15 subjects who had complete 3D photos had significant shape differences compared to the control group (p=0.0010). There was lengthening of the face, widening of the lips, and underdevelopment of the maxilla and mandible. We found evidence suggestive of shape differences among the different clinical and/or molecular diagnoses. Cases had significantly increased variance but also greater levels of integration, suggesting that the shape changes that occur in facial weakness disorders are strongly coordinated.
Conclusions: Our study demonstrates distinct skeletal and facial shape variations among patients with facial weakness disorders that may segregate with specific diagnoses. These shape variations appear strongly coordinated, suggestive of correlation with cranial nerve and craniofacial development. Future work is focused on increasing cohort sizes and improving classification criteria among congenital facial weakness disorders.