Non-recurrent inferior laryngeal nerve: An overlooked anatomical variant: A case series of four patients

Background: Identification and preservation of the recurrent laryngeal nerve (RLN) are essential steps in thyroid surgery to prevent vocal cord dysfunction. The non-recurrent inferior laryngeal nerve (NRILN) represents a rare anatomical variant, most commonly occurring on the right side, and is associated with an increased risk of iatrogenic nerve injury due to its atypical course. Awareness of this variant and its anatomical predictors is crucial for safe surgical practice.
Cases: We report a case series of four patients undergoing thyroidectomy in whom a right-sided NRILN was identified intraoperatively. The patients included three women and one man, aged 45–55 years, all operated on for benign thyroid disease or indeterminate nodules. In each case, the RLN was not found in its usual position within the tracheoesophageal groove. Careful dissection revealed a slender, non-recurrent nerve branching directly from the cervical vagus nerve and coursing transversely toward the larynx. In one patient, preoperative imaging demonstrated an aberrant right subclavian artery, raising suspicion for NRILN prior to surgery. Intraoperative nerve monitoring was used in all cases and aided in nerve identification and preservation. No postoperative vocal cord dysfunction occurred.
Discussion: NRILN is an uncommon but clinically significant anatomical variant that poses a heightened risk of nerve injury if unrecognized. Its presence is strongly associated with aberrant vascular anatomy, particularly Arteria Lusoria, which may be detected using preoperative ultrasonography or cross-sectional imaging. Early suspicion, meticulous surgical technique, and the use of intraoperative nerve monitoring are key strategies for minimizing morbidity.
Conclusion: Although rare, NRILN should be anticipated when the RLN is not identified in its expected location or when vascular anomalies are present. Preoperative imaging and intraoperative nerve monitoring, combined with thorough anatomical knowledge, are effective tools for preventing nerve injury and ensuring optimal surgical outcomes during thyroidectomy.