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Background: Patients with Crouzon syndrome develop various types of anatomic deformities due to different forms of craniosynostosis, yet they have similar craniofacial characteristics. However, exact homology is not evident. Different pathology then may be best treated by different forms of surgical technique. Therefore, precise classification of Crouzon syndrome, based on individual patterns of cranial suture involvement is needed., Methods: Ninety-five computed tomography (CT) scans (Crouzon, n = 33; control, n = 62) were included in this study. All the CT scans are divided into 4 types based on premature closure of sutures: class I = coronal and lambdoidal synostosis; class II = sagittal synostosis; class III = pansynostosis; and class IV = "Others." The CT scan anatomy was measured by Materialise software., Results: The class III, pansynostosis, is the most prevalent (63.6%). The classes I, III, and IV of Crouzon have significantly shortened entire anteroposterior cranial base length, with the shortest base length in class III. The external cranial measurements in class I show primarily a decreased posterior facial skeleton, while the class III presented with holistic facial skeleton reduction. Class II has the least severe craniofacial malformations, while class III had the most severe., Conclusion: The morphology of patients with Crouzon syndrome is not identical in both cranial base and facial characteristics, especially when they associated with different subtypes of cranial suture synostosis. The classification of Crouzon syndrome proposed in this study, summarizes the differences among each subgroup of craniosynostosis suture involvement, which, theoretically, may ultimately influence both the timing and type of surgical intervention.

Background: From infancy to adulthood, the mandible develops increased ramus height, prominence of the chin, and laterally widened gonial angles. In Crouzon and Apert syndromes, both relative retrognathia and prognathic jaws have been reported. Growth is influenced by a variety of factors, including the growth and relative position of the skull base, functional coordination, and the spatial influence of the laryngopharynx. Thus, this study aimed to explore in detail the evolution of the mandible in both syndromes and its relationship with the entire facial structure and skull base., Methods: One hundred twenty-three preoperative computed tomographic scans (Crouzon, n = 36; Apert, n = 33; control, n = 54) were included and divided into 5 age subgroups. Computed tomographic scans were measured using Materialise software. Cephalometrics relating to the mandible, facial structures, and cranial base were collected. Statistical analyses were performed using t test and statistical power analysis., Results: In Crouzon syndrome, the angle between the cranial base and gnathion was increased prior to 6 months of age by 10.29 degrees (P < 0.001) and by adulthood to 11.95 degrees (P = 0.003) compared with normal. After 6 months of age, the distance between bilateral mandibular condylions (COR-COL) was narrower by 15% (P < 0.001) in Crouzon syndrome compared with control subjects. Before 6 months of age, Apert COR-COL decreased 16% (P < 0.001) compared with control subjects and 13% (P = 0.006) narrower than Crouzon. During 2 to 6 years of age, Apert mandibular ramus height caught up to, and became longer than, Crouzon by 12% (P = 0.011). The nasion-sella-articulare angle of the Apert skull was 5.04 degrees (P < 0.001) less than Crouzon overall., Conclusions: In Crouzon syndrome, the changes of the spatial relationship of the mandible to the cranial base develop earlier than the mandibular shape deformity, whereas in Apert syndrome, the spatial and morphological changes are synchronous. The morphological changes of the mandible are disproportional in 3 directions, initially significant shortening of the mandibular width and length, and, subsequently, reduced height. Crouzon has more shortening in mandibular height compared with Apert, reflecting the more shortened posterior cranial base length. The narrowed angle between the mandible and the posterior cranial base in Apert skulls is consistent with the more limited nasopharyngeal and oropharyngeal airway space.

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 mm vs 26077.96 ± 4465.74 mm, 52%), with proportionate volume reduction of the anterior (7312.21 ± 2435.97 mm vs 10520.63 ± 2400.43 mm, 30%) and posterior cranial fossa (33487.29 ± 5598.93 mm vs 48325.04 ± 14700.44 mm, 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.

Background: Considerable craniofacial features of Crouzon syndrome are attributed to the dysmorphology of the cranial base. As cephalometric studies have focused mainly on the facial deformity, rather than the cranial base, the underlying cause of deformity is not as well understood. Therefore, the authors compared the cranial base development of Crouzon syndrome to controls to trace the timing of deformity in the cranial base and face, to analyze their temporal correlation., Methods: Ninety computed tomographic scans were included (Crouzon, n = 36; controls, n = 54) and divided into five age subgroups. Craniofacial cephalometric measurements were analyzed by Materialise software., Results: The overall cranial base length in Crouzon syndrome compared with controls decreased 8 percent (p = 0.014) on average. The posterior cranial fossa shortening accounted for most of this reduction. The cranial base displaced with the distances from basion, sella, and ethmosphenoid to posterior nasal spine shortened by 21%, 18%, and 16%, respectively (all p < 0.01) during life. Although the cranial base angle on intracranial surface remains normal, the angles on facial surface narrowed were reduced., Conclusions: The cranial base deformity of Crouzon syndrome consists of the whole skull base and particularly anterior skull base shortening early, leading to a compensatory widened anterior skull base. However, when this widening did not compensate fully for the rapid enlargement of the brain, the posterior skull base displaced inferiorly and became kyphotic. The cranial base deformity develops sequentially anterior to posterior in a probable cascade of influence pattern., Clinical Question/level of Evidence: Risk, II.

The facial malformations of Crouzon syndrome involve the entire cranio-orbito-zygomatic region. The detailed sequence of changes in orbit, zygoma, and maxilla over time, the mutual influence among these three anatomical structures, and their relationship with the cranial base were studied to determine the sequence and timing of deformity. Preoperative CT scans of 36 patients with Crouzon syndrome (mean age 10.84±14.70years; 14 male, 22 female) and CT scans of 54 control subjects (mean age 8.53±13.22years; 29 male, 25 female) were divided into five subgroups by age: 0-6 months, 6 months-2 years, 2-6 years, 6-18 years, and 18-62 years. Craniofacial morphometric cephalometrics were analyzed using Materialise software. Crouzon orbit anteroposterior length was shorter before 6 months (P=0.021) and remained shorter into adulthood (P<0.001). Globe projection was greater across all age subgroups (P<0.001), reaching a peak at 6 months to 2 years (P<0.001). The increased medial orbital width was the most remarkable and persistent secondary deformity (P<0.001). The zygoma anterior protrusion was retruded before 6 months of age (P<0.001), but then improved gradually. The width of maxilla was greater by 24% in the Crouzon cohort (P<0.001), with a difference of 16% before 6 months (P=0.024), and was developed earlier than the shortened anteroposterior length. Crouzon high and shallow orbital walls are distinctive. Maxillary widening developed before the malformation of sphenoid. The anteroposterior position of zygoma is likely a principal deformity, rather than a reflection of the intrinsic shape of the bone. Level of Evidence: II., (Copyright © 2018 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.)