Illustrated Encyclopedia of Human Anatomic Variation: Opus III: Nervous System: Cranial Nerves and Ganglia

Recurrent Laryngeal Nerve

Ronald A. Bergman, PhD
Adel K. Afifi, MD, MS
Ryosuke Miyauchi, MD
Peer Review Status: Internally Peer Reviewed

Stedman (1823) reported his discovery of the right recurrent laryngeal nerve as follows: "While employed in dissecting the neck, in the Dissecting-room of the Royal Academy at Copenhagen, in the beginning of May 1823, I discovered a singular distribution of the nerves and arteries on the right side, which may not be uninteresting to the medical public. The subject was a thin aged female. I had dissected the upper part of the neck with great care, when, after displaying the superior laryngeal nerve on the right side, I discovered that a great number of branches were sent off about the middle of the neck, from the trunk of the nervus vagus, some of which proceeded to the thyroid gland, while the largest were reflected a little up, and entered the larynx, in the same manner as the branches sent off from the recurrent nerve. Of the lowest filaments, some entered the trachea, while others were lost upon the back of it. Proceeding further down, I could not at first find the right subclavian artery, and could only see the right carotid arising from the arch of the aorta. I dissected with greatest care for the recurrent nerve, but I could not find it; to my surprise, however, I discovered the right subclavian artery coming from behind the oesophagus. I traced the nervus a considerable way down the thorax, in order, if possible, to discover the recurrent; but I could not find it. I then proceeded to dissect the other side of the neck. Here I found the recurrent nerve with great ease, and traced from its origin to its termination in the larynx. I next dissected the arteries. The left subclavian rose from the arch of the aorta behind, and a little to the left side of the left subclavian, and, forming an arch, pierced between the oesophagus and vertebral column, in the region of the first vertebra of the back, and then passed over the first rib on the right side. It is probable that, in this case, the nerves coming directly from the trunk of the vagus, on the right side, performed the same function as the recurrent; for they were distributed very much in the same manner as the branches of that nerve. Nature seems to be forced to have recourse to this arrangement, from the singular situation of the subclavian."

The right recurrent laryngeal nerve usually passes around and behind the subclavian artery and then ascends to enter the larynx. In cases in which the subclavian artery arises dorsally either between the esophagus and trachea (arteria lusoria) or retroesophageal, the right "recurrent" laryngeal nerve branches passes directly downward and medially from the vagus nerve to the larynx. In these cases there are no recurrent laryngeal nerves.

In three of 153 cadavers (506 dissections) Reed found "the right inferior laryngeal nerve to arise high in the neck and therefore did nor follow a recurrent course." He did not mention whether an unusual subclavian artery was involved. Numerous studies (see References) report nonrecurrent, recurrent laryngeal nerves.

The recurrent (inferior) laryngeal nerve, more commonly the right, tends to lie anterior to the inferior thyroid artery (50% of cases).

The left recurrent laryngeal, three times more frequently than the right, lies behind the inferior thyroid artery.

In thirty-one cadavers which Nordland studied, the relations were quoted as follows: On the right side: 15 nerves anterior to artery (2 were posterior to a small branch of the artery). 8 nerves posterior to artery (3 anterior to small branch of artery). 7 nerves between equal branches of artery. In one, the inferior thyroid artery was not present.

On the left side: 11 nerves anterior to artery (2 posterior to small branch of artery). 11 nerves posterior to artery (1 anterior to small branch of artery). 7 nerves between equal branches of artery, 2 nerves branch around artery.

Both sides: Similar in 8 cadavers; 5 had nerve anterior to artery, 1 had nerve posterior to artery, 2 had nerve between equal branches.

The nerve may be posterior to the lower branch of the inferior thyroid and anterior to the upper branch, or vice versa. It has been reported (Reed) that the right and left recurrent laryngeal nerve were alike in only 17% of 253 cadavers studied. Reed also reported that the frequencies in which the nerve passed (a) superficial to the artery and its branches (18.6%), (b) deep to the artery and its branches (39,1%), and (c) between the branches of the artery (36.5%).

In addition to supplying the inferior constrictor muscle of the pharynx, the nerve may supply the cricothyroid muscle.

Nobles (and others, see References) reported a right nonrecurrent laryngeal nerve; a large branch , which originated from the cervical trunk of the vagus at the level of the thyroid cartilage and then passing directly to the larynx. A nonrecurrent laryngeal nerve has not been reported to occur on the left side. Stewart, et al reported that of a total of 3496 recurrent laryngeal nerves (1776 on the right side and 1720 on the left side) only 6 were found to be nonrecurrent, all occuring on the right side.

The recurrent laryngeal nerve may exist as two bundles on one side.

Above the level of the inferior border of the cricoid cartilage the recurrent laryngeal nerve is renamed the inferior laryngeal nerve.

Al-Salihi and Dubbagh reported that the right recurrent laryngeal nerve (33/106), and the left recurrent laryngeal nerve (21/106), were found to consist of more than one trunk, sometimes as many as five. These occur at the level of the usual thyroidectomy dissection. It behooves the surgeon to avoid damage by avoiding, not just one vertically oriented nerve, but any vertically oriented nerve at the level of the pharynx and thyroid gland. These authors also state that the location of the nerves is, most often, in the tracheo-oesophageal groove. The nerve is usually located behind (posterior) to the inferior thyroid artery on the left side, while its relation is very variable on the right side. Further, they state that the inferior cornu of the thyroid cartilage is the best guide to the site of entry of the nerve into the larynx.

Abouna reported that Al-Razi discovered (cited in Castigilioni) the recurrent laryngeal nerve as arising near the trachea.

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References

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