A 58-year-old man with a history of smoking and hypertension presents with right arm claudication and episodes of vertigo during right arm exercise. On examination, the right radial pulse is diminished compared to the left. CT angiography of the thorax shows occlusion of the structure marked **B** in the diagram. Which of the following clinical presentations is most consistent with the pathophysiology of this vascular occlusion?

Explanation

## Why option 1 is correct The structure marked **B** is the brachiocephalic (innominate) artery, the first and largest branch of the aortic arch. Occlusion of the brachiocephalic artery proximal to its bifurcation into the right common carotid and right subclavian arteries causes ipsilateral right arm claudication (from right subclavian insufficiency) and right-sided cerebrovascular insufficiency (from right common carotid territory ischemia). When the occlusion is proximal to the right vertebral artery origin, subclavian steal syndrome develops: during right arm exercise, the arm's metabolic demand causes reversal of flow in the right vertebral artery to supply the limb, diverting blood from the vertebrobasilar circulation and causing vertigo and other posterior circulation symptoms. This is the classic presentation of brachiocephalic artery occlusion. [Gray's Anatomy 42e Ch 56; Harrison 21e Ch 274] ## Why each distractor is wrong - **Option 2**: Left-sided cerebrovascular insufficiency and left arm claudication would result from occlusion of the left common carotid or left subclavian artery, not the brachiocephalic artery. The brachiocephalic artery supplies the RIGHT side only. - **Option 3**: Bilateral lower limb claudication indicates aortoiliac disease or aortic bifurcation stenosis, which is unrelated to brachiocephalic artery pathology. The brachiocephalic artery supplies the upper right body and right head, not the lower limbs. - **Option 4**: Dysphagia lusoria (dysphagia from an aberrant right subclavian artery crossing behind the esophagus) is a congenital anomaly where the right subclavian arises as the last branch of the aortic arch—not from brachiocephalic occlusion. It presents as chronic dysphagia in infancy/childhood, not acute claudication and vertigo. **High-Yield:** Brachiocephalic artery occlusion → right arm claudication + right cerebrovascular insufficiency + subclavian steal syndrome (vertebrobasilar symptoms with arm exercise). [cite: Gray's Anatomy 42e Ch 56; Harrison 21e Ch 274]