Gabrick, Kyle S.

Background: The morphologic effect of squamosal synostosis has not been clarified, due to its low occurrence rate, and its inclination to be combined with premature closure of other major sutures, especially in syndromic synostosis. This study's goal is to explore the morphological influence of squamosal synostosis in both syndromic and nonsyndromic craniosynostosis patients. Methods: Twenty-five computed tomography (CT) scans from nonsyndromic squamosal synostosis (NSS), Crouzon syndrome with squamosal synostosis (CSS), Crouzon syndrome without squamosal synostosis, and normal controls were included. Three-dimensional (3D) cephalometry, entire cranial volume and cranial fossa volume were measured using Materialise software. Results: The entire cranial volume of all groups was similar. The NSS developed a gradual reduction in the severity of reduced segmental volume from the anterior cranial fossa, to the middle cranial fossa, and to the unaffected volume of posterior cranial fossa. The CSS developed the most severe volume reduction of middle cranial fossa (12608.30 ± 2408.61 mm3 vs 26077.96 ± 4465.74 mm3, 52%), with proportionate volume reduction of the anterior (7312.21 ± 2435.97 mm3 vs 10520.63 ± 2400.43 mm3, 30%) and posterior cranial fossa (33487.29 ± 5598.93 mm3 vs 48325.04 ± 14700.44 mm3, 31%). The NSS developed a narrower anterior cranial fossa, a clockwise rotated Frankfort horizontal plane, and a retracted chin (pogonion). Conclusion: Squamosal synostosis may alter the development of cranial fossa volume, especially the volume of middle cranial fossa. However, the development of cranial base, and related facial features are determined largely by major vault sutures and associated syndromic conditions, rather than the squamosal suture alone. Level of Evidence: II

Abstract Complicated craniofacial malformations interfacing with multiple intracellular regulatory mechanisms, lead to ambiguous growth patterns in Apert syndrome. This study aims to explore the chronology and pathogenesis of the development of craniofacial anatomic relationships and to verify the positional correlates between skull and facial structures in Apert syndrome. Fifty-four computed tomography scans (Apert, n = 18; control, n = 36) were included and divided into 3 age subgroups. Craniofacial 3-dimensional cephalometries were analyzed by Materialize software. The angle between sella-nasion plane and maxillary plane widens 7.74° (P = 0.003) prior to 6 months of age; thereafter, this widening increases by 10.36° (P < 0.001) in 6 months to 2 years of age, and remains increased by 8.9° (P = 0.046) throughout childhood. The angle between Frankfort horizontal plane and maxillary plane widens 5.17° (P = 0.022) before 6 months. Angles SNA, SNB, and ANB showed decreases, averaging 12.23° (P < 0.001), 5.19° (P = 0.004), and 6.72° (P = 0.001), respectively. The linear measurements showed synchronicity and continuing deformity into adulthood. Between 6 months to 2 years of age, the distance from sella to nasion (S-N), anterior nasal spine (S-ANS), and posterior nasal spine (S-PNS) decreased 8% (P = 0.006), 16% (P < 0.001), and 19% (P = 0.002), respectively, and remained shortened into adulthood. The angulation changes occur earlier in development than linear distance reduction in Apert syndrome patients compared with controls. Angular adjustments were not sufficient to maintain normal cranial base length. Facial deformity of Apert syndrome temporally begins with the midface, and affects orbit and mandible later in life.