A recurrent-like course of the external branch of the superior laryngeal nerve associated with a right-sided aortic arch: a rare anatomical variation.

Accurate identification of the laryngeal nerves during thyroid surgery is essential to prevent nerve injury and preserve vocal function. While variations of the recurrent laryngeal nerve (RLN), particularly the non-recurrent laryngeal nerve (NRLN), are well recognized and often anticipated in association with vascular anomalies, variations of the superior laryngeal nerve are less commonly expected. We report a case of a 60 year-old female with papillary thyroid carcinoma who underwent total thyroidectomy. Preoperative computed tomography revealed a right-sided aortic arch with an aberrant left subclavian artery (ALSA), raising consideration of possible laryngeal nerve variation. Intraoperatively, both RLNs demonstrated a normal recurrent course. Instead, an unusual variation of the external branch of the superior laryngeal nerve (EBSLN) was identified, originating from the cervical vagus nerve and following a recurrent-like ascending course that initially mimicked NRLN. This case demonstrates that laryngeal nerve anatomy may not always correspond to expected vascular findings and highlights the importance of careful intraoperative nerve identification and systematic surgical dissection to prevent misidentification and nerve injury.