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In patients with proximal middle cerebral artery occlusion undergoing endovascular stroke treatment, collateral vessels are a pivotal factor in determining reperfusion success, final infarct size, and clinical outcome.


To determine the impact of collateral vessel status on clinical and imaging outcomes in patients undergoing endovascular therapy (EVT) for proximal middle cerebral artery (MCA) occlusion.

Materials and Methods

There were 160 patients with proximal MCA occlusion at six centers in this institutional review board–approved multicenter EVT registry. Angiograms were analyzed at a blinded core laboratory, and collateral vessel status was assessed by using the American Society of Interventional and Therapeutic Neuroradiology (ASITN)/Society of Interventional Radiology (SIR) collateral vessel grading system, while reperfusion was assessed by using the Thrombolysis in Cerebral Infarction (TICI) scale. Good outcome was defined as a modified Rankin Scale score of 0–2 at follow-up. Binary logistic regression analysis was performed by using parameters with P < .2 in univariate analysis.


Good clinical outcome was attained in 62 (39%) of the 160 patients, and TICI 2b–3 reperfusion was achieved in 94 (59%) patients. Nineteen patients had ASITN/SIR collateral vessel grades of 0 or 1, 63 patients had a grade of 2, and 78 patients had grades of 3 or 4. Better collateral vessels were associated with higher reperfusion rates (21%, 48%, and 77% for ASITN/SIR grades of 0 or 1, 2, and 3 or 4, respectively; P < .001), a higher proportion of infarcts smaller than one-third of the MCA territory (32%, 48%, and 69% for ASITN/SIR grades of 0 or 1, 2, and 3 or 4, respectively; P < .001), and a higher proportion of good clinical outcome (11%, 35%, and 49% for ASITN/SIR grades of 0 or 1, 2, and 3 or 4, respectively; P = .007). At multivariable analysis, collateral vessel status independently predicted reperfusion, final infarct size, and clinical outcome. Within an onset-to-treatment time (OTT) of 0–3 hours, collateral vessel status predicted final infarct size and reperfusion. Within an OTT of 3–6 hours, it additionally predicted clinical outcome, with 53% of patients with ASITN/SIR grades of 3 or 4 having a good outcome, as compared with 0% of patients with grades of 0 or 1 and 27% of patients with a grade of 2 (P = .008).


In this patient population, collateral vessel status independently predicted the pivotal outcome parameters of reperfusion, infarct size, and clinical outcome. These data underscore the utility of patient selection for EVT on the basis of collateral vessel status.

© RSNA, 2015

Online supplemental material is available for this article.


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Article History

Received April 22, 2014; revision requested June 6; revision received August 15; accepted September 10; final version accepted September 19.
Published online: Dec 29 2014
Published in print: Mar 2015