Three-dimensional orbital dysmorphology in metopic synostosis

Background: Metopic synostosis is characterized by trigonocephaly, lateral supraorbital retrusion, and hypotelorism. Most phenotypic evaluations have focused on the forehead without much emphasis on the orbits. The study seeks to explore differences in orbital dysmorphology for metopic and control patients, along with different degrees of metopic synostosis.

Methods: Demographic and craniometric data were compiled. CT scans were digitized (Materialise) and metopic and control groups were compared. Degree of trigonocephaly was classified into moderate and severe cases based on endocranial bifrontal angle. Orbital plane angle, width, depth, volume, and corneal projection were measured. Statistical two-paired t-tests were used, with significance determined as p<0.05.

Results: Forty-six CT scans were analyzed (23 affected, 23 controls). Mean ages (6 months metopic, 7 months control) and genders (18 males metopic, 10 males control) were determined. Orbital plane angle measurements showed differences between the metopic and the control (p=0.0002), along with a correlation to trigonocephaly (p=0.0097). Orbital width and height were insignificant between controls and overall metopics, though height was less in severe metopics (p=0.046 left, p=0.0337 right). Orbital Depth was significant between control and metopics (p=0.0106 left, p=0.0025 right), and pronounced in severe cases p=0.0349 left, p=0.0071 right). Corneal Projection correlates with metopic severity (p<0.01 left, right), while orbital volume showed insignificant change between control and metopic cases.

Conclusions: Orbital dysmorphology worsens with increasing degree of trigonocephaly, presenting additional functional defects. The true exorbitism most directly correlates with worsening trigonocephaly. Expanding and advancing the lateral orbital wall is a critical treatment element in correction.

Level of evidence: III.