Laryngeal Nerve In Thyroid Surgery Research Articles

Injury of the external branch of the superior laryngeal nerve in thyroid surgery.

The external branch of the superior laryngeal nerve (EBSLN) innervates the cricothyroid muscle (CTM) to promote lengthening and thinning of the vocal fold, thus increasing voice pitch. The close relation with the superior thyroid vessels (STV) puts the EBSLN in risk every time the superior pole of the thyroid is dissected. It travels downward to innervate the CTM, lateral to the thyroid cartilage and to the inferior pharyngeal constrictor muscle (IPCM), being eventually covered by this muscle fibers as it approaches its entry point. During its descending course, the EBSLN curves and crosses the STV posteriorly. The lower this crossing occurs in the neck, the higher the risk of surgical damage to the nerve by transection, traction, entrapment, thermal damage or disrupted blood supply. The chances of surgical trauma are also increased by size and weight of the specimen, shorter neck length and non-white ethnicity. Voice changes following thyroid surgery are common and multifactorial. The actual rate of vocal impairment due to EBSLN injury is unclear, since changes to the everyday speaking voice can be minimal and laryngeal findings are usually subtle and controversial. CTM electroneuromyography (EMG) is the most accurate tool to diagnose abnormal EBSLN conductivity, but it is technically difficult and barely applicable in routine practice. Recommended approaches to prevent injury include: (I) individual distal ligature of the STV by the thyroid capsule; (II) visual identification of the nerve and its trajectory and (III) electrostimulation with either observation of CTM twitch or intraoperative nerve monitoring (IONM) via dedicated endotracheal tube electrodes. There is accumulating evidence that a combination of visual and standardized electrophysiological EBSLN identification with meticulous division of the STV improves preservation rates. IONM bears the additional benefits of prognostication, quantification and documentation of neural function once it allows intraoperative laryngeal EMG.

Superior laryngeal nerve in thyroid surgery: anatomical identification and monitoring.

The aim of this study was to validate a procedure to identify and preserve the external branch of the superior laryngeal nerve (EBSLN) during thyroid surgery. The present study also aimed to analyze the EBSLN and the vagus nerve activities after stimulation and demonstrate an operative association between all the laryngeal muscles. Dissection of the cervical region was performed bilaterally in four adult cadavers. In a second step, 144 patients undergoing total thyroidectomy were included. Intraoperative stimulations of the cervical vagus nerve and the EBSLN in the sternothyroid-laryngeal triangle were performed bilaterally. Potentials in the thyroarytenoid muscle and the cricothyroid muscle were registered on each side using the NIM3 Medtronic System. EBSLN was identified according to Cernea's classification as type 1 in 62.5%, type 2a in 25%, and type 2b in 12.5% of cadaver's dissection. According to Friedman's classification, 50% of EBSLN were classified type 1, 25% type 2 and 25% type 3. The EBSLN was identified in 267 cases out of 288 peroperative dissections (92.7%). Direct stimulation (1mA) of this branch led to a recordable contraction of the cricothyroid muscle with a mean latency of 1.42±0.66ms on the right side and 1.43±0.61ms on the left side. The stimulation of the EBSLN also led to a recordable contraction of the thyroarytenoid muscle in 211 cases (73.3%) with the same latencies. A contraction of the cricothyroid muscle was also recorded when the vagus nerve was stimulated in 219 cases (76.0%). The sole visual identification of the EBSLN during thyroid surgery is not a reliable method to prevent nerve injury. Direct stimulation of the EBSLN in the sternothyroid-laryngeal triangle is a simple and rapid procedure to detect and preserve the nerve during surgery. Functional associations between vagus nerve and EBSLN in laryngeal muscles' contractions were also identified.

Intraoperative neuromonitoring in thyroid surgery

Abstract Background Intraoperative neuromonitoring of the recurrent laryngeal nerve in thyroid surgery facilitates the identification of anatomical structures in cervical endocrine surgery reducing the frequency of vocal cord paralysis. Objective To study the normal electrophysiological values of the vague and recurrent laryngeal nerves before and after thyroid surgery. To compare rates of injury of recurrent nerve before and after the introduction of the intraoperative neuromonitoring in thyroid surgery. Material and methods An observational, descriptive and prospective study in which a total of 490 patients were included. Between 2003 and 2010, surgery was performed on 411 patients (703 nerves at risk) with systematic identification of recurrent laryngeal nerves. Between 2010 and 2011 neuromonitorisation was also systematically performed on 79 patients. Results Before the introduction of intraoperative neuromonitoring of 704 nerves at risk, there were 14 recurrent laryngeal nerve injuries. Since 2010, after the introduction of the intraoperative neuromonitoring in thyroid surgery, there has been no nerve injury in 135 nerves at risk. Conclusions We consider the systematic identification of the recurrent laryngeal nerve is the ‘gold standard’ in thyroid surgery and the intraoperative neuromonitoring of nerves can never replace surgery but can complement it.

Clinical anatomy and features non-recurrent inferior laryngeal nerve in thyroid surgery. Case report

В последние десятилетия отмечается значительный успех в хирургии щитовидной железы, однако частота развития пареза гортани вследствие повреждения возвратного гортанного нерва остается высокой. Детальное изучение разных вариантов топики нерва – одно из направлений, дающих возможность снизить его травматизацию. Невозвратный нижний гортанный нерв является редкой анатомической особенностью, которая выявляется при операциях на щитовидной железе в 0,3–1% случаев. Несмотря на такую редкую встречаемость, к сожалению, атипичное расположение невозвратного гортанного нерва создает предпосылки для его ятрогенного повреждения. В статье проведен анализ литературы, описаны причины возникновения, связь с аномалией магистральных сосудов и клиническое значение. Описаны два случая выявления невозвратного нижнего гортанного нерва в хирургической клинике ФГБУ РНЦРР МЗ РФ.

Experience of monitoring the recurrent laryngeal nerve in thyroid surgery with endotracheal intubation

Purpose:To analysis clinical experience of applying recurrent laryngeal monitoring endotracheal tube (NIM EMG Endotracheal Tube) in the surgery of thyroid. Method: A retrospective analysis of 84 patients who underwent endotracheal intubation laryngeal nerve monitoring by thyroid surgery in the Chinese-Japanese Friendship Hospital of Jilin University from March to December in 2015. To summarize the experience of intubation with NIM EMG Endotracheal Tube. Result 77 (91.7%)had initial intubation achievement in the 84 patients.FROM the 77 cases we had gotten s atisfactory nerve monitoring signal.Whereas there are 7 cases (8.3%) appear abnormal EMG or signal missing, in the 7 cases there is one which being intubated too deep, 3 cases which being intubated too shallow and 3 cases with malrotation intubation.Conclusion: We got the satisfactory signals after adjust1ing the tube by using the visual laryngoscope.

Neuromonitorización intraoperatoria en cirugía tiroidea

BackgroundIntraoperative neuromonitoring of the recurrent laryngeal nerve in thyroid surgery facilitates the identification of anatomical structures in cervical endocrine surgery reducing the frequency of vocal cord paralysis. ObjectiveTo study the normal electrophysiological values of the vague and recurrent laryngeal nerves before and after thyroid surgery. To compare rates of injury of recurrent nerve before and after the introduction of the intraoperative neuromonitoring in thyroid surgery. Material and methodsAn observational, descriptive and prospective study in which a total of 490 patients were included. Between 2003-2010, surgery was performed on 411 patients (703 nerves at risk) with systematic identification of recurrent laryngeal nerves. Between 2010-2011 neuromonitorization was also systematically performed on 79 patients. ResultsBefore the introduction of intraoperative neuromonitoring of 704 nerves at risk, there were 14 recurrent laryngeal nerve injuries. Since 2010, after the introduction of the intraoperative neuromonitoring in thyroid surgery, there has been no nerve injury in 135 nerves at risk. ConclusionsWe consider the systematic identification of the recurrent laryngeal nerve is the ‘gold standard’ in thyroid surgery and the intraoperative neuromonitoring of nerves can never replace surgery but can complement it.

The learning curve for intraoperative neuromonitoring of the recurrent laryngeal nerve in thyroid surgery

PurposeIntraoperative neuromonitoring (IONM) of the recurrent laryngeal nerve (RLN) is often used in thyroid surgery. However, this procedure is complex and requires a learning period to master the technique. The aim of the study was to evaluate the learning curve for IONM.MethodsA 3-year period (2012–2014) of working with IONM (NIM3.0, Medtronic) was prospectively analyzed with a special emphasis on comparing the initial implementation phase in 2012 (101 patients, 190 RLNs at risk) with subsequent years of IONM use in 2013 (70 patients, 124 RLNs at risk) and 2014 (65 patients, 120 RLNs at risk).ResultsThe rate of successful IONM-assisted RLN identification increased gradually over the 3-year study period (92.11 % in 2012 vs. 95.16 % in 2013 vs. 99.16 % in 2014; p = 0.022), with a corresponding decrease in the rate of technical problems (12.87, 4.3, and 4.6 %, respectively; p = 0.039). The rate of RLN injuries tended to decrease over time: 3.68, 1.55, and 0.83 %, respectively (p = 0.220). Between 2012 and 2014, increases in the sensitivity (71.4 vs. 100 %), specificity (98 vs. 99 %), positive predictive value (62.5 vs. 75 %), negative predictive value (98 vs. 100 %), and overall accuracy of IONM (97.4 vs. 99.6 %) were observed (p = 0.049). Increasing experience with IONM resulted in more frequent utilization of total thyroidectomy (92 % in 2012 vs. 100 % in 2013–2014; p = 0.004).ConclusionsThere was a sharp decrease in the number of technical problems involving equipment setup from 2012 to 2014.

Prognostic value of intraoperative neural monitoring of the recurrent laryngeal nerve in thyroid surgery

PurposeThe diagnostic accuracy of intraoperative recurrent laryngeal nerve (RLN) monitoring (IONM) remains controversial. The aim of this study was to evaluate IONM diagnostic accuracy in prognostication of postoperative nerve function in thyroid surgery.MethodsThis prospective study was conducted in 2011–2013. Five hundred consenting patients qualified for total thyroidectomy with IONM (1000 nerves at risk) using NIM 3.0 Response equipment were included. Laryngoscopy was used to evaluate and follow up RLN injury. The primary outcome was diagnostic accuracy of IONM. The receiver operating characteristics (ROC) were used for evaluation of IONM diagnostic accuracy.ResultsLoss of signal (LOS) occurred in 31 cases, including 25 patients with LOS and corresponding vocal fold paresis found in postoperative laryngoscopy (2.5 %), including 20 (2.0 %) temporary and 5 (0.5 %) permanent nerve lesions. The following diagnostic accuracy values were calculated for the criterion recommended by INMSG (V2 amplitude ≤ 100 μV): sensitivity 92.0 %, specificity 99.3 %, positive predictive value (PPV) 76.7 %, and negative predictive value (NPV) 99.8 %. The ROC curve analysis allowed for calculation of the most optimal criterion in prognostication of postoperative vocal fold paresis, namely, V2 amplitude ≤ 189 μV. For this criterion, PPV was 77.4 %, while NPV was 99.9 %.ConclusionsAdherence to the standardized protocol recommended by the International Neural Monitoring Study Group allows for optimizing predictive values of IONM in prognostication of postoperative RLN function. Any changes in the cutoff values for the definition of LOS only marginally improve PPV and NPV of IONM and need to be carefully assessed in multicenter studies.

Identifying Recurrent Laryngeal Nerve in Thyroid Surgery Using Relationship with Superior Parathyroid Gland and Tubercle of Zuckerkandl

Introduction: Recurrent laryngeal nerves (RLN) are particularly prone to injury during thyroid surgeries due to its intimate relationship and proximity with the gland. Zuckerkandl’s tubercle (ZT) helps in preserving RLN intra operative.
 Material and Methods: A prospective study for identifying RLN in thyroid surgery using relationship with superior parathyroid gland and tubercle of Zuckerkandl was conducted on 50 thyroidectomy patients between August 2013 and February 2014.
 Results: In all cases ZT was identified. Temporary paralysis of RLN was seen in 3 (6%) cases and permanent paralysis in 2 (4%) of cases.
 Discussion: The site of greatest risk during thyroidectomy to the RLN is in the last 2-3 cm extralaryngeal course of the nerve. Relationship of recurrent laryngeal nerve with superior parathyroid gland and tubercle of Zukerkandl (ZT) is known.
 Conclusion: Use of ZT and superior parathyroids as a landmark allows safe dissection of RLN.

Electrophysiological neural monitoring of the laryngeal nerves in thyroid surgery: review of the current literature.

Recurrent laryngeal nerve (RLN) injury is one of the most common complications of thyroid surgery. RLN injury can cause vocal cord paralysis, affecting the patient's voice and the quality of life. Injury of the external branch of the superior laryngeal nerve (EBSLN) can cause cricothyroid muscle denervation affecting high vocal tones. Thus, securing the laryngeal nerves in these surgeries is of utmost importance. Visual identification of the nerves has long been the standard method for this precaution. Intraoperative neuromonitoring (IONM) has been introduced as a novel technology to improve the protection of the laryngeal nerves and reduce the rate of RLN injury. The aim of this article is to provide a brief description of the technique and review the literature to illustrate the value of IONM. IONM can provide early identification of anatomical variations and unusual nerve routes, which carry a higher risk of injury if not detected. IONM helps in prognosticating postoperative nerve function. Moreover, by detecting nerve injury intraoperatively, it aids in staging bilateral surgeries to avoid bilateral vocal cord paralysis and tracheostomy. The article will discuss the value of continuous IONM (C-IOMN) that may prevent nerve injury by detecting EMG waveform changes indicating impending nerve injury. Herein, we are also discussing anatomy of laryngeal nerves and aspects of its injury.

Opportunity of voice spectrology for diagnostics of damage of external branch of superior laryngeal nerve in thyroid surgery

Opportunity of voice spectrology for diagnostics of damage of external branch of superior laryngeal nerve in thyroid surgery

Increased prediction of right nonrecurrent laryngeal nerve in thyroid surgery using preoperative computed tomography with intraoperative neuromonitoring identification.

BackgroundA nonrecurrent laryngeal nerve (NRLN) is a rare but potentially serious anatomical variant. Although the incidence is reported to be 0.3% to 1.3%, it carries a much higher risk of palsy during thyroid surgery. The objective of this study is to investigate the usefulness of computed tomography (CT) for preoperative identification and intraoperative neuromonitoring identification (IONM) of NRLN in thyroid cancer patients.MethodsThe preoperative neck CT scans from 1,574 patients who needed thyroid surgery were examined. Absence of the brachiocephalic artery (BCA) and the presence of arteria lusoria were defined as positive with NRLN. Systematic intraoperative neuromonitoring (IONM) was also carried out for these 1,574 patients to localize and identify NRLN. A negative electromyography (EMG) response from lower vagal stimulation but a positive EMG response from the upper position indicated the occurrence of an NRLN.ResultsNine NRLN (0.57%) were intraoperatively identified out of the 1,574 patients, and no patient with a NRLN showed preoperative clinical symptoms related to NRLN. Prior to the operation, surgeons identified only seven suspected NRLN cases based on identification of arteria lusoria. But a review of CT scans revealed that all cases could be identified by vascular anomalies. All patients were successfully detected at an early stage of operation using intraoperative neuromonitoring (IONM). Postoperative vocal cord function was normal in all patients.ConclusionsCT of the neck is a reliable method for predicting NRLN before thyroid cancer surgery. However, some image features can be easily missed. Neurophysiology helps the surgeon to identify the NRLNs more precisely. Combining the two evaluation methods may decrease the incidence of nerve palsy, especially in cases of NRLN. Considering that CT is expensive, requires an X-ray, and achieves less information than ultrasound (US) concerning thyroid nodules, we suggest that applying US and IONM is more reasonable.

English

The variations in the distribution pattern of superior thyroid artery are of great importance for head and neck surgeons because of its vital relationship to the external laryngeal nerve. In this case an unusual unilateral variation in the arterial supply of thyroid gland was found during routine dissection of an elderly male cadaver in the Department of Anatomy, GGS Medical College, Faridkot, Punjab. The left superior thyroid artery took origin from the anterior aspect of left common carotid artery and it exhibited a usual relationship with the left external laryngeal nerve. The inferior thyroid arteries did not show any unusual distribution. Knowledge of such arterial variations related to the thyroid gland is immensely helpful for surgeons in order to put ligature on anomalous artery and to avoid damage to vital structures in this area. It is also helpful to the INTRODUCTION: The Superior Thyroid Artery (STA) is the main source of arterial blood to the thyroid gland, upper part of the larynx and neck region. It is a branch of external carotid artery (ECA) and arises from its anterior surface, just below the level of greater cornu of the hyoid bone. It runs downwards from its origin and gives a branch i.e. superior laryngeal artery (SLA) which pierces the thyrohyoid membrane along with the internal laryngeal nerve. It also gives an infrahyoid branch, a branch to the sternocleidomastoid muscle and a crico-thyroid branch. 1 The relationship of the superior thyroid artery to the external laryngeal nerve is important to the surgeon during thyroid surgery. The artery and nerve are close to each other higher up but diverge near the gland. Thus in order to avoid injury to the external laryngeal nerve, the superior thyroid artery is ligated as near to the gland as possible. The STA is frequently used as a recipient vessel for microvascular free tissue transfer in head and neck surgery, for selective embolization of thyroid and head and neck tumors, and as a landmark for identifying the external laryngeal nerve in thyroid surgery. 2 Surgical procedures involving the thyroid gland require a thorough knowledge not only of the normal gross anatomy of the structures within the region but also of the anatomical variations of the structures located within it. Thyroid surgery being a major surgery and quite often performed, a thorough knowledge of variations in arterial supply is very essential for surgeons to prevent alarming number of table deaths in patients with thyroid disease due to excessive and uncontrollable bleeding. It is also of help to the radiologists and physicians for proper physical examination and treatment of the patient and to the anatomists for learning the variant patterns.

Variation of recurrent laryngeal nerve in thyroid surgery

Objective To reduce the injury of recurrent laryngeal nerve (RLN) in thyroid operation summarizing the characteristics of the anatomic variation of recurrent laryngeal nerve.Methods The distribution,incidence of variation,etc.of 1772 fully revealed RLN in 1270 patients were statistically analyzed,then the anatomical variation characteristics of RLN were summarized.Results 396 nerves (22.35％) were natural variation and 59 (3.33％) conditional variation.8 RLN (0.45％) were injuried; of which,6 (0.34％) got unilateral temporary injury,and recovered 2-14 weeks after the surgery; 1 (0.06％) bilateral temporary injury,and the patient got delayed respiratory tract obstruction after the operation and his vocal cord function returned to normal 6 months after symptomatic treatment; and 1 (0.06％) unilateral permanent damage.Conclusions RLN variation has a high incidence and various types.In the operation of thyroid gland,the anatomic charactaristics of RLN should be fully understood to reduce the incidence of RLN injury. Key words: Thyroid operation; Recurrent laryngeal nerve; Anatomic variation; Injury

Routine exposure of recurrent laryngeal nerve in thyroid surgery can prevent nerve injury.

To determine the value of dissecting the recurrent laryngeal nerve during thyroid surgery with respect to preventing recurrent laryngeal nerve injury, we retrospectively analyzed clinical data from 5 344 patients undergoing thyroidectomy. Among these cases, 548 underwent dissection of the recurrent laryngeal nerve, while 4 796 did not. There were 12 cases of recurrent laryngeal nerve injury following recurrent laryngeal nerve dissection (injury rate of 2.2%) and 512 cases of recurrent laryngeal nerve injury in those not undergoing nerve dissection (injury rate of 10.7%). This difference remained statistically significant between the two groups in terms of type of thyroid disease, type of surgery, and number of surgeries. Among the 548 cases undergoing recurrent laryngeal nerve dissection, 128 developed anatomical variations of the recurrent laryngeal nerve (incidence rate of 23.4%), but no recurrent laryngeal nerve injury was found. In addition, the incidence of recurrent laryngeal nerve injury was significantly lower in patients with the inferior parathyroid gland and middle thyroid veins used as landmarks for locating the recurrent laryngeal nerve compared with those with the entry of the recurrent laryngeal nerve into the larynx as a landmark. These findings indicate that anatomical variations of the recurrent laryngeal nerve are common, and that dissecting the recurrent laryngeal nerve during thyroid surgery is an effective means of preventing nerve injury.

Neuromonitoring of the laryngeal nerves in thyroid surgery: a critical appraisal of the literature

One of the most significant complication of thyroid surgery is injury of the recurrent laryngeal nerve. Injury of the external branch of the superior laryngeal nerve is a less obvious but occasionally significant problem. Recently, neuromonitoring during thyroidectomy has received considerable attention because of literature encouraging its use, but there is no consensus about its advantages and utility. A critical assessment of the literature on neuromonitoring was conducted in order to define its effectiveness, safety, cost-effectiveness and medical-legal impact. Available data does not show results superior to those obtained by traditional anatomical methods of nerve identification during thyroid surgery. Data about cost-effectiveness is scarce. The literature shows inconsistencies in methodology, patient selection and randomization in various published studies which may confound the conclusions of individual investigations. The current recommendation for use in "high risk" patients should be assessed because definition heterogeneity makes identification of these patients difficult. As routine use of neuromonitoring varies according to geography, its use should not be considered to be the standard of care.

Identification of External Branch of the Superior Laryngeal Nerve in Thyroid Surgery: Is it Always Possible?

The External Branch of the Superior Laryngeal Nerve (EBSLN), which innervates the cricothyroid muscle, is important for voice quality. However, different identification rates for the nerve have been reported in thyroid surgery, with few surgeons not being able to identify the nerve at all. Different variants of the nerve have been described and various techniques have been used in order to identify the nerve. Our study aims to quote the identification rate of the EBSLN in thyroid surgery using standard dissection techniques. We feel that the definite prevalence of the Type III Friedman variant explains why the nerve may not be identified in a definite number of patients. The clinically relevant message of our study is that, even though it may not be possible to routinely identify the EBSLN in all cases of thyroid surgery, yet this nerve would be preserved by the standard extra capsular dissection techniques.

Vagal nerve stimulation without dissecting the carotid sheath during intraoperative neuromonitoring of the recurrent laryngeal nerve in thyroid surgery

Vagal nerve stimulation (VNS) has been recommended as a routine procedure during intraoperative neuromonitoring (IONM) of the recurrent laryngeal nerve (RLN). However, many surgeons have been discouraged from performing VNS because of the need for opening the carotid sheath. The purpose of this study was to investigate the feasibility and reliability of VNS without carotid sheath dissection. Two hundred twenty patients with 376 nerves at risk were enrolled in this study. VNS without nerve exposure during IONM was applied by simply pressing a ball-tip stimulator on the space between the carotid artery and jugular vein. VNS without nerve exposure was feasible in all cases and did not result in any morbidity. All VNS signals were successfully obtained within 30 minutes of the start of the operation and all showed a clear and reliable laryngeal electromyography (EMG) response that was similar to that from the conventional method in which nerve exposure for VNS is applied. VNS without dissecting the carotid sheath is feasible and reliable, rendering it a simple, safe, and surgeon-friendly procedure during IONM.

Motor and sensory branching of the recurrent laryngeal nerve in thyroid surgery

Recognition of extralaryngeal bifurcation of the recurrent laryngeal nerve (RLN) is crucial, because inadvertent intraoperative division may lead to significant morbidity. The purpose of this study was to examine the incidence of extralaryngeal bifurcation of the RLN and the distance that the initial bifurcation occurs from the cricothyroid insertion site of the RLN. We also sought to demonstrate the location of the RLN branches containing a predominance of motor fibers. This prospective study of 220 patients with data on 310 RLNs collected the type of operation, incidence of bifurcation, distance from the cricothyroid insertion point to the point of initial bifurcation, and location of the motor fibers by assessing a stimulus response on the Medtronic NIMS as they relate to the laryngeal muscles. A total of 310 RLNs in 220 patients were studied. There were 133 RLNs (42.9%) that bifurcated before entering the larynx. These bifurcations occurred 51.1% on the right, 48.9% on the left, and 33.3% bilaterally. The median branching distance from the cricothyroid membrane on the right was 6.33 mm, and on the left was 6.37 mm. In all bifurcated RLNs, the motor fibers were located exclusively in the anterior branches. Extralaryngeal bifurcation was found in 42.9% of the RLNs in this case series. The motor fibers are located in the anterior branches. Great caution is therefore required after the presumed identification of the RLN to ensure there is no unidentified anterior branch.

Thyroid tubercle of zuckerkandl: Importance in thyroid surgery

The Tubercle of Zuckerkandl (TZ), which is the remant of the lateral thyroid process, is an important anatomic structure that serves as a reliable landmark for the recurrent laryngeal nerve in thyroid surgery. Furthermore, removal of the TZ is critical for the adequate performance of a total thyroidectomy. However, there is little mention of the TZ in surgical textbooks or papers. Prospective observational study of 138 consecutive thyroid surgeries. The presence of the TZ, its size, and relationship to the recurrent laryngeal nerve, were recorded. A total of 211 thyroid lobes were included in the study. The TZ was identified in 61.1% of all thyroid lobes. The median size was 8 mm (range = 3-40 mm). A TZ was more commonly identified on the right (69.6%) than on the left side (53.2%) (P = .02). The recurrent laryngeal nerve was found deep to the TZ in 98.4% of cases. A TZ is present in the majority of thyroid lobes. Awareness of the TZ is critical in performing an adequate total thyroidectomy, and is very useful as a landmark for the recurrent laryngeal nerve.