Purpose WEB device shape modification (WShM) is a potential cause of poor angiographic outcome during follow-up, despite an initial complete aneurysmal occlusion. The prevalence, the factors affecting WShM and the ways to prevent this phenomenon are only partially established.

Materials and Methods Patients treated in Bicêtre hospital with a WEB device between were included October 2015 and January 2019. Exclusion criteria were the lack of follow-up or a combined treatment. Thanks to rotational cone-beam CT (CBCT) acquisitions, systematically performed after implant and during follow-up, we have analyzed WEB morphology over time. WshM was correlated with anatomical and procedures parameters. Angiographic occlusion was evaluated according to the Bicêtre occlusion scale (BOSS).

Results 92 aneurysms were treated with a WEB device and 68% were finally included in this register. 87% of WEB devices presented WShM during follow-up (at least 20% of height reduction). We did not find a direct relationship between the extent of WShM and occlusion rates. But in the worsening occlusion group the average WShM was significantly higher than in the stable occlusion group (50% vs 43%, p<0.01). WEB width oversizing at implant was significantly associated with a reduced WShM rate.

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Abstract O-009 Figure 1 Average WEB shape modification as a function of time in months. Most of the WEB reduction in height is depicted in the first 9 months then it tends to stabilize on longer follow-ups

Conclusion CBCT allowed us to perform the first precise and quantitative analysis of WEB shape modification during follow-up. WShM is a very frequent phenomenon, negatively affecting occlusion rates. But it can be partly overcome with an appropriate oversizing strategy.

Disclosures J. Caroff: None. C. Mihalea: None. L. Ikka: None. A. Ozanne: None. S. Gallas: None. V. Chalumeau: None. J. Moret: None. L. Spelle: None.