During right thyroid lobectomy, the surgeon cannot find the recurrent laryngeal nerve in the tracheo-oesophageal groove, yet the patient later develops complete unilateral cord palsy. CT performed earlier had shown the right subclavian artery arising directly from the aortic arch distal to the left subclavian origin. The most likely explanation is:

• A A non-recurrent right laryngeal nerve running directly from the vagus into the larynx ✓
• B Compression injury of a normally coursing nerve by haematoma
• C Traction injury of the vagus nerve at the thoracic inlet
• D Anatomical variant in which the nerve loops under the right brachiocephalic vein

Explanation

When the right subclavian artery arises abnormally from the descending aorta (arteria lusoria), the right recurrent laryngeal nerve fails to loop under it and instead runs as a non-recurrent nerve directly from the vagus to the larynx, often entering horizontally. Because the surgeon expects the nerve in the usual groove, it may be unknowingly divided while clearing ligament of Berry attachments. This anomaly occurs in about 0.5 to 1 percent of rightsided explorations and essentially never on the left.

Reference: Schwartz's Principles of Surgery, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.