The sphenoidal emissary foramen and the emissary vein: Anatomy and clinical relevance.

Although the sphenoidal emissary foramen (SEF) and its content are anatomically and clinically relevant, accurate description of them in the modern literature is lacking. This study aimed to examine and describe the SEF and its content (the sphenoidal emissary vein [SEV]). We analyzed 1,000 computed tomography (CT) images, 170 dry skulls, 50 formalin-fixed specimens, and three specimens (heads) following guidelines proposed by Dr. Albert L. Rhoton Jr. MD for latex injection. SEV morphology was determined by histological staining and electron microscopy. The SEF was observed in 46.8% of the CTs studied (25.4% bilateral and 21.4% unilateral), and 45.2% of the dry skulls (18.8% bilateral and 26.4% unilateral). In 9.5% of CTs and 21.1% of dry skulls there was a blind channel in the external surface of the cranial base; since there was no communication with the cranial cavity, it was not considered as the SEF. During the dissections, the SEF was found in seven individuals. In three of them, the SEV was an alternative route for venous drainage of the venous plexus of the foramen ovale. Its walls were composed of collagen fibers and its endothelium contained rhomboid cells resembling those commonly found in the superior sagittal sinus. The presence of the SEF and SEV can anatomically explain the spread of certain cranial base pathologies from or toward Meckel's cave or the cavernous sinus, and should be taken into account during procedures in the middle cranial fossa, percutaneous approaches, odontological procedures, and treatment of dural arteriovenous fistulas. Clin. Anat., 33:767-781, 2020. © 2019 Wiley Periodicals, Inc.

Topographic and microscopic anatomical description of the emissary sinus of foramen ovale in adult humans.

OBJECTIVE: Although the Emissary Sinus of Foramen Ovale (ESFO) was first described by Trolard in 1868, its definition remains confused and neglected in the medical literature. This structure represents a vein, two veins, a venous plexus, or a dural sinus? Does it really exist? To understand this topic, this work aimed to describe the anatomy, topography, and microscopic features of the ESFO, precisely characterizing its structure, routes and anatomical correlations. PATIENTS AND METHODS: ESFO from the skull's base of adults were dissected into fifty anatomical blocks and evaluated using Hematoxylin and Eosin, Picro-sirius red and Weigert staining, and by Scanning Electron Microscopy (SEM). RESULTS: ESFO was always present between cavernous sinus and pterygoid plexus on both antimeres, its inferior route passing through the foramen ovale and/or sphenoidal emissary foramen (foramen of Vesalius), anterior to the mandibular branch of trigeminal nerve. Its microscopic arrangement resembled what was found on transverse sinus, that is composed by layers of collagen fibers oriented on transversal and longitudinal planes. It wasn't possible to identify the media and adventitial tunica, features seen in veins, and the elastic layer was very thin near its lumen. SEM analysis showed that, like the transverse sinus, the ESFO was composed by parallel cells that presented a rhombus shape containing central rounded nuclei. CONCLUSION: In summary, the venous channel passing through the foramen ovale and/or sphenoidal emissary foramen (foramen of Vesalius) is a dural venous sinus constituted by dura mater layers and should be considered during surgical approaches near the foramen ovale in the middle cranial fossa.