Emissary veins

They drain from the scalp, through the skull, into the larger meningeal veins[citation needed] and dural venous sinuses.

[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.

[3] This is an important route for the spread of infection as cranial nerve VI and the internal 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 septic cavernous sinus thrombosis, with resultant damage to the cranial nerves contained within, as well as further spread of the infection leading to meningitis.

[4] Rupture of an emissary vein can result in a subgaleal hemorrhage, a rare but serious injury most often seen as a complication of vacuum extraction.