Noninvasive detection of internal carotid artery occlusion

Flow in the common carotid artery is normally quasisteady with flow never approaching zero during diastole. With total occlusion of the internal carotid artery, flow in the common carotid assumes the pattern observed in the external carotid, which supplies a relatively high-resistance vascular bed. In 34 instances of total internal carotid obstruction, flow went to zero in diastole in 33 cases and also demonstrated flow reversal in 22. In addition, there was a significant reduction in peak systolic velocity when the low-resistance internal carotid was obstructed. These observations, which are simple to determine using an ultrasonic duplex scanner, are of value in suspecting total occlusion of the internal carotid artery, thus obviating the need for arteriography in some cases.