DIFFERENTIATION OF EMBOLIC AND THROMBOTIC MIDDLE CEREBRAL-ARTERY OCCLUSION USING ULTRASONIC CAROTID FLOW VELOCITY ANALYSIS

The purpose of this study was to determine the value of Duplex ultraso und of the carotid arteries in the differentiation of embolic from thr ombotic middle cerebral artery (MCA) occlusion. We report here the res ults of carotid Duplex ultrasound study from 164 patients with acute i schemic stroke. Flow velocity and diameter were measured in bilateral common carotid arteries (CCA). The end-diastolic flow velocity (V-ed) and the pulsatility index (PI) were calculated from Doppler waves. The PI is an index of peripheral vascular resistance. We compared the rel ationship between percent carotid stenosis and percent decrease in V-e d. The patients studied could be classified into three groups using ul trasound parameters. Group I was characterized by > 30% decrease in V- ed and < 80% carotid stenosis, group II by < 30% decrease in V-ed and and < 80% carotid stenosis, and group III by > 30% decrease in V-ed an d > 80% carotid stenosis. All 23 patients in group I had embolic MCA s tem occlusion. 28 out of 115 patients in group II had thrombotic MCA s tem occlusions. All 26 patients in group III had internal carotid arte ry occlusion or severe stenosis. V-ed was markedly reduced in group I and group III compared to group II (p < 0.01). PI in the affected arte ry was increased in groups I and III (p < 0.01). Embolic occlusion was characterized by > 30% decrease in V-ed in the absence of > 80% carot id stenosis, and an increase in PI. The results indicate that these tw o conditions can be differentiated using Duplex ultrasound in carotid arteries.