cerebral vasospasm cerebral vasospasm cerebral vasospasm is the prolonged, intense vasoconstriction of the larger conducting arteries in the subarachnoid space which is initially surrounded by a clot. significant narrowing of the blood vessels in the brain develops gradually over the first few days after the aneurysmal rupture. this kind of narrowing usually is maximal in about a week's time following intracerebral haemorrhage. vasospasm is one of the leading causes of death after the aneurysmal rupture along with the effect of the initial haemorrhage and later bleeding.