Non-recurrent inferior laryngeal nerve.

Surgical damage to the inferior laryngeal nerve is one of the most feared complications of thyroid surgery. Prevention of surgical injuries requires systematic, early exposure of the inferior laryngeal nerve. A detailed knowledge of anatomical variations is necessary. Non-recurrent inferior laryngeal nerve is a rare anomaly on the right side and is exceptional on the left. Whereas the typical course of the inferior laryngeal nerve is due to the embryological development of the aortic arch and supra-aortic vessels, non-recurrence is associated with a vascular anomaly such as a right retro-oesophageal subclavian artery. The nervous anomaly on the left side is possible only with the occurrence of cardiac dextroposition (situs viscerum inversus) and a left retro-oesophageal subclavian artery. The situation is more dangerous when a non-recurrent branch of the inferior laryngeal nerve is associated with a recurrent branch. This anomaly does not appear to be associated with a vascular anomaly in all cases. The authors describe three cases of right non-recurrent inferior laryngeal nerve observed and one recent case of combined non-recurrent and recurrent nerve, highlighting the anatomical and surgical features of this anomaly.