Reversible basilar artery blood flow in subclavian steal syndrome.

Transcranial Doppler ultrasound examination of intracranial vertebral and basilar arteries was performed on a 61-year-old man who presented with symptoms of amaurosis fugax and subclavian steal syndrome. During arm exercise, flow in the basilar artery reversed direction from cephalad to caudal, coincident with symptoms of vertebrobasilar insufficiency. Following bilateral carotid endarterectomies, exercise-induced reverse flow velocities in the basilar artery were markedly increased, and the patient remained asymptomatic. These findings suggest that collateral flow from the anterior cerebral circulation may play an important role in the pathogenesis of brainstem ischemia in subclavian steal syndrome and that transcranial Doppler may identify a subgroup of patients who will benefit from procedures to augment cerebral blood flow.