Noncontrast CT for Mechanical Thrombectomy in Extended Time Window: The Outcomes

Interventional neuroradiology, Pasteur 2 Hospital, Nice, France, Emergency treatment of an ischemic stroke through thrombectomy. This procedure consists of mechanically removing the clot endovascularly using fluoroscopy. Inserting the introducer into the femoral artery. (Photo by: BSIP/Universal Images Group via Getty Images)
In a multinational cohort study, researchers compared the clinical outcomes of patients selected for mechanical thrombectomy by noncontrast CT vs those selected by CTP or MRI in the extended time window.

No difference was observed between noncontrast computed tomography (NCCT) compared with advanced imaging modalities among patients undergoing proximal anterior circulation mechanical thrombectomy in the extended time window. These findings were published in JAMA Neurology.

Advanced imaging is currently recommended for the selection of patients. However, there remains limited access to these modalities across stroke centers. The current objective of the study was to compare clinical outcomes of patients chosen for mechanical thrombectomy by NCCT vs those chosen by computed tomography perfusion (CTP) or magnetic resonance imaging (MRI) in the extended window.

The CT for Late Endovascular Reperfusion (CLEAR) study was a multicenter cohort study conducted at 15 sites in 5 countries between 2014 and 2020. Patients (N=1604) with proximal anterior circulation stroke undergoing mechanical thrombectomy in the extended time window were selected to undergo NCCT, CTP, or MRI. The extended time window was defined as 6-24 hours between time last seen well to arterial puncture. Successful reperfusion was defined by modified Treatment in Cerebral Infarction (mTICI) scale 2b-3.

Patients were aged median 70 (interquartile range [IQR], 58.5-80) years, 52.9% were men, 70.7% had hypertension, 32.9% atrial fibrillation, and 23.9% diabetes. Among the 534 who underwent NCCT, 752 CTP, and 318 MRI, the groups differed significantly at baseline by National Institutes of Health Stroke Scale (NIHSS), transfer status, and site of occlusion (all P <.001).

Time last seen well to puncture was shortest among the NCCT cohort (median, 10.4; IQR, 7.8-14.4 h) followed by CTP (median, 11.3; IQR, 8.4-15.2 h) and MRI (median, 12.4; IQR, 9.4-15.4 h; P <.001). Among the patients who were not transferred, the time from arrival at the endovascular center to puncture was shortest for NCCT (median, 76; IQR, 50-107 min) followed by CTP (median, 93; IQR, 72-118 min) and MRI (median, 98; IQR, 78-135 min; P <.001).

More CTP (89.5%) and NCCT (88.9%) recipients had a successful reperfusion compared with MRI (78.9%; P <.001).

NIHSS scores at discharge were lower among CTP (median, 6; IQR, 2-14) and NCCT (median, 7; IQR, 3-17) than MRI (median, 11; IQR, 3-19) recipients (P <.001).

Mortality at 90 days ranged between 19.5% and 23.4% (P =.38).

Significant predictors of outcomes included Alberta Stroke Program Early CT Score (ASPECTS; odds ratio [OR], 1.17; P <.001), age (OR, 0.97; P <.001), baseline NIHSS (OR, 0.90; P <.001), transfer status (OR, 0.79; P =.02), MRI (OR, 0.79; P =.03), diabetes (OR, 0.72; P =.01), and baseline modified Rankin Scale (mRS) of 1 (OR, 0.70; P =.01) or 2 (OR, 0.40; P <.001).

Predictors of ordinal mRS score shift at 90 days were ASPECTS (OR, 1.18; P <.001), age (OR, 0.97; P <.001), baseline NIHSS (OR, 0.91; P <.001), internal carotid artery occlusion (OR, 0.83; P =.049), transfer status (OR, 0.79; P =.002), and baseline mRS of 1 (OR, 0.68; P =.001) or 2 (OR, 0.48; P <.001).

This study was limited by its strict inclusion criteria which were mRS 0-2, occlusion location, and median ASPECTS of 8.

Patients undergoing proximal anterior circulation mechanical thrombectomy in the extended time window for large-vessel occlusions did not have significantly different outcomes on the basis of NCCT compared with advanced imaging.

“In patients undergoing proximal anterior circulation mechanical thrombectomy in the extended time window, there were no significant differences in the clinical outcomes of patients selected with noncontrast CT compared with those selected with CTP or MRI,” concluded the researchers.

Disclosure: Multiple authors declared affiliations with industry. Please refer to the original article for a full list of disclosures.


Nguyen TN, Abdalkader M, Nagel S, et al. Noncontrast Computed Tomography vs Computed Tomography Perfusion or Magnetic Resonance Imaging Selection in Late Presentation of Stroke With Large-Vessel Occlusion. JAMA Neurol. November 8, 2021. doi:10.1001/jamaneurol.2021.4082