Sphenoid Bone Structure and Its Influence on the Cranium in Syndromic Versus Nonsyndromic Craniosynostosis

Little is known about the detailed growth of the sphenoidal and temporal bones, even though they contribute significantly to the cranial base and cranial fossa skeletons. They also serve to connect the cranial vault with facial structure. This study details their morphologic development in isolated bicoronal synostosis and associated syndromes.

Eighty-one CT scans were included (nonsyndromic bicoronal synostosis, n = 28; Apert syndrome associated with bicoronal synostosis, n = 19; Crouzon syndrome associated with bicoronal synostosis, n = 8; and controls, n = 26), and measured using Materialize software.

Sphenoidal and temporal bone volumes in nonsyndromic bicoronal synostosis are reduced 23% (P = 0.005) and 24%(P = 0.003) at 6 months of age, compared to controls. Apert and Crouzon syndrome patients developed similar reduced volumes. The greater wing of the sphenoid and pterygoid processes in nonsyndromic bicoronal synostosis are initially inferiorly rotated at 2 months of age, by 9.60° (P = 0.002) and 4.33° (P = 0.023), respectively. In Apert syndrome, these rotations were reduced by 4.82° (P = 0.003) and 12.60° (P < 0.001), (like Crouzon syndrome). However, in Apert syndrome, the length of pterygoid processes is shortened by 11% (P = 0.018) compared to nonsyndromic bicoronal synostosis. Crouzon syndrome skulls did not develop a statistically significant shortening relative to nonsyndromic bicoronal synostosis. Mediolateral expansion of the sphenoid in nonsyndromic bicoronal synostosis was less than normal (P = 0.023), and it was further reduced in syndromic skulls.

Isolated bicoronal synostosis tends to reduce the volume of sphenoidal and temporal bones, and inferior and posterior rotation of the entire sphenoid. Syndromic conditions restrict sphenoidal rotation, and limit the expansion of sphenoidal greater wing and pterygoid plate.