3D laser surface scanning and geometric morphometric analysis of craniofacial shape as an index of cerebro-craniofacial morphogenesis: initial application to sexual dimorphism

Background: Over early fetal life, when disturbances in schizophrenia have been posited and craniofacial dysmorphogenesis reported, cerebral morphogenesis proceeds in embryological intimacy with craniofacial morphogenesis. Digitization technologies now allow 3D recording of craniofacial surface landmarks and modeling of craniofacial shape differences using geometric morphometrics. Methods: Using normal sexual dimorphism as an exemplar, facial surfaces of 131 Medical School employees [82 females, 49 males] were recorded in 3D using a portable, handheld laser scanner; 3D coordinate data were then analyzed using geometric morphometrics. Results: Males and females differed markedly on an omnibus test of craniofacial shape. Logistic regression analysis of 16 principal components of shape variability, explaining 84.9% of the overall sample variance, generated 8 principal components as significant and independent discriminators. On visualization, the female face is wider and flatter; the eyes are more lateral, anterior and are further apart, and nasal bridge is posterior; the nose is smaller; the lips are fuller and the chin more forward. These findings are complementary to sexual dimorphism in cerebral structures. Conclusions: This technique reliably discriminates geometric features of craniofacial morphology that are associated with aspects of cerebral morphology, and may inform on putative neurodevelopmental disorders characterised by dysmorphogenesis.