Anatomical Variations of Recurrent Laryngeal Nerve During Thyroid Surgery: How to Identify and Handle the Variations With Intraoperative Neuromonitoring

Abstract

Recurrent laryngeal nerve (RLN) palsy is the most common and serious complication after thyroid surgery. Visual identification of the RLN during thyroid surgery has been shown to be associated with lower rates of palsy, and although it has been recommended as the gold standard for RLN treatment, it does not guarantee success against postoperative vocal cord paralysis. Anatomical variations of the RLN, such as extra-laryngeal branches, distorted RLN, intertwining between branches of the RLN and inferior thyroid artery, and non-recurrent laryngeal nerve, can be a potential cause of nerve injury due to visual misidentification. Therefore, intraoperative verification of functional and anatomical RLN integrity is a prerequisite for a safe thyroid operation. In this article, we review the literature and demonstrate how to identify and handle the anatomical variations of the RLN with the application of intraoperative neuromonitoring in the form of high resolution photography, which can be informative for thyroid surgeons. Anatomical variations of the RLN cannot be predicted preoperatively and might be associated with higher rates of RLN injury. The RLN injury caused by visual misidentification can be rare if the nerve is definitely identified early with intraoperative neuromonitoring.

Enlargement of “SHENOY Node”: A Risk Factor for Temporary Recurrent Laryngeal Nerve Paralysis after Thyroid Surgery

“…There are several technical issues that increase the risk of nerve injury. It may be due to unintentional stretching, thermal injury, entrapment by a ligature, excessive use of suction near the nerve, aggressive surgical dissection or ischemic injury [7,9,21]. Tumor factors include extra-thyroidal extension, substernal extension of enlarged thyroid, recurrent disease, enlarged central compartment lymph node.…”

“…Recently, intraoperative nerve monitoring (IONM) to identify the nerves during thyroid surgery was shown to help lower the incidence of nerve injury, resulting better post-operative vocal cord outcomes [3]. The literature shows evidence of the rate of RLN paralysis with an overall range of 1% to 8.6%, with 1% to 5.1% as temporary paralysis, and 0 to 2.9% reported as permanent nerve paralysis [4][5][6][7][8].…”

Extralaryngeal division of the recurrent laryngeal nerve: A common and asymmetric anatomical variant

“…One factor increasing the risk of RLN paralysis is anatomical variation of the RLN. Variations in the RLN can be produced by changes in the course of the nerve due to previous surgery or the impaction of a mass, the relationship between the RLN and inferior thyroid artery (ITA),the nonrecurrent laryngeal nerve course, and extralaryngeal branching (3,4).…”

“…It is usually seen on the right side and arises during embryological development (6). Extralaryngeal branching of the RLN is a frequently seen anatomical specialty (3,4). The risk of developing nerve paralysis is higher in extralaryngeal branching of the RLN (7,8).…”

“…The nerve may be vulnerable to compression, traction, and transection due to the diminished caliber of the nerve due to the branching (9). A wide range of branching rates have been reported in studies on branching of the RLN (4). We aimed to assess the prevalence of RLN branching, the median branching distance, and the symmetry of the nerve.…”