Foramen ovale and its neighbourhood: skull variations that influence procedural safety

The foramen ovale (FO) is a key landmark in percutaneous procedures for trigeminal neuralgia (TN), with the lateral pterygoid plate (LPP) aiding its localization. TN interventions through FO have been reported to cause haemorrhage, cranial nerve palsy, and muscle weakness. Although studies have suggested potential neurovascular risks, there is limited scientific evidence to support them. This study aimed to evaluate whether specific skull types pose a higher risk due to the proximity of the FO to neurovascular structures. Thirty dry human skulls were classified into four types based on the LPP and the FO positions. The distances from the FO to the sphenoidal spine, foramen spinosum, alveolar tuberosity, foramen lacerum, carotid canal, inferior orbital fissure (IOF), and foramen of Vesalius were recorded. There were no statistically significant differences in the position of the FO relative to most neighbouring structures across skull types. However, the removed type was significantly farther from the IOF, while the direct type was closer. While previous studies have highlighted technical difficulties with needle insertion in the removed skull type, our findings emphasize the importance of carefully assessing the relationship between the FO and the LPP, as the direct skull type may increase the risk of injury to neurovascular structures traversing the IOF. • The removed skull type showed the greatest mean distance from the inferior orbital fissure (23.4 ± 2.9 mm) • The direct skull type was positioned closest to the inferior orbital fissure • Excessive cranial needle angulation risks ocular injury in about one quarter of the population