The recurrent laryngeal nerve (RLN) is a branch of the vagus nerve, which carries motor, sensory and parasympathetic fibers to the larynx. The RLN is consistently present superior to the inferior thyroid artery before it ascends behind the inferior constrictor to the nerve's entry point into the larynx. This relationship is a major landmark for its identification during thyroid surgery. However, anatomical variations of the RLN represent a well-known risk factor of RLN injury in thyroid surgery. Injury to the RLN can cause RLN paralysis with symptoms ranging from almost undetectable hoarseness in unilateral lesions to stridor and acute airway obstruction in bilateral damage 1,2 . Transient post-operative RLN paralysis occurs in approximately 3-8% of cases and permanent paralysis in 0.3-3% of cases [3][4][5] . Hence, it is of importance to identify the anatomical variants of the RLN in order to preserve the nerve and its function during surgery.Although recent monitoring advances have allowed intraoperative neuromonitoring to reduce the incidence of RLN injury, visual identification of the RLN remains the gold standard for RLN injury prevention 6 . Fully understanding the anatomical variations of the RLN may help surgeons dissect the RLN in a safe, fast, and correct way. Therefore, it is vital to determine the anatomical position of the RLN in thyroid surgery.In this study, we identified the anatomical variations of the RLN in a large population of Chinese patients undergoing thyroid surgery to explore RLN variations and compare with those reported in Western patients. Patients and MethodsPatients. The study was approved by the institutional review board of Ruijin Hospital and performed in accordance with the ethical principles of the Declaration of Helsinki (Ruijin LL-14-2006). Written informed consent was obtained from each participant before study entry. This prospective study included all patients consecutively hospitalized for elective thyroidectomy due to benign or malignant thyroid diseases between January 2007 and December 2013. The inclusion criteria were as follows: age of 18 years or greater; diagnosis of a surgically indicated thyroid disease, namely, thyroid cancer suspected on ultrasound or diagnosed via fine-needle aspiration biopsy, undetermined single or multiple solid nodules at the maximum size over 30 mm, goiter of any nature compressing the trachea, or retrosternal goiter. The exclusion criteria were as follows: pregnancy, lactation, a history of previous neck surgery or radiation, pre-existing RLN impairment on preoperative laryngoscopy, complicating serious cardiopulmonary, hepatorenal and coagulation disorder.

It is safe and feasible to perform either total or near-total thyroidectomy in patients with bilateral multinodular goiter. These treatments provide decisive advantages over partial and subtotal thyroidectomies in terms of the recurrence and reoperation rate with comparable postoperative complications.

This newly discovered variation of the RLN is more vulnerable to injury and should be brought to the attention of surgeons.