Brain haemorrhage. Computer artwork of a transverse section through the head of a person with a subdural haematoma (red). Front of the head is at top. A subdural haematoma is the bleeding and subsequent formation of a blood clot between the membranes surrounding the brain. This is often fatal as the mass puts pressure on the brain, damaging the tissue. It can be caused by impact injuries and is more common in the elderly, as the blood vessels involved become more fragile with age. Treatment is usually with the surgical removal of the clot.