Background: Non-recurrent laryngeal nerve, a rare anomaly, passes transversely into larynx with or without its recurrent branches directly arising from the vagus nerve. The paper investigates clinical significance of non-recurrent laryngeal nerve during thyroid surgery. Clinical data from 5 cases of non-recurrent laryngeal nerve and related literature reviews were made to acknowledge its incidence, variant types and matters concerned during thyroid operations.
Case Report: 821 recurrent laryngeal nerves were anatomized during 2496 thyroid operations, from which 5 were confirmed to hold non-recurrent laryngeal nerves (0.61%). 3 patients were found to have non-recurrent laryngeal nerves during re-operation because of voice horse after the first operation which improved much after re-operation. The other two patients were recognized during the first operation. All 5 cases were not diagnosed preoperatively.
Conclusions: Non-recurrent laryngeal nerve, a rare anomaly, is very vulnerable during thyroid surgery. It is helpful to avoid injuring non-recurrent laryngeal nerve that identification of the non-recurrent laryngeal nerve and its types.

Keywords: Thyroidectomy - adverse effects, Thyroid Gland - surgery, Surgical Procedures, Operative, Subclavian Artery - surgery, Postoperative Complications, Laryngeal Nerves - pathology, Intraoperative Period, Vagus Nerve - anatomy & histology, Vocal Cord Paralysis - prevention & control