Background and purpose: We performed the present study to determine whether the site of occlusion in the vertebrobasilar circulation could be identified by the measurement of blood flow velocity in the bilateral vertebral arteries.
Methods: Using color-coded duplex carotid ultrasonography, we measured the time-averaged mean and end-diastolic flow velocities with incident angle correction in 130 bilateral vertebral arteries between the C3 and C6 segments of the spine in 65 stroke patients with or without occlusive diseases in the vertebrobasilar circulation. The site of occlusion was confirmed by cerebral angiography. The subjects included 12 patients with unilateral subclavian artery occlusion (SA group), 11 patients with unilateral occlusion at the origin of the vertebral artery (V1 group), 6 patients with unilateral vertebral artery occlusion before the branching of the posterior inferior cerebellar artery (V2 group), 14 patients with unilateral vertebral artery occlusion after the branching of the posterior inferior cerebellar artery (V3 group), 5 patients with basilar artery occlusion (BA group), 5 patients with unilateral posterior cerebral artery occlusion (PCA group), and 12 patients without any occlusive lesions in the vertebrobasilar circulation (control group).
Results: In the control group the mean and end-diastolic blood flow velocities were 25.5 +/- 6.9 cm/s and 16.2 +/- 4.3 cm/s, respectively, and the side-to-side differences of these velocities were 4.8 +/- 5.2 cm/s and 4.7 +/- 4.1 cm/s, respectively. All patients in the SA group demonstrated retrograde flow on the affected side. In the V1 group no flow signals were detected on the occluded side. In the V2 group the mean velocity (7.2 +/- 3.1 cm/s) was lower than in the control group, and the end-diastolic velocity was zero on the affected side. In the V3 group the mean and end-diastolic velocities (11.5 +/- 3.1 cm/s and 5.9 +/- 2.8 cm/s, respectively) on the occluded side were lower than in the control group. Flow velocities on the unaffected side were higher than those on the affected side in the SA, V1, V2, and V3 groups. However, there were no differences in flow velocity between the control, BA, and PCA groups.
Conclusions: Measurement of vertebral artery blood flow velocity may help in localizing the site of occlusion in the subclavian and vertebral arteries.