Abstract
Aim: This study aimed at describing the anatomical variations of the external branch of the superior laryngeal nerve and at estimating the frequency of nerves at risk during the thyroid surgery. Methodology: We realized a forward-looking study from September, 2016 in May 31st, 2018 in the laboratory of anatomy of the Faculty of Medicine and Odontostomatology of Bamako in Mali. All the fresh anatomical subjects not carrying trauma and or a scar at the level of the previous region of the neck were held. The anatomical subjects were not included presenting a traumatic lesion and\or a scar of the previous region of the neck. Results: We realized 34 dissections of the external branch of the superior laryngeal nerve to 17 deathly subjects (11 men and 6 women with a sex-ratio of 1.8). The average age of the subjects was of 42 years (extremes: 18 and 70 years). Our study allowed highlighting in 100% of the cases, the external branch of the superior laryngeal nerve and the superior thyroid artery so to the right as to the left. On 34 dissected external branch of the superior laryngeal nerve, none had a previous route. However we found 28 nerves (82.4%) having a later route, stuck to the external face of the lower constrictor of the pharynx. These were not mixed with the superior thyroid artery and its branch of division and were situated outside the thyroid capsule. In 17.6% of the cases (6 cases), the nerve had a route mixed in the branch of the superior thyroid artery. These were found inside of the capsule (11.8% adhered to the artery and 5.8% crossed its branch of division). Conclusion: The risk of injury of the external laryngeal nerve during thyroid surgery procedure is never zero. It is more important on the left side.
Highlights
The external branch of the superior laryngeal nerve ( BENLS), is a mixed nerve, hail, assuring the innervation of the cricothyroid muscle [1]
We found 28 nerves (82.4%) having a later route, stuck to the external face of the lower constrictor of the pharynx. These were not mixed with the superior thyroid artery and its branch of division and were situated outside the thyroid capsule
Origin Our study allowed to highlight in 100% of the cases the external branch of the superior laryngeal nerve and the superior thyroid artery so to the right as to the left. 34 dissected external branch of the superior laryngeal nerve was born at the level of the big horn of the bone hyoid
Summary
The external branch of the superior laryngeal nerve ( BENLS), is a mixed nerve, hail, assuring the innervation of the cricothyroid muscle (muscle tensor of vocal cords) [1]. It has an intimate and variable route with the superior thyroid pedicle what explains its vulnerability during the thyroid surgery [2]. Its lesion is responsible for a fatigability of the voice, for a modification of its tone which becomes graver as well as of disorders of the gulp. This study aimed at describing the anatomical variations of the external branch of the superior laryngeal nerve and at estimating the frequency of nerves at risk during the thyroid surgery
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