The Lesion Patterns and Mechanisms of Ischemic Stroke Contralateral to the Internal Carotid Artery Occlusive Disease

Background: In previous studies on unilateral internal carotid artery (ICA) occlusive disease, contralateral strokes have been ignored or excluded, probably because of their heterogeneity in etiology. The purpose of this study was to analyze the acute ischemic lesions contralateral to ICA occlusive disease and characterize the patterns and mechanisms of these strokes. Methods: Eight patients, who had an acute ischemic stroke contralateral to the ICA occlusion, were enrolled. All patients underwent routine clinical evaluation including history and physical examination, laboratory tests and magnetic resonance imaging (MRI). Both magnetic resonance angiography and digital subtraction cerebral angiography, along with carotid duplex sonography, transcranial Doppler sonography, electrocardiography and echocardiography were performed to confirm the stroke subtypes. Results: There were three distinctive stroke lesion patterns: (1) multiple infarcts in the border zone with or without a territorial lesion (4 patients), (2) multiple infarcts in the arterial territories sparing the border zone (2 patients), and (3) a small (<15 mm in MRI) single infarct in the internal border zone (2 patients). Overall, the patterns of ischemic lesions contralateral to the ICA occlusion were multiple and had a border zone distribution. Conclusion: These results suggest that the pathogenic mechanisms underlying these strokes could be the synergistic effects of both the embolism and a low flow state.