Which imaging modality is best for evaluating carotid atherosclerosis as a cause of amaurosis fugax?

• A. Brain MRI
• B. Echocardiography
• C. Duplex ultrasonography of the carotid arteries
• D. Abdominal CT scan

Answer: (C)

Amaurosis fugax occurs when emboli from a carotid plaque temporarily block the retinal arteries. To determine carotid disease as the cause, you need an imaging test that directly visualizes the carotid arteries and measures how narrowed they are. Duplex ultrasonography of the carotid arteries uses both B-mode imaging to see plaques and Doppler flow to assess velocity, letting you estimate the degree of stenosis. This information is pivotal for management decisions, since symptomatic patients with significant carotid stenosis may benefit from interventions like carotid endarterectomy or stenting. It’s noninvasive, widely available, inexpensive, and free of radiation, making it the best initial test.

Brain MRI can show brain tissue damage but doesn’t evaluate the carotid vessels themselves. Echocardiography looks for cardiac sources of emboli, not carotid artery disease. Abdominal CT scan isn’t relevant to the carotid circulation or retinal ischemia. If needed, CT or MR angiography can provide further detail, but duplex ultrasound remains the primary, most appropriate test for assessing carotid atherosclerosis in this scenario.