Recurrent Laryngeal Nerve Branching

Abstract

Recurrent laryngeal nerve (RLN) dysfunction is among the most common and feared complications of thyroidectomy and is an increasingly common cause for malpractice suits against endocrine surgeons. Temporary or permanent vocal cord palsy may carry a significant burden of disease. Thorough knowledge of the normal anatomy and its variants, a meticulous surgical technique, and a gentle handling of tissues with routine identification of the RLN represent the standard of care for a safe thyroidectomy. Temporary palsy of the RLN occurs in up to 10 % of cases and permanent paralysis in <2 % of patients. Inadvertent injury to the nerve is directly influenced by the common anatomic variations of the RLN along its expected and unexpected cervical course. These variations include the extralaryngeal bifurcation of the RLN that constitutes a frequent event present in up to 30–40 % of cases. Branching of the nerve typically occurs at the level of the ligament of Berry along the distal 1 or 2 cm of the RLN cervical course before its entry into the larynx. Branching of the RLN represents a major risk factor for both transient and permanent nerve palsy. Thus, intraoperative recognition and verification of functional and anatomic integrity of premature division of the nerve is crucial during thyroid operations. Initial studies using intraoperative nerve monitoring suggest that the anterior branch of the bifid RLNs is the one supplying motor fibers to the posterior cricoarytenoid muscle and vocalis muscle. Identification, exposure, and preservation of extralaryngeal branches of the RLN are mandatory and represent basic surgical principles in thyroid surgery to prevent nerve injury and its associated morbidity.