Variations of the external branch of the superior laryngeal nerve during its course and its importance in surgical approaches: an experimental cadaveric study

Abstract

Introduction: Injury of the external branch of the superior laryngeal nerve can cause a hoarse or weak voice due to the functional loss (dysergia) of the cricothyroid muscle. Defining the anatomical variations of the external branch of the superior laryngeal nerve and estimating their frequency are crucial for surgical interventions. Aim: To reveal the topography of the external branch in the Anatolian population, to prevent injury of it during the surgical intervention in the anterior neck region. Material and Methods: 26 bilateral hemilarynges (4 females, 22 males) were dissected. The morphometric and morphological features of the external branch were examined. The obtained results were compared statistically, left and right. Results: Landmarks such as the thyroid gland and laryngeal prominence were determined for the detection of the external branch. The variations of the course of the external branch and the points of piercing the cricothyroid muscle or inferior pharyngeal constrictor muscle were evaluated. Discussion: Although safe approaches have been described for nerve protection during neck surgeries, injuries may occur during preliminary surgery as the mentioned nerve is thinner and more superficial than other branches of the vagus nerve. However, it can be detected more easily and safely by knowing the defined anatomical landmarks and morphological variations of the external branch. Conclusion: The anatomical variations described can be a safe and important guide in surgeries of the anterior neck region.