Racial Disparity of Crouzon Syndrome in Skull and Orbit Morphology, and Their Spatial Relationships

Abstract

BACKGROUND: Racial disparity in pathological consequences in skull and orbit growth may impact the treatment plan for different patient populations. This study explores skull anatomy for potential differences between Asian and Caucasian cranial morphology in Crouzon syndrome. METHOD: Ninety-one computed tomographic scans were included (Asian Crouzon, n = 12; Asian controls, n = 22; Caucasian Crouzon, n = 16; Caucasian controls, n = 41), and measured using Mimics and 3-matics software. Unique cephalometric measurements related to the orbit were designed. 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 with 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). The orbital roof anteroposterior length of Caucasian Crouzon syndrome patients was shortened by 4.03 mm (P = 0.009) compared with Caucasian controls. However, this dimension in Asian patients developed normally. The orbital anteroposterior floor length significantly reduced in both Asian and Caucasian Crouzon syndrome patients, to a similar extent. The medial horizontal angle of single orbit was narrower in Asian patients, compared with Asian controls (19.24°; P = 0.002), yet only insignificantly reduced in Caucasian patients. The visual axes of Caucasian Crouzon syndrome patients had more inferior rotation, by 5.21° (P = 0.005) than in Caucasian controls but did not achieve a statistically significant difference in other comparison pairs. A widened ethmoid sinus is the major shortening in the restricted orbit cone angle in Asian Crouzon syndrome patients, while statistically significant widening of the sphenoid is noted only in Caucasian patients. CONCLUSION: The influence of Crouzon syndrome on cranial and orbital malformation is race influenced. Asian Crouzon patients developed more kyphotic basicranium evaluated intracranially, whereas Caucasian Crouzon patients developed more widened lateral pterygoid bones. The unaffected orbital roof length and shortened orbital floor in Asian Crouzon syndrome patients indicates the Lefort III osteotomy probably is more beneficial in this group of patients than in monobloc advancement.