Topographic anatomy of the external branch of the superior laryngeal nerve

Abstract

The authors have studied the anatomy of the external branch of the superior laryngeal nerve in its entirety on 40 fresh cadavers, and they have drawn the following conclusions: the nerve ramifies from the vagus immediately below the nodose ganglion or in the ganglion itself. The nerve splits into two branches approximately 1.5 cm below the ganglion nodosum. In four cases, both branches originated from the vagus itself. In one case, anastomosis of the external branch of the superior laryngeal nerve with the recurrent nerve was found. The external branch of the superior laryngeal nerve is not usually severed at supraglottic laryngectomy but the nerve is at risk during neck dissections, resection of Zenker's diverticula and thyroidectomy. An accurate knowledge of its course should reduce the incidence of injury to the branches of the superior laryngeal nerve during surgery.

Superior laryngeal nerve anatomy in corpses not preserved in formaldehyde: contribution to the operative technique

“…In 54 of the 56 dissected superior laryngeal nerves, the bifurcation in internal and external branches has occurred in the carotid region or within its limits with the infrahyoid region, never at the level or after the GHHB. 3,[12][13][14][15] . The ibSLN has presented an oblique, descendent, anterior and superomedial topography related to the superior laryngeal artery, passing across the lateral thyrohyoid ligament.…”

Injury of the external branch of the superior laryngeal nerve in thyroid surgery

“…The EBSLN was measured as thin as 0.2 mm in cadaveric studies (3) and less than 0.55 mm in vivo (10). It is usually encountered within the sternothyroid-laryngeal triangle, described by Moosman and DeWeese (11) in a study of 200 cadavers dissections.…”

“…Approximately 1.5 cm bellow its origin and posterior to the internal carotid artery, it divides into an internal and an external branch (3,4). Such bifurcation can occur at the level of the ganglion in about 5% of the individuals (3,5) and the EBSLN eventually arises directly from the vagus nerve (6).…”

“…Approximately 1.5 cm bellow its origin and posterior to the internal carotid artery, it divides into an internal and an external branch (3,4). Such bifurcation can occur at the level of the ganglion in about 5% of the individuals (3,5) and the EBSLN eventually arises directly from the vagus nerve (6). The internal branch runs inferior to the greater cornu of the hyoid bone and pierces the thyrohyoid membrane to innervate the mucosa of the epiglottis, part of the anterior wall of the vallecula, the aryepiglottic folds, the interarytenoid muscles and the inferior constrictor muscle (4).…”

“…The external branch crosses the common carotid artery posteriorly, crosses the middle sympathetic ganglion medially and then runs lateral to the thyroid cartilage along the pretracheal fascia superficial to the inferior pharyngeal constrictor muscle (IPCM) and travels to the CTM parallel to the superior thyroid artery (STA). Close to the lower edge of the thyroid cartilage it is usually covered by muscle fibers of the IPCM (3,7,8). The nerve crosses the STA posteriorly as it approaches the superior thyroid pole.…”