Extradural haematoma. Magnetic resonance imaging (MRI) scan of an axial section through the skull of a patient with an extradural haematoma (light grey, left centre), a solid mass of blood between the dura mater, the outer membrane of the brain, and the skull. It is due to a haemorrhage caused here by the patient being hit by a bus. The haematoma increases pressure within the skull, causing headache, drowsiness, vomiting, paralysis, and in some cases death. Treatment is with surgical drainage of the haematoma and sealing of the bleeding blood vessel.