Nonrecurrent inferior laryngeal nerve without vascular anomaly as a genuine entity

Inferior laryngeal nerve (ILN), which usually arises from vagus nerve, runs recurrent course and is called recurrent ILN (RILN). Intimate knowledge of normal and anatomic variants of the ILN reduces the risk of nerve injury and vocal cord paralysis in thyroid and parathyroid surgery. The nonrecurrent ILN (NRILN) is a rare nerve anomaly that is associated with a right aberrant subclavian artery. We encountered 2 patients with NRILN during thyroid surgery. Patient 1, a 57-year-old woman, had mediastinal thyroid tumor without vascular anomaly. Patient 2, a 47-year-old woman with a history of esophageal foreign body (fish bone), was suspected to have NRILN with vascular anomaly before surgery, as judged by preoperative enhanced CT. In the patient 1, we verified laryngeal mobility function of the NRILN by nerve stimulation, and confirmed the absence of RILN in usual recurrent course. The findings in the patient 1 indicate that NRILN without subclavian artery anomaly is a genuine entity. In both patients we performed thyroid surgery safely and fast by expectation and identification of NRILN by use of nerve stimulator. In conclusion, we confirm the existence of NRILN without vascular anomaly and show effectiveness of preoperative enhanced CT and valuable use of nerve stimulator for nerve preservation in the patients with NRILN.