Relation between size of aneurysms and risk of rebleeding in patients with subarachnoid haemorrhage

Background and purpose. Few risk factors have been identified for rebleeding in patients with subarachnoid haemorrhage. We studied whether size of aneurysm after rupture is a risk factor for rebleeding. Since intracranial aneurysms develop during life and may therefore be larger at an older age, we also assessed whether age confounds a relation between size and rebleeding. Methods. We studied all patients with aneurysmal subarachnoid haemorrhage admitted between 1995 and 2000. Since 1995 CT-angiography is obtained in all patients on admission. Patients were followed until rebleeding, operation, discharge or death. For the relation between size and risk of rebleeding we used Cox proportional hazards modelling. Results. We included 354 patients. Rebleeding occurred in 22 (30%) of the 73 patients with a large (>10 mm) aneurysm, and in 68 (24%) of the 281 patients with a small (≤10 mm) aneurysm (hazard ratio for large aneurysms 1.6 (95% confidence interval [CI] 1.0-2.6)). Within the first three days rebleeding occurred in 14 (19.2%) patients with a large aneurysm and in 25 (8.9%) patients with a small aneurysm (hazard ratio 2.4 (95% CI 1.2-4.5)). After adjustment for age, all hazard ratios remained essentially the same. Conclusion. Patients with large aneurysms have a higher risk for rebleeding, in particular within the first three days after the initial haemorrhage. This increased risk is independent of age.