CT angiography clot burden score and collateral score: correlation with clinical and radiologic outcomes in acute middle cerebral artery infarct

Abstract

Background and purpose: Clot extent, location, and collateral integrity are important determinants of outcome in acute stroke. We hypothesized that a novel clot burden score (CBS) and collateral score (CS) are important determinants of clinical and radiologic outcomes and serve as useful additional stroke outcome predictors.

Materials and methods: One hundred twenty-one patients with anterior circulation infarct presenting within 3 hours of stroke onset were reviewed. The Spearman correlation was performed to assess the correlation between CBS and CS and clinical and radiologic outcome measures. Patients were dichotomized by using a 90-day modified Rankin scale (mRS) score. Uni- and multivariate logistic regression models were used to assess variables predicting favorable clinical and radiologic outcomes. Receiver operating characteristic and intraclass correlation coefficient (ICC) analyses were performed. Diagnostic performance of a CBS threshold of >6 was assessed.

Results: There were 85 patients (mean age, 70 +/- 14.5 years). Patients with higher CBS and CS demonstrated smaller pretreatment perfusion defects and final infarct volume and better clinical outcome (all, P < .01). CBS (P = .009) and recanalization (P = .015) independently predicted favorable outcome. A CBS >6 predicted good clinical outcome with an area under the curve of 0.75 (95% confidence interval [CI], 0.65-0.84; P = .0001), sensitivity of 73.0 (95% CI, 55.9-86.2), and specificity of 64.6 (95% CI, 49.5-77.8). The recanalization rate with intravenous recombinant tissue plasminogen activator was higher in patients with CBS >6 (P = .04; odds ratio, 3.2; 95% CI, 1.1-9.4). The ICC was 0.97 (95% CI, 0.95-0.98) and 0.87 (95% CI, 0.80-0.91) for CBS and CS, respectively.

Conclusions: CBS and CS are useful additional markers predicting clinical and radiologic outcomes.

Fig 1.

Illustration of CBS. A, A 10-point score is normal, implying absence of thrombus. Two points (as indicated) are subtracted for thrombus found on CTA in the supraclinoid ICA and each of the proximal and distal halves of the MCA trunk. One point is subtracted for thrombus found in the infraclinoid ICA and A1 segment and for each affected M2 branch. B, Occlusion of infra- and supraclinoid ICAs with a CBS of 7. C, Distal M1 and 2 M2 branch occlusions produce a CBS of 6. D, Occlusion of the terminal ICA, proximal M1, and A1, with a resultant CBS of 5.

Fig 2.

MTT and CTA source images (CTA-SI) of 4 different cases, each demonstrating prolonged MTT from a left MCA territory ischemia. CS grading is demonstrated for each collateral grade. A, Absence of vessels on CTA-SI is consistent with a CS of 0. B, A score of 1 indicates collateral supply filling ≤50% but >0% of the occluded MCA territory. C, A score of 2 is given for collateral supply filling >50% but <100% of the occluded MCA territory. D, A score of 3 is given for 100% collateral supply of the occluded MCA territory.

Fig 3.

ROC for CBS prediction of good clinical outcome (mRS score, ≤2). A threshold of >6.5 was found with an AUC of 0.73 (95% CI, 0.62–0.82; P = .0001).

Fig 4.

An 88-year-old woman presented with left-sided weakness treated with intravenous rtPA without recanalization. A, Noncontrast head CT scan demonstrates loss of gray-white matter differentiation within the right frontal lobe and caudate body with an ASPECTS of 3 and a baseline NIHSS score of 17. B, Coronal MIP image demonstrates poor contrast opacification of right supra- and infraclinoid ICAs (arrowhead) and M1 segment extending into the proximal M2 branches (arrow), scoring a CBS of 1. C, Axial CTA source image demonstrates a CS of 1. The patient was not treated with thrombolysis, was not recanalized, and achieved an mRS score of 4 at 90 days.