Duplex ultrasonography of vertebral and subclavian arteries.

Duplex ultrasonography of the vertebral artery is an integral part of extracranial cerebrovascular screening and provides noninvasive diagnostic clues for subclavian or vertebral artery stenosis. This review describes technique for the ultrasound examination of the vertebral and subclavian arteries. Duplex images from various patients are used to illustrate a spectrum of hemodynamic changes that occur in the vertebral artery Doppler signal caused by subclavian artery stenosis and subclavian-vertebral steal.