Mastoidal Emissary Foramina: An Anatomic Morphological Study with a Note on Their Evolutionary and Clinical Implications

Background: The recognition of mastoidal emissary veins is important in the neurosurgical practice to distinguish normal from potentially abnormal structures. Objective: The present study aims to determine the prevalence of mastoidal emissary foramina in the temporal bones of the adult skull and to study their number and morphology. Methods: The present study included 48 adult human skulls (96 temporal bones), which were obtained from the gross anatomy laboratory of our institution. The mastoid parts of the temporal bones were macroscopically observed for the prevalence, number, and morphology of the emissary foramina. Results: We observed that, the mastoidal emissary foramen was present in 88 temporal bones (91.7%) of our specimens. The foramen was observed single in 60 temporal bones (62.5%), found double in 22 bones (22.9%), and triple in 6 temporal bones (6.2%). The mastoidal emissary foramen was absent in eight (8.3%) temporal bones. The foramen was bilaterally absent in three (3.1%) skulls. Conclusion: The mastoidal emissary vein is prevalent in a large number (91.7%) of cases. It was observed that the accessory mastoidal emissary foramina were present in 29.1% of cases. Recognition of these emissary veins and accessory emissary veins during otologic surgery is critical to avoid the potentially catastrophic bleeding. In the neurosurgical practice, the knowledge is important due to variability in their number in the human skull and their relation to the sigmoid sinus.