In traumatic and ischaemic (especially in middle cerebral artery occlusion and aneurysmal subarachnoid haemorrhage) brain injury in humans, a phase of delayed deterioration often associated with severe and refractory brain swelling develops between 2 and 5 days after the initial ictus, and is associated with poor or fatal outcome. The cause and mechanism of this deterioration remain poorly understood, and the possibility exists that CSD/PID events might contribute to deterioration.