High-Resolution 3-Tesla-MRI of the Carotid Arteries in the Evaluation of Cryptogenic Stroke

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Approximately 70% of ischemic strokes are caused by cardioembolism, small vessel disease or large artery atherosclerosis. Despite extensive workup the etiology remains unknown in up to 25% of cases (cryptogenic stroke). However, atherosclerotic plaques in the carotid vessels are only considered as causative if significant stenosis is present (e.g. >50%; TOAST-classification system). From a pathophysiological viewpoint this classification may seem questionable. Technical limitations of routinely applied imaging methods however limit the elaborate analysis of non-stenosing atherosclerotic changes of the vessel wall and the identification of vulnerable plaque (VP). High-resolution MRI of the carotid vessels is a relatively novel non-invasive approach, allowing for identification of VP with good correlation to histopathology. Based on previous work of our study group which suggests a substantial correlation between VP and ischemic stroke, the prospective, multicenter Carotid Plaque Imaging in Acute Stroke (CAPIAS)-study was initiated. Objectives of the study are to examine the prevalence of VP in patients with cryptogenic stroke and whether the presence of VP has influence on the recurrence rate of clinical manifest or silent stroke as well as on the progression of atherosclerotic changes in the vessel wall. Vessels contralateral to stroke and a group of patients with known stroke etiologies serve as controls. This Proposal is aimed at a research grant to support/enable an efficient analysis of MRI data of the carotid arteries as well as of the neurocranium which has already been and is still being acquired during the CAPIAS-study (at baseline and 12 month follow-up). Image data of the carotids is going to be evaluated using dedicated software algorithms. Atherosclerotic lesions are characterized according to the AHA-classification system and quantitative parameters of the vessel wall and singular plaque components (e.g. intraplaque hemorrhage, lipid-rich/necrotic core, calcifications) are obtained. Based on this data correlations between presence of VP and cryptogenic stroke, VP and stroke recurrence, and the effect of VP on progression of atherosclerosis are evaluated. Furthermore the establishment of a professional data base is going to ensure the long-term and effective availability of the assessed phenotypical data.