Hemodynamic effects of proximal supra-aortic artery stenosis on anterior cerebral artery.

Alternating flow in the anterior cerebral artery is a rare finding, associated with innominate artery stenosis. We present a series of four patients with this finding on transcranial color coded sonography, under basal conditions. In all of these patients, vascular studies detected an ipsilateral proximal stenosis, three in the innominate artery and, for the first time, one at the left common carotid artery origin. Successful angioplasties with stenting were performed, resulting for the first time in the normalization of orthograde flow in all cases. We conclude that an early systolic hemodynamic compromise in the first segment of the anterior cerebral artery, in the form of alternating flow, is an indirect indicator of ipsilateral proximal stenosis in the supra-aortic arteries, either in the innominate artery or at the origin of the left common carotid artery.