Introduction/purpose Compare the outcomes of coil embolization alone (CA) versus stent-assisted coil embolization (SAC) in aneurysms of internal carotid artery (ICA) with unfavorable anatomic characteristics.

Materials and methods Institutional Review Board approval was obtained for this study. Retrospective review of the patient registry containing 767 patients with 1,170 aneurysms was performed. Inclusion criteria: 1. Previously untreated aneurysm internal carotid artery aneurysm 2. Complex morphology: Neck size of ≥4mm or a dome to neck ratio <1.5 if the neck size <4mm 3. Suitable for stenting: Parent vessel diameter of ≥2.5 mm, and 4. No contraindications to anticoagulation therapy. This included 41 treated with CA and 42 with SAC. Safety (stroke with increase of The National Institute Stroke Scale ≥4 points up to 180 days) and effectiveness (complete occlusion of the aneurysm with one treatment attempt, not leading to a parent vessel stenosis of ≥50%) was assessed. Clinical follow-up to assess safety was performed at discharge, 1, 3 and 6-months interval. Imaging follow-up to measure effectiveness was performed at 6-months, 18-moths, 3 and 5-years following the procedure.

Results Patients characteristics and number of aneurysms treated did not differ significantly between the two groups. Aneurysm baseline characteristics in the two groups are similar except for significantly wide neck size in SAC group (CA: 4.4 ± 1.7 versus SAC: 5.5 ± 1.8, P = 0.003). No significant change between the study groups demonstrated for safety end-point (p = 0.99). In spite of similar effectiveness in both the CA and SAC groups at immediate post treatment phase (n = 18 (45%) vs. n = 18 (41.9%) respectively, P = 0.827) and at 6-months follow-up (n = 17 (58.6%) vs. n = 24 (70.6%) respectively, P = 0.428), patients in the SAC group shows significantly higher effectiveness (n = 13 (43.3%) vs. n = 26 (68.4%), P = 0.038, in the CA vs. SAC groups respectively) beyond 6 months.

Conclusion Stent-assisted coil embolization in unruptured complex internal carotid artery aneurysms with an unfavorable anatomy offers a more effective long-term treatment option while having a similar safety profile to coil embolization alone.

Disclosures S. Boddu: None. A. Banihashemi: None. P. Gobin: None. J. Knopman: None. A. Patsalides: None.