Cardioembolic stroke: Protective effect of a severe internal carotid artery stenosis in a patient with cardiac embolism.

Cardioembolic stroke is generally caused by intracranial artery occlusion. Clots may be identified in the intracranial vessels by means of conventional neuroimaging in the acute phase. High-resolution ultrasonography may show some features suggestive of cardiac emboli when occluding extracranial carotid arteries. We describe a patient with cardioembolic ischemic stroke in the right hemisphere in whom a left internal carotid artery stenosis paradoxically protected the ipsilateral hemisphere from distal intracranial embolism. The patient also presented multiple acute ischemic embolic lesions in the right middle cerebral artery territory and in the right occipital lobe, which was fed by the posterior cerebral artery, anomally originating from the right carotid siphon. Interestingly, the left internal carotid artery—which showed a severe preexisting stenosis—was occluded by the cardiac clot, whereas the right internal carotid artery only presented a moderate stenosis that had probably allowed the clots to pass. Therefore, the severe left internal carotid artery stenosis may have blocked the cardiac embolus, preventing it from reaching the ipsilateral hemisphere. © 2013 Wiley Periodicals, Inc. J Clin Ultrasound 41:22–27, 2013