Ontogenetic changes of diploic channels in modern humans

Abstract

The diploic channels are bony passages of veins, running within frontal, parietal, and occipital bones. In this study, we investigate ontogenetic changes of these channels in a sample of nonadult and adult modern humans. Using computed tomography scans of dried crania, we provide quantitative comparisons of lumen size, branch length, volume, and vascular asymmetries, and correlations with age, cranial size, and bone thickness. The vascular system displays progressive but nonlinear changes throughout ontogeny, becoming even more complex with adulthood. Vascular variables are significantly different in frontal, parietal, and occipital bones for most of the postnatal ontogeny. Diploic channels of the left and right sides are developed similarly. Vascular variables display a nonlinear association with age and cranial size in modern humans. Cranial bone thickness is shown to be a major determinant of lumen size, branch length, and volume. A previous radiographic survey suggested that diploic channels are more developed in adult modern humans than in nonadults. Recent advances in digital anatomy have been used in this study to investigate this craniovascular structure. The complexity of the channels increases during development, with a noticeable boost in adults. Taking into account the potential metabolic differences and constraints associated with modern human brain size and shape, the vascular differences found might be related to endocranial thermoregulation.