Neurocranial Morphology in Mandibulofacial Dysostosis (Treacher Collins Syndrome)

An abnormal cranial base could exert a negative influence on neurocranial development. Because patients with mandibulofacial dysostosis (MFD) present an abnormal cranial base (basilar kyphosis), a retrospective mixed longitudinal cephalometric study was designed with the purpose of ascertaining the presence of abnormalities of neurocranial form and size in this population of patients. The lateral and frontal cephalometric radiographs from 33 patients with MFD (15 males, 18 females) ranging in age from 3 years 4 months to 19 years 6 months were used. For comparison cephalometric radiographs from two samples were obtained: one from 24 children (12 male, 12 female) with repaired cleft lip only, and the other from 41 normal young adults (21 male, 21 female). All films were traced, and 9 linear, 1 angular, and 3 derived measurements were obtained from the neurocranium and cranial base. Differences between groups according to age and sex were tested with Student's t-test at the 5% level of significance. A correlation analysis between the cranial base angle and selected neurocranial variables was also conducted. The results showed that although the neurocranium in MFD had normal dimensions in length, height, and volume, it had an abnormal shape. The neurocranium had reduced length anteriorly and increased length posteriorly. The upper cranial height was decreased and the lower cranial height was increased. The difference in shape was evident during childhood and remained in adulthood. The dimensions of the anterior and posterior cranial base, as well as the cranial base angle, were smaller in MFD. A significant negative correlation was found between the cranial base angle and the lower cranial height in MFD.