Anatomic Predictors of Unruptured Anterior Communicating Artery Aneurysm Growth

OBJECTIVE: Anatomic variations of the anterior communicating artery (ACOM) complex have been shown to influence ACOM aneurysm morphology. It is not known whether these variations predispose unruptured ACOM aneurysms to grow over time. METHODS: We retrospectively reviewed the course of patients with untreated, unruptured ACOM aneurysms monitored with serial imaging at our institution. The primary outcome of interest was aneurysm growth. Predictors of aneurysm growth were determined using a Cox proportional hazards model. RESULTS: There were 81 patients with an unruptured ACOM aneurysm who were included in our study. Growth occurred in 9 (11.1%) patients, yielding a yearly growth rate of 2.8%. Aneurysms that grew were larger on initial detection than were those that remained stable in size (8.3 mm vs. 6.2 mm; P = 0.031). The ratio of the diameter of A1 segments was greater in patients with aneurysms that grew (2.1 vs. 1.4; P = 0.003), as was the frequency of patients with an A1 ratio >2.3 (25.0% vs. 6.6%; P = 0.023). Among aneurysms that grew, location at the A1-A2 junction was more common than origination solely from the ACOM (88.9% vs. 11.1%). When follow-up time was adjusted for, increasing aneurysm size (unit relative risk [RR] 1.25, 95% confidence interval [CI] 1.06-1.45; P = 0.011) and location at the A1-A2 junction (RR 6.15, 95% CI 1.12-114.49; P = 0.035) were significant predictors of aneurysm growth. CONCLUSIONS: We identify several anatomic characteristics that may be associated with increased risk of ACOM aneurysm growth. These data could influence management strategies of unruptured ACOM aneurysms.