Emissary Veins

Description

The emissary veins are small veins which pass through various foramina inside the skull to connect the intracranial venous sinuses with the extracranial veins. Learning their anatomy has clinical implications as these venous channels could provide a route for the spread of infection from outside the cranium into the venous sinuses intracranially. For instance, the spread of infection from the paranasal sinuses to the cavernous sinus.

Examples of a few important emissary veins have been given below:

- mastoid emissary vein interconnects auricular or occipital veins from suboccipital venous plexus with the sigmoid sinus;

- parietal emissary vein interconnects the veins of the scalp with the superior sagittal sinus;

- condylar emissary vein interconnects the sigmoid sinus with veins in the suboccipital triangle;

- occipital emissary vein interconnects the confluence of sinuses with the occipital vein;

- venous plexus of foramen ovale, a plexus of emissary veins, which passes through the foramen ovale and interconnects the cavernous sinus and the pterygoid plexus of veins;

- internal carotid venous plexus, which passes through the carotid canal, connects the cavernous sinus and the internal jugular vein;

- venous plexus of foramen lacerum contains two or three small veins which traverse the foramen lacerum and interconnect the cavernous sinus and the pharyngeal veins and pterygoid plexus;

- emissary vein through the sphenoidal foramen (of Vesalius) connects the cavernous sinus with the pharyngeal veins and pterygoid plexus.

The ophthalmic veins are potentially emissary veins, as they interconnect intra- and extracranial veins.

It should be noted that emissary veins are valveless channels and, hence, the venous blood can flow in either direction (Tubbs, Shoja and Loukas, 2016; Mortazavi et al., 2012).