Antegrade Internal Carotid Artery Collateral Flow and Cerebral Blood Flow in Patients With Common Carotid Artery Occlusion

OBJECTIVES: To determine the incidence of antegrade internal carotid artery collateral flow in patients with common carotid artery occlusion, which artery supplies blood to the internal carotid artery, and whether the flow affects regional cerebral blood flow in the middle cerebral artery territory. METHODS: We determined the incidence of antegrade internal carotid artery collateral flow and identified its arterial origins using carotid sonography in 10 patients with common carotid artery occlusion and evaluated middle cerebral artery territory regional cerebral blood flow by single-photon emission computed tomography in these patients and 30 age- and sex-matched patients with internal carotid artery occlusion. RESULTS: Six (60%) of the 10 patients with common carotid artery occlusion had antegrade internal carotid artery collateral flow, which was supplied through the carotid bifurcation from retrograde flow of the external carotid artery in 5 and by a small artery directly into the internal carotid artery in 1. The regional cerebral blood flow ipsilateral to the occlusion at rest was higher in patients with common carotid artery occlusion than those with internal carotid artery occlusion (mean ± SD, 40.4 ± 8.5 versus 34.3 ± 6.2 mL/100 g/min; P = .02). The regional cerebral blood flow was significantly higher in the 6 patients with antegrade internal carotid artery flow than those with internal carotid artery occlusion at rest (42.2 ± 7.2 versus 34.3 ± 6.2 mL/100 g/min; P = .02) but not in the other 4 patients without antegrade internal carotid artery flow. CONCLUSIONS: Antegrade collateral internal carotid artery flow was found in 60% of patients with common carotid artery occlusion and was mainly supplied by retrograde external carotid artery flow. It contributes to maintenance of middle cerebral artery territory regional cerebral blood flow.