Effect of internal carotid artery occlusion on vertebral artery blood flow- A duplex ultrasonographic evaluation

The aim of this study was to evaluate the effect of unilateral internal car otid artery occlusion on blood flow volume and blood flow velocities in bot h vertebral arteries using duplex Doppler ultrasonography in the cervical s egment. Forty patients with unilateral extracranial internal carotid artery occlusion confirmed by angiography were studied, and the results were comp ared with those obtained in 57 age-matched patients in whom cervical duplex ultrasonography showed no abnormalities. We measured the diameter, flow ve locities, and blood flow volume in both vertebral arteries, and the side-to -side differences were also calculated. Eleven patients (27.5%) with an occ luded internal carotid artery had increased peak systolic velocity in the i psilateral vertebral artery, and 6 (15%) had increased peak systolic veloci ty in the contralateral vertebral artery. The mean peak systolic velocity a nd the mean blood flow volume were statistically greater in the ipsilateral vertebral arteries than in the same-side vertebral arteries of the control group (P < .05). We also detected a mean increase of 14.29% of the net blo od flow volume in the vertebral arteries compared with the control group. P atients with extracranial unilateral internal carotid artery occlusion may have a compensatory increase in both the peak systolic velocity and the blo od flow volume in both vertebral arteries.