Between 1978 and1988, the diagnosis of atheromatous pseudo-occlusion of the internal carotid artery was made in 34 patients by angiography. Results of noninvasive tests were abnormal in 33 of the 34 patients examined. Twenty-five patients had carotid endarterectomy, and the other nine were treated medically. Four of the 34 patients (12%) had significant complications, two related to angiography and two to surgery. Twenty-three of the 25 operated patients were seen in long-term follow-up; 19 (83%) were found to have a patent operated vessel by noninvasive testing. None of the 23 operated patients followed up suffered recurrent neurologic deficits following surgery; two had distant contralateral strokes. Three of the nine patients treated medically (33%) experienced delayed ipsilateral stroke. This study shows that the risks associated with angiography and surgery for atheromatous pseudo-occlusion are significant and are higher than previously reported. (Stroke 1989;20:1168-1173 H ighly stenotic but patent internal carotid arteries (ICAs) can easily be misdiagnosed as occluded by both noninvasive testing and by angiography. Blood flow distal to a site of extreme stenosis may be so minimal that it remains undetected. The term "atheromatous pseudo-occlusion" was first used by Lippman et al in 1970.] They described layering of contrast material along the dependent posterior wall of the ICA distal to a site of high-grade stenosis at the time of angiography. Other descriptive terms used to categorize the angiographic appearance of such extremely stenotic lesions are the poststenotic slim sign, the string sign, and the nearly occluded carotid artery.2 -8 Once identified, urgent carotid endarterectomy seems to be automatically accepted as appropriate for pseudo-occlusion. However, surgery for pseudo-occlusion should be attempted only if surgically treated patients are shown to have better prognoses than those treated medically and if longterm patency of the operated vessel is high. These issues have not been previously addressed.This report describes our experience with 34 patients with atheromatous pseudo-occlusion. All 34 underwent selective carotid angiography, and 25 subsequently had carotid endarterectomy. We report on the complications associated with both procedures. We also report the long-term clinical out-

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SUMMARY To assess the impact of noninvasive testing of the carotid vessels upon patient management, we analyzed the angiographic findings in 494 patients studied between 1978 and 1983 for suspected extracranial cerebrovascular disease. This longitudinal study revealed two changes in the pattern of angiographic results after introduction of noninvasive testing in the final months of 1979. The proportion of examinations that revealed less than 49% stenosis decreased significantly from 49% in 1978 to 19% in 1983 (p < 0.001). During the same time, the proportion of examinations identifying 75-99% stenosis increased from 20% to 62% (p < 0.001). The referring physicians and their patient population appeared to remain unchanged over these years. We believe the decline in patients with little or no disease is a consequence of better patient selection due to screening with noninvasive tests. We credit the increase in patients with 75-99% disease to additional patients identified by noninvasive tests. This study also points out that the role of noninvasive studies will necessarily be restricted because of inherent limitations in the techniques and that clinical judgement will remain the final arbiter with regard to the management of patients at risk for stroke. Stroke Vol 16, No 2, 1985 NONINVASIVE tests for evaluating carotid atherosclerosis have proliferated in number and sophistication in the past decade, and studies have shown they can be quite accurate in detecting stenosis of greater than 50% of the lumen.

Groups of human cholesterol gallstones were subjected to monooctanoin with and without agitation, methyl-tert-butyl ether (MTBE) with and without agitation, and monooctanoin and MTBE used in succession with agitation. In this in vitro study, agitation greatly expedited the rate of dissolution with MTBE, by far the more potent of the two solvents. An additive effect was suggested when the solvents were used sequentially, monooctanoin followed by MTBE. Cholesterol-calcium stones were also dissolved by MTBE but at a slower rate, depending on the amount and distribution of calcium. Computed tomographic (CT) scans and mammographic images clearly delineated the amount and distribution of calcification, but plain radiographs did not. On the basis of these findings, the authors instituted two changes in their clinical protocol: All patients with gallstones are now examined by means of CT before chemical dissolution begins, and monooctanoin is instilled overnight before the MTBE procedure.

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