RT Journal Article SR Electronic T1 P133/254  Clinical significance of subarachnoid hyper densities on flat panel CT after mechanical thrombectomy – does it matter? JF Journal of NeuroInterventional Surgery JO J NeuroIntervent Surg FD BMJ Publishing Group Ltd. SP A65 OP A65 DO 10.1136/jnis-2023-ESMINT.161 VO 15 IS Suppl 2 A1 Mousa, Zidan A1 Dorn, Franziska A1 Bode, Felix A1 Petzold, Gabor A1 Weller, Johannes A1 Paech, Daniel YR 2023 UL http://jnis.bmj.com/content/15/Suppl_2/A65.2.abstract AB Introduction Subarachnoid hyperdensities (SH) after mechanical thrombectomy (MT) has been discordant and are mostly considered insignificant.Aim of Study: We aim to identify the prevalence of SH following MT, associated predictors and the following functional outcomes.Methods 369 patients from our stroke registry were analyzed for the presence of SH on flat detector computer tomography (FDCT) directly after the MT, and on follow-up dual-energy CT (DECT), then classified according to a visual grading scale. 178 were included with anterior circulation occlusions were included. Regression analysis was performed to identify significant predictors and Kruskal-wallis analysis was performed to test the variables among the different groups. The primary outcome was the modified Rankin score (mRS) at 90 days and was analyzed with the Wilcoxon-Mann-Whitney rank-sum test.Results Prevalence of SH on FDCT was 37.1% in patients experiencing a significant unfavorable outcome (p=0.035). Significantly fewer patients with SH achieved a mRS ≤3 at 90 days (37.9% vs. 53.6%, p=0.043). In addition, mortality was significantly higher in the SH group (34.8% vs. 19.6%, p=0.024). Distal occlusions and a higher number of device passes were significantly associated with SH (p=0.035) and (p=0.001), respectively. Patients who received IV rt-PTA had significantly less SH (p= 0.024).Conclusion Postinterventional SH are a frequent finding after MT and are associated with neurological decline and an unfavourable outcome. They are more common with distal occlusions and multiple device passes.Disclosure of Interest FD serves as a consultant/proctor for Balt, Cerenovus, Microvention, received scientific grant from Cerenovus and received speaker honoraria from Acandis, Asahi, Stryker.