Limitations of noninvasive testing in assessing the "occluded" carotid artery.

Over a 3 year period eight cases of atherosclerotic pseudoocclusion were detected by carotid angiography. The diagnosis was based on the detection of a thin, delayed antegrade trickle of contrast medium distal to an area of extreme stenosis. In six of these cases both direct and indirect noninvasive tests were interpreted as showing total occlusion. In one case these tests were thought to demonstrate a normal bifurcation, and only once were they successful in suggesting the diagnosis of high-grade stenosis. Five of these eight patients subsequently underwent carotid endarterectomy. Patients who present with appropriate clinical indications for carotid endarterectomy should undergo angiography even when the noninvasive tests indicate a total occlusion of the internal carotid artery. In such circumstances the angiographic technique should be altered specifically to detect the possible presence of atheromatous pseudoocclusion.