Emissary veins passing through the foramen ovale, jugular foramen, foramen lacerum, and hypoglossal canal. 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 but the flow can be altered by increased intracranial pressure. A type of emissary vein goes through the sphenoidal emissary foramen inferior to the zygomatic arch with the cavernous sinus on the inside of the skull. This is an important route for spread of infection because cranial nerve VI and the
Fascial spaces of the head and neck rare and are associated with marked trismus. The pterygomandibular space lies between the medial side of the ramus of the mandible and the lateral surface of the medial pterygoid muscle. The infra-temporal space is the inferior portion of the deep temporal space. Modern understanding of the fascial spaces of the head and neck developed from the landmark research of Grodinsky and Holyoke in the 1930s. They injected a dye into cadevers to simulate pus. Their hypothesis was that infection in the head and neck mainly spread by hydrostatic pressure. This is now accepted to be true for most infections in