Reversal of Blood Flow through the Vertebral Artery and Its Effect on Cerebral Circulation

WE have recently studied 2 patients with symptoms of cerebral ischemia in whom a reversal of blood flow through the left vertebral artery was demonstrated. In both cases the anatomic lesion producing the reversal of blood flow was a stenosis of the left subclavian artery proximal to the origin of the vertebral artery. The cause of the reversed flow in these circumstances can be attributed to a fall of pressure distal to the stenosis below that at the vertebral-basilar junction so that the pressure gradient in the vertebral artery is reversed. We had not previously encountered this phenomenon and were . . .