Vertebrobasilar insufficiency: evaluation by quantitative duplex flow measurements. A preliminary report.

With the use of duplex sonography, quantitative vertebral artery flow measurements have been made in 283 patients who had nonlocalizing symptoms of cerebral ischemia suggestive of vertebrobasilar insufficiency. Net vertebral artery flow was calculated by adding flows from the right and left sides. When net vertebral flow was greater than 200 ml/min, 89 of 148 patients (60%) were found to have a significant stenosis (greater than 50% diameter reduction) in one or both internal carotid arteries. Conversely, when net flow was less than 200 ml/min, 101 of 135 patients (75%) had normal or only mildly diseased carotid system (p less than 0.001). When compared with otherwise matched groups of asymptomatic patients or patients with lateralizing hemispheric symptoms, those with nonlocalizing symptoms were much more likely to have net flow less than 200 ml/min. For the nonlocalizing symptom group this was 135 of 283 patients (48%) compared with only 72 of 208 asymptomatic patients (35%, p = 0.005) and 110 of 310 patients with hemispheric symptoms (35%, p = 0.003). Duplex sonography appears to offer a noninvasive technique for the functional hemodynamic evaluation of patients with suspected vertebrobasilar insufficiency, with the capability to distinguish those patients whose symptoms may be related to thromboembolic carotid artery disease, true vertebrobasilar ischemia, or some other cause.