Size of cerebral aneurysms and related factors in patients with subarachnoid hemorrhage

BACKGROUND: As the indication for surgical treatment of incidentally discovered small aneurysms remains controversial. METHODS: We retrospectively investigated the characteristics of small ruptured aneurysms and examined the relationship between the size and location of ruptured intracranial aneurysms and the sex, age, lifestyle, and medical history of 280 patients with ruptured aneurysm treated at our institute. RESULTS: The mean diameter of ruptured aneurysms in this series was 7.6 mm. In diameter, 135 (48.2%) ranged between 5 and 10 mm; 73 (26.1%) were smaller than 5 mm. The size of the ruptured aneurysms was significantly smaller (mean 6.5 mm) in patients with non- or poorly controlled hypertension than in normotensive patients (mean 8.3 mm) (p < 0.05). Ruptured aneurysms in the anterior communicating artery (AcomA) and anterior cerebral artery (ACA) were significantly smaller (p < 0.01) than those in the internal carotid artery or middle cerebral artery. Among 58 patients with multiple aneurysms, only 7 (12%) suffered rupture of aneurysms smaller than 5 mm (p < 0.01). Patients younger than 40 years and patients with a family history of subarachnoid hemorrhage appeared to predispose to the rupture of small-sized aneurysms, although those did not affect the statistical significance. CONCLUSIONS: This study shows that even aneurysms smaller than 10 mm may rupture. However, treatment decisions for unruptured aneurysm should not be based solely on the size of the unruptured aneurysms. Our data implies that even small aneurysms in the AcomA and ACA had an increased tendency for rupture, and that hypertensive patients were at higher risk for the rupture of small aneurysms.