Predictors for a Collar Sign and Its Association with Outcomes in Aneurysms after Pipeline Embolization.

BACKGROUND: The collar sign has been previously described as an angiographic indicator of incomplete occlusion after deployment of Pipeline Embolization Device (PED) for intracranial aneurysms.

OBJECTIVE: To explore the predictors for a collar sign in aneurysms treated with the PED.

METHODS: Aneurysms with a collar sign at initial follow-up angiogram were identified in retrospective review of a single center data. Predictors of a collar sign were analyzed through univariate and multi-variate analyses.

RESULTS: A total of 492 cases of cerebral aneurysm treated with the PED were identified. Among them, 53 were found to have a collar sign on the initial follow up angiogram. Univariate analysis showed that previous treatment of the same aneurysm (OR 2.46, p=0.01), branch vessel from the aneurysm neck or dome (OR 6.2, p<0.001), and smaller aneurysm neck size (OR 0.75, p=0.01) were all predictors for the presence of a collar sign. Larger diameter (OR 0.92, p=0.06), increased dome-to-neck ratio (OR 1.38, p=0.1) and increased aspect ratio (OR 1.14, 0.17) and previous treatment tend to have an association with a collar sign. However, after a multivariate analysis, branch from aneurysm neck/dome (OR 6.23, p < 0.001), aneurysm diameter (OR 0.75, p=0.032), increased dome-to-neck ratio (OR 4.62, p=0.006) and previous treatment were the strongest predictors for a collar sign.

CONCLUSION: Presence of a branch vessel arising from the aneurysm neck or dome, increased dome-to-neck ratio, aneurysm diameters, and previous treatment are the strongest predictors factors for a collar sign in the angiographic follow up of PED-treated aneurysms.