Topographical relations between the posterior cricothyroid ligament and the inferior laryngeal nerve

Anatomy of the Cricothyroid Articulation: Differences between Men and Women

A greater difficulty in exposing the arytenoid cartilage during rotation surgeries has been observed for men. The objective of the present study was to describe the position of the cricothyroid articulation and the distance between the right and left articulations, and to compare these findings between genders. The following measurements were obtained for 16 cadavers (9 men and 7 women): angulation of the cricothyroid articulation in the cricoid ring, dimensions of the thyroid articular surface of the cricoid cartilage, and distance between the cricothyroid and cricoarytenoid articulations. The cricothyroid articulation angle was narrower in men than in women (p = .04). The major diameter of the articular facet of the thyroid cartilage was wider in men (p = .001). The longer lamina of the thyroid cartilage, as well as the more posterior position of the cricothyroid articulation, in men might explain the greater difficulty in exposing the arytenoid cartilage during laryngeal framework surgeries observed for this group of patients.

Topographic anatomy of the internal laryngeal nerve: surgical considerations

BACKGROUND

This study is focused on the topographic features of the internal branch of the superior laryngeal nerve (ibSLN) at the thyrohyoid membrane area using as anatomic landmarks the posterior border of the thyrohyoid muscle and the superior border of the thyroid cartilage.

METHODS

Thirty-six fresh adult cadavers were dissected to determine the topography and branching pattern of the ibSLN and the superior laryngeal artery.

RESULTS

The ibSLN prior to thyrohyoid membrane's penetration was divided into 3 or 2 branches, in 72.22% and 27.78% of cases. The trifurcated ibSLN was more common than the bifurcated in both sexes and in both sides of the neck. In over 80% of cases the ibSLN penetrated the thyrohyoid membrane 0.1 to 0.9 cm far from the posterior border of the thyrohyoid muscle and 0.1 to 1.2 cm far from the superior border of the thyroid cartilage.

CONCLUSIONS

We provide a schematic overview of the ibSLN penetration zone at the thyrohyoid membrane, the so-called danger zone, to avoid ibSLN damage.

Atypical anastomosis of laryngeal nerves

The larynx and its associated structures derive their chief source of innervation from the superior and recurrent laryngeal nerves. Surgery of the larynx requires a sound knowledge of the normal anatomy as well as variations that may be encountered in this region. We report the presence of rare communications between the right external and internal laryngeal nerves as well as between the right external and inferior laryngeal nerves via a thyroid foramen. In addition, we report on bilateral innervation of the respective ipsilateral aryepiglottic, transverse, and oblique arytenoid muscles by the internal laryngeal nerve, which is contrary to the classical descriptions of this nerve. The anatomic features are described and clinical implications are highlighted.

Benign Anatomical Mistakes: The Correct Anatomical Term for the Recurrent Laryngeal Nerve

The term recurrent laryngeal nerve has been adopted by Nomina Anatomica (1989) and Terminologia Anatomica (1998) to describe this vagus branch from its origin, its turn dorsally around the subclavian artery and the aortic arch, and its cranial pathway until it reaches its terminal organs in the neck. However, there is still much confusion, and either the terms inferior and recurrent laryngeal nerve are used interchangeably or inferior laryngeal nerve is considered the terminal branch of the recurrent laryngeal nerve. We hereby feel that it is necessary to reassess the term and we propose the term inferior laryngeal nerve for the entire nerve under consideration, from its orgin from the vagus nerve to its destinations, including traheal, esophageal, and pharyngeal branches. If the term superior laryngeal nerve is a given, standard and accepted term in the anatomical terminology, then logically the term inferior laryngeal nerve should also be accepted, as opposed to it. Of course the upward travel of the inferior laryngeal nerve is “recurrent”. When nonrecurrence is encountered together with an arteria lusoria, a retroesophageal right subclavian artery or a right aortic arch, we consider that the term nonrecurrent inferior laryngeal nerve should be used to describe the deviation from the normal.

A Loop-Forming Duplicate Recurrent Laryngeal Nerve: Report of a Case and Clinical Relevance in Thyroid Surgery

This is a report of a unilateral loop-forming duplicate recurrent laryngeal nerve and its clinical relevance. A 72-year-old woman with a giant goiter underwent a total thyroidectomy. At operation we identified two recurrent laryngeal nerves on the right side and one on the left side. The nerve on the right was smaller and displaced laterally by the. goiter, whereas the other was adjacent to the trachea and behind the goiter, and it was accidentally divided. Both nerves were united before innervating the larynx. The divided nerve was microsurgically reanastomosed but a postoperative assessment revealed hoarseness. This case report of an anomalous loop-forming duplicate recurrent laryngeal nerve indicates that it may not be sufficient to identify a single recurrent laryngeal nerve on one side during thyroid surgery especially when the observed recurrent nerve is relatively smaller than usual.