Mobile Thrombus with an Ulcerative Plaque Diagnosed Using Ultrasonography in a Patient with Nonstenotic Carotid Artery Disease

More than 50% relevant artery stenosis is regarded as significant and may be responsible for an ischemic lesion in the corresponding brain area. However, a lesion with less than 50% stenosis with carotid plaque is classified as an embolic stroke of an undetermined source and might be underestimated as a potential source of stroke. A 53-year-old woman with motor weakness of the left limb showed multiple scattered small infarct lesions in the right middle cerebral artery territory with less than 50% stenosis of the right carotid artery on magnetic resonance angiography. No embolic source was detected from cardiac assessments. Carotid duplex sonography showed a mobile thrombus and an ulcerative plaque in the right carotid artery, and these were confirmed by digital subtraction angiography. Our case report suggests that carotid duplex sonography can be useful in patients who have ischemic stroke with an embolic pattern without significant arterial stenosis.