A functional assessment of anatomical variants of the recurrent laryngeal nerve during thyroidectomies using neuromonitoring

Abstract

PurposeThe aim of the study was to assess the usefulness of intraoperative neuromonitoring (IONM) in identifying anatomical variants of the recurrent laryngeal nerve (RLN) during thyroidectomies, with emphasis on the nerve’s relationship to the inferior thyroid artery (ITA), Zuckerkandl’s tubercle, nonrecurrent laryngeal nerves (NRLNs), and extralaryngeal bifurcation.MethodsA total of 128 subjects undergoing surgery for thyroid disorders were enrolled in the study, and the course and anatomical variants of RLN were assessed with IONM application.ResultsThe standard relationship between RLN and ITA was that the artery and nerve intersect (100%). The right RLN was below the ITA in 76.67% of the patients, and the left RNL was below it in 75.81%. There were no statistically significant differences in the relationship between RLN and ITA on the two sides; and gender did not significantly influence the relationship between the RLN and ITA on either side. In one patient a nonrecurrent inferior laryngeal nerve was present on the right side (0.83%). RLN bifurcation was observed in 33.33% of the patients on the right and in 19.35% on the left side; the difference between sides was statistically significant (p < 0.05). Posterior tubercle (Zuckerkandl’s tubercle) was observed on the right in 83% of the subjects and on the left in 69%. The age, thyroid volume and body mass index (BMI) did not influence the size of the tumor.ConclusionsThe utilization of IONM of the RLN in thyroid surgery adds a new dimension to the standard of visual nerve identification allowing for functional nerve testing at the most vulnerable area of the dissection: at the level of Berry’s ligament, posterior tubercle (Zuckerkandl’s tubercle) and crossing of the RLN with the inferior thyroid artery.

Voice quality preservation in thyroid surgery with neuromonitoring

“…Nowadays IONM is a common technique which is gaining more and more acceptance among surgeons as an adjunct to the routine of visual recurrent laryngeal nerve injury identification [ 7 ]. With the application of IONM, the rate of RLN injury identification is almost 100% [ 21 – 24 ] and the incidence of transient RLN palsies is lower, particularly in difficult thyroid operations [ 21 , 25 , 26 ]. The introduction of IONM also focused our interest on the EBSLN [ 8 ].…”

Nonrecurrent Laryngeal Nerve: Precise Detection by Electrophysiological Nerve Monitoring

“…Anatomical variations of the RLN, including the non-RLN, deserve special attention for safer thyroid surgery. Prediction of the presence of the non-RLN preoperatively or at an early stage of surgery can eventually minimize injury risk to the nerve [ 2 - 4 ]. Since July 2011, we have been using IONM in all patients undergoing thyroid surgery.…”

“…The incidence of the non-RLN is very low and has been reported to be between 0.5% and 3% [ 2 - 5 ]. Preservation of anatomical integrity and motor activity of the nerve has paramount importance for successful thyroid surgery.…”

“…Preservation of anatomical integrity and motor activity of the nerve has paramount importance for successful thyroid surgery. The utilization of IONM of the RLN in thyroid surgery adds a new dimension to the standard of visual nerve identification since it enables functional nerve testing at the most vulnerable area of the dissection [ 2 ]. Nerve monitoring begins with the first step of VN stimulation (V1) at the level of the lower third of the thyroid.…”

“…It depends on the integrity of motor function that requires electrophysiological confirmation during surgery by intraoperative nerve monitoring (IONM). It is a widely accepted method to evaluate the motor activity of the RLN during thyroid surgery [ 1 , 2 ]. The proper and standard use of IONM may help to detect a nonrecurrent course of the inferior laryngeal nerve.…”