Impacts of a Size Ratio on Outcome in Patients with Surgically Treated Unruptured Nondissecting Anterior Cerebral Artery Aneurysms.

BACKGROUND: Anterior cerebral artery aneurysms (ACAs) are characterized by higher rupture rate and small size at rupture. It was shown that the aneurysm/vessel size ratio, and not the absolute size, might predict the risk of rupture in small unruptured intracranial aneurysms. The present study aimed to investigate the relationship between a size ratio and outcome in patients with unruptured nondissecting ACA aneurysms (UNDAs).

METHODS: A total of 187 consecutive patients with 12 A1 (6.2%), 149 anterior communicating artery (77%), and 33 distal ACA (17%) aneurysms were retrospectively evaluated. The size ratio was defined as (size of aneurysm)/(size of parent artery). Neurologic worsening (NW) was defined as an increase in score of 1 or more on the modified Rankin Scale (mRS).

RESULTS: The mean age of the patient population was 63 ± 11 years and 132 UNDAs (68%) were seen in women. Complete, partial neck clipping, and aneurysm trapping were archived in 188 (97%), 2 (1.0%), and 4 (2.1%) UNDAs, respectively. An excellent outcome (mRS score 0) at 12 months was archived in 177 (93%) UNDAs overall and 177 (95%) in UNDAs with preoperative mRS score of 0 (n = 186). Postoperative ischemic lesions (odds ratio, 193; 95% confidence interval, 17-2205; P < 0.0001) and the size ratio >3.0 (odds ratio, 11; 95% confidence interval, 1.2-105; P = 0.031) were related to 12-month NW on multivariate analysis. The aneurysm size was not related to 12-month NW.

CONCLUSIONS: The present study showed that the size ratio, and not the absolute size, was related to 12-month NW in surgically treated UNDAs.