(From extra, and vasa, out of the vessels). Extravasation; applied to any part of the fluids of the body out of their proper vessels: thus an ecchymosis. sugillation, or aneurism, may be called extravasation. Extravasated blood, if the air has no access, will not putrefy.

An extravasation on the brain produces apalsy of one leg or arm, or both; dizziness; sleepiness; impaired sight; ravings; bleeding at the nose or ears; vomiting; loss of sense, or stupor. See Cerebri compressio, and Concussio.

Wounds on the head with extravasations are very fallacious, because the extravasation may be between the skull and the dura mater, and under it at the same time; under the pia mater, or in several other parts of the brain: but when these happen, the symptoms immediately portend danger.

When ever the dura mater, either by depression, fissure or fracture, loses its adhesion, there will be, from its broken blood vessels, an extravasation immediately under the bone. An extravasation is less considerable when a fracture of the skull happens, that when there is a fissure. An extravasation is also more or less dangerous, according to the part of the brain injured. Extravasations from a blow are most commonly found between the skull and the dura mater; in this case a lethargy or other symptom will continue, until the extravasation be removed.

The practice recommended by Mr Bromfield in fractures and concussions of the brain (see Concussio) may be useful in some degrees of extravasation; but he adds, that when violent accidents have happened to the head, an issue in the opening, formed by the separation of the additamentum of the temporal bone, is of singular advantage. See his Chirurgical Observations, vol. i.