Prevalence of the sphenoid emissary foramen and its clinical relevance in a selected South African population

Abstract

Background: The sphenoid bone is an intricate bone with several features, such as sphenoid emissary foramen (SEF). The SEF serves as a passage for the veins of Vesalius that connects the pterygoid plexus to the cavernous sinus, which acts as a means of transferring extracranial thrombosis to the cavernous sinus. SEF and its content are usually absent in individuals, and it mainly varies in morphology, laterality, and age if present. Notably, the prevalence of SEF regarding sex, laterality, and age remains underexplored. Therefore, this study aims to document the prevalence of SEF about sex, age, and laterality in a selected South African (SA) population.
Materials and Methods: 137 skulls were bilaterally analysed. The middle cranial fossa of each skull was observed for the presence and absence of the SEF. The patency of the SEF was confirmed by inserting a bristle through each probable foramen, and only patent foramina was used for this study.
Results: Out of 137 skulls that were analysed, the SEF was found present in 48 (35.8%) skulls, with a high incidence in the White SA population and the lowest incidence amongst the Black SA population. 29.2% were unilateral (correct 17.5%; left 11.7%), while 6.6% were bilateral. A high prevalence of the SEF was noted in males on the right side. A statistically significant association was obtained between laterality and absence of the foramen about age, p = 0.02. In addition to age, a fluctuating trend was noted in the occurrence of the SEF, where the prevalence was very high in the <29 years age group and decreased from 30-39 years to 60-69 years age group. It then increased again during age advancement. The incidence of SEF is associated with a pathway of the sphenoid emissary veins as it sometimes travels along the mandibular division of the trigeminal nerve through the foramen ovale. Thus making the trigeminal rhizotomy procedure problematic.
Conclusion: SEF was highly prevalent in the SA population, particularly the White SA sample, and on the right side in males. Knowledge of the SEF variations is important during trigeminal rhizotomy procedures to avoid damage to sphenoid emissary veins.