Purpose Growth of intracranial fusiform aneurysm (IFA) may become clinically problematic through mass effect or rupture. We investigated growth rate and factors contributing to growth in asymptomatic untreated IFAs.

Method As a retrospective review, we assessed patients diagnosed with asymptomatic IFAs between August 2000 and September 2014, all untreated. No acute or symptomatic dissecting lesions were considered. Clinical and serial angiographic follow-up data were analyzed, defining growth as expansion >2 mm in one or more dimensions. A binary logistic regression model and Kaplan-Meier method were applied for statistical analysis.

Results Mean follow-up in the 82 eligible patients was 63 months (range, 15–190 months). Among them, 7 aneurysms (8.5%, 2.1%/aneurysm year) demonstrated growth (in any dimension). In univariate analysis, height and multiplicity of aneurysm emerged as significant factors in terms of growth. Height remained an independent risk factor in the binary logistic regression model, with receiver operating curves indicating a threshold of 6.9 mm initial height in determining IFA growth (area under the curve, 0.804). Six patients (except one undertaken endovascular treatment) were observed during continued follow-up monitoring. All 6 lesions were stable in serial imaging tests, without further detectable growth or rupture (mean, 33 months).

Conclusion Most (91.5%) of the asymptomatic and untreated IFAs studied proved to be stable, with no continued growth. However, because aneurysm height proved independently predictive of growth (lesions>6.9 mm being at risk), periodic imaging is required in those left untreated. Growing yet asymptomatic aneurysms call for the utmost caution and care in decision making.

Disclosures Y. Cho: None. H. Kang: None. M. Han: None.