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Updated: Oct 14, 2025
Optimized Management of Endovascular Treatment for Acute Ischemic Stroke
Published on: January 18, 2018
Symmetric CTA Collaterals Identify Patients with Slow-progressing Stroke Likely to Benefit from Late Thrombectomy
Robert W Regenhardt1, R Gilberto González1, Julian He1
1From the Departments of Neurology (R.W.R., A.B.S.), Neurosurgery (R.W.R.), and Radiology (R.G.G., J.H., M.H.L.), Massachusetts General Hospital, Harvard Medical School, 55 Fruit St, WACC 729C, Boston, MA 02114; Athinoula A Martinos Center for Biomedical Imaging, Charlestown, Mass (R.G.G.); and Mass General Brigham Center for Clinical Data Science, Boston, Mass (R.G.G.).
Insights
Symmetric collateral patterns on CT angiography indicate a slow ischemic core growth rate and small infarcts in large vessel occlusion stroke patients. This finding may help identify candidates for delayed endovascular thrombectomy.
Area of Science:
- Neurology
- Radiology
- Medical Imaging
Background:
- Understanding ischemic core growth rate (IGR) is crucial for selecting patients with large vessel occlusion (LVO) stroke who might benefit from delayed endovascular thrombectomy (EVT).
- Assessing collateral circulation on CT angiography (CTA) is a potential method to identify slow-progressing LVO strokes.
Purpose of the Study:
- To determine if a symmetric collateral pattern on CTA can identify patients with LVO stroke who have a low IGR and small 24-hour diffusion-weighted MRI (DW-MRI) ischemic core volume.
- This evaluation was conducted in patients who did not receive reperfusion therapies.
Main Methods:
- A secondary analysis of clinical trial data (January 2007-June 2009) included 31 patients with anterior proximal LVO who did not receive reperfusion therapy.
- Patients underwent admission CTA and serial DW-MRI over 48 hours.
- Collateral patterns were categorized (symmetric, malignant, other), and IGR and ischemic core volumes were calculated.
Main Results:
- Symmetric collaterals were observed in 45% of patients.
- Median ischemic core volumes at presentation and 24 hours were significantly smaller in patients with symmetric collaterals compared to other patterns (16 cm³ vs. 69 cm³ and 28 cm³ vs. 156 cm³, respectively; P < .001).
- Symmetric collaterals demonstrated high sensitivity (87%) and specificity (94%) for predicting a 24-hour ischemic core volume < 50 cm³.
Conclusions:
- In LVO stroke patients not treated with reperfusion, a symmetric collateral pattern on CTA is common and highly specific for a low IGR and small 24-hour ischemic core volume.
- Collateral status assessed by CTA may aid in patient triage for EVT, particularly when advanced imaging like MRI perfusion is unavailable.
Abstract:
Background Understanding ischemic core growth rate (IGR) is key in identifying patients with slow-progressing large vessel occlusion (LVO) stroke who may benefit from delayed endovascular thrombectomy (EVT). Purpose To evaluate whether symmetric collateral pattern at CT angiography (CTA) can help to identify patients with low IGR and small 24-hour diffusion-weighted MRI ischemic core volume in patients with LVO not treated with reperfusion therapies. Materials and Methods In this secondary analysis of clinical trial data from before EVT became standard of care from January 2007 to June 2009, patients with anterior proximal LVO not treated with reperfusion therapies were evaluated. All patients underwent admission CTA and at least three MRI examinations at four time points over 48 hours. Arterial phase CTA collaterals at presentation were categorized as symmetric, malignant, or other. Diffusion-weighted MRI ischemic core volume and IGR at multiple time points were determined. The IGR at presentation was defined as follows: (ischemic core volume in cubic centimeters)/(time since stroke symptom onset in hours). Multivariable analyses and receiver operator characteristic analyses were used. Results This study evaluated 31 patients (median age, 71 years; interquartile range, 61-81 years; 19 men) with median National Institutes of Health Stroke Scale (NIHSS) score of 13. Collaterals were symmetric (45%; 14 of 31), malignant (13%; four of 31), or other (42%; 13 of 31). Median ischemic core volume was different between collateral patterns at all time points. Presentation was as follows: symmetric, 16 cm3; other, 69 cm3; and malignant, 104 cm3 (P < .001). At 24 hours, median ischemic core volumes were as follows: symmetric, 28 cm3; other, 156 cm3; and malignant, 176 cm3 (P < .001). Median IGR was also different, and most pronounced at presentation: symmetric, 4 cm3 per hour; other, 17 cm3 per hour; and malignant, 20 cm3 per hour (P < .001). After multivariable adjustment, independent determinants of higher presentation IGR included only higher NIHSS (parameter estimate [β = 0.20; 95% CI: 0.05, 0.36; P = .008) and worse collaterals (β = -2.90; 95% CI: -4.31, -1.50; P < .001). The only independent determinant of 24-hour IGR was worse collaterals (β = -2.03; 95% CI: -3.28, -0.78; P = .001). Symmetric collaterals had sensitivity of 87% (13 of 15) and specificity of 94% (15 of 16) for 24-hour ischemic core volume less than 50 cm3 (area under the receiver operating characteristic curve, 0.92; 95% CI: 0.81, 1.00; P < .001). Conclusion In patients with large vessel occlusion not treated with reperfusion therapies, symmetric collateral pattern at CT angiography was common and highly specific for low ischemic core growth rate and small 24-hour ischemic core volume as assessed at diffusion-weighted MRI. After further outcome studies, collateral status at presentation may prove useful in triage for endovascular thrombectomy, especially when MRI and CT perfusion are unavailable. Clinical trial registration no. NCT00414726. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Messina in this issue.
