Prediction of delayed cerebral ischaemia after subarachnoid haemorrhage by computed tomography.

Computed tomography was performed in 100 patients within 4 days of aneurysmal subarachnoid haemorrhage. The CT appearances have been divided into five grades by the thickness and extent of the subarachnoid blood. Delayed cerebral ischaemia occurred in 62.5% of patients with most blood on CT, in 33.3% of those in the next grade and in none of the other grades with less amounts of blood. The outcome from delayed ischaemia was worse in those with most CT blood.