Background Posterior circulation (PC) aneurysms are relatively rare but associated with worse natural course and increased surgical morbidity. Flow diversion (FD) in PC is often criticized for high rate of complications and poor treatment outcomes. However, there is lack of data comparing the two methods under similar circumstances, and it is unclear whether the two methods really may be alternative to each other.

Aim To compare clinical and angiographic outcomes of FD versus balloon- and stent-assisted coiling (BAC/SAC) in complex PC aneurysms.

Methods Among 203 aneurysms treated with FD in single institution between January 2012 and December 2015, 35 were located in PC. Of them, two were lost for follow-up and excluded from the analysis, while the rest 33 were included into the comparison with 48 patients in whom PC BAC/SAC performed during the same period. Median follow-up duration was 9 months in BAC/SAC group and 10 months in FD group (p=0.27).

Results The rate of poor outcomes (combined severe morbidity and mortality at follow-up) was significantly higher in the FD group (33.3%, n=11/33 vs 10.4%, n=5/48 in BAC/SAC group, p=0.021). However, in the FD group there was significantly higher rate of aneurysms with unfavorable (giant and fusiform) morphology (33.3% n=11/33 in FD vs 4.1%, n=2/48 in BAC/SAC group, p=0.0011). After giant and fusiform aneurysms were excluded from clinical outcome analysis (two aneurysms from BAC/SAC group and eleven from FD group), the rate of poor outcomes did not differ significantly between groups (15.7%, p=3/22 in FD group vs 9.5%, n=4/46 in BAC/SAC group, p=0.67). Follow-up DSA was available for 42 patients from BAC/SAC group and 20 patients from FD group. Total occlusion of index aneurysm was achieved in 70% (n=14/20) of FD cases and 80.1% (n=32/42) of BAC/SAC cases, however the difference was statistically non-significant (p=0.1893).

Conclusion In this series, flow diversion in posterior circulation was associated with worse outcomes due to significantly larger proportion of giant and fusiform aneurysms in FD group. After giant and fusiform aneurysms were excluded from the both groups, the difference in clinical outcomes became non-significant. In PC aneurysms suitable for treatment with both methods, FD may by safe and effective alternative to balloon- and stent-assisted coiling.

Disclosures A. Gorbatykh: None. D. Kislitsin: None. R. Kiselev: None. T. Shayakhmetov: None. A. Moskalev: None. K. Orlov: None.