QS3: Influence Of Nonsyndromic Bicoronal Synostosis And Syndromic Influences On And Periorbital Malformation

Abstract

Background Oculo-orbital disproportion in patients with craniosynostosis have similarities and dissimilarities between syndromic and nonsyndromic cases. We hypothesize these two conditions have specific individual influences as it relates to development of the orbital and periorbital skeletons. Method A total of 133 preoperative CT scans (nonsyndromic bicoronal synostosis, n=38; Apert syndrome bicoronal synostosis subtype, n=33; Crouzon syndrome bicoronal synostosis subtype, n=10; controls, n=52) were included. Craniometric and volumetric analyses related to the orbit and periorbital anatomy were performed. Results The orbital cavity volume is mildly restricted in nonsyndromic bicoronal synostosis (7%, p=0.147), but more so in Apert and Crouzon syndromes, 17% (p=0.002) and 21% (p=0.005), respectively. The sphenoid side angle in Apert syndrome is wider than when compared to Crouzon syndrome (p=0.043). The ethmoid side angle in Apert patients however is narrower (p=0.066) than that in Crouzon patients. Maxilla anteroposterior length is more restricted in Apert syndrome than Crouzon syndrome (21%, p=0.003) and nonsyndromic cases (26%, p<0.001). The posterior nasal spine position is retruded in Crouzon syndrome (39%, p<0.001), yet the anterior nasal spine position is similar in Apert and Crouzon syndromes. Conclusion Orbit and periorbital malformation in syndromic craniosynostosis is likely the combined influence of syndromic influences and premature suture fusion. Apert syndrome expands the anteriorly contoured lateral orbital wall associated with bicoronal synostosis, while Crouzon syndrome has more infraorbital rim retrusion, resulting in more severe exorbitism. Apert syndrome develops maxillary hypoplasia, in addition to the maxillary retrusion, observed in Crouzon syndrome and nonsyndromic bicoronal synostosis patients.