Collateral circulation in internal carotid artery occlusion. A study by duplex scan and magnetic resonance angiography.

Our data show: 1) a clear-cut prevalence of collateral circulation through homolateral external carotid artery branches with respect to other possible collateral circulation; 2) an inverse relationship between the development of collateral circulation and the appearance of permanent symptoms; 3) a good diagnostic accuracy of duplex scan in revealing collateral circulation in the case of ICA occlusion.