Laryngeal Entry Point Research Articles

Mechanisms of recurrent laryngeal nerve injury in endoscopic thyroidectomy for papillary thyroid carcinoma: A large data from China.

To investigate the mechanisms of recurrent laryngeal nerve (RLN) injury during endoscopic thyroidectomy via breast approach (ET-BA) in patients with papillary thyroid carcinoma (PTC). The records of 416 PTC patients who underwent ET-BA with intraoperative neural monitoring (IONM) from May 2015 to May 2021 in Beijing Friendship Hospital affiliated to Capital Medical University were retrospectively analyzed. All patients were women. Mean age was 37.80 (7.87) years. The ET-BA was performed in 416 patients. Overall incidence of RLN injury was 4.3% (18 patients). Injury was transient in 13 patients (3.1%) and permanent in five (1.2%). Macroscopic physical changes were apparent in the injured nerve in five patients (27.8%) and postoperative hoarseness or cough after drinking water were present in 11 (61.1%). Two RLN injuries occurred during nerve identification at the RLN laryngeal entry point into the surgical field, 15 during early nerve dissection somewhere between the first 0.5 and 2cm of the nerve's course through the surgical field, and one occurred distal to 2cm. The percentage of patients with separation, transection, traction and thermal mechanisms of injury was 27.8%, 22.2%, 22.2%, and 16.7%, respectively. The mechanism of injury was unknown in 11.1%. RLN injury may still occur during ET-BA despite endoscopic magnification and early nerve identification even when IONM is used. Separation, transection, and traction injuries were the most frequent causes of injury.

Clinical and Anatomical Factors Affecting Recurrent Laryngeal Nerve Paralysis During Thyroidectomy via Intraoperative Nerve Monitorization.

BackgroundDespite all the technical developments in thyroidectomy and the use of intraoperative nerve monitorization (IONM), recurrent laryngeal nerve (RLN) paralysis may still occur. We aimed to evaluate the effects of anatomical variations, clinical features, and intervention type on RLN paralysis.MethodThe RLNs identified till the laryngeal entry point, between January 2016 and September 2021 were included in the study. The effects of RLN anatomical features considering the International RLN Anatomical Classification System, intervention and monitoring types on RLN paralysis were evaluated.ResultsA total of 1,412 neck sides of 871 patients (672 F, 199 M) with a mean age of 49.17 + 13.42 years (range, 18–99) were evaluated. Eighty-three nerves (5.9%) including 78 nerves with transient (5.5%) and 5 (0.4%) with permanent vocal cord paralysis (VCP) were detected. The factors that may increase the risk of VCP were evaluated with binary logistic regression analysis. While the secondary thyroidectomy (OR: 2.809, 95%CI: 1.302–6.061, p = 0.008) and Berry entrapment of RLN (OR: 2.347, 95%CI: 1.425–3.876, p = 0.001) were detected as the independent risk factors for total VCP, the use of intermittent-IONM (OR: 2.217, 95% CI: 1.299–3.788, 0.004), secondary thyroidectomy (OR: 3.257, 95%CI: 1.340–7.937, p = 0.009), and nerve branching (OR: 1.739, 95%CI: 1.049–2.882, p = 0.032) were detected as independent risk factors for transient VCP.ConclusionPreference of continuous-IONM particularly in secondary thyroidectomies would reduce the risk of VCP. Anatomical variations of the RLN cannot be predicted preoperatively. Revealing anatomical features with careful dissection may contribute to risk reduction by minimizing actions causing traction trauma or compression on the nerve.

Prevention of non-recurrent laryngeal nerve injury in robotic thyroidectomy: imaging and technique.

The aim of this report was to summarize observations, evaluate the feasibility, provide detailed information concerning proper techniques, and address limitations for non-recurrent laryngeal nerve (NRLN) dissection and release during the robotic bilateral axillo-breast approach (BABA) for thyroidectomy. The BABA approach was used in two cases of thyroidectomy in the setting of NRLN. Preoperative CT imaging findings suggesting the aberrant anatomy are reviewed and technical planning, inclusive of intraoperative nerve monitoring, was employed. Intraoperative videos with narrative discussion of technique for safe dissection are provided, along with supplementary video of additional technical guidance. In both cases, the NRLNs were identified, dissected, and preserved. We dissected the proximal segment of each NRLN to its origin. We determined that the use of only the NRLN proximal to distal robotic dissection jeopardized the nerve. The BABA approach with the Type I NRLN is similar to the dissection of the recurrent laryngeal nerve (RLN) in transoral thyroidectomy. Due to interference with endoscopic viewing caused by the thyroid cartilage, the Type I NRLN is more challenging to manage both at the laryngeal entry point and its origin from the vagus nerve (VN). For the Type II NRLN, it is essential to identify its point of origin and the reflection of the nerve from the VN. Therefore, modification of nerve dissection to mirror open surgery with bidirectional nerve dissection assisted in avoidance of traction injury to the nerve. We presented a video, a detailed description of methods, and discussed limits for NRLN management in robotic BABA. This report included (i) a description of the aberrant anatomy and CT scans to inform surgeons of the possible NRLN locations, (ii) a description of a technique for using the nerve monitor in the robotic surgeries, and (iii) a description of the techniques used to isolate and protect the NRLN during the robotic surgery. In robotic BABA, our NRLN-sparing technique and degree included mainly a multi-directional nerve dissection (i.e., medial-grade, later-grade approach together with proximal to/from distal) using athermal technique. The NRLN-sparing technique is predominantly carried out in an anterior dissection plane.

Warning criterion to predict recurrent laryngeal nerve injury with percentage reduction of the amplitude of V2/R2d in neuromonitoring thyroidectomy

ObjectiveTo evaluate the contribution of amplitude reduction compared vagal stimulation at the end of thyroid dissection (V2) to the most distal RLN stimulation during thyroidectomy in predicting postoperative vocal cords paralysis (VCP). MethodsPatients with intact preoperative RLN function who underwent monitored thyroidectomy between August 2017 and April 2018 were included. We routinely tested the exposed RLN at the lowest proximal end (R2p signal) and the most distal end near the laryngeal entry point (R2d signal), and then routinely detected the vagal nerve at the horizontal plane of the inferior pole of thyroid with 2mA stimulation current. The cut-off value was calculated with Receiver Operating Characteristic curve. Rates of specificity, sensitivity, negative predictive value, positive predictive value (PPV) for V2/R2d and R2p/R2d were compared. ResultsPercentage reduction of the amplitude of V2/R2d ranged from 34.8% to 76.7%. Twenty-two (1.5%) nerves developed temporary VCP, in which one nerve with VCP showed no significant amplitude reduction at the end of the surgery. There was no permanent or bilateral VCP. Sensitivity, specificity, PPV, NPV, and accuracy for the amplitude reduction of V2/R2d> 60% were 95.5%, 99.8%, 99.9%, 98.2%, respectively, for R2p/R2d were 99.5%, 99.2%, 63.6%, 99.9%, 97.7%, respectively. ConclusionPercentage reduction of the amplitude of V2/R2d is a reliable and practical warning criterion for RLN injury. When the amplitude reduction> 60% surgeons should consider the possibility of postoperative VCP and correct some surgical maneuvers.

The Most Common Anatomical Variation of Recurrent Laryngeal Nerve: Extralaryngeal Branching.

Objective:Extralaryngeal branching of recurrent laryngeal nerve (RLN) is frequent. In various studies, detection rate of extralaryngeal nerve branching was increased by intraoperative neuromonitorization (IONM). Our aim was evaluation of the relationship between the features of extralaryngeal branching of RLN and other anatomic variations in thyroidectomy patients under the guidance of IONM.Methods:Patients underwent thyroidectomy using IONM between January 2016 and December 2019 and whose RLNs were fully explored till the nerve’s entry point to the larynx, were enrolled to the study. Extralaryngeal branching of RLN was accepted as branching of the nerve at a ≥5 mm distance from its laryngeal entry point and having its all branches entering the larynx. Entrapment of RLN at the region of ligament of Berry (BL) by a vascular structure or posterior BL and relationship between RLN and inferior thyroid artery (ITA) was evaluated.Results:Out of 696 patients meeting the inclusion criteria, 1127 neck sides (536F and 160M) were evaluated. Mean age was 49.1±13.4 (range; 18–89). Nerve branching ratio was 35.3% and was higher in females than males (38.2%vs.25.8%, p<0.0001, respectively). Extralaryngeal branching of RLN was detected in 398 (35.3%) out of 1127 nerves. A total of 368 (92.5%) RLNs had two, 27 (6.8%) nerves had three, and 3 (0.7%) had multiple branches. RLN crossed anterior to and between branches of ITA more frequently in branching nerves than non-branching nerves (47.7 vs. 44.4% and 12.8% vs. 7.6%, respectively) but crossed posterior to ITA less frequently in branching nerves (38.5% vs. 48%, respectively, p=0.001). Entrapment of RLN at the region of BL was higher in branched nerves (25.9% vs. 17.5%, respectively, p=0.001). Entrapment of RLN wasmore frequent at the right side than left side both in branching (31.5% vs.19.4%, respectively, p=0.008) and non-branching nerves (20.6% vs. 14.4%, respectively).Conclusion:Extralaryngeal branching of RLN is not rare and mostly divided into two branches. Branching ratio is higher in females than males. In branching nerves, rate of crossing anterior to and between branches of ITA was higher, in non-branching nerves, rate of crossing posterior to ITA was higher. In branching nerves, possibility of entrapment of RLN at the region of BL was higher. Both in branching and non-branching nerves, entrapment of RLN at the region of BL was higher at the right side. Extralaryngeal branching, relationship between RLN and ITA, and entrapment of RLN at the region of BL are frequently seen and variable anatomic variations and cannot be foreseen preoperatively. Most of the extralaryngeal branches and their relationship with other variations can be detected by finding RLN at the level of ITA and following RLN until its entry point to the larynx.

Recurrent laryngeal nerve management in transoral endoscopic thyroidectomy.

The mechanism of recurrent laryngeal nerve (RLN) injury was investigated during a TransOral Endoscopic Thyroidectomy Vestibular Approach (TOETVA). The function of 185 nerves at risk (NAR) was recorded with intermitted intraoperative neural monitoring (I-IONM). The RLN electromyography (EMG) was delineated during: (a) a pre-dissection vagal nerve stimulation; (b) a RLN stimulation at initial visualization; (c) at nerve dissection; and (d) at the final verification of the entire RLN route. The location, genesis, segmental or diffuse and the outcomes of RLN injuries were catalogued. Twelve nerves (6.4%) lost the EMG signal and the incidences of temporary and permanent RLN dysfunction were 5.9% and 0.5%. A disrupted point (type 1 injury) could be identified in 7/12 nerves (58%). Five (42%) nerve injuries were classified as global (type 2). Of the seven type 1 injuries, 3 lesions occurred at the RLN laryngeal entry point during the nerve identification. Four type 1 injuries were at the distal 1cm of the RLN course and during the early nerve dissection. No proximal (>2cm) injuries occurred. The mechanisms of the injuries were thermal (58%) during the energy-based device use at the ligament of Berry dissection or at the dividing small branches of the inferior thyroid artery. Two (16%) traction injuries occurred during the early nerve dissection. In 2 cases we could not elucidate the mechanism of RLN injury (16%) and 1 injury (8%) was caused by the connective tissue constricting band of. The thermal RLN lesions had longer recovery times. The RLN palsy occurs in TOETVA, even when combined with an endoscopic magnification, IONM, early nerve identification, cranial to caudal dissection and top-down view. The thermal RLN injury was the most frequent cause and all injuries occurred at the distal RLN course.

Lymph node metastasis around the entrance point to recurrent laryngeal nerve in papillary thyroid carcinoma

There are few reports on the lymph nodes of entrance point to recurrent laryngeal nerve (LN-epRLN) in patients with papillary thyroid carcinoma (PTC). Thus, we investigated the clinical significance of LN-epRLN and implications it may have. An observational analysis of 878 consecutive patients with PTC who underwent thyroidectomy from April 2016 to March 2017 was conducted. We explored the surrounding tissue of laryngeal entry point, during routine central lymph node dissection (CLND). The lymph node specimens were sent separately for routine histopathological examination. Thereafter, complications and follow-ups were recorded. LN-epRLNs were found in 73 of the 878 patients, with the metastatic rate of 3.76%. Univariate and multivariate analysis showed central lymph node metastases can serve as independent predictors for LN-epRLN metastasis. In summary, we confirmed the significance of LN-epRLN in metastasis and recurrence, which required precise anatomy and thorough CLND. In PTC patients, especially in suspicious presence of central cervical lymph node metastasis, attention should be given to excising the nodal tissue at the laryngeal entry point.

Safety of medial dissection of the thyroid gland along the trachea based on anatomic constancy of the laryngeal entry point of the recurrent laryngeal nerve.

PurposeThe purpose of this study was to determine the extent of safety of medial dissection of the thyroid gland along the trachea. Medial to lateral dissection of the thyroid gland along the trachea after early division of the isthmus has been known to be a useful technique in thyroid surgery, especially for difficult cases, but the risk of injury of the recurrent laryngeal nerve (RLN) has constrained thyroid surgeons from utilizing this technique to its full extent.MethodsDistances of the laryngeal entry point (LEP) of 134 RLNs of 71 patients from the midline of the trachea, and some other anatomical distances, were measured intraoperatively. The relationships of the intraoperatively measured data with circumferences of the cartilaginous portion of the trachea (CCT) around LEP measured preoperatively by CT scan were evaluated.ResultsLEP was always located within 2 mm vertically from the horizontally extended line of the inferior border of the cricoid cartilage and was the closest point from the midline in the whole course of the RLN. The distance between LEP and the midline was very closely correlated with CCT measured on preoperative CT scan, and it can be accurately calculated with a regression equation; Distance between LEP and the midline = (0.42 × CCT) + (1.2 × sex) + 3.2 (mm) (sex: female=0, male=1; R2 = 0.85).ConclusionEarly division of the isthmus and dissecting the thyroid off the trachea to the calculated extent is a safe and effective procedure.

Some posterior branches of extralaryngeal recurrent laryngeal nerves have motor fibers.

Anatomical variations of the recurrent laryngeal nerve (RLN), such as extralaryngeal branching, are a well-known risk factor for RLN injury during thyroid surgery. This study aimed to analyze the surgical anatomy and to investigate the existence of posterior branch motor fibers of extralaryngeal RLNs. Prospective consecutive observational study. This was a prospective cohort study of 366 patients between January 2014 and February 2016. Operative data included the type of operation, incidence of nerve bifurcation, the distances among anatomical landmarks. The motor fibers were evaluated using neurostimulation with laryngeal palpation. A total of 667 RLNs at risk were analyzed in this study, and of these 103 (14.5%) nerves were bifurcated or trifurcated before the laryngeal entry point (LEP). More extralaryngeal branched RLNs were observed on the right side than on the left (17.5% vs. 13.3%, P = .294). The mean distance of the LEP point of division was longer on the left side (16.2 ± 6.7 mm) than on the right (14.7 ± 5.9 mm, P = .132). All branched RLNs had a palpable laryngeal twitch when stimulating anterior branches. When stimulating posterior branches, 28.2%(29/103) of branched RLNs showed palpable laryngeal twitch. Overall incidence of posterior motor branch in total RLNs was 4.3% (29/667). The motor fibers of the RLN are all located in the anterior branch, whereas some posterior branches have motor function. Identification of all of the branches of the RLN may be mandatory to decrease the risk of postoperative nerve injury. 4. Laryngoscope, 127:2678-2685, 2017.

Extralaryngeal Terminal Division of the Inferior Laryngeal Nerve: Anatomical Classification by a Surgical Point of View

Background. Complete anatomic knowledge including all variations of the inferior laryngeal nerve (ILN) is mandatory for thyroid surgeon. Extralaryngeal terminal division (ETD) of the ILN has significant importance for the safety of thyroidectomy. Material and Methods. Surgical dissection of 200 ILNs was performed on 100 cases. The presence of ETD of the nerve was determined intraoperatively. We propose by a surgical point of view a regional (segmental) classification of ETD of the ILN along its cervical course. Results. ETD has been observed in 54/200 nerves (27%). Great majority are bifurcated nerves (trifurcation 2%). Four types of ETD are classified. In type 1 (arterial; 46.3%), ETD has occurred near inferior thyroid artery (ITA). In type 2 (postarterial; 31.5%), division has been found on postarterial segment. In type 3 (prelaryngeal; 11%), division has been located very close to laryngeal entry point. In type 4 (prearterial; 11%), ETD has occurred before the nerve crossing the ITA. Conclusions. ETD of the ILN is a common anatomical variation. The bifurcation occurs in the ILN at various distances from laryngeal entry point. The classification increasing surgeons' awareness may help to simplify identification and exposure of terminal branches. Preservation of both extralaryngeal terminal branches of the ILN has paramount importance for the safety of thyroid operations.

Thyroidectomy with late identification of recurrent laryngeal nerve

Thyroidectomy with late identification of recurrent laryngeal nerve

The place of radical surgical approach in the treatment of benign multinodular goitre from the aspect of the anatomical variations of the recurrent laryngeal nerve

From time to time there is a surprise at the end of surgery - even after subtotal resection - when a vocal cord is observed on indirect laryngoscopy to be non-functional. Surgeons are highly individualistic and develop their own special ways of locating and protecting the nerve. The present study has tried to clarify whether relying on palpation alone during surgery is safe enough in each case. Between 01.01.2001 and 31.12.2008, 1228 recurrent laryngeal nerve (RLN) were exposed in 702 patients on thyroid surgery. The RLN was found and traced until the laryngeal entry point in all patients. Substernal spreading was noted in 38.6% (271/702), while tracheal compression or dislocation was present in 19.5% (137/702). Recurrent thyroid disease counted for 8.4% (59/702) of all cases. Total thyroid lobectomy was carried out in 82.2% (1009/1228), near-total thyroidectomy in 15.5% (191/1228), and subtotal resection only in 2.3% (28/1228). Palpation was helpful in 80.7% (991/1228), proved false positive in 8.7% (107/1228), while in 10.6% (130/1228) it did not provide any help in the localization. The palpability of the RLN showed marked discrepancy between the two sides. False positivity was noted with palpation in 3.4% (21/625) and 14.3% (86/603) on the right and left side, respectively. On the other hand, palpation helped localization in 4.8% (29/603) on the left side, while the same figure was 16.2% (101/603) on the right side. Definitive RLN palsy was experienced in 0.8% of all cases (10/1228), whilst transient paresis was encountered in 1.4% (17/1228). Occult malignancy was noticed in 5.6% (39/702). No indication has been left for subtotal resection. Even if benign multinodular goitre is present, since the clinical and pathophysiological evidences suggest that multinodular goitre affects the entire gland, any surgery that leaves potentially abnormal thyroid tissue in situ carries a risk of recurrent disease. RLN palpatory method is a useful part of thyroid surgery but it is suitable for rough orientation only.

Surgical Anatomy of the Recurrent Laryngeal Nerves and its Clinical Applications in Chinese Adults

When removing the thyroid gland, great care must be taken to avoid damaging the recurrent laryngeal nerves (RLNs). The present study aims to present a clear picture of certain anatomical features of the RLNs in relation to the inferior thyroid artery (ITA), the tracheoesophageal groove (TE), Berry's ligament, and the inferior cornu of the thyroid cartilage in Chinese adults. We removed a collective 120 RLNs from 60 Chinese adult cadavers (52 men and 8 women), and examined their anatomic course and relationship on both sides. The right and left RLNs were found in the tracheoesophageal groove in 78.3% and 91.3% of cases, respectively. Both RLNs were found posterior to and to the right of the ITA in 80% of cases, and one was found on the left side of the ITA in 91.7%. Most of the RLNs were within 3 mm of Berry's ligament, with a laryngeal entry point about 0.8 cm below and just anterior to the inferior horn of the thyroid cartilage. The inferior cornu of the thyroid cartilage is a reliable landmark in identifying the RLNs. Racial variations between Caucasians and Chinese may explain some anatomic differences.