Effects of Carotid Endarterectomy or Stenting on Arterial Diameters in the Circle of Willis

Background: In patients with internal carotid artery (ICA) stenosis, the circle of Willis (CoW) is the primary collateral pathway. We compared luminal diameters in the CoW before and after carotid revascularization and compared the effects of carotid endarterectomy (CEA) and stenting on these diameters. Methods: At a single center in the International Carotid Stenting Study, 139 patients with symptomatic ICA stenosis of 50% or more were randomized to stenting (n = 81) or CEA (n = 58). The diameters of all segments of the CoW were assessed on computed tomography angiography (CTA), before and 30 days after revascularization. All evaluations were performed blinded to treatment allocation and order of CTA. Results: A .10-mm increase (95% confidence interval [CI], .02-.17; 7%; P = .01) in diameter after revascularization occurred in the ipsilateral precommunicating anterior cerebral artery (A1), whereas both the ipsilateral and contralateral posterior communicating arteries decreased in diameter by. 12 mm(95% CI, .04-.21; 14%; P = .01) and .08 mm(95% CI, .00-.17; 10%; P = .05), respectively. The increase in diameter of the A1 was larger after stenting (.15 mm; 95% CI, .07-.24; P = .001) than after CEA (.02 mm; 95% CI, 2.11 to.15; P = .79). Only in patients treated with CEA, the diameters of the contralateral A1 and ipsilateral precommunicating posterior cerebral artery were reduced after revascularization. Conclusions: Carotid revascularization improves anterior collateralization and reduces reliance on posterior collateral pathways via the CoW. Carotid stenting and endarterectomy appear to have different early effects on collateralization.