Vascular Microforamina in Adult Human Braincase: A Survey on Dry Skulls

Microforamina are small vascular passages on the endocranial surface of the braincase, connecting the diploe of the vault bones with the endocranial space. Recently, they have been hypothesized to be involved in brain immune response and inflammation. At present, they have been described through biomedical imaging, but information on their general anatomy is still missing.

A sample of 94 dry skulls from a mid-20th-century Northern-Spanish collection has been examined to supply a morphological description of the dimensions and distribution of these channels in adult humans. The size of the channels was measured through digital photographs, and their distribution was investigated throughout the vault endocranial surface.

The size of the visible channels ranges from 0.03 to 2.00 mm, although most of them may range between 0.05 and 0.15 mm. The individual variation in terms of prevalence and distribution is noticeable. The main regions presenting these vascular passages are the midsagittal posterior part of the parietal bones and the anterior branch of the middle meningeal vessels. Very small vessels can be found spotted along the minor branches of the middle meningeal artery, spreading through the parietal squama. The lambdoid region also frequently displays scattered channels.

The association of these microforamina with venous sinuses and meningeal vessels stresses further the possible relationships with immune responses, clearance, and the glymphatic system. Future surveys should be devoted to investigating sexual differences, ontogenetic changes, pathological conditions, and the presence of these craniovascular features in other primates and fossil hominids.