Branching pattern of the external branch of the superior laryngeal nerve and its clinical importance

Abstract

The external branch of the superior laryngeal nerve gives off many branches above the upper pole of the thyroid gland. Differentiating the branch innervating the cricothyroid muscle from the others may be important during surgery. Therefore, we aimed to demonstrate the branching pattern of this nerve in detail. In 34 human cadavers (59 sides), branches of the nerve were exposed and measurements related to them and neighboring structures were made. A cricothyroidal branch was present on all sides. This branch pierced the inferior pharyngeal constrictor muscle 3.9-17.6 mm above, 3.1-9.9 mm below, or at the level of the upper pole of the thyroid gland. On all sides, the nerve provided one or two thyroidal branches. The thyroidal branch was generally thinner than the cricothyroidal branch. But they were equal in size on three (5%) sides. The external laryngeal nerve provided two or three pharyngeal branches on all sides. These branches arose from the nerve 3.5-12.7 mm from the upper pole of the thyroid gland. Although the branch was generally thinner than the cricothyroidal branch, both branches were equal on four (6.7%) sides. Two cardiac branches were observed on two (3.3%) left sides. In conclusion, the cricothyroidal branch was generally thicker than the other branches. But on seven (11.8%) sides, thyroidal or pharyngeal branches and the cricothyroidal branch were equal in size. These data may be important during surgery as the surgeon may confuse the cricothyroidal branch with other branches of the external laryngeal nerve.

A Closer Look at Laryngeal Nerves during Thyroid Surgery: A Descriptive Study of 584 Nerves

“…In cadaveric studies it has been shown that the EBSLN gives off many branches above the upper pole of the thyroid gland. The clinically important cricothyroidal branch has been found to be thicker and it pierces the IC muscle about 3.9–17.6 mm above, 3.1–9.9 mm below, or at the level of the upper border of thyroid gland [9]. One or two thyroidal and pharyngeal branches arise from the EBSLN which may be mistaken as cricothyroidal branch; however, these are very thin.…”

“…One or two thyroidal and pharyngeal branches arise from the EBSLN which may be mistaken as cricothyroidal branch; however, these are very thin. Hence, during the routine thyroidectomy the thicker cricothyroidal branch has to be safeguarded [9]. …”

“…Based on the course of the EBSLN; classifications were also put forward by Cernea et al and Friedman et al [4, 8]. EBSLN has several branches to pharynx and thyroid gland apart from the clinically important cricothyroidal branch [9]. The RLN is routinely exposed and traced during all thyroid surgeries.…”

Anatomical Study about the Intra Individual Variability of the Superior Laryngeal Nerve: What is the Helpful Surgical Take-Away?

“…13 Another hypothesis may be an insufficient blood support from the branches of STA to the nerve, especially the posterior and the anterior glandular branches, due to a devascularization during STA ligation. 14 The different relationships of the EBSLN with the other anatomical structures led to many classifications with the aim of detecting the nerve. The Cernea classification, which analyzes the relationship between the nerve and the STA, remains the simplest.…”

Relationship between Inferior Thyroid Artery and Recurrent Laryngeal Nerve - A Study of 200 Cases

“…1 Anatomical relationship between RLN and ITA is very important in order to preserve the RLN. 2,3 Mostly the morbidity is due to technical failure(inadequate anatomical knowledge ,lack of surgical skill & experience, distorted anatomy as in cancer & large multinodular goiter) to identify the vital structures and the variations in the surgical anatomy. Several studies have been published revealing the anatomy of the RLN in thyroid surgery.…”