haematoma (heem-ă-toh-mă) n. an accumulation of blood within the tissues that clots to form a solid swelling. Injury, disease of the blood vessels, or a clotting disorder of the blood are the usual causative factors. extradural h. a haematoma caused by tearing of the middle meningeal artery, as a result of injury to the head. intracerebral h. a haematoma caused by bleeding into the brain resulting either from atherosclerosis of the cerebral arteries and high blood pressure or from severe head injury. subdural h. (SDH) a haematoma caused by tearing of the veins where they cross the space beneath the dura. See also perianal haematoma.

haematoma A discrete internal collection of blood which has leaked from damaged blood vessels. At some sites blood can seep away between layers of tissue, but where there are tighter compartments it remains a circumscribed mass which can cause problems by putting pressure on its surroundings. A small one, for example, appears under a fingernail which has been hit with a hammer. At the other extreme a life-threatening one can occur on the surface of the brain (subdural haematoma) following a head injury.

Stuart Judge