Small versus Large Ruptured Intracranial Aneurysm: Concerns with the Site of Aneurysm

Abstract

Background: Although size is one of the strongest predictors, small aneurysms often rupture. We compared the characteristics of small and large ruptured intracranial aneurysms (RIAs) according to their location to find the factors associated with small RIAs in each location. Methods: Patients with subarachnoid hemorrhage due to saccular RIAs were consecutively enrolled. The sizes were dichotomized as small (<5 mm) or large, and the location was classified as paraclinoid-distal internal carotid artery, sidewalls of anterior or middle cerebral artery (MCA; sidewall), MCA-bifurcation, anterior or posterior communicating artery (Acom or Pcom, respectively), and posterior circulation RIAs. Independent factors associated with small RIAs compared to large RIAs were investigated in each location. Results: Small RIAs were observed in 384 of 791 patients (48.5%), and were most commonly located at Acom (17.1%) followed by Pcom (9.0%) and sidewalls (7.2%). Female sex (OR 3.038; 95% CI 2.099-4.395), young age (OR 0.971; 95% CI 0.958-0.985), hypertension (OR 1.412; 95% CI 1.033-1.930) and multiple aneurysms (OR 1.942; 95% CI 1.335-2.824) were associated with small RIAs. By location, sidewall aneurysms (OR 2.183; 95% CI 1.049-4.542) were associated with small RIAs, whereas MCA-bifurcation (OR 0.318; 95% CI 0.168-0.599) and Pcom aneurysms (OR 0.511; 95% CI 0.277-0.944) were associated with large RIAs. The presence of multiple aneurysms (OR 4.69; 95% CI 1.45-21.19) was associated with small RIAs at sidewalls, and young age, female sex, hypertension and the presence of bilateral A1 (OR 1.85; 95% CI 1.09-3.13) were associated with small RIAs at Acom. Acom RIAs with bilateral A1 was smaller than those with unilateral A1 (4.7 ± 2.1 vs. 5.8 ± 2.6 mm; p < 0.001). Conclusions: Intracranial aneurysms which rupture below 5 mm are not uncommon, and the factors associated with small-sized RIAs differ according to location. Sidewall aneurysms, with multiple aneurysms and Acom aneurysms with bilateral A1 may rupture even at small size.

Response to Letter to the Editor “Preoperative Digital Subtraction Angiography in Incidental Unruptured Intracranial Aneurysms”

“…Important risk factors for rupture being, e.g. side wall location, multiple aneurysms, young age, female and hypertensive patients [6]. Furthermore, we believe that all aneurysms were small aneurysms in the first place.…”

“…It is also a well-known fact that the annual risk of hemorrhage is lower for small aneurysms when compared to large aneurysms, as again proven by the study of Malhotra et al [3]; however, although size is one of the strongest predictors, even small aneurysms do rupture [5]. Growth and risk of hemorrhage does not only depend on the mere diameter but also on factors concerning the configuration and localization of the aneurysm as well as patient characteris-M. Herzberg moriz.herzberg@gmail.com 1 Department for Diagnostic and Interventional Neuroradiology, University of Munich (LMU), Campus Grosshadern, Munich, Germany tics [6]. Important risk factors for rupture being, e.g.…”

Influence of Age-Related Complications on Clinical Outcome in Patients With Small Ruptured Cerebral Aneurysms

“…In the past 10 years of cerebral aneurysm research, the proportion of small ruptured aneurysms has increased to nearly 50% (26)(27)(28). Kim et al believed that a sidewall aneurysm found with multiple aneurysms or an AcomA aneurysm found from a patient with hypertension may be prone to rupture at smaller sizes.…”

Endovascular Treatment of Small Ruptured Intracranial Aneurysms (<5 mm)

“…As reported by experienced neurosurgeons and interventionalists, most ruptured aneurysms are small in size [1,2]. Subarachnoid hemorrhage (SAH) is more extensive in these aneurysms than in the larger aneurysms [3].…”