Abstract Number: Esoc2026a1260 Spatiotemporal Pattern of Aneurysmal Subarachnoid Hemorrhage Manifestation

Abstract Background and aims Aneurysmal subarachnoid haemorrhage (aSAH) is a form of stroke frequently complicated by cerebral vasospasm. Although vasospasm is thought to occur in vessels near the ruptured aneurysm, it is not clear whether this phenomenon could be used to identify patients at low risk of subsequent vasospasm. We hypothesize that vasospasm develops earlier and is more pronounced in the artery anatomically closest to the rupture site. Methods We conducted a retrospective observational study using TCD readings from 200 patients admitted to The Ottawa Hospital from 2019-2024. We collected highest mean blood flow velocities in all vessels throughout the admission and sought to identify the artery that was the first to demonstrate an increase in velocity above standard thresholds according to Sloan's criteria ( MCA 120 cm/s, ICA 80 cm/s, ACA 90 cm/s, PCA 60 cm/s, BA 70 cm/s, VA 60 cm/s). Results Of 188 patients with aSAH, 111 met inclusion criteria. In each artery tested, the most common artery to reach a ratio 1 over baseline velocities was the ipsilateral proximal vessel, though this did not occur for every aneurysm. The absence of vasospasm in the ipsilateral proximal vessel was associated with low but not very low rates of subsequent vasospasm. Conclusions Our study demonstrates a predictable pattern of vasospasm in patients with aneurysmal SAH. This could inform prospective studies aiming to rule out vasospasm risk, by identifying time points at which the absence of vasospasm in the most likely artery may reliably indicate low likelihood of later vasospasm. Conflict of interest Sanaz Biglou: nothing to disclose Laurence Poirier: nothing to disclose Vincent Brissette: nothing to disclose Dar Dowlatshahi: nothing to disclose Célina Ducroux: nothing to disclose Michel Shamy: nothing to disclose