Association between the A1 Segment Asymmetry and Severe Clinical Presentation in Ruptured Anterior Communicating Artery Aneurysms.

The asymmetry of the A1 segment of the anterior cerebral artery has been implicated in the development and rupture of anterior communicating artery aneurysms; however, its relationship with the severity of subarachnoid hemorrhage remains unclear. We retrospectively analyzed 114 patients with subarachnoid hemorrhage due to ruptured anterior communicating artery aneurysms (mean age, 64.2 ± 13.9 years; 56 males, 58 females) treated at 2 institutions between January 2014 and March 2024. Patients were categorized into Symmetric and Asymmetric A1 groups, with asymmetry defined as a diameter ratio of ≥2 between sides. Among the 114 patients, 72 (63.2%) and 42 (36.8%) had symmetric and asymmetric A1 segments, respectively. The Asymmetric A1 group demonstrated significantly larger aneurysm size, a higher incidence of World Federation of Neurosurgical Surgeons grade IV-V, and more frequent intracerebral hemorrhage. Surgical clipping was more frequently performed in the Asymmetric A1 group (p = 0.04), likely due to associated intracerebral hemorrhage. The A1 diameter ratio was negatively correlated with aneurysm angle (r = -0.27, p < 0.01) and positively correlated with aneurysm length (r = 0.28, p < 0.01). Multivariate analysis showed an association of A1 asymmetry with severe clinical presentation but not with functional outcome. The effect of A1 asymmetry on severity was attenuated after adjustment for intracerebral hemorrhage, the strongest predictor of both severity and outcome. These findings suggest that in ruptured anterior communicating artery aneurysms, A1 asymmetry is associated with larger aneurysms, more severe subarachnoid hemorrhage, and higher rates of intracerebral hemorrhage.