How is the recurrent laryngeal nerve identified in a thyroidectomy?

Updated: May 08, 2018
  • Author: Neerav Goyal, MD, MPH; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Answer

Answer

As described in the anatomy section, slight variations in the anatomy and location of the recurrent laryngeal nerves (RLNs) can exist. During surgery, a few anatomic landmarks can assist in identification of the nerves. The Tubercle of Zuckerkandl marks the posterolateral aspect of the thyroid lobe and is most often found lateral to the recurrent laryngeal nerve. The tubercle can be found in 80% of thyroids and when found can lead directly to the recurrent laryngeal nerve, as 93% of the nerves are found medial to this tubercle. [22, 23] Most often, the nerve is found in a groove between the tubercle and the lobe of the thyroid gland. [24]

As described before, both the left and right nerve follow closely with the course of the inferior thyroid artery, and this landmark can also help identify the nerve. Veyseller et al compared identifying the nerve from a superior-to-inferior approach (from its insertion into the larynx) to an inferior-to-superior approach (identification at the inferior pole) and found a lower rate of hypoparathyroidism using the superior-to-inferior approach for identifying the RLN. However, while this was a prospective trial, it was not randomized and could be confounded by both surgeon preference/experience and the indication for the thyroidectomy. [25]

Of note, many variations of the anatomic relationship between the artery and the nerves exist. Additionally, Berry’s ligament can be used for identification, since the nerves are found in close proximity to the ligament; however, the literature describes various anatomic relationships between the 2 structures. [12]

Berlin described the nerve penetrating the ligament in 25% of cases; however, a recent study by Sasou et al described 24 cases showing the nerve travelling posteriorly and dorsally to the ligament. [26] The inferior thyroid artery can also be used as a landmark for the RLN, with its close association with the pathway of the nerve. Again variations exist, and the branches of the inferior thyroid artery can be anterior or posterior to the nerve, or the nerve can run in between the branches of the artery.

Once the nerve is identified anatomically, its identity and integrity may be confirmed with nerve stimulation. A threshold value may be obtained to determine the minimum current necessary to stimulate the nerve. The course of the nerve should be bluntly dissected using the Reinhoff or a right angle clamp. A sufficient portion of the nerve should be dissected to ensure its safety during dissection and removal of the thyroid gland. Of note, too extensive of a dissection of the nerve can increase the risk of neurapraxia or injury to the nerve.

Recurrent laryngeal nerve. Recurrent laryngeal nerve.

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