Opercular Index Score: A CT angiography-based predictor of capillary robustness and neurological outcomes in the endovascular management of acute ischemic stroke

Background Many CT angiography (CTA) collateral scoring systems are either subjective or complex and time consuming. Objective To evaluate the correlation between a CTA collateral scoring system - the Opercular Index Score (OIS) - with neurological outcomes at 90days following endovascular treatment for acute ischemic stroke (AIS) secondary to large vessel occlusion. Methods Fifty-five patients with AIS due to distal internal carotid artery, M1, or proximal M2 occlusions who underwent endovascular treatment were included. OIS was retrospectively calculated from CTA images, reconstructed from CT perfusion imaging, as the ratio of opacified M3 opercular branches in the Sylvian fissure on the unaffected side to those on the stroke side and dichotomized into favorable (OIS≤2) and poor (OIS>2). The ability of OIS to predict good neurological outcomes (modified Rankin Scale score ≤2 at 90days) was assessed using sensitivity, specificity, and area under the curve (AUC) with receiver operating characteristic analysis. Results Thirty-five patients had a favorable OIS and 20 patients had a poor OIS. Patients with favorable OIS had an 80.0% (n=28) rate of good neurological outcomes compared with 15.0% (n=3) of patients with a poor OIS (p<0.0001). On multivariate logistic regression analysis adjusting for baseline National Institutes of Health Stroke Scale score, OIS, and device used, favorable OIS was the only variable independently associated with good neurological outcome (OR=17.2, 95% CI 3.8 to 104.3) and demonstrated a sensitivity of 90.3% and specificity of 70.8% with an AUC of 0.822. Conclusions OIS is a simple and practical non-invasive scoring system that can be used to predict collateral robustness and good neurological outcome among patients with AIS undergoing endovascular treatment.