Vascular microforamina: A preliminary quantitative study on prevalence and cranial correlates in adult humans

Microforamina are small vascular channels connecting the cranial diploe to the endocranial space, hypothesized to play a role in thermoregulation and neuroimmune functions, yet their quantitative anatomy is poorly documented in humans and, in general, in vertebrates. This preliminary study provides the first analysis of their number, size, and correlation with skull thickness in 10 modern human crania, using high-resolution industrial tomography (0.25 mm voxel size). Results show substantial interindividual variability, with an inverse relationship between channel size and frequency. Although the smallest channels were most numerous, the larger ones contributed to a comparable total luminal area. Medium-sized channels show statistically significant correlations with cranial thickness: negative correlations with inner table thickness and positive correlation with diploic space proportion, specifically in the parietal and occipital bones. These preliminary findings establish a quantitative baseline, indicating that microforamina prevalence is more influenced by the thickness of the vault layers than with general cranial size.