The time course of aneurysmal haemorrhage on computed tomograms.

We performed serial CT scans in a prospective series of 100 patients with a ruptured aneurysm who were first scanned within 2 days of the haemorrhage. In all patients the early CT scan showed evidence of extravasated blood. In 96 patients the source of bleeding was clearly at the base of the brain, and 32 of these had a haematoma. We estimated from the results of 139 repeat scans that the probability of recognizing an aneurysmal haemorrhage on CT is 85% after 5 days, 50% after 1 week, 30% after 2 weeks (mostly patients with haematomas), and almost nil after 3 weeks.