Near Occlusionに対するCarotid Endarterectomy : MRIプラーク性状評価と術後内頸動脈の開存性について  [in Japanese] Carotid Endarterectomy in Atherosclerotic Near Occlusion of the Internal Carotid Artery: Relationship between MRI Plaque Evaluation and Post-operative Patency of the Distal Internal Carotid Artery  [in Japanese]

The use of carotid endarterectomy(CEA) for near occlusion(NO) of the internal carotid artery(ICA) has not been evaluated with respect to the diagnostic procedures required, the risks, the appropriate timing, or the benefit of revascularization. Some reports note that the operative risks of CEA in NO patients and in some atherosclerotic total occlusion(TO) patients are not greater than those in patients with ordinary ICA stenosis. However, it is generally accepted that the rate of restenosis after CEA in NO/TO is very high. In the treatment of atherosclerotic ICA stenosis, it is important to consider not only the stenosis rate but also the plaque characteristics; in recent years, many reports that have used these criteria have demonstrated the usefulness of carotid MRI. We report the therapeutic results of CEA done in cases with NO/TO, particularly with respect to the relationship between the MRI plaque findings and the postoperative patency of the distal ICA. Seven CEAs were done in carotid NO/TO cases between March 2003 and October 2005 in our hospital. The morphology of the ICA stenosis and the characteristics of the carotid plaque were evaluated with digital subtraction angiography(DSA) and carotid black-blood(BB) MRI, respectively. Plaques were excised as single masses during CEA and then processed for histology. One asymptomatic case with de novo small infarction was confirmed on diffusion-weighted MRI images. In our study, neither hemorrhagic complications nor hyper-perfusion syndromes were observed. The overall safety of CEA for NO/TO was acceptable. The BB-MRI findings on T1-weighted images included: an extremely high signal in 3 cases; a slightly high signal in 2 cases; an isosignal in 1 case; and a low signal in 1 case. On histology, there was massive fresh intra-plaque hemorrhage(IPH) in 3 cases, subacute IPH in 1 case, chronic IPH in 1 case, and recanalization of occlusive thrombosis in 2 cases. One patient had asymptomatic thrombotic occlusion. Another patient had a poorly dilated distal ICA. These patients' pre-operative DSA showed NO with a string-like lumen, the BB-MRI revealed iso/low signals and histology demonstrated chronic IPH/recanalization. CEA for "chronic" NO/TO is of little benefit, since satisfactory post-operative patency of the distal ICA cannot be obtained. BB-MRI appears to be a useful modality for differentiating "acute" from "chronic" NO/TO.