Color-coded duplex ultrasonography of the origin of the vertebral artery: normal values of flow velocities

The introduction of color-coded duplex ultrasonography has improved the ease of performing ultrasound investigations of the vertebral arteries. So far, normal values of flow velocities have been reported only for the intertransverse region of the vertebral artery (V2 segments). Atherosclerotic disease at the origin of the vertebral arteries (V0 segment) is frequent and is one of the risk factors for vertebrobasilar ischemic disease. Normal values of flow velocities of the vertebral artery origin are needed to assess pathologic findings, such as vertebral artery origin stenosis or dissection. The aim of this study was to describe the normal flow velocities of vertebral artery origin (V0 segment) and the pre- (V1 segment) and intertransverse (V2 segment) part in 50 age-matched neurologic patients (mean age 54) without ischemic cerebral disease. The V0 segment could be visualized in 46 persons (92%) on the right side and in 43 (86%) on the left. The peak systolic blood velocity ranged from 30 to 100 cm/s (mean 63.6 +/- 17.5 cm/s), and end-diastolic blood velocity ranged from 10 to 35 cm/s (mean 16.1 +/- 5.1 cm/s). Analysis of side-to-side differences showed no significant differences of flow velocities in all subjects. It is concluded that color duplex ultrasonography is a feasible method to insonate the origin of the vertebral artery, and that nomogram data could be established. It is suggested that color-coded duplex ultrasonography of the vertebral artery origin should be performed in all patients with clinical symptoms or signs of vertebrobasilar ischemic disease. Nevertheless, further studies are needed to determine the normal and pathologic values of flow velocities of the vertebral artery origin and their reproducibility.