Persing, John A.

Background: 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. Methods: 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. Results: 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. Conclusion: 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.

Background: The association of isolated craniosynostosis and the influence of syndromic forms confound the understanding of craniofacial morphologic development. This study attempts to clarify the individual influences of isolated bicoronal synostosis, Apert syndrome, and Crouzon syndromes on skull base morphology. Methods:: One hundred seventeen computed tomographic scans were included (nonsyndromic bicoronal synostosis, n = 36; Apert syndrome with bicoronal synostosis, n = 25; Crouzon syndrome with bicoronal synostosis, n = 11; controls, n = 45). Cephalometric measurements were analyzed using Materialise software. Results: Nonsyndromic bicoronal synostosis patients developed a shortened cranial base length, with a significantly shortened distance between nasion and sella (p = 0.005). The cranial base angles of nonsyndromic bicoronal synostosis in both the cranial side (N-S-BA) and facial side (N-SO-BA) increased significantly, by 17.04 degrees (p < 0.001) and 11.75 degrees (p < 0.001), respectively. However, both the N-S-BA and N-SO-BA angles of Apert syndrome and Crouzon syndrome were narrowed more than that of nonsyndromic bicoronal synostosis [by 12.11 degrees (p < 0.001) and 12.44 degrees (p < 0.001), respectively, in Apert syndrome; and by 11.66 degrees (p = 0.007) and 13.71 degrees (p = 0.007), respectively, in Crouzon syndrome]. However, there is no statistically significant difference of these two angles between Apert syndrome and Crouzon syndrome, when they were only associated with bicoronal synostosis. Contrary to the relatively normal subcranial space of nonsyndromic bicoronal synostosis, both Apert and Crouzon syndromes developed a reduced subcranial space. Conclusions: Isolated bicoronal synostosis resulted in a flattened cranial base, whereas Apert syndrome and Crouzon syndrome developed a normal cranial base angle when only associated with bicoronal synostosis. The syndromic skulls had additional significantly reduced subcranial space.

Background: Racial disparity in pathological consequences in skull growth may impact the treatment plan for different patient populations. This study attempts to explore the differences between Asian and Caucasian cranial morphology in Crouzon syndrome. Method: Ninety-one computed tomographic scans were included (Asian Crouzon syndrome, n = 12; Asian controls, n = 22; Caucasian Crouzon syndrome, n = 16; Caucasian controls, n = 41), and measured using Mimics and 3-matics software. Results: The entire cranial base length was reduced 11.92 mm (P = 0.004) in Asian Crouzon patients, and 14.58 mm (P < 0.001) in Caucasian Crouzon patients, compared to respective controls. The cranial base angle on the facial side of basicranium was more narrowed in Crouzon syndrome in both races, with similar changes of degrees (9.61°, P = 0.002, in Asian Crouzon; 9.20°, P = 0.019, in Caucasian Crouzon). However, the intracranial side was statistically more narrowed only in the Asian group (9.86°, P = 0.003). Both Asian and Caucasian Crouzon patients developed reduced posterior fossa volume, by 15% (P = 0.034) and 17% (P = 0.004), respectively. However, Caucasian Crouzon patients developed a more shortened anterior and middle cranial base, than that of Asian patients. The separation of lateral pterygoids was only significantly increased in Caucasian patients (5.49°, P < 0.001). Conclusion: Crouzon syndrome causes a shortened, widened, and kyphotic cranial base across both races. It also restricts the development of the posterior cranial fossa. However, the skull malformation is not the same between populations: Asian Crouzon patients developed more narrowed cranial base angulation on the intracranial side of basicranium, while Caucasian Crouzon patients developed more widened lateral pterygoids.

Background: Apert syndrome causes normal or enlarged intracranial volume overall as patients grow. This study aimed to trace the segmental anterior, middle, and posterior cranial fossae volume and structural morphology in these patients, to help discern a more focused and individualized surgical treatment plan for patients with Apert syndrome. Methods: This study included 82 preoperative computed tomographic scans (Apert, n = 32; control, n = 50) divided into five age-related subgroups. The scans were measured using image processing and three-dimensional modeling software. Results: The middle cranial fossa volume was increased and was the earliest change noted. It was increased by 45 percent (p = 0.023) compared with controls before 6 months of age and remained increased into adulthood (161 percent, p = 0.016), with gradually increasing severity. The anterior and posterior cranial fossae volumes also increased, by 35 percent (p = 0.032) and 39 percent (p = 0.007), respectively. Increased depth of cranial fossae contributed most to the increase in volumes of patients with Apert syndrome, with correlation coefficients of 0.799, 0.908, and 0.888 for anterior, middle, and posterior cranial fossa, respectively. The intracranial volume was increased 12 percent (p = 0.098) across the entire test age range (0 to 26 years old), but only had statistical significance during the age range of 6 to 18 years (22 percent, p = 0.001). Conclusions: Malformation of the middle cranial fossa is an early, perhaps the initial, pivotal cranial morphologic change in Apert syndrome. Increased cranial fossae depth is an inherent characteristic of the maldevelopment. Normalization of cranial volume and circumference overall may not achieve a normal skull structure, as it does not correct regional craniocerebral disproportion.

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: Based on an established classification system of Crouzon syndrome subtypes, detailed regional morphology and volume analysis may be useful, to clarify Crouzon cranial structure characteristics, and the interaction between suture fusion and gene regulated overall growth of the calvarium and basicranium. Methods: CT scans of 36 unoperated Crouzon syndrome patients and 56 controls were included and subgrouped as: type I. Bilateral coronal synostosis; type II. Sagittal synostosis; type III. Pansynostosis; type IV. Perpendicular combination synostosis. Results: Type I of Crouzon syndrome patients developed a slightly smaller posterior fossa (22%), and increased superior cranial volume (13%), which is the only subtype that develops a greater superior cranial volume. The effect of competing increased and decreased segmental volume is associated with a 24% enlargement of overall cranial volume (P = 0.321). In class III, the anterior fossa volume was increased by 31% (P = 0.007), while the volume of posterior fossa was decreased by 19% (P < 0.001). These resulted in a 7% (P = 0.046) reduction in the overall intracranial volume. Type II and type IV patients developed a trend toward anterior, middle, and posterior fossae, and entire cranial volume reduction. Conclusions: Pansynostosis is the most often form of associated craniosynostoses of Crouzon syndrome, however bilateral coronal synostosis may not dominate this form of Crouzon syndrome. The anterior, middle and posterior cranial fossae may have simultaneously reduced volume if the midline suture synostosis is involved. Individualized treatment planning for Crouzon syndrome patient, theoretically should include the patient's age and temporal associated maldevelopment suture sequence.

Background: Based on an established classification system of Apert syndrome subtypes, detailed regional morphology and volume analysis may be useful to provide additional clarification to individual Apert cranial structure characteristics, and treatment planning. Methods: Computed tomography scans of 32 unoperated Apert syndrome and 50 controls were included and subgrouped as: type I, bilateral coronal synostosis; type II, pansynostosis; type III, perpendicular combination synostosis. Three-dimensional analysis of craniometric points was used to define structural components using Materialise Mimics and 3-Matics software. Results: Occipitofrontal circumference of all subtypes of Apert syndrome patients is normal. Intracranial volumes of types I and II were normal, but type III was 20% greater than controls. Middle cranial fossa volume was increased in all 3 types, with the greatest increase in type II (86%). Type II developed a 69% increase in anterior cranial fossa volume, whereas type III had 39% greater posterior cranial fossa volume. Increased cranial fossa depth contributed most to above increased volume. The anteroposterior lengths of middle and posterior cranial fossae were reduced in type I (15% and 17%, respectively). However, only the anterior cranial fossa was significantly shortened in type III. Conclusions: Occipitofrontal circumference and overall intracranial volume is not always consistent in individual subunits of Apert syndrome. Detailed and segmental anterior, middle, and posterior cranial fossae volumes and morphology should be analyzed to see what impact this may have related to surgical planning.