Carotid artery stenosis is associated with better intracranial collateral circulation in stroke patients

Background: Adequate collateral circulation improves the clinical outcome of ischemic stroke patients. We evaluated the influence of ipsilateral carotid stenosis on intracranial collateral circulation in acute stroke patients. Methods: We collected the data of 385 consecutive acute stroke patients who underwent mechanical thrombectomy after multimodal computed tomography (CT) imaging in a single high-volume stroke center. Patients with occlusion of the first segment (M1) segment of the middle cerebral artery were included. We recorded baseline clinical, laboratory, procedural, and imaging variables and technical, imaging, and clinical outcomes. The effect of carotid stenosis on intracranial collateral circulation was studied with appropriate statistical tests and ordinal regression analysis. Results: Fifty out of the 247 patients eligible for analysis had severe ipsilateral carotid stenosis (≥75%). These patients were 4-times more likely to have very good intracranial collaterals (Collateral Score 3-4, p = 0.001) than the nonstenotic and slightly stenotic (<75%) patients. The severely stenotic patients had a longer mean operation time (41 vs. 29 min to reperfusion, respectively, p = 0.001). Nevertheless, 54% of severely stenotic patients had good 3-month clinical outcome (modified Rankin Scale ≤2) with no significant difference between the 2 groups. Conclusions: Carotid artery stenosis of over 75% of vessel diameter was associated with better intracranial collateral circulation of patients with acute ischemic stroke. This did not significantly change the 3-month clinical outcome.