Brain haemorrhage. Coloured computed tomography (CT) scan showing a subarachnoid haemorrhage (yellow top centre) affecting the right (left of image) frontal lobe. It was caused by a ruptured aneurysm, a balloon-shaped swelling of a cerebral artery. The bleeding takes place in the space between the arachnoid and the pia mater, the middle and the innermost of the three membranes that cover the brain. Symptoms include paralysis of eye movements, drooping of the lid, dilation of pupil, severe headache and unconsciousness. Treatment consists of general life-support procedures; in some cases a burst aneurysm is surgically treated.