The relation between aneurysm size and outcome in patients with subarachnoid hemorrhage.

The balance of risks of treatment for unruptured aneurysms might change if the prognosis after rupture depends on the size of the aneurysm. In a prospective series of patients with subarachnoid hemorrhage in whom aneurysmal size was measured by CT angiography performed on admission, poor outcome occurred more often in patients with large (> or =10 mm) aneurysms (63%) than in patients with small (<10 mm) aneurysms (41%; RR = 1.5; 95% CI 1.0 to 2.2). The relative risk remained essentially the same after adjustment for age, gender, location of the aneurysm, and amount of cisternal blood.