Investigation of Carotid Stenosis and Blood Flow in Patients with Middle Cerebral Artery Thrombosis and Embolism by Duplex Ultrasonography

We used duplex ultrasonography to evaluate extracranial carotid artery lesion and common carotid blood flow in 249 patients with ischemic cerebrovascular disease. The equipment used was the EUB-415 (Hitachi Medico) with a 7.5 MHz linear type probe with an attached 20°coupler. We investigated the relation between carotid artery stenosis (%Stenosis) and end-diastolic flow velocity (%Dec-Ved) . We also investigated the possibility of differentiating embolic middle cerebral artery (MCA) occlusion from thrombotic MCA occlusion using these two parameters.In order to investigate the relationship between %Stenosis and %Dec-Ved in all the patients studied with and without carotid stenosis, a two-dimensional graph was prepared for each patient plotting %Stenosis on the abscissa and %Dec-Ved on the ordinate. The patients studied were classified into four groups by drawing a line at the 80% carotid stenotic point and another line at the 30% reduction point in the end-diastolic flow velocity. The critical point of reduction in the %Dec-Ved was 80% stenosis of the carotid artery, and the critical point differentiating embolism from thrombosis was 30% decrease in %Dec-Ved. The incidence of carotid atherosclerotic lesions among the patients with cardiogenic cerebral embolism was much lower than that among those with cerebral thrombosis. The end-diastolic flow velocity in the affected common carotid artery was significantly decreased in embolic MCA occlusion, but was not decreased in thrombotic MCA occlusion.In conclusion, we suspect that ultrasonographic classification of patients with ischemic strokes on the basis of %Dec-Ved and %Stenosis is useful in differentiating acute embolic MCA occlusion from thrombotic MCA occlusion and locating the site of vessel occlusion.