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Thrombi within the carotid artery usually occur in vessels with severe atherosclerotic lesions and may embolize to cause TIAs and ischemic brain infarctions. The risk factors and potential causes for carotid artery thrombus formation in the absence of atherosclerosis are currently only speculative (e.g., embolic occlusion from a cardiac source).1 Furthermore, a focal adherent thrombus involving the CCA is even more exceptional because of the rarity of severe atherosclerotic disease in this large and nonturbulent vessel.1,2 A thrombus lodged in the CCA has been reported in only a very few cases in the literature.2 We present two patients with a focal adherent thrombus in the CCA diagnosed by ultrasonography and confirmed by neuroimaging. The aim of this work is to investigate the ultrasonographic features of this very uncommon finding in young stroke patients.

Vertebrobasilar intracranial stenoses seem to carry a higher risk of brain stem ischemia than proximal vertebral artery stenoses. Our aim was to assess the value of transcranial Doppler sonography versus angiography in detecting and quantifying these intracranial stenoses. All consecutive patients who underwent transcranial Doppler sonography prior to angiography from 1989 to 1994 and whose sono-grams showed a stenosis of greater than 50% of one vertebral artery (21 cases) or of the basilar artery (eight cases) were included in the study. These patients were compared with 60 other consecutive stroke patients studied via transcranial Doppler sonography prior to normal vertebrobasilar angiography. The transcranial Doppler sonographic criteria for stenosis were a peak systolic frequency shift greater than 2 KHz. A tight stenosis was identified by this pattern combined with direct and reverse low frequencies of high spectrum energy. The sensitivity of transcranial Doppler sonography using a peak systolic frequency shift in diagnosing stenoses reached 80% and its specificity was 97% if only atheromatous stenoses were considered. The main diagnostic failures concerned bilateral stenoses or contralateral occlusion, tandem lesions, and upper basilar artery stenosis. Transcranial Doppler sonography underestimated the degree of stenosis compared to angiography in 55% of the cases. We conclude that transcranial Doppler sonography is accurate in recognizing a stenosed vessel in the intracranial vertebrobasilar circulation, but if this finding will alter therapy, the examination must be complemented by magnetic resonance angiography.

Noninvasive diagnosis of vertebral artery disease is difficult, but the combined use of Doppler ultrasonography and dynamic radionuclide studies, with measurement of the carotid-basilar delay (CBD), increases the sensitivity and can indicate the level (cervical or distal) of the lesion. Forty patients with cerebrovascular disease were studied by continuous wave Doppler and CBD and the results were compared with vertebral angiograms. The mean normal CBD value was determined for a control group of 18 patients. Sensitivity and specificity were 87.5 per cent and 75 per cent, respectively, for Doppler alone, and 100 per cent and 60 per cent for combined Doppler and CBD.

Symptomatic stenoses of the middle cerebral artery (MCA) are not uncommon, although Corston observed the occurrence of stroke in 24% of patients with MCA stenoses during a 6-year follow-up study. We tried to use transcranial Doppler (TCD) sonography for the detection and evaluation of MCA stenoses. Intra-arterial angiography demonstrated 16 MCA stenoses of more than 30% diameter reduction in 15 patients (14 atheromatous stenoses, 2 dysplasias). Severe associated lesions were present in 2 cases (more than 75% internal carotid artery stenosis). These 15 patients with MCA stenosis were examined with TCD in a blind study. A Doppler signal from the MCA was obtained through the temporal bone and was recognized on the result of common carotid artery compression test. We ascertained MCA stenosis when TCD demonstrated 1) segmental flow acceleration with peak systolic frequency of more than 3 KHz with or without high energy low frequency direct or reverse components; or 2) segmental increase in systolic peak frequency of more than 20%. Using these criteria, we confirmed through TCD the presence of MCA stenosis in nine out of 12 cases with diameter reduction of at least 50%, and one among four cases with less than 50% diameter reduction. Although our results are consistent with Aaslid and von Reutern's figures, methodological problems and diagnostic criteria have to be improved. Nevertheless, TCD seems to be a useful tool for the detection of stenosis with at least 50% diameter reduction, where it proved to offer a 75% sensitivity. Further studies are necessary to improve sensitivity and specificity.