Der Ramus externus des Nervus laryngeus superior (RELS): Ein Stiefkind in der Chirurgie der Schilddrüse

Abstract

Injury to the external branch of the superior laryngeal nerve (EBSLN) during thyroid surgery can cause serious consequences for patients who depend on control of pitch and a clear and forceful voice, like singers or professional speakers. We used the Neurosign 100(R) nerve monitor to identify 157 nerves in 108 patients undergoing thyroid surgery. The EBSLN was successfully identified in 98.7 % of cases. The recording electrode could be placed either into the cricothyroid muscle or the vocal cord. The latter position proved superior if the recurrent laryngeal nerve had to be identified as well. 16 percent of the nerves crossed the branches of the superior thyroid artery at or below the upper pole of the gland, posing a "high risk" for intraoperative lesions. Our data confirm the results of smaller studies reporting this type of nerve course in 12 % to 14 % of patients. The present findings show a significant number of EBSLN to be in danger of injury when the superior thyroid artery is ligated during thyroid surgery. Neuromonitoring proofed to be a reliable method to identify the nerve, which is an important element in concepts to prevent its injury.

The Advantages and Disadvantages of Nerve Monitoring During Thyroid Surgery in Childhood

“…The superior laryngeal nerve arises from the vagal nerve and divides into an external and an internal branch, which carry sensory fibers for the larynx. In most cases, the external branch of the superior laryngeal nerve (EBSLN) runs superficially along the inferior pharyngeal constrictor muscle to the cricothyroid muscle, providing motor branches for both muscles [8,12]. From the surgeon's point of view -anterolaterally -the nerve passes beneath the attachment of the sternothyroid muscle to the larynx and follows approximately the course of the superior thyroid artery.…”

Functional anatomy of the recurrent and superior laryngeal nerve

“…Clinically, an injury of the SLN causes dysphonia, with lowering of voice pitch [41,42]. Hence, in thyroid surgery (also in other neck surgeries), SLN integrity has equal priority to the integrity of the RLN [43][44][45]. According to Lang et al…”

Impact of modern technologies on quality of thyroid surgery

“…Prospective randomized studies comparing the efficacy of these methods or analyzing the functional outcome with or without neuromonitoring have not been performed. However, it could be shown that the method improved identification not only of the recurrent laryngeal nerve [3, 11] but also of the external branch of the superior laryngeal nerve [16]. However, based on the hypothesis that better nerve identification lowers the rate of postoperative laryngeal nerve dysfunction, the link between nerve identification and decreased paralysis rate has to be substantiated further by anatomical and clinical studies.…”