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
Drug delivery to the brain these characteristics that makes a drug able to pass through the blood–brain barrier. The study found that barrier permittivity is "based on the measurement of the surface activity and as such takes into account the molecular properties of both hydrophobic and charged residues of the molecule of interest." They found that there is not a simple answer to what compounds transverse the blood–brain barrier and what does not. Rather, it is based on the complex analysis of the surface activity of the molecule as well as relative size. Other problems persist besides just simply getting through the blood–brain barrier. The