ABSTRACTBACKGROUND AND PURPOSEThe authors describe a case of a proatlantal intersegmental artery seen in the setting of external carotid artery dissection and subclavian steal due to proximal subclavian artery stenosis.METHODSAn 83‐year‐old woman presented with left homonymous hemianopsia and a right posterior cerebral artery distribution stroke. She was found to have severe left subclavian artery stenosis proximal to the vertebral artery (VA) and an occluded contralateral VA. Doppler ultrasonography and angiography both showed a dissection of the proximal left external carotid artery. Left common carotid artery angiography also demonstrated a connection between the external carotid and vertebral arteries at the C1 level with anterograde flow into the vertebrobasilar system and retrograde flow toward the vertebral origin, consistent with subclavian steal.RESULTSThe patient underwent successful stenting of the subclavian and external carotid arteries with resolution of anterograde flow in the left VA.CONCLUSIONSThis case represents an interesting presentation of both subclavian steal and an external carotid artery to VA anastomosis. Also, the presence of a dissection of the external carotid artery represents a rare finding.