• Mi Kyung Kim and Yong Cheol Lim.
• Department of Neurosurgery, Ajou University Hospital, Suwon, South Korea.
• World Neurosurg. 2019 Jul 1; 127: e488-e496.

ObjectiveThis study aimed to investigate the characteristics of A1 aneurysms according to their locations and to compare their imaging appearances so as to identify factors associated with their rupture.MethodsWe retrospectively reviewed the medical records of 31 patients harboring 32 A1 aneurysms diagnosed and treated between March 2009 and September 2018 at our institute.ResultsThirteen (41.9%) of the patients had vascular abnormalities, and multiple aneurysms were found in 13 (41.9%) patients. A total of 16 (53.3%) aneurysms were located on the proximal A1 segment, whereas the middle segments were affected in 7 (23.3%) and the distal segments in 7 (23.3%). Altogether, 93.8% of proximal A1 aneurysms projected posteriorly, 85.7% of middle aneurysms projected superiorly, and 85.7% of distal aneurysms projected inferiorly (P = 0.000). Four (33.3%) of the 12 total ruptured aneurysms were located on the distal A1 segment. Nine (69.2%) ruptured aneurysms were elongated or irregular in shape (P = 0.004). The aspect and height-width ratios of the ruptured aneurysms were higher than those of the unruptured aneurysms (P = 0.001, P = 0.018, respectively).ConclusionsMost A1 aneurysms showed a directional predilection according to the location of the A1 segment. Additionally, A1 aneurysms with elongated or irregular shapes, high aspect or height-width ratios, and distal locations of the A1 segment showed high risks of rupture. Therefore, a thorough assessment of the characteristics of A1 aneurysms can enhance the selection of proper treatment strategies.Copyright © 2019 Elsevier Inc. All rights reserved.

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