Intracranial Aneurysms Treated by Flow-Diverting Stents: Long-Term Follow-Up with Contrast-Enhanced Magnetic Resonance Angiography

Purpose Long-term data on aneurysm treatment with flow-diverting stents are still sparse, and follow-up protocols differ widely between institutions. We present long-term results, with a focus on the usefulness of contrast-enhanced MR angiography (ceMRA). Materials and Methods Interventions and follow-up imaging of patients with aneurysms treated by flow-diverting stents (“Pipeline,” “Silk” and “FRED” models) without additional coiling were analyzed. All MRI scans included dedicated two-phase ceMRA. Aneurysm occlusion rates, size of the aneurysmal sac and complications were evaluated on MRI and digital subtraction angiography (DSA), where available. The ability of ceMRA to depict aneurysm occlusion and stent patency was graded on a three-point scale. Results Twenty-five patients with 102 MRI scans were included. The median duration of follow-up was 830 days. Aneurysm occlusion rates were 52% at 3 months (10 of 19 patients), 72% at 6 months (18/25) and 84% overall (21/25). Shrinkage of the aneurysmal sac was found in 19 patients (76%) and in 12 cases to <50% of the original size (48%). CeMRA assessability of aneurysmal occlusion was graded as good in all cases. When compared to DSA (18 cases), ceMRA had a sensitivity of 100% and specificity of 91% regarding aneurysm remnant detection. Assessability of the stent lumen varied and was limited in most cases. Conclusions Flow-diverter treatment achieves high occlusion rates and can cause major aneurysm shrinkage. CeMRA is highly valuable regarding imaging of the aneurysmal sac. There are limitations regarding the assessability of the stent lumen on ceMRA. Level of Evidence Level 4, Case Series.