Spectrum of fibromuscular dysplasia - acute vertebral artery occlusion, internal carotid and renal artery involvement, and renal infarct

Discussion:

Spectrum of imaging findings of fibromuscular dysplasia (FMD), which is a noninflammatory angiopathy of small to medium size arteries most commonly involving the renal arteries, but can also involve the internal carotid and vertebral arteries.

This patient presented with right neck pain and dizziness (no diagnosis of FMD). Noncontrast CT brain shows subtle but definite asymmetric high attenuation of the right vertebral artery indicating thrombosis (similar to the dense MCA sign). If you detected this on the noncontrast CT of the brain, great job! I thought I made a great discovery when I noticed this, however, I was called by both the technologist and the emergency room physician wondering about the same finding, so clearly suspicion was high for everyone. 

CT angiography shows segmental occlusion of the right vertebral artery, which is likely related to dissection and thrombosis. The abnormal configuration of the internal carotid arteries makes fibromuscular dysplasia the most likely cause. Acute cerebellar and lateral medullary infarct was confirmed on MR the next day.

Further workup of the renal arteries shows fibromuscular dysplasia of the renal arteries, involving the right main renal artery and one of the three accessory left renal arteries.

Subsequently, the patient developed acute abdominal pain and was reimaged with portal venous phase CT, showing segmental infarcts in the right kidney, likely related to dissection/embolism within the right renal artery. The area of hypoattenuation in the right upper pole cortex was not present on the angiogram from two days prior, and the lower pole abnormality may have been present but would be difficult to distinguish given that only arterial phase images were performed.

See the companion case.

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