Two Cases of Nonrecurrent Inferior Laryngeal Nerve －Different Branching Levels from Vagus Nerve

We observed two cases of nonrecurrent inferior laryngeal nerve (NRILN). Case 1, a 71 year old man was diagnosed as having papillary carcinoma. NRILN was found during his operation. It directly branched from the right cervical trunk of the vagus nerve at the level of the cricoid cartilage and then entered the larynx after running behind the thyroid gland. Case 2, a 64 year old woman was diagnosed as having primary hyperparathyroidism. In this patient, the NRILN branched at the level of the inferior pole of the thyroid gland, rose up beside the tracheal wall and entered the larynx. In both patients, preoperative CT scan and postoperative MR angiography revealed the aberrant right subclavian artery. A postoperative barium swallow test showed the compression of the esophagus by this anomalous artery in case 1. Although it is possible to predict the presence of NRILN by preoperative imaging tests, the branching level from the vagus nerve is unpredictable. Surgery must be performed with this point in mind, if the presence of NRILN is suspected.