Enlarged parietal foramina: a rare finding in a female Greek skull with unusual multiple Wormian bones and a rich parietal vascular network

Abstract

Enlarged parietal foramina (>5 mm) is an extremely rare developmental defect of the parietal bone, which is distinguished from the normal small parietal foramina, as genes associated with this entity have been identified, suggesting that it is hereditary in nature. We describe a dry skull of a 35-year-old female, with enlarged parietal foramina symmetrically situated bilaterally, oval in shape, measuring 4.5 × 9.3 mm (right) and 4.9 × 9.2 mm (left) in size. The foramina coexisted with multiple Wormian bones in several sites of the skull. On the inner parietal bone surface, the anterior, posterior and lateral foramina's rims carried grooves, which were continuous with the middle meningeal vessels' branches, indicating that a rich vascular network existed around the foramina. These vascular grooves also notched the external table at the margin of the foramina, which suggests a potential communication between the meningeal and the scalp vessels. In addition, this vascular variation should be taken into consideration when performing surgical interventions in the area, because the large vascular supply to the foramina is a possible source of extensive bleeding. Moreover, the interaction of intracranial and extracranial veins and the fact that the blood flows in them in both directions, as they are valveless, could represent a possible pathway for infections to spread in the cranial cavity.