The left vagus nerve crosses the aortic arch at which specific location, giving off the left recurrent laryngeal nerve that hooks under which structure?

• A Crosses posterior to the aortic root; left RLN hooks under the subclavian artery
• B Crosses over the bifurcation of the trachea; left RLN hooks under the left subclavian artery
• C Crosses the ascending aorta; left RLN hooks under the brachiocephalic artery
• D Crosses the lateral aspect of the aortic arch anterosuperior to the ligamentum arteriosum; left RLN hooks under the arch of the aorta at the level of the ligamentum arteriosum ✓

Explanation

The left vagus nerve descends in the thorax between the left common carotid artery and the left subclavian artery, crosses the lateral aspect of the aortic arch, and gives off the left recurrent laryngeal nerve (RLN). The left RLN hooks under the aortic arch at the level of the ligamentum arteriosum (or ductus arteriosus), then ascends in the tracheo-oesophageal groove to reach the larynx. This explains why mediastinal masses, lung cancer (particularly at the aortopulmonary window), or aortic aneurysms can compress the left RLN causing hoarseness — the right RLN, by contrast, hooks under the right subclavian artery in the neck.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.