Recurrent Laryngeal Nerve In Thyroid Surgery Research Articles

Vagus Nerve Stimulation in the Carotid Triangle: An Effective Method for Monitoring the Recurrent Laryngeal Nerve in Thyroid and Parathyroid Surgery.

Our objective is the description of the technique of vagus nerve stimulation in carotid triangle in order to monitor the recurrent laryngeal nerve (RLN) during thyroid and parathyroid surgery. We stimulated the vagus nerve in the carotid triangle during 150 thyroid or parathyroid surgeries using a monopolar electromyography electrode inserted under the mastoid process towards the jugular foramen as a cathode, and using another subdermal electrode in the mastoid as an anode. Another complementary method of vagus stimulation was achieved with a pair of subdermal electrodes, placing the cathode at the mandibular angle and the anode at the mastoid. In all patients, compound muscle action potential (CMAP) was recorded in the vocal cords with both stimulation techniques, allowing semi-continuous monitoring to be carried out. Intraoperative lesions were detected in 16 of the cases; 9 of them were transient with CMAP recovery achieved when modifying surgical maneuvers. Vagus nerve stimulation in the carotid triangle is a reliable technique for monitoring the RLN in thyroid surgery. Vagus nerve stimulation in the carotid triangle is effective and safe for RLN monitoring, and it is a clear alternative to direct continuous stimulation of the nerve that by contrast requires its dissection in the carotid sheath.

Improving Voice Outcomes After Thyroid Surgery - Review of Safety Parameters for Using Energy-Based Devices Near the Recurrent Laryngeal Nerve.

Technological advances in thyroid surgery have rapidly increased in recent decades. Specifically, recently developed energy-based devices (EBDs) enable simultaneous dissection and sealing tissue. EBDs have many advantages in thyroid surgery, such as reduced blood loss, lower rate of post-operative hypocalcemia, and shorter operation time. However, the rate of recurrent laryngeal nerve (RLN) injury during EBD use has shown statistically inconsistent. EBDs generate high temperature that can cause iatrogenic thermal injury to the RLN by direct or indirect thermal spread. This article reviews relevant medical literatures of conventional electrocauteries and different mechanisms of current EBDs, and compares two safety parameters: safe distance and cooling time. In general, conventional electrocautery generates higher temperature and wider thermal spread range, but when applying EBDs near the RLN adequate activation distance and cooling time are still required to avoid inadvertent thermal injury. To improve voice outcomes in the quality-of-life era, surgeons should observe safety parameters and follow the standard procedures when using EBDs near the RLN in thyroid surgery

Comparison of Recurrent Laryngeal Nerve Identification Time in the Lower Central Triangle during Thyroid Surgery Using Neurophysiological Mapping and Monitoring.

Background and Objectives: Preserving the recurrent laryngeal nerve (RLN) is important in thyroid surgery. However, no standardized surgical method for locating the RLN has been established. We defined a new anatomical definition termed “lower central triangle” (LCT) for consistent identification of RLN and used intraoperative nerve monitoring (IONM) to aid in identification and dissection of RLN. Materials and Methods: Patients undergone thyroidectomy were reviewed retrospectively in Seoul National University Bundang Hospital from January to September 2017. Patients with papillary thyroid carcinoma, follicular neoplasm, and Graves’ Disease were included while right side non-RLN in arteriosus lusoria, cancer invasion, pre-existing vocal cord palsy, or under the age of 18 were excluded. RLNs were tested with IONM within LCT consisting of the lower pole as the apex and the common carotid artery as the opposite side. The samples were divided into two groups, IONM and non-IONM. Results: Forty lobes in total were included, 22 in IONM group and 18 in non-IONM group. Groups were not significantly different in age, cancer proportion, and accompanying thyroiditis while sex and nodule size differed. RLN detection time was 10.43 s shorter (p < 0.001), and confirmation time was 10.67 s shorter (p = 0.09) in IONM group than in non-IONM group. Both right and left RLNs were located predominately in the middle of LCT. No transient or permanent vocal cord palsy occurred. Conclusions: While IONM is an appropriate aid for thyroidectomy, our approach using LCT to locate the RLN is a novel definition of anatomy that provides prompt identification of the RLN in thyroid surgery.

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

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.

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.&#x0D; 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.&#x0D; 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.&#x0D; 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.&#x0D; Conclusion: Use of ZT and superior parathyroids as a landmark allows safe dissection of RLN.

Stimulating dissecting instruments during neuromonitoring of RLN in thyroid surgery.

During intraoperative neuromonitoring (IONM) of recurrent laryngeal nerve (RLN) in thyroid surgery, the need for frequent shifting between the dissecting instruments and stimulating probe is troublesome and time-consuming. Therefore, use of these two instruments in combination would be a noticeable future direction. This study aimed to investigate the feasibility and safety of using stimulating dissecting instruments (SDIs) that combine the function of surgical dissection and nerve stimulation during IONM. Prospective outcomes research. One hundred consecutive patients with 168 RLNs at risk were enrolled. We developed prototypes of SDIs and applied them to early detect adverse EMG changes during the risky phase of RLN dissection. In the case of substantial EMG change (amplitude decrease > 50%) during dissection, the surgical maneuver was paused and thyroid traction was released immediately. The application of SDIs was feasible in all cases and did not result in any morbidity. Nineteen RLNs were detected with substantial EMG change that was caused by traction stress during dissection with SDIs and that featured progressive gradual EMG recovery after releasing thyroid traction. After thyroid resection, 10 RLNs had a weak point of nerve conduction detected at region of Berry's ligament, but only one nerve with 79% amplitude reduction developed postoperative temporary vocal palsy. The application of SDIs is a simple and effective way to monitor the nerve's function instantly during the risky phase of RLN injury in thyroid surgery. It provides surgeons with real-time feedback of EMG response and can be applied as a tool for the early detection of adverse EMG change caused by traction distress. 4.

Influence of intravenous anesthetics on neuromonitoring of the recurrent laryngeal nerve during thyroid surgery

Limited reports are available in the literature on the impact of intravenous administration of anesthetics on laryngeal electromyographic (EMG) activity. The purpose of this study was to determine the influence of the two commonly used intravenous anesthetics (propofol and thiamylal) on EMG amplitude evoked from the recurrent laryngeal nerve (RLN) during thyroid surgery. A total of 40 patients were randomized to receive a bolus of propofol (0.5 mg/kg; n = 20) or thiamylal (1.5 mg/kg; n = 20) to increase anesthetic depth when the surgeon found patient movement intraoperatively. Evoked potentials were obtained before and every 1 minute after the administration of each agent for up to 5 minutes by stimulating the RLN. The magnitude of evoked potentials at each time point and hemodynamic response were compared within groups. The mean amplitude of evoked potentials did not change significantly after administration of either propofol or thiamylal (p > 0.05 within groups). Mean arterial pressure measured from 1 minute to 5 minutes was significantly lower in the propofol group than in the thiamylal group (p < 0.05). Heart rate measured within 5 minutes did not differ significantly within groups. Low dose of propofol (0.5 mg/kg) or thiamylal (1.5 mg/kg) did not affect EMG readings during neuromonitoring of the RLN in thyroid surgery. Our results show that thiamylal provides better hemodynamic stability than propofol, and is therefore a preferable agent to increase anesthesia depth and prevent further patient movement during intraoperative neuromonitoring.

A comparison between succinylcholine and rocuronium on the recovery profile of the laryngeal muscles during intraoperative neuromonitoring of the recurrent laryngeal nerve: A prospective porcine model

The use of succinylcholine and rocuronium are reportedly feasible during intraoperative neuromonitoring (IONM) of the recurrent laryngeal nerve (RLN) in thyroid surgery. This study aimed to investigate and compare the recovery profiles of succinylcholine and rocuronium on the laryngeal muscle during IONM of the RLN in a porcine model. Nine male Duroc-Landrace piglets were anesthetized with thiamylal and underwent tracheal intubation without neuromuscular blocking agents (NMBAs). Needle electrodes were inserted into the vocalis muscles through the cricothyroid ligament. The RLN was exposed and stimulated. Electromyographic (EMG) signals were obtained before and after the intravenous administration of a NMBA. The EMG amplitudes were measured before and after (at 1-minute intervals) the administration of the study drug until complete recovery. The study NMBA regimen included succinylcholine (1 mg/kg), low-dose rocuronium (0.3 mg/kg), and standard dose rocuronium (0.6 mg/kg). The maximal neuromuscular blockade and 80% recovery (i.e., duration) of the control responses were recorded and analyzed. The 80% recovery of the control response for succinylcholine (1 mg/kg) was 19.7 ± 1.5 minutes; low-dose rocuronium (0.3 mg/kg), 16.3 ± 2.5 minutes; and standard dose rocuronium (0.6 mg/kg), 29.3 ± 5.7 minutes. Succinylcholine (1 mg/kg) and low-dose rocuronium (0.3 mg/kg) had significantly shorter durations than standard dose rocuronium (0.6 mg/kg). The EMG signal recovery returned to baseline within 30 minutes in the succinylcholine and low-dose rocuronium groups, but it did not return to baseline until 1 hour after surgery in the rocuronium (0.6 mg/kg) group. In this study, succinylcholine (1 mg/kg) and low-dose rocuronium (0.3 mg/kg) had favorable recovery profiles on the laryngeal muscle. It is recommended that low-dose rocuronium may replace succinylcholine for the induction of general anesthesia during IONM of the RLN in thyroid surgery.

Significance of exposure of recurrent laryngeal nerve in the thyroid surgery

Objective To discuss the method of preventing injury of recurrent laryngeal nerve in thyroid surgery. Methods 362 cases of thyroid operation in our hospital were retrospectively studied, which consists of 188 cases with single lateral partial or total thyroidectomy, 127 with double lateral partial thyroidectomy,31 with single lateral total thyroidectomy plus isthmectomy, 16 with thyroid carcinoma radical correction. Results There was no injury,except for 3 cases damage to validate the recurrent laryngeal nerve in thyroid surgery,which were fully recov- ered after treatment. Conclusion To dissect recurrent laryngeal nerve routinely in inthyroid surgery can prevent and reduce the injury. Key words: Thyroid ectomy; Reeurrent laryngeal nerve; Injuries

Intraoperative Neuromonitoring in Thyroid Surgery

BACKGROUND: Employment of intraoperative neuromonitoring (IONM) of the recurrent laryngeal nerve (RLN) is not unusual nowadays. But up to now, no prospective beneficial studies have been available that evaluate whether the additional use of IONM is beneficial and safe in comparison with conventional thyroid surgery. METHODS: Between 1 August 1999 and 31 January 2001, surgery for benign and malignant goitre was performed on 8900 patients with 16148 nerves at risk. Twenty-eight German hospitals participated. Data were collected prospectively by a questionnaire. Employment of IONM depended on the performing surgeon and was not randomized or controlled. RESULTS: IONM was used in 95.9% (range 57.2–100%) of all thyroid operations. The use of IONM significantly decreased the early RLN palsy rate (3.3% vs. 4.9%; P = 0.04). As for the permanent RLN palsy rate, there was still an advantage gained by using IONM (0.7% vs. 0.9%); however, this difference lacked statistical significance. Overall, IONM was beneficial in high-risk procedures such as recurrent goitre, thyroid carcinoma and extended resections. Employment of the translaryngeal needle electrode of IONM has no influence on general morbidity such as haematomas or wound infections. CONCLUSIONS: The technique of IONM of the RLN in thyroid surgery is safe and decreases the overall RLN palsy rate. IONM in thyroid surgery is especially recommended in high-risk procedures such as recurrent goitre, thyroid carcinoma and extended resections.

Recurrent laryngeal nerve in thyroid surgery: a critical appraisal.

Identification and preservation of the recurrent laryngeal nerve (RLN) is of major concern in surgery of the thyroid gland. The purpose of this study was to review the surgical anatomy of the nerve and to describe its relationship to other important structures. A total of 325 patients were accrued in this prospective non-randomized study from January 1999 to December 2000. All patients who had total, subtotal and hemithyroidectomies were included in this study. Each side of the thyroid gland was considered as a separate unit in the analysis of the results. Two hundred and seventy-six patients had thyroidectomies as their primary operation, while 49 patients had them as a reoperative procedure. There were 276 women and 46 men (6:1 female to male ratio) with a mean age of 43.1 years (range: 10-84 years). The total number of dissections was 502. The RLN was clearly identified in 491 (97.8%) dissections: single trunk in 323 dissections (65.8%), two extralaryngeal branches in 164 dissections (33.4%), and three extralaryngeal branches in three dissections (0.6%). One non-recurrent laryngeal nerve was encountered (0.2%) in the series. The proximity of the RLN to the inferior thyroid artery (ITA) was noted in 444 (90.4%) dissections: 372 (83.8%) nerves were described to be posterior and intertwined between the branches of the ITA, and in 72 (16.2%) RLNs, they were observed to be anterior to the ITA. The close association of RLN to an enlarged tubercle of Zuckerkandl was documented in 381 dissections (73.7%). A total of 231 RLNs (60.8%) was seen in the tracheoesophageal groove, 18 (4.9%) nerves were observed to be lateral to the trachea, and in 109 (28.3%), they were posterior in location. Of concern in 23 (6.0%) dissections the RLN was on the anterior surface of the thyroid gland, which is at highest risk of injury before curving down to pass behind the tubercle of Zuckerkandl. It appears that the anterior course of the RLN was seen more often in the reoperative procedures to the thyroid gland (20%). Although various methods of localizing the RLN have been described, surgeons should be aware of the variations and have a thorough knowledge of normal anatomy in order to achieve a high standard of care. This will ensure the integrity and safety of the RLN in thyroid surgery. The anatomical variation may be minor in degree, but is of great importance as it may affect the outcome of the surgery and the patient's quality of life.

Intraoperative neuromonitoring of surgery for benign goiter.

Recurrent laryngeal nerve (RLN) palsy is one of the most serious complications in thyroid surgery. No prospective studies are available that evaluate if the additional use of intraoperative neuromonitoring reduces the rate of RLN palsy. Between January 1 and December 31, 1998, surgery for histologically benign goiter with intraoperative identification with and without additional intraoperative RLN neuromonitoring was performed on 4,382 patients in 45 hospitals. Data were collected prospectively by questionnaire. The rate of transient and permanent RLN palsy based on nerves at risk were 1.4% and 0.4% with intraoperative neuromonitoring. These rates were significantly lower (P <0.05) compared with intraoperative visual RLN identification without intraoperative neuromonitoring which resulted in rates of 2.1% and 0.8%, respectively. A multivariate logistic regression analysis confirmed that the use of intraoperative neuromonitoring decreases the rate of postoperative transient (P <0.008) and permanent (P <0.004) RLN palsies as an independent factor by 0.58 and 0.30, respectively. Intraoperative neuromonitoring of the RLN in thyroid surgery is recommended because of significantly lower rates of transient and permanent RLN palsy rates in comparison with conventional RLN identification.

Suspensory ligament of Berry: its relationship to recurrent laryngeal nerve and anatomic examination of 24 autopsies.

It is important to clarify the relationship between the recurrent laryngeal nerve (RLN) and the ligament of Berry to prevent damage to the RLN in thyroid surgery. The purpose of the present paper is to identify this relationship to prevent surgical complications. Among the 486 thyroid surgery cases, 689 RLNs were identified and their course detected. Topography of the laryngotracheoesophageal region and the histology of the ligament of Berry were studied in detail in 25 autopsied cadavers. All nerves identified by surgery and autopsy were located laterodorsally to the ligament of Berry. They were clearly separated, and no nerve penetrated the ligament nor was medially located to it. The ligament of Berry strongly connected the thyroid gland to the trachea and was identified as a whitish connective tissue band. No paralysis of the RLN occurred during identification of the nerve during surgery. It was confirmed that the RLN never penetrates the ligament of Berry but is located laterally to it. From these topographic findings, no injury to the RLN will occur from a separation close to the goiter in thyroid surgery.