Surgical anatomy of the recurrent laryngeal nerve in human fetuses

Abstract

The larynx is innervated by the superior laryngeal nerve (SNL) and the recurrent laryngeal nerve (RLN). The right recurrent laryngeal nerve
surrounds the subclavian artery and ascends to the lower border of the larynx; an anatomical variation is presented when the aberrant right subclavian artery (ASDA) begin as the last branch of the aortic arch, making a posterior course towards the right upper extremity, the laryngeal nerve arises from the vagus nerve at the level of the thyroid gland and above the upper pole of the gland, without the recurrent course. The left recurrent laryngeal nerve crosses below the aortic arch at the level of the aortic arch and ascends vertically behind the thyroid gland in relation with branches of the inferior thyroid artery (ITA) and arrives to the lower border of the larynx.

The objective of the proyect is to determine anatomical variations of the relationship between the NLR and the ATI, in human fetuses from Córdoba, Argentina.

It has been made the anatomical dissection of fetal cadaveric corpse, less than 500 grams, provided by the Misericordia Hospital, Córdoba. Twenty-four high neck regions corresponding to 12 human fetuses, from 13 to 24 weeks of age, were dissected. It was accessed through an anterolateral approach with resection of the musculocutaneous component and cervical venous system. The instrumental waicrodissection instruments and binocular loupes.

The anatomical findings obtained were: 1 - RLN behind ITA (50%); 2 - NLR previous to ITA (28.6%); 3 – NLR branches between ITA branches (14.3%); 4 – non-recurrent laryngeal nerve (7.1%).

Knowledge of the anatomical variations is important at a surgical intervention. It is concluded that the incidence of the type "3" variant is higher than that described in the bibliography, this variety represents a large difficulty to maintain the RLN idamne. Knowing the frequency of the varieties will avoid making mistakes during procedures in the cervical region, mainly thyroidectomies. A unilateral lesion of the RLN gives rise to dysphonia, which may be irreversible.