| Emissary veins | |
|---|---|
| Details | |
| Identifiers | |
| Latin | vena emissaria |
| TA98 | A12.0.00.033 A12.3.05.301 |
| TA2 | 4872 |
| FMA | 50790 |
| Anatomical terminology | |
Theemissary veins connect the extracranial venous system with the intracranial venous sinuses. They connect theveins outside the cranium to the venous sinuses inside the cranium. They drain from the scalp, through theskull, into the largermeningeal veins[citation needed] anddural venous sinuses. They may also connect todiploic veins within the skull.[1]
Emissary veins have an important role in selective cooling of the head. They also serve as routes where infections are carried into the cranial cavity from the extracranial veins to the intracranial veins.
There are several types of emissary veins including the posterior condyloid, mastoid,occipital and parietal emissary veins.[1]
There are also emissary veins passing through theforamen ovale,jugular foramen,foramen lacerum, andhypoglossal canal.[citation needed]
Because the emissary veins are valveless, they are an important part in selective brain cooling through bidirectional flow of cooler blood from the evaporating surface of the head. In general, blood flow is from external to internal[2] but the flow can be altered by increased intracranial pressure.
One notable emissary vein, thevein of Vesalius, travels through thesphenoidal emissary foramen inferior to thezygomatic arch, connecting thepterygoid plexus with thecavernous sinus.[3] This is an important route for the spread of infection ascranial nerve VI and theinternal carotid pass through the cavernous sinus, with cranial nerves III, IV, V1, and V2 passing alongside the lateral wall of the sinus. Subsequent infection or inflammation in the cavernous sinus can result in septiccavernous sinus thrombosis, with resultant damage to the cranial nerves contained within, as well as further spread of the infection leading tomeningitis.[4]
Rupture of an emissary vein can result in asubgaleal hemorrhage, a rare but serious injury most often seen as a complication ofvacuum extraction.[5]
