Imaging of the internal carotid artery: The dilemma of total versus near total occlusion

PURPOSE: To evaluate ultrasonography (US) and magnetic resonance (MR) angio graphy in the differentiation between occlusion and near occlusion of inter nal carotid artery (ICA). MATERIALS AND METHODS: Consecutive patients with occlusion or near occlusio n of ICA at catheter angiography and who underwent MR angiography and US we re included. MR angiography and US were compared with catheter angiography, the standard, for the ability to help distinguish occlusion from near occl usion. Noninvasive examinations were evaluated for the ability to classify near occlusions as having severe focal stenosis with distal luminal collaps e versus diffuse nonfocal disease. The 95% Cls were calculated. RESULTS: In 55 of 274 patients with 548 ICAs, catheter angiography depicted 37 total occlusions and 21 near occlusions. US depicted all total occlusio ns; MR angiography depicted 34 (92%) (95% CI: 0.78, 0.98). US depicted 18 ( 86%) of 21 (95% CI: 0.64, 0.97) near occlusions; MR angiography depicted al l (100%). Of 18 vessels that were determined to be patent at US, 17 (94%) ( 95% CI: 0.73, 0.99) were classified as having focal stenosis or diffuse dis ease. Because flow gaps were identified in vessels with focal and diffuse d isease, MR angiography was not effective in helping to differentiate these lesions. CONCLUSION: Assuming US is the initial imaging examination, when occlusion is diagnosed, MR angiography can depict it. If occlusion is confirmed, no f urther imaging is necessary. US performed well in helping to differentiate vessels with focal severe stenosis from those with diffuse disease. MR angi ography added little in this group. Catheter angiography remains beneficial for vessels with diffuse nonfocal narrowing.