Background To examine the effect of stenting on progressive occlusion of small and incompletely occluded unruptured intracranial aneurysms (UIAs) ≤10 mm in size using a propensity score matched case controlled analysis.

Methods 715 small UIAs consecutively treated by coiling between 2008 and 2010 were eligible for study. Time of flight MR angiography and/or catheter angiography were used to estimate extent of occlusion after coiling. Complete occlusion at 6 months post embolization of a sac filled with contrast immediately after coiling constituted progressive occlusion. A propensity score matched analysis was conducted, based on the probability of stent deployment.

Results 206 (28.8%) small UIAs showed residual sac filling directly after coiling. Of these, 182 (88.3%) displayed progressive occlusion at 6 months. Aneurysm size (p<0.01), neck size (p<0.01), and embolization attempt (p<0.01) differed significantly for stented and non-stented lesions, but the incidence of progressive occlusion did not differ (p=0.78) between the groups. After 1:1 propensity score matching, however, the rate of complete occlusion in stented subjects (97.5%) surpassed that of the non-stented counterparts (OR=9.75, p=0.01).

Conclusions Small UIAs with residual sac filling after coiling showed a complete occlusion rate of 88.3% at 6 months post embolization. Stent deployment seems to promote complete occlusion in such lesions.