Susceptibility-Weighted MRI as an Imaging Marker for Reperfusion Injury in Acute Ischemic Stroke Following Mechanical Thrombectomy

Background/Purpose: Following endovascular intervention for stroke, hyperattenuated areas are common in brain parenchyma and it is difficult to differentiate on non-contrast CT whether it is contrast staining or reperfusion hemorrhage. Differentiation between contrast staining from reperfusion hemorrhage is of paramount importance for early initiation of antiplatelets and/or anticoagulants to prevent reocclusion of vessel. This study demonstrates signal characteristics of contrast-staining and reperfusion hemorrhage on susceptibility weighted MRI and its role to differentiate between two. Materials/Methods: Between July 2017 to March 2019, 36 patients who presented with acute ischemic stroke due to large vessel occlusion underwent mechanical thrombectomy. Low-osmolar non-ionic (Iopromide 300 mg/L) iodinated contrast was used in all patients who underwent endovascular intervention. All patients underwent noncontrast CT brain and SWI on 3T MRI within 30 minutes of endovascular intervention. MRI was evaluated by two neuroradiologists. Reperfusion hemorrhage was defined as ECASS criteria II. Symptomatic ICH was defined as hemorrhagic transformation temporally related to a negative shift in NIHSS score >/=4. Results: Out of 36 patients, 15 had hyperattenuated areas in brain on NCCT. Out of 15, 13 patients had blooming on SWI, suggestive of bleed. Two patients had no blooming on SWI, suggestive of contrast staining. Two patients didnot show any hyperdensity on NCCT but blooming on SWI, suggestive of bleed. Conclusion: All patients with hyperdensity on NCCT secondary to bleed showed blooming on SWI whereas those with contrast staining didnot show any signal changes on SWI. Thus, it is possible to differentiate reperfusion hemorrhage from contrast staining using SWI MRI. The significance of SWI in normal CT may be low where a small bleed maynot have any clinical significance.