RLN

Recurrent laryngeal nerve (RLN) is a branch of the vagus nerve (cranial nerve X) that supplies the intrinsic muscles of the larynx and provides sensory input below the vocal cords. It has two main branches, right and left, which differ in their anatomical course but share a common function in voice production and airway protection.

The right RLN loops around the right subclavian artery in the superior mediastinum before ascending in the tracheoesophageal groove to the larynx. The left RLN loops under the aortic arch, near the ligamentum arteriosum, and then also ascends in the tracheoesophageal groove to reach the larynx. In the larynx, the RLN innervates most intrinsic muscles, including the thyroarytenoid, lateral and posterior cricoarytenoid, and interarytenoid muscles. The cricothyroid muscle is supplied by the external branch of the superior laryngeal nerve, not the RLN. The RLN provides motor control for voice and, below the vocal cords, sensory innervation of the laryngeal mucosa.

Clinical significance centers on injury risk. Due to its lengthy intrathoracic and cervical course, the RLN is at risk during thyroid, mediastinal, or thoracic surgery. Unilateral RLN injury can cause hoarseness and dysphonia; bilateral injury may compromise the airway and require urgent management. Variants exist, including nonrecurrent laryngeal nerves, often associated with vascular anomalies; such variants have important implications for surgical planning.

See also: vagus nerve, laryngeal nerve injuries, thyroid surgery.