Imaging Indicators for Parenchymal Hemorrhage After Mechanical Thrombectomy in Acute Stroke

Background: In patients with acute ischemic stroke with large vessel occlusion, the presence of hyperintense lesions on fluid-attenuated inversion recovery (FLAIR-positive) before mechanical thrombectomy (MT) and that of hyperdense lesions on noncontrast computed tomography (CT-positive) after MT are associated with parenchymal hemorrhage, but the significance of these findings is unclear. Methods: Patients with acute stroke with large vessel occlusion underwent magnetic resonance imaging, including diffusion-weighted imaging and FLAIR, before MT. Noncontrast CT was obtained within 60 minutes after MT. The occurrence of parenchymal hemorrhage type 2 (PH2) was assessed on CT within 7 days after MT. FLAIR and CT-positive were defined as a case with hyperintense and hyperdense lesions immediately before and after MT, respectively. Clinical and imaging factors associated with PH2 were evaluated by multivariate regression analysis. Results: Enrolled were 412 patients (median age, 76 years; men, 58.3%; median National Institutes of Health Stroke Scale score, 16). The site of occlusion was the internal carotid artery (n=122, 29.6%), M1 (n=180, 43.7%), and M2 (n=96, 23.3%). FLAIR-positive, CT-positive, and PH2 were found in 149 (36.2%), 223 (54.1%), and 34 patients (8.3%), respectively. PH2 was significantly more frequent in CT-positive than CT-negative patients (14.3% versus 1.1%; P<0.001), but not in FLAIR-positive than FLAIR-negative patients (10.7% versus 6.8%; P=0.193). Regardless of FLAIR status, PH2 was significantly more frequent in CT-positive than CT-negative patients (12.8% versus 0.8% [P<0.001] for FLAIR-negative, and 16.7% versus 1.7% [P=0.003] for FLAIR-positive). Multivariate regression analysis demonstrated that CT-positive was the only independent factor associated with PH2 (odds ratio, 12.699 [95% CI, 2.964-54.416]; P<0.001). Sensitivity, specificity, positive predictive value, and negative predictive values of CT-positive for predicting PH2 occurrence were 94.1%, 49.5%, 14.3%, and 98.9%, respectively. Conclusion: In patients with acute ischemic stroke with large vessel occlusion, CT-positive immediately after MT was strongly predictive of PH2, but no such relationship was found for FLAIR-positive before MT.