Anatomy of the thyroarytenoid branch of the recurrent laryngeal nerve

Objective To determine the position and anatomic variability of the thyroarytenoid (TA) branch of the recurrent laryngeal nerve (RLN). Methods The RLN on 13 human cadaver specimens (24 sides) was dissected to the termination of the TA branch in the TA muscle. A pin was placed at the inferior aspect of the thyroid cartilage at the inferior tubercle. Using a caliper, the distance from the pin to the TA branch of the RLN was measured. The direction of the nerve and number of branches were recorded. Results The average distance to the TA branch of the RLN is 4.23 mm with a standard deviation of 2.86 mm. The median distance is 3.75 mm. Most of the specimens fell in a range of 1 to 4 mm. Overall, 54% of the nerves traveled in a horizontal direction, but vertical and oblique orientations were observed. About 20% of specimens demonstrated branching of the TA nerve. Conclusion Measuring 4 mm from the inferior tubercle along a perpendicular line from the thyroid tubercle on the inferior border of the thyroid cartilage provides a good estimate of the location of the TA branch of the RLN. This information is useful when creating a posterior thyrotomy for TA neurectomy for patients with adductor spasmodic dysphonia. Knowledge of the course and possible branching of the nerve, will aid in localizing the nerve as well as ensuring adequate resection.