The Recurrent Laryngeal Nerve

The recurrent laryngeal nerve was first identified and named by Galen in the second century. GalEn found that vagal sectioning in a pig resulted in aphonia. The recurrent laryngeal nerve carries branchial efferents to the inferior constrictor muscle of the pharynx, cricopharyngeus muscle and all intrinsic laryngeal muscles except for the cricothyroid muscle. It also carries sympathetic and parasympathetic innervation to the lower pharynx, larynx, trachea and upper oesophagus. The anatomy of the recurrent laryngeal nerve is complex and different on both sides of the body. The right recurrent laryngeal nerve travels up the paratracheal region from lateral to medial as it ascends the neck. It typically holds a more oblique course relative to the side of the trachea than the left recurrent laryngeal nerve. The left recurrent laryngeal nerve derives as an upward-going branch of the vagus nerve and ascends the neck, typically in the tracheo-oesophageal groove in the left paratracheal region. The recurrent laryngeal nerve is most often considered in the context of thyroid surgery. Iatrogenic damage to the nerve is a serious complication and may leave the patient with a breathy or raspy voice if unilateral and in severe respiratory distress if bilateral. Preoperative laryngeal examination is tremendously helpful to the endocrine surgeon because we cannot rely on the patient's vocal symptoms to predict glottis function. The surgeon should endeavour to identify the recurrent laryngeal nerve in all cases of thyroidectomy. Principles for identifying the recurrent laryngeal nerve include variable approaches depending on the thyroid pathology at the time of thyroidectomy. The superior, lateral and inferior approaches may be used. Anatomical landmarks for identifying the recurrent laryngeal nerve include the laryngeal entrance point of the nerve, the ligament of Berry, the tubercle of Zuckerkandl and the inferior thyroid artery. Neural monitoring as an adjunct for nerve identification has great utility but does not replace the need for visualization of the nerve. Neural stimulation can be used as an aid in dissection once the nerve is visualized as it is being followed through the surgical field