Effect of various head and neck positions on vertebral artery blood flow.

The purpose of this study was to assess blood flow velocity in the vertebral arteries with duplex Doppler ultrasound during various positions of the head and neck. Vertebral artery morphology and blood flow velocity were assessed in a control group and in a group of subjects who displayed clinical signs and symptoms of vertebrobasilar insufficiency. The two groups did not differ in vertebral artery gross morphology as assessed by ultrasound. The arteries were examined for vascular impedance by calculating the ratio of peak systolic velocity to end diastolic velocity (systolic/diastolic ratio). In the context of this study, a lower velocity ratio implied less resistance to vascular flow. These velocity ratios were established during several positions of the head and neck, including a widely used provocational test manoeuvre for vertebrobasilar insufficiency. No meaningful significant differences in mean velocity ratios were found between the two groups. None of the subjects had abnormal spectral flow patterns during the different testing positions.