During right thyroid lobectomy, the surgeon finds the recurrent laryngeal nerve absent from its usual tracheo-oesophageal groove despite careful dissection. Preoperative CT had shown the right subclavian artery arising directly from the arch of the aorta and passing behind the oesophagus. What anomaly explains this operative finding?

• A The nerve lying anterior to the inferior thyroid artery instead of posterior
• B Congenital absence of the right recurrent laryngeal nerve
• C Non-recurrent right laryngeal nerve arising from the vagus at the level of the cricothyroid joint ✓
• D Duplication of the recurrent laryngeal nerve within the ligament of Berry

Explanation

An aberrant right subclavian artery (arteria lusoria) arises as the last branch of the aortic arch and crosses behind the oesophagus, so the right recurrent laryngeal nerve never hooks under it and runs directly from the vagus to the larynx as a non-recurrent nerve. It occurs in about 0.5 to 1 percent of right-sided operations and places the nerve at high risk of injury. Congenital absence does not occur, killing option B.

Reference: Gray's Anatomy, 42nd ed.

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Written and medically reviewed by the StethoPrep medical team.