Background: Midface retrusion is the hallmark of the syndromic dysostoses (i.e., Crouzon and Apert). Lack of forward projection and/or structural deficiency could be responsible, but neither has been adequately assessed three-dimensionally. The authors examined both the cranial base/facial interface and the midface volume to provide an understanding of the etiopathogenesis of midface deficiency.
Methods: Children with computed tomographic scans in the absence of any surgical intervention were included. Demographic information was recorded for three groups: Apert, Crouzon, and control. Scans were digitized and manipulated using Materialise software (Surgicase CMF). Craniometric data relating to the midface and sphenoid were collected. Volumetric assessment of the midface was tabulated. Statistical analysis was performed using the t test.
Results: Thirty-six scans were included (control, n=17; Crouzon/Apert, n=19). All children were in the early mixed dentition stage. The anterior cranial fossa proved to be shorter and wider in Crouzon/Apert patients compared with controls. The cranial base angles (N-S-BA, N-S-SO, N-SO-BA, S-SO-BA, and N-S-AR) were not statistically different across the groups. The Crouzon/Apert group showed angles more obtuse between the greater wings of the sphenoid, and more obtuse (more splayed) between the pterygoid plates. Nasion-sella-pterygomaxillary fissure angle was more obtuse (flatter) in the Crouzon/Apert group. There was no volumetric difference in the maxilla, zygoma, and sphenoid comparing the Crouzon/Apert group to controls.
Conclusions: Midface retrusion in the Crouzon/Apert group is associated with altered sphenoid morphology (widened and retruded pterygoid plates), with a flatter and wider maxilla, suggesting diminished growth inferiorly and anteriorly. There is no volumetric deficiency in Crouzon/Apert patients compared with controls.
Clinical question/level of evidence: Risk, II.