Recurrent Laryngeal Nerve

Origin

The recurrent laryngeal nerves originate as branches of the vagus nerve at or slightly above where the vagus nerve meets the right subclavian artery or aortic arch.

The sensory neurons of the recurrent laryngeal nerve are general visceral with cell bodies in the inferior ganglion of the vagus nerve and projections to the solitary nucleus. Efferent fibers are parasympathetic with neurons located in the dorsal vagal nucleus or branchial motor with neurons located in the nucleus ambiguus.

Course

The course of the right and left recurrent laryngeal nerves differ due to the vascular asymmetry in the upper thorax.

On the right side, the recurrent laryngeal nerve originates as a branch from the main vagus nerve as the vagus nerve passes over the anterior surface of the subclavian artery. The recurrent laryngeal nerve loops under the brachiocephalic artery and starts to ascend in the groove between trachea and the esophagus on the right side. It continues in this groove until at the level of the cricoid cartilage it passes deep to the suspensory ligament of the thyroid (or Berry’s ligament) and inferior pharyngeal constrictor muscle. It enters the larynx posterior to the cricothyroid joint (Liebermann-Meffert et al, 1999).

On the left side, the recurrent laryngeal nerve originates as a branch from the main vagus nerve as the vagus nerve passes over the anterior surface of the aortic arch. It loops under the arch just lateral to the ligamentum arteriosum, then ascends in the groove between the trachea and esophagus on the left side. It continues in this groove until it reaches the level of the cricoid cartilage and follows the same route as its fellow nerve.

Branches

The recurrent laryngeal nerve gives rise to a number of branches, most of which are named for the tissue they innervate.

The first branch given off are the inferior cervical and thoracic cardiac branches. These run from the recurrent nerve as it approaches the trachea at the start of its ascent, to the deep cardiac plexus that sits close by. On the right side, inferior cervical cardiac branches can also emerge directly from the vagus nerve.

As the recurrent nerve ascends, it gives off fairly regular branches that run medially into the lateral walls of the esophagus and trachea. Typically, the right recurrent nerve gives off more branches to the esophagus and trachea than the left recurrent nerve.

After entering the larynx, the recurrent nerve gives off branches to each of the laryngeal muscles, the inferior pharyngeal constrictor muscle, and the mucosa of the lower larynx.

In most individuals, the terminal portion of the recurrent laryngeal nerve, now better described as the inferior laryngeal nerve, will connect to fibers of the internal branch of the superior laryngeal nerve (Liebermann-Meffert et al, 1999).

Supplied Structures & Function

The recurrent laryngeal nerve is a mixed nerve. It conveys general visceral sensory innervation from the lower larynx (below the level of the vocal fold), posterior laryngopharynx, trachea, esophagus, and heart.

Branchial motor efferent fibers of the recurrent laryngeal nerve innervate all the muscles of the larynx, except the cricothyroid muscle. The recurrent laryngeal nerve also innervates the inferior pharyngeal constrictor muscle and the cricopharyngeal part of the superior esophageal sphincter muscle.

Parasympathetic efferent fibers of the recurrent nerve innervate the mucosal glands and smooth muscle of the lower larynx, esophagus, and trachea. The parasympathetic fibers that travel to the deep cardiac plexus contribute to slowing the rate of cardiac contraction.

List of Clinical Correlates

—Hoarseness

—Aphonia

—Dyspnea

References

Liebermann-Meffert, D. M., Walbrun, B., Hiebert, C. A. & Siewert, J. R. (1999) Recurrent and superior laryngeal nerves: a new look with implications for the esophageal surgeon. Ann Thorac Surg, 67(1), 217-23.