Pre-vertebral subclavian artery stenosis/occlusion can cause subclavian artery steal syndrome.
Patient was noticed to have discrepancy of the blood pressures on bilateral upper extremities. Intra-operative left subclavian artery and right vertebral artery angiographies revealed pre-vertebral occlusion of the left subclavian artery.
Occluded left subclavian artery with retrograde contrast flow into the aorta and left common carotid artery (arrow).
Right vertebral artery run in the same patient showed retrograde flow into the left vertebral artery and left subclavian artery. Notice there is also absence of bilateral posterior cerebral arteries due to bilateral fetal posterior communicating arteries.