Capillary Index Score Derived from Computed Tomography Angiography as An Indicator of Collateral Flow after Acute Ischemic Stroke

Abstract Background The capillary index score (CIS) determined from DSA is used to evaluate cerebral collateral flow in acute ischemic stroke (AIS) caused by cerebral artery occlusion. Our aim was to determine the reliability of CIS calculated from MIP-CTA images as an alternative to DSA-based CIS, as CTA is less invasive and less expensive. Methods Clinical and imaging data of 40 patients with AIS caused by cerebral artery occlusion within 6 h from symptom onset were collected. CIS was calculated from CTA and DSA images. Patients were classified into the favorable collateral flow group if CIS was ≥2 (fCIS), and into the poor collateral flow group if CIS was <2 (pCIS). Agreement between the methods was evaluated using the Kappa test. Logistic regression was performed to explore the relationship between CTA-based CIS and clinical outcomes. Results The two methods had high consistency (Kappa = 0.72), and the diagnostic accuracy of CTA for CIS classification was 87.5%. The decrease in the NIHSS score at discharge was not significantly different between the fCIS and pCIS groups according to CTA (p = 0.156), while the 90-day mRS was higher in the pCIS group (p = 0.04). High CTA-based CIS and low blood glucose at admission were significantly correlated with good outcome. Conclusion CIS calculated using CTA is as reliable as DSA-based CIS for assessing collateral flow in AIS, and is also a good predictor of clinical outcome. This index could be useful for guiding patient selection and treatment strategies for AIS.