The Clinical Analysis of Small (Less than 5 mm) Ruptured Aneurysms

Abstract

Background: Aneurysms less than 5 mm in diameter (small aneurysms) are generally believed to have a low rupture rate. In our clinical experience, they are often found ruptured, causing subarachnoid hemorrhage (SAH). Herein, we report our investigation on the characteristics, severity, and prognosis of cases of ruptured small aneurysm.Patients and Methods: We reviewed the data of 158 consecutive patients with aneurysmal SAH (except for those with dissecting aneurysms) treated in our hospital between 2009 and 2014. The maximum size, configuration, location, and distribution of aneurysms were examined using computed tomography angiography or digital subtraction angiography. We chose the following 7 risk factors for rupture to examine 53 cases of small ruptured aneurysms: age (< 50 years old), aneurysm with daughter sac, past medical history of hypertension, multiple aneurysms, family history of SAH, smoking habits, and excessive alcohol intake. In addition, we compared these 53 cases to the rest of the group with regard to symptoms (Hunt and Hess grade [H&H]), amount of hemorrhage (modified Fisher grade [mFisher]), prognosis (modified Rankin Scale [mRS]), and number of risk factors.Results: Of the 158 cases of ruptured aneurysms, 49 involved the anterior communicating artery (Acom), 41 involved the middle cerebral artery (MCA), 29 involved the internal carotid-posterior communicating artery (IP-PC), and 39 involved other locations. The average maximum diameter was 6.6 mm (range: 1.2-30 mm). Among the 53 small aneurysm cases (34% of the total), 33% were located in the Acom, 28% in the IC-PC, and 17% in the MCA. In low sites with infrequent aneurysms such as the internal carotid-anterior choroidal artery (IC-ACh) or the basilar top artery (BA top), small aneurysms accounted for more than 50%. After analysis of the risk factors for the 53 small aneurysm cases, 4 patients (8%) had no risk factors. There was no statistically significant difference between H&H grade, mFisher grade, mRS, and the number of risk factors between the groups with small aneurysms and aneurysms 5 mm or larger.Conclusion: Cases with ruptured small aneurysms (<5 mm in diameter) accounted for approximately one-third of aneurysmal SAH cases in our institution. Many ruptured small aneurysms were located in the Acom or IC-PC. Four patients (8%) with ruptured small aneurysms had no risk factors. Further study is needed to identify the characteristics of ruptured small aneurysms.