Intravascular clot formation in the middle cerebral artery as demonstrated by plain CT scan

It has been known that plain computerized tomography may show a thrombosed middle cerebral artery as a high-density cord. We reviewed the plain CT scans of 17 patients with middle cerebral artery occlusion and found that 4 of the 9 cases with occlusion at the M1 portion, 2 of the 4 with occlusion at the M2 portion, and 1 of the 4 with occlusion at the M3 portion showed high-density cords corresponding to the middle cerebral artery. None of the patients with the middle cerebral artery stenosis or occlusion of the internal carotid artery origin revealed such a finding. Angiographically, an extension of the thrombus to the internal carotid artery was seen in 3 cases. Thrombus formation or adherence of the embolus proximal to the site of occlusion was seen as a defect in the dye column in 3 cases. One patient had known mitral valve stenosis. It appeared that the high-density cord can be demonstrated when the intravascular clot exists in the long segment of the artery. In most of the cases, embolism was suspected as the mechanism producing this unique CT scan finding. (author)