Abstract 038: Fusiform/Dissecting vs. Saccular Posterior Circulation Aneurysms Treated with Flow Diversion: A Multicenter Study
Authors: Suarez Juan Vivanco , Dibas Mahmoud , Rodriguez‐Calienes Aaron , Cortez Gustavo , Hanel Ricardo , Nishi Hidehisa , Pereira Vitor , Feigen Chaim , Altschul David , Matsoukas Stavros , Fifi Johanna , Hafeez Muhammad , Kan Peter , Kühn Anna , Puri Ajit , Rabinovic Margarita , Wakhloo Ajay , Khandelwal Priyank , Galecio‐Castillo Milagros , Farooqui Mudassi , Ortega‐Gutierrez Santiago 
Published: March 2024

Introduction
Flow diverters have demonstrated reliable safety and effectiveness for the treatment of selected anterior circulation intracranial aneurysms. However, posterior circulation aneurysms comprise around 10‐15% of all aneurysms, and they frequently present atypical morphological and anatomical characteristics. Furthermore, these lesions have an increased risk of rupture (compared to those in the anterior circulation) with respect to size and higher treatment risks (regardless of the technique). Flow diversion in posterior circulation aneurysms has been described previously with inconsistent clinical and radiological results. Hence, we aimed to compare the safety and effectiveness of FDs in fusiform/dissecting vs. saccular aneurysms located in the vertebrobasilar vessels.

Methods
We performed a multicenter, retrospective cohort study including 9 centers. All patients treated with FDs for aneurysms located in the posterior circulation (vertebral and basilar arteries) between 2015 and 2022 were included. Patients were divided into two groups according to the morphology of the aneurysm (fusiform/dissecting vs. saccular). The effectiveness outcome was complete aneurysm occlusion (Raymond‐Roy Class 1) at the latest follow‐up. Safety outcomes included the incidence of ischemic/hemorrhagic and mortality. After adjusting for confounders multivariable logistic regressions were performed to compare outcomes of interest.

Results
A total of 147 patients with 147 aneurysms were included. The fusiform/dissecting group included 85 cases, while the saccular group 62. The saccular group had older patients (median age: fusiform/dissecting, 55 years [45‐64] vs. saccular, 63 years [51‐70.0]; p=.02). The number of female patients was not different between groups (fusiform/dissecting, 42% vs. saccular, 58%; p=.05). Clinical presentation, comorbidities, modified Fisher, and Hunt and Hess were similar. Baseline modified Rankin Score (mRS) was different (mRS 0‐2: fusiform/dissecting, 84% vs. saccular, 98%; p=.030). Previous endovascular treatment (p=.396) was similar. Aneurysm location (most were in the vertebral artery: fusiform/dissecting, 60% vs. saccular, 42%; p=.009) was different. Median aneurysm size (fusiform/dissecting, 10.0 mm [6.5‐18.8] vs. saccular, 5.9 [3.0‐10.0]; p=<.001), and proximal (fusiform/dissecting, 3.6 mm [2.7‐4.1] vs. saccular, 2.8 [2.4‐3.3]; p=<.001) and distal landing (fusiform/dissecting, 3.2 mm [2.5‐3.5] vs. saccular, 2.4 [2.0‐3.0]; p=<.001) zones were different. The number of FDs per patient (>1 FD: fusiform/dissecting, 36% vs. saccular, 10%; p=<.001) and adjunctive coiling (fusiform/dissecting, 89% vs. non‐F, 74%; p= .015) were different. The most commonly implanted was Pipeline Flex (fusiform/dissecting, 55%, vs. saccular, 40%). Thromboembolic (fusiform/dissecting, 8.2%, vs. saccular, 8.1%; p=.97) and hemorrhagic (fusiform/dissecting, 4%, vs. saccular, 10%; p=.125). Mortality was increased in the fusiform/dissecting group (19%) vs saccular (12%) but not different (p=.365). At an overall median follow‐up time of 13.5 [7.4‐28.8] months, complete occlusion was lower in the fusiform/dissecting group (61% vs. F, 63%) but not statistically different (p=.356). Follow‐up mRS was not different (mRS 0‐2: fusiform/dissecting, 73% vs. saccular, 76%; p=.365). 172 (71%) of the cases achieved complete aneurysm occlusion. Multivariable analysis showed that age (OR: 0.96; 95%CI: 0.93‐0.99; p=.008) and location in the basilar artery (OR: 0.09; 95%CI: 0.03‐0.29; p=<.001) were associated with incomplete occlusion at follow‐up.

Conclusion
Our results suggest that flow diversion can be an effective treatment for fusiform/dissecting and saccular aneurysms located in the posterior circulation. Although the occlusion rates after flow diversion in fusiform/dissecting aneurysms showed a lower rate compared to saccular, the favorable safety profile of FDs allows them to be considered a valuable tool in the neuroinventionalist armamentarium.