Fig. 2.

Reversed OA flow in a patient with proximal ICA occlusion. a Flow direction of left OA is reversed (away from probe) and pulsatility index is significantly decreased (0.73). b Flow direction of left supratrochlear artery is also reversed with decreased pulsatility index, which is consistent with OA spectra. Flow velocity of left supratrochlear artery significantly reduced by compression of ipsilateral superficial temporal artery and mandibular artery (white arrowhead), indicating which is supplied by ECA. c, d TCD shows a normal flow velocity and waveforms in right OA and supratrochlear artery, respectively. e Corresponding angiography confirms the TCD recordings. Cerebral angiography shows left proximal ICA occlusion (black arrow). Blood source of OA (white arrow) is from ECA (black arrowhead). OA provides blood supply for distal ICA (white arrowhead), indicating ECA to ICA collateral channels filling.