Abstract T P174: Intra-Arterial Signal on Arterial Spin Labeling Perfusion MRI Can Identify Stagnant Flow in Patients with Acute Middle Cerebral Artery Occlusion

Abstract

Introduction: T2*-weighted imaging (T2*WI) can detect acute endovascular clots by the susceptibility vessel sign (SVS). Stagnant flow in front of middle cerebral artery (MCA) occlusion sites may contribute to intra-arterial high-intensity signal on arterial spin labeling (ASL) magnetic resonance imaging (MRI), making it another potential marker of MCA occlusion. We compared intra-arterial high-intensity signal and SVS in patients with symptomatic and asymptomatic MCA occlusion and patients without major vessel occlusion. Methods: We identified transient ischemic attack or ischemic stroke patients by (a) 3-T MRI, diffusion-weighted imaging, ASL, T2*WI, and magnetic resonance angiography (MRA) performed within 24 h after stroke onset and (b) the presence of MCA occlusion (n=34 patients) or the absence of major vessel occlusion (n=24 patients). We included asymptomatic patients with MCA occlusion (n=6). The presence or absence of intra-arterial high-intensity signal and SVS was recorded as was its coincidence with the presence of MCA occlusion on MRA. Results: In patients with acute ischemic stroke the sensitivity of intra-arterial high-intensity signal was significantly higher than of the SVS (88% vs 50%; p<0.05). The accuracy of intra-arterial high-intensity signal was also higher than of the SVS (93% vs 71%; p<0.05). Neither the intra-arterial high-intensity signal nor the SVS was observed in patients without major vessel occlusion. The presence or absence of intra-arterial high-intensity signal was highly consistent with the presence or absence of MCA occlusion on MRA (κ=0.74). Positivity for the intra-arterial high signal was higher in symptomatic than asymptomatic patients with MCA occlusion (88% vs 17%; p<0.05), suggesting that acute rather than chronic arterial occlusion contributes to the visibility of the intra-arterial high-intensity signal. Conclusions: The intra-arterial high-intensity signal on ASL could identify stagnant flow in front of occlusion sites due to acute arterial occlusion.