Abstract WMP95: External Validation Of Acute Atherosclerotic Ischemic Stroke Radiological Markers

Introduction: Intracranial atherosclerosis-related acute large vessel occlusion (ICAS-LVO) is the dominant cause of acute middle cerebral artery (MCA) occlusions that can be passed with wire or microcatheter but cannot be completely opened (5-15% of all middle cerebral artery (MCA) infarcts). The major challenge of ICAS-LVO is the tendency of reocclusion or cause a residual, fixed severe stenosis rendering the vessel with suboptimal revascularization. These patients carry a poor functional outcome and high mortality despite mechanical thrombectomy (MT). We aimed to externally validate three preidentified markers of ICAS-LVO on early non-contrast computed tomography (NCCT) and CT Angiogram (absent hyperdense MCA sign (HMCAS), Hounsfield measurements (HU ratio≤1.1 and Delta HU<6) and CTA truncal occlusion). Methods: We conducted a retrospective analysis of 77 consecutive patients presenting with acute M1 occlusions undergoing MT. Based on our previous observational experiences, NCCT and CTA patterns that had been associated with ICAS-LVO included the absent HMCAS, HU ratio and Delta HU between site of occlusion and contralateral MCA and CTA truncal occlusion. ICAS-LVO was identified if an occlusion was difficult to cross, had tendency to reocclude after successful recanalization or demonstrated residual fixed severe stenosis. These markers were also compared with reperfusion rates and functional outcomes at 3 months. Results: Out of 77 patients, 13 (16%) had suspected ICAS-LVO. Absent HMCAS had a sensitivity of 91% and specificity of 90% (AUC 0.91), HU ratio ≤1.1 and delta HU <6 had sensitivity of 100% and specificity of 98% (AUC 0.992) and CTA truncal occlusion had sensitivity of 91% and specificity of 97% (AUC 0.943), in predicting ICAS-LVO. These radiological markers were also significantly associated with unsuccessful reperfusion (TICI 0-2a) and poor functional outcomes (mRS>2) at 3 months. Conclusion: Initial non-contrast CT and CTA markers are highly sensitive and specific in predicting atherosclerotic M1 occlusions and significantly associated with failed reperfusion, and poor functional outcomes after mechanical thrombectomy.