Teaching NeuroImage: subclavian steal syndrome.

A 65-year-old woman presented with recurrent episodic vertigo lasting hours, accompanied only by headache. While golfing, she experienced transiently blurred vision. She denied arm claudication. Blood pressure was 160/78 in the right arm and 140/65 in the left arm. The left radial pulse was diminished. Cranial nerves, strength, sensation, and coordination were normal. Maneuvers to provoke symptoms were not attempted. MR angiography revealed an occlusion in the proximal left subclavian artery. Digital subtraction angiography was performed (see figure and video). Proximal occlusion of the subclavian artery causes retrograde flow through the ipsilateral vertebral artery.1 Insufficient compensation by other arteries may result in posterior circulation ischemia, as in this case. However, many cases of “subclavian steal” may be asymptomatic. In these cases, invasive therapy should be withheld.2