Influence of Anatomic Changes on the Outcomes of Carotid Siphon Aneurysms After Deployment of Flow-Diverter Stents

Background: Flow-diverter stent (FDS) deployment can cause morphological and hemodynamic changes in the carotid siphon (CS), influencing the occlusion rate of aneurysms in this location.

Objective: To evaluate morphological changes to the CS after FDS deployment and their relationship with the rate of occlusion of intracranial aneurysms.

Methods: A cohort of 183 patients with CS aneurysms were treated by deployment of Pipeline® FDS (Medtronic Inc, Dublin, Ireland). Their CSs were classified as type U, V, C, or S, depending on morphology. The posterior and anterior bend angles were measured on strict lateral cerebral angiogram with digital subtraction before FDS deployment, immediately after deployment, and at 6 mo. Differences between angles were analyzed to identify any correlations with rates of aneurysm occlusion, using the O'Kelly-Marotta classification.

Results: FDS deployment was associated with immediate changes in CS morphology. The mean anterior angle increased from 3.97 ± 25.06° to 22.05 ± 25.18° (P  < .001) and the mean posterior angle increased from 71.98 ± 31.27° to 79.43 ± 31.80° (P  <  .001). Multivariate analysis revealed a progressive, statistically significant increase in frequency of complete (grade D) occlusion at 6-mo follow-up with increasing anterior bend angle (prevalence ratios (PR) = 1.42 for increases between 5.3° and 12°, P  =  .017; PR = 1.56 for increases between 12.1° and 27.6°, P  =  .002; PR = 1.83 for increases >27.6°, P  <  .001, all vs increases <5.3°).

Conclusion: FDS deployment induces changes in CS morphology. Specifically, increases in mean anterior angle are associated with better radiological results on 6-mo follow-up digital subtraction angiography.