Efficacy of Heavily T2-weighted MRI to Diagnose Vessel Course Distal to Occluded Artery in Mechanical Thrombectomy for Acute Ischemic Stroke

Objective: In endovascular thrombectomy for acute ischemic stroke due to large-vessel occlusion, occluded vessels are invisible on MRA or DSA. Heavily T2-weighted MRI sequence, which offers good contrast between cerebrospinal fluid and other brain structures, may contribute to resolve this issue. This study aimed to evaluate the efficacy of this sequence in estimating vessel courses including unexpected aneurysms of the portion more distal to the occlusion site in endovascular thrombectomy. Methods: In all, 23 consecutive patients diagnosed with acute ischemic stroke due to large-vessel occlusion underwent endovascular thrombectomy subsequent to evaluation of several thin-slice coronal sections of heavily T2-weighted MRI in addition to the usual diagnostic MRI. To clarify the usefulness of the heavily T2-weighted MRI, the matching degree of vessel courses diagnosed using this sequence before and after recanalization, intraor postoperative subarachnoid hemorrhage, reperfusion rate of thrombolysis in cerebral infarction (TICI) 2b-3, and the rate of functional independence (modified Rankin Scale [mRS] score ≤ 2) at 90 days were assessed. And also the following time intervals were calculated: start of imaging to arterial puncture, arterial puncture to first deployment of device, and arterial puncture to reperfusion. Results: The site of occlusion at diagnosis was the internal cerebral artery (ICA) in eight patients, the middle cerebral artery (MCA) in 13, and the anterior cerebral artery and basilar artery in 1 each. The matching of vessel courses before and after treatment was observed in 20 patients (91.3%) except for two patients that useful images could not be provided because of intense body movement and a technical failure. Procedure-related subarachnoid hemorrhage was not recognized in any patient. Successful recanalization of TICI 2b-3 was achieved in 82.6%. The median time from start of imaging to arterial puncture was 51 minutes (interquartile range [IQR]: 38.75–72), arterial puncture to first deployment of device was 41 minutes (32–57), placement of a guiding catheter or completion of carotid stenting to first deployment of device was 20 minutes (13.75–28.5), and arterial puncture to reperfusion was 59 minutes (43.5–99.5), respectively. Functional independence (mRS ≤2) at 90 days was achieved in 43.5% of patients. Heavily T2-weighted MRI was extremely useful in facilitating secure navigation of a microguidewire and microcatheter into invisible vessels during thrombectomy by confirming the courses of occluded vessels in advance. On the other hand, this sequence neither delayed the time to arterial puncture remarkably nor reduced the time required for procedure by estimating of occluded vessels. Conclusion: The heavily T2-weighted MRI sequence can contribute to improve the safety of maneuvers by clarifying the course of occluded vessels in endovascular thrombectomy for large-vessel occlusion.