Ultrasonography of carotid stenosis

The classification of internal carotid artery stenosis is of great impact. The degree of stenosis is the main criterion for the decision between an invasive or non-invasive treatment of extracranial internal carotid artery (ICA) stenoses. By now the North American Symptomatic Carotid Endarterectomy Trial (NASCET) criteria have been internationally approved for radiological grading. According to NASCET the stenosed lumen is compared with the lumen of the distal internal carotid artery. All ultrasound criteria do have limitations and can therefore cause pitfalls in determining the degree of stenosis using one criterion exclusively. Therefore a multi-parametric grading of stenoses should be favored. The multi-parametric “DEGUM” ultrasound criteria have been revised and a novel differentiation between main (primary) and additional (secondary) criteria has been proposed. Recently a similar consensus was reached by the Neurosonology Research Group (NSRG) of the World Federation of Neurology (WFN). Main criteria include the following: imaging of the stenosis in B-mode sonography; visualization of the stenosis by color-coded imaging of flow; measurement of the maximum systolic flow velocity in the area of greatest narrowing of the lumen; systolic flow velocity measurement in the poststenotic segment; assessment of the collateral supply. Additional criteria include the following: indirect findings of an internal carotid artery stenosis in the common carotid artery; evidence of flow disturbances; end-diastolic flow velocity in the area of greatest narrowing of the lumen; the so-called confetti-sign; the carotid ratio. The main advantage of a multi-parametric grading of ICA stenoses is the synergetic effect of the different single criterion. Combining these ultrasound criteria, neurosonography allows reliable grading of carotid stenoses as a basis for decision making.