A 78 year-old man presented with over 20 spells of transient loss of vision in the right eye. Othewise, her neurologic examination was normal.
(Left) Right Carotid Angiogram; (Right) MRI axial diffusion weighted images. On the angiogram, note the high grade internal carotid artery stenosis. In addition, the external carotid artery is tightly occluded with a "string sign." On MRI diffusion images, there are several small infarcts which were clinically silent. All are in the distribution the watershed between the middle and anterior cerebral arteries. When a watershed infarction is seen on one side, this usually occurs due to hemodynamic narrowing of a proximal artery (e.g., in this case, the carotid artery).
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