Fig. 1From: Four collateral circulation pathways were observed after common carotid artery occlusionTCD showed the blood flow in CCA, ECA and ICA on both sides of the 16 patients. a No blood flow in the occluded CCA. b Normal blood flow in the healthy CCA. c Retrograde blood flow in the ipsilateral ECA. d Normal blood flow in the contralateral ECA. e Lower but antegrade blood flow in the ipsilateral ICA. f Normal blood flow in the contralateral ICABack to article page