Computed tomography and subarachnoid hemorrhage.

CT scans have been made on 39 of 41 patients who presented with subarachnoid hemorrhage. Blood could be visualized in the cisterns of 18 of 32 examinations performed within five days of the hemorrhage all having aneurysms. Among the other 14 there were three in whom no aneurysm was found on angiography. The distribution of blood in those that showed it was useful in pointing to the position of the aneurysm. Much other information was obtained, for instance about rebleeding and infarction. CT should routinely be the primary examination, followed by selective angiography.