Characteristics of intracranial aneurysms in patients with familial subarachnoid hemorrhage

Background: Compared with sporadic aneurysms, familial aneurysms rupture at an earlier age and are more often located at the middle cerebral artery. Other characteristics of familial aneurysms may also differ from sporadic aneurysms. The authors compared the size of ruptured aneurysms and the number of aneurysms between patients with familial subarachnoid hemorrhage (SAH) and those with sporadic SAH. Methods: The authors included all patients with familial SAH admitted to the University Medical Center Utrecht (UMCU) and their first-degree relatives with proven aneurysmal SAH, including admissions elsewhere. As reference group the authors used a consecutive series of patients with sporadic SAH admitted to the UMCU from December 1995 to March 1997. Criteria for sporadic SAH were absence of a positive family history and exclusion of aneurysms in first-degree relatives by means of MR angiography. The authors dichotomized sizes of aneurysms into small (less than or equal to10 mm) and large (>10 mm). Size and number of aneurysms between patients with familial SAH and sporadic SAH were compared with relative risks (RR) with corresponding 95% CI. Results: The authors found 58 patients with familial SAH (48 with information on aneurysm size) and 88 patients with sporadic SAH. Twenty of 48 patients with familial SAH (41%) had large aneurysms, versus 17 (19%) with sporadic SAH (RR 2.1, 95% CI 1.2 to 3.6). Fifteen of 58 patients with familial SAH (26%) had multiple aneurysms, versus 9 (10%) with sporadic SAH (RR 2.5, 95% CI 1.2 to 5.4). Conclusions: Familial aneurysms are generally larger at time of rupture and more likely to be multiple than sporadic aneurysms. The development of large and multiple aneurysms may be related to genetic factors that determine defects of the arterial wall.