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

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 the frequency of it, it makes 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.

Materials and methods: Twenty-six 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 constrictor pharyngeal muscle were evaluated.

Discussion: Although safe approaches have been described for nerve protection during neck surgeries, it can expose injuries during preliminary surgery approaches as the nerve is thinner and more superficial than other branches of the vagus nerve. However, it can be detected more easily and safely during the surgical approach 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 surgical approaches to be applied in the anterior neck region.