Background: Collateral status at baseline is an important predictor of clinical outcome in patients with acute ischemic stroke (AIS). Non-contrast time-of-flight MR angiography (TOF-MRA) might provide information of blood flow features non-invasively. TOF-MRA could become a marker of collateral status and clinical outcome in patients with AIS.
Methods: We retrospectively reviewed patients with AIS who had internal carotid artery or middle cerebral artery occlusion in three comprehensive stroke centers from August 2011 to July 2015. Those who underwent TOF-MRA sequence before endovascular therapy were investigated. Collateral status on TOF-MRA was graded by the previously-published regional leptomeningeal collateral (rLMC) score on CT angiography (0-20); collateral grade on angiography was assessed with the American Society of Interventional and Therapeutic Neuroradiology Collateral Grading System (0-4). We analyzed the relationship between rLMC score on TOF-MRA and patient characteristics, collateral flow grade, and good clinical outcome (modified Rankin Scale [mRS] of 0-2 at 90 days).
Results: A total of 38 patients (aged 71.7 ± 10.3 years; men, 71%; NIHSS score, 20 ± 6; median DWI-ASPECTS, 8) were included. Collateral grade on angiography was 0 to 1 in 10 (26%) patients, 2 in 6 (15%), 3 in 19 (50%), and 4 in 3 (7%), which was correlated to rLMC score on TOF-MRA (p < 0.001). Higher rLMC score on TOF-MRA was not related to baseline DWI-ASPECTS and reperfusion (Thrombolysis in Cerebral Infraction [TICI] 2b/3) after endovascular treatment, but was related to mRS 0-2 at 90 days (p = 0.021). All patients with high rLMC score (15-20) demonstrated mRS 0-2 at 90 days, whereas 69% of those with medium rLMC score (8-14) and 31% of those with low rLMC score did. In multivariate analysis, both rLMC score on TOF-MRA (OR, 1.5 per 1 point; p = 0.009) and reperfusion (TICI 2b/3 reperfusion; OR, 49.9; p < 0.001) were independent predictors of mRS 0-2 at 90 days.
Conclusions: rLMC score on TOF-MRA is a noninvasive and feasible parameter of collateral flow status and related to clinical outcome in patients with AIS. TOF-MRA might be a useful non-invasive imaging method to select candidates for endovascular therapy.