Added Prognostic Value of MRI to CT in Acute Ischemic Stroke Patients Undergoing Mechanical Thrombectomy in the Extended Time Window

Abstract

Background In the 6–24-hour window, imaging must identify patients with salvageable tissue while avoiding delays and reperfusion of large established infarcts. The optimal imaging strategy remains controversial. Although computed tomography (CT) is widely used because of its accessibility and speed, magnetic resonance imaging (MRI) provides more sensitive tissue characterization. This study evaluated whether adding MRI to CT was associated with clinical outcomes in patients with acute ischemic stroke (AIS) undergoing mechanical thrombectomy (MT). Methods We conducted a retrospective, single-center cohort study of consecutive patients with AIS due to large vessel occlusion who underwent MT between January 2022 and December 2024. Patients were grouped according to pre-procedural imaging: CT alone or MRI plus CT. Propensity score matching (1:1) was used to reduce measured baseline imbalances. The primary outcomes were excellent functional outcome (modified Rankin Scale [mRS] 0–1) and 3-month mortality; symptomatic intracranial hemorrhage (SICH) was the secondary outcome. Multivariable logistic regression was used to estimate adjusted associations. Results After propensity score matching, 364 patients (182 pairs) were included in the final analysis. Compared with CT alone, the MRI plus CT group demonstrated significantly lower 3-month mortality (7.1% vs 18.7%, P < 0.01) and reduced incidence of SICH (2.2% vs 7.7%, P = 0.02). No significant difference was observed in excellent functional outcome at 3 months between groups. Multivariate logistic regression confirmed that MRI plus CT was independently associated with lower risks of mortality (adjusted OR=0.32, 95% CI 0.14–0.72; P < 0.01) and SICH (adjusted OR=0.23, 95% CI 0.05–0.96; P=0.04). Conclusion Among patients with AIS undergoing MT within the 6–24-hour window, MRI plus CT was associated with lower 3-month mortality and SICH than CT alone, without a significant difference in excellent functional outcome. Because imaging allocation was non-randomized and quantitative infarct-core and perfusion data were unavailable, these findings should be interpreted as hypothesis-generating and require prospective multicenter validation.