REVERSAL of vertebral blood flow in the presence of a proximal subclavian artery occlusion is an established cause of transient cerebral ischemia. Recognized as the subclavian steal syndrome, the cerebrovascular insufficiency occurs in the presence of lowered pressures in the distal subclavian artery.1 As a result of the unfavorable gradient, blood is siphoned from the vertebrobasilar circulation to the upper limb. When stenosis of the subclavian artery appears in the course of or distal to the origin of its main branches, the collateral network from the thyrocervical, costocervical, and intercostal vessels serves to bypass the block. In this situation diversion of blood flow from the cephalic circulation to the arm does not take place. In their comprehensive review of 125 cases of the steal syndrome, Patel and Toole2 cited no instance associated with peripheral subclavian obstruction.
The present report is the first to describe a patient with clinical