Subdural haematomas occur when bridging veins between the cortical veins and dural sinuses are torn as they cross the subdural space following trauma, often minor. The risk increases with brain atrophy which allows increased relative movement between the brain and fixed dural sinuses. The haemorrhages are bilateral in 10 per cent, mainly occurring over the cerebral hemispheres. Acute lesions show clotted blood overlying a flattened brain. Chronic lesions show an organizing membrane arising from the dural surface.
Recurrent haemorrhages can arise in the vessels of the granulation tissue of the membrane.
Subarachnoid haemorrhages when associated with trauma are usually associated from contusions with vessel rupture at the surface of the brain. Traumatic extradural haematoma. There was no haemorrhage into the brain substance. Early surgical intervention would probably have saved this patient's life. The diagnosis was missed during life, illustrating the clinically treacherous nature of this condition.