PMC6195921_01
Time-of-flight MR angiography of the arterial neck vessels at the level of the hyoid bone, axial section, shows normal flow signal (white) within both internal carotid arteries (larger anterior vessels) and the right vertebral artery, seen end on. Arrow indicates the expected location of the left vertebral artery but no flow is demonstrated.
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fig1
Figure 1 demonstrates a complete absence of flow within the left vertebral artery (arrow indicates artery location) on TOF angiography.
Contrast-enhanced MR angiography of the arterial neck vessels, axial (top image) and coronal (bottom image) sections. Normal flow signal is now demonstrated within the left vertebral artery on the axial section taken at the same location as Figure 1. The coronal section demonstrates a flow gap (arrows) within the proximal left subclavian artery but normal contrast filling of the distal left subclavian artery beyond the origin of the left vertebral artery.
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fig2
Contrast-enhanced MR angiography was then performed and demonstrated an apparently normal left vertebral artery (Figure 2).
Contrast-enhanced CT angiography of the arterial neck vessels, coronal section. This image better demonstrates the flow gap within the proximal left subclavian artery and again demonstrates normal contrast filling of the left vertebral artery (arrows).
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fig3
Follow-up CT angiography more clearly delineates the subclavian artery occlusion (Figure 3; again the apparently normal contrast opacification of the left vertebral artery within the neck, as indicated by the arrows, is noteworthy).