Extradural haemorrhage. Coloured computed tomography (CT) scan of an extradural haemorrhage (extreme right). This is a bleeding into the space between the inner surface of the skull and the external surface of the dura mater, the outer layer of the meninges, which protect the brain. This condition usually results from a blow to the side of the head. A haematoma, a collection of clotted blood, forms and enlarges, increasing pressure within the skull and causing symptoms such as headache, drowsiness, vomiting and paralysis on one side of the body. It is treated surgically by draining the blood clot and clipping the ruptured blood vessels.