Bleeding from vessels either outside or inside the dura mater.
Tearing of blood vessels which may be traumatic or spontaneous. Extradural haemorrhage results from tearing of the middle meningeal artery. Subdural haemorrhage is caused by traumatic tearing of an epiploic vein. Risk factors include a tendency to fall and clotting abnormalities (including anti-coagulant therapy).
Extradural bleeds may result from a skull fracture (usually the temporal bone with which the middle meningeal artery is closely associated), causing the rapid accumulation of a haematoma in the potential space between the skull and the dura.
Acute subdural haematomas may be seen after a head injury, the large bleed causes a rise in intracranial pressure and neurological deterioration.
Chronic subdural haematoma usually occurs as a result of minor trauma, particularly in the elderly and alcohol abusers. Blood accumulates over days or weeks causing a slow growing haematoma. There may be further accumulation of fluid due to the osmotic pressure of the degenerating blood, or further acute bleeds.
Extradural: There is generally a history of head injury. Classically the patient has a brief loss of consciousness at the time of injury, then a lucid interval followed by development of headache, progressive hemiparesis and loss of consciousness. Cerebellar herniation (coning) causes an ipsilateral dilated pupil, followed by bilateral fixed dilated pupils, tetraplegia and death
Subdural: The onset may be indolent, and symptoms may fluctuate. Headache, drowsiness, and confusion (dementia if chronic) are common. Focal signs may be present and epilepsy may occur.
The diagnosis is confirmed by a CT brain scan.
Extradural bleeds usually require emergency neurosurgery. Subdural haematomas may require surgery, but are often managed conservatively with serial CT scans in patients without an acute history.