The relation of recurrent laryngeal nerve to inferior thyroid artery and extralaryngeal nerve branching may increase the risk of vocal cord paralysis in thyroidectomy.

PURPOSE: The anatomical variations of the recurrent laryngeal nerve (RLN) are common during thyroidectomy. We aimed to evaluate the risk of RLN paralysis in case of its anatomical variations, retrospectively. METHODS: The patients with primary thyroidectomy between January 2016 and December 2019 were enrolled. The effect of age, gender, surgical intervention, neuromonitorisation type, central neck dissection, postoperative diagnosis, neck side, extralaryngeal branching, non-RLN, relation of RLN to inferior thyroid artery (ITA), grade of Zuckerkandl tubercle on vocal cord paralysis (VCP) were investigated. RESULTS: This study enrolled 1070 neck sides. The extralaryngeal branching rate was 35.5%. 45.9% of RLNs were anterior and 44.5% were posterior to the ITA, and 9.6% were crossing between the branches of the ITA. The rate of total VCP was 4.8% (transient:4.5%, permanent: 0.3%). The rates of total and transient VCP were significantly higher in extralaryngeal branching nerves compared to nonbranching nerves (6.8% vs. 3.6%, p = 0.018; 6.8% vs. 3.2%, p = 0.006, respectively). Total VCP rates were 7.2%, 2.5%, and 2.9% in case of the RLN crossing anterior, posterior and between the branches of ITA, respectively (p = 0.003). The difference was also significant regarding the transient VCP rates (p = 0.004). Anterior crossing pattern increased the total and transient VCP rates 2.8 and 2.9 times, respectively. CONCLUSION: RLN crossing ITA anteriorly and RLN branching are frequent anatomical variations increasing the risk of VCP in thyroidectomy that cannot be predicted preoperatively. This study is the first one reporting that the relationship between RLN and ITA increased the risk of VCP.

Condition of Adrenergic Innervation Apparatus of the Thyroid Gland, Blood and Lymph Vessels, and Lymph Nodes during Correction of Hypothyrosis.

We used specific histochemical fluorescence-microscopic method of visualization of catecholamines to study adrenergic innervation of the thyroid gland tissue, blood vessels of the thyroid gland, cervical lymphatic vessel and lymph nodes in rats during correction of hypothyroidism with a bioactive formulation (Vozrozhdenie Plus balm with Potentilla alba L.). In experimental hypothyroidism, adrenergic innervation of the thyroid gland and the wall of the cervical lymph node, concentrated mainly along the arterial vessels and the cervical lymphatic vessel, retained its structural formations (plexuses and varicosities), but diffusion of catecholamines outside these formations was observed. Correction with the bioactive formulation restored of the contours of the nerve plexuses and varicosities and their brighter fluorescence in the thyroid gland and cervical lymphatic vessel and node. During correction of hypothyroidism with the bioactive formulation, reorganization of regional lymphatic vessels and nodes was more pronounced than reorganization of the thyroid gland.

Recurrent Laryngeal Nerve Injury After Thyroid Surgery: An Analysis of 11,370 Patients.

BACKGROUND: Recurrent laryngeal nerve (RLN) injury is a well-known, potentially serious complication of thyroid surgery. We investigated factors associated with RLN injury during thyroid surgery using a multi-institutional data set. MATERIALS AND METHODS: Patients who underwent either lobectomy or total thyroidectomy were abstracted from the American College of Surgeons National Surgical Quality Improvement Program thyroidectomy-specific database (2016-2017). Baseline and operative factors associated with RLN injury ≤30 d of surgery were analyzed using bivariate and multivariate methods. Secondary complications of interest included unplanned reintubation and hypocalcemia. RESULTS: RLN injury occurred in 6.0% (n = 677) of the 11,370 patients included in the study. The RLN injury rate varied significantly based on the primary indication for surgery, from 4.3% in patients undergoing surgery for a single nodule to 9.0% in patients undergoing surgery for differentiated cancer (P < 0.01). RLN injury occurred more often in thyroidectomies than lobectomies (6.9% versus 4.3%, P < 0.01) and in surgeries without intraoperative nerve monitoring (6.5% versus 5.6%, P = 0.01). After multivariate adjustment, RLN injury was independently associated with age ≥65 y [odds ratio (OR) 1.6, 95% confidence interval (CI) 1.3-2.0], total thyroidectomy (OR = 1.4, 95% CI 1.1-1.6), and diagnosis of thyroid malignancy (OR = 2.1, 95% CI = 1.6-2.7) (all P < 0.001) but not intraoperative RLN monitoring (OR = 0.9, 95% CI = 0.7-1.0, P = 0.06). CONCLUSIONS: In this large multi-institutional study, RLN injury ≤30 d of surgery occurred in nearly 6% of thyroid surgeries. This comprehensive analysis of RLN injury can be used to guide informed consent discussions and aid surgeons in identifying candidates who may be at higher risk for injury.

Association Between Recurrent Laryngeal Nerve Calibre and Body Figure: A Preoperative Tool to Assess Thin-Diameter Nerves in Thyroidectomy.

Inadvertent recurrent laryngeal nerve (RLN) injury is a major complication of thyroidectomy. This study aimed to investigate the association between preoperative clinical parameters and RLN size prediction. Total thyroidectomy and thyroid lobectomy data were collected between January 2014 and April 2017. Routine identification of the recurrent laryngeal nerves was performed, while intraoperative findings (nerve diameter, thyroid gland weight, intraoperative neuromonitoring (IONM) use, and signal recording) and demographic data were collected for analysis. A total of 848 patients with 1357 RLNs at risk were enrolled in this study. RLN diameter was thinner in females, those with body height <160 cm, and those with a BMI <25 (all p < 0.001). RLN diameter was directly proportional to age, body weight, height, and BMI. RLN diameter was thinner (1.71 mm vs. 1.55 mm, p = 0.039) and branched nerve incidence was higher (18.5% vs. 29.7%, p = 0.09) in the postoperative RLN injury group. Branched nerves were more frequently encountered in female patients (female vs. male: 28.8% vs. 18.7%, p = 0.004). The risk of RLN palsy in intraoperative IONM loss patients was 27 times higher compared to that in IONM normal patients (1.55% vs. 30%, p < 0.001). Thinner nerves did not yield a higher rate of IONM signal loss. Thinner nerves and higher palsy rates could be anticipated in females, younger age groups, those with shorter stature, and those with low BMI. RLN diameter was not associated with the rate of IONM signal loss.

Anatomical variation in the right non-recurrent laryngeal nerve reported from studies using pre-operative arterial imaging.

The right non-recurrent (inferior) laryngeal nerve (NRLN) is a rare anatomical variant associated with an arterial anomaly, the aberrant right subclavian artery (ARSA), that is detectable by pre-operative imaging (POI) using computed tomography and/or ultrasound. Most surgical studies have utilized two major types, NRLNs arising near the upper pole of the thyroid gland (type 1), vs. at a lower level (type 2) but with two subtypes defined by relationships to the inferior thyroid artery (ITA). This review found 8 English language surgical studies using POI that reported at least 1 NRLN and had anatomical information; of the 88 right NRLNs, 69.3% were classified as type 2 and 30.7% as type 1. Meta-analysis yielded a weighted proportion of 74.0% for type 2, but with substantial heterogeneity. For a subgroup of 5 POI studies with information on subtypes, 22 (59.5%) of 37 type 2 nerves were type 2a (i.e., running at or above the ITA). Similarly, a separate review of large surgical series without POI found that 60.4% of all 91 type 2 NRLNs were type 2a. The study findings should be relevant to the increasing numbers of anterior neck surgeries including bilateral thyroidectomies. A need was identified for studies on inter-observer reliability (agreement) among surgeons on NRLN types, and on injury rates (and related symptoms) by the type of NRLN.

Adrenergic Innervation of the thyroid Gland, Blood and Lymph Vessels, and Lymph Nodes in Hypothyroidism.

Adrenergic innervation in the tissue of the thyroid gland, blood vessels of the thyroid gland, cervical lymphatic vessel, and lymph nodes in rats with hypothyroidism was studied by using a specific histochemical fluorescent-microscopic method of visualization of catecholamines. The presence of adrenergic innervation in the blood and lymph vessels and nodes was demonstrated. In hypothyroidism, diffusion of norepinephrine from nerve fibers and varicose thickenings was observed in the wall of the upper and lower thyroid arteries and adjacent cervical lymphatic vessels and nodes.

Correlation analyses of thyroid-stimulating hormone and thyroid autoantibodies with differentiated thyroid cancer.

PURPOSE: To investigate the feasibilities and clinical values of thyroid-stimulating hormone (TSH) and thyroid autoantibodies in predicting differentiated thyroid cancer (DTC). METHODS: 500 patients with thyroid nodules who underwent surgery for the first time in our hospital from January 2014 to December 2016 were selected, including 250 patients definitely diagnosed pathologically with DTC and 250 patients definitely diagnosed with benign thyroid nodules after operation. Serum thyroglobulin antibody (TgAb), thyroid peroxidase antibody (TPOAb) and TSH levels before operation were evaluated in both groups. According to the reference ranges of TgAb and TPOAb, they were divided into negative and positive groups. According to the TSH reference range, they were divided into decreased, normal and increased groups. Statistical analyses were conducted, respectively. RESULTS: The serum TgAb level in the DTC group was significantly increased compared with that in benign thyroid nodule group (p=0.01). The positive rate of TgAb in DTC group was also significantly higher than that in benign thyroid nodule group (p<0.01). The level of serum TPOAb in the DTC group was not significantly different from that in the benign thyroid nodule group (p=0.25). The level of serum TSH in the DTC group was significantly increased compared with that in the benign thyroid nodule group (p<0.01). There was a statistically significant difference in the comparison of the distribution of TSH between the DTC group and benign thyroid nodule group (p<0.01). Univariate analysis showed that TgAb and TSH were correlated with DTC. Multivariate logistic regression analysis results showed that serum positive TgAb and increased TSH wre significantly correlated with DTC. TSH level in DTC with cervical lymph node metastasis group was significantly increased compared with DTC without such metastasis group (p<0.01). CONCLUSIONS: Increased levels of serum TgAb and TSH may be risk factors for DTC. Whether the two indicators can be used as predictors of DTC screening needs to be confirmed in large-sample prospective trials. Increased serum TSH level is closely related to DTC with cervical lymph node metastasis.

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 (1 mA) of this branch led to a recordable contraction of the cricothyroid muscle with a mean latency of 1.42 ± 0.66 ms on the right side and 1.43 ± 0.61 ms 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.

Sympathetic Nerve Injury in Thyroid Cancer.

The double innervation of the thyroid comes from the sympathetic and parasympathetic nervous system. Injury rates during surgery are at 30% but can be minimized by upwardly preparing the thyroid vessels at the level of thyroid capsule. Several factors have been accused of increasing the risk of injury including age and tumor size. Our aim was to investigate of there is indeed any possible correlations between these factors and a possible increase in injury rates following thyroidectomy. Seven studies were included in the meta-analysis. Statistical correlation was observed for a positive relationship between injury of the sympathetic nerve and thyroid malignancy surgery (p 2 = 74%) No statistical correlations were observed for a negative or positive relationship between injury of the sympathetic nerve and tumor size. There was also no statistically significant value observed for the correlation of the patients' age with the risk of sympathetic nerve injury (p = 0.388). Lack of significant correlation reported could be due to the small number of studies and great heterogeneity between them.

[Transoral approach to thyroid gland in the experiment]. / Transoral'nyi dostup k shchitovidnoi zheleze v eksperimente (s kommentariem P.S. Vetsheva).

AIM: To develop minimally invasive and safe endoscopic access to thyroid gland. MATERIAL AND METHODS: Transoral pre-mandibular video-assisted gas-free access to thyroid gland was developed in experimental study that included 19 human cadavers. Stereometric modeling defined the evaluation criteria including the form of basal arch of lower jaw and its height. There was no conflict of instruments in working chamber under platysma. Additional trocar was deployed to resolve the conflict between working parts of instruments during thyroid gland mobilization. The angle of operative action between the instruments is close to 90°. Trocar hole is used for drainage. RESULTS: The access provides good visualization of recurrent laryngeal nerve, upper and lower thyroid arteries and parathyroid gland. It is less traumatic compared with other extra-cervical accesses to thyroid glands.

The thyroid foramen: a systematic review and surgical considerations.

This study presents an analytic review about the trait of the thyroid foramen. A detailed description about the demographics, frequency, embryology, morphometry, possible content, topography, clinical and surgical considerations is provided. The overall frequency was 28.3% in adults, 15% in children and neonates, 40.6% in embryos and fetuses. The content of the thyroid foramina was a neurovascular bundle in 41.2% of studies. An equal number of studies define a nerve as the common content, while only in 17.6% the usual content was a vessel. Interestingly, in 11.8% the content was just connective tissue or a pit. An updated classification is presented taking into account all the possible content that can cross through a thyroid foramen. The variant is of high interest for surgeons intervening in the larynx due to potential complications such as local bleeding and unwanted neural impairment. The oblique line of the thyroid lamina acts as the best topographical landmark to identify any aberrant anatomy related to a thyroid foramen.

[Nervous regulation of thyroid function].

Review examines the autonomic regulation of thyroid function. Review examines the issues of autonomic regulation of the thyroid gland. Activation of the central a-adrenergic mechanisms increases the release of thyroid-stimulating hormone of pituitary mainly due to the stimulation of its secretion. Dopamine inhibits the secretion of this hormone, acting on D2-receptors tireotropotsitov. Acetylcholine and other cholinomimetics inhibit the functional activity of thyrocitebl with the participation of muscarinic receptors. Along the sympathetic and parasympathetic special attention paid to the role of the serotonergic division of vegetative system. Serotonin can inhibit the secretion of thyrotropin by the pituitary gland, but has a direct stimulatory effect on thyrocytes. This stimulatory effect is mediated by the serotonin 5-HT2 receptors. In hypothyroidism synthesis and metabolism of serotonin in the brain are slowed down. Depression is accompanied by inhibition of the enzyme activity deiodinase type 2, thereby reducing the concentration of serotonin. Activation of 5-HTI receptor lead to increased levels of intracellular calcium, causing inhibition of the promoter of calcitonin gene-associated peptide.

Administration of neostigmine after tracheal intubation shortens time to successful intraoperative neuromonitoring during thyroid surgery: a randomized controlled trial.

This prospective, randomized controlled trial evaluated the effect of neostigmine for intraoperative neuromonitoring (IONM) during thyroid surgery. Forty subjects undergoing thyroidectomy with IONM, randomized into neostigmine administration after tracheal intubation (Group N, n = 20) or control treatment with normal saline (Group C, n = 20), completed the trial. Electromyography amplitudes of the vagus nerve (V1) were recorded before thyroid dissection. The time from the initial V1 signal check to successful V1 stimulation was recorded. In Group N, all the patients had a successful V1 signal at the first check, whereas ten (50%) patients in Group C had a time delay between the initial V1 check and successful V1 (p < 0.001). The mean delay time among the delayed patients in Group C was 11.2 ± 1.4 min. The mean time from skin incision to successful V1 stimulation was significantly shorter in Group N than in Group C (15.4 ± 2.4 min vs. 19.9 ± 5.7 min, p = 0.003). In Groups N and C, the mean V1 amplitudes were 962.2 ± 434.5 µV vs. 802.3 ± 382.7 µV (p = 0.225), respectively, and the mean R1 amplitudes were 1240.0 ± 836.5 µV vs. 1023.4 ± 455.8 µV (p = 0.316), respectively. There was one bucking event in Group N. In conclusion, neostigmine administration immediately after tracheal intubation can be useful to reverse neuromuscular blockade for successful IONM in thyroid surgeries.

Thyroidectomy in Australia 2022: lessons from 21,000 consecutive cases.

In this article, we aim to describe our modern-day approach to total thyroidectomy, detailing the subtle refinements of our technique, as it has evolved over three decades and 21 000 cases. Since Delbridge's seminal paper in 2003, the major changes to our approach include a retrograde approach to the recurrent laryngeal nerve that allows dissection of the distal RLN from fascial bands within the ligament of Berry before medialisation of the thyroid lobe. Routine use of intraoperative nerve monitoring systems has increased our awareness of temporary neuropraxia, facilitated a reduction in the risk of bilateral RLN palsy and improved our identification and preservation of the external branch of the superior laryngeal nerve. The increasing use of advanced energy devices has been associated with a reduction in post-operative haematoma rates. We adopt a low threshold to parathyroid auto-transplantation, unless all glands are assessed to be clearly not at risk, and routinely supplement patients with Caltrate in the immediate post-operative period to minimize the risk of symptomatic hypocalcaemia. Ultimately, when we reflect on the subtle refinements that have contributed to improved outcomes, the fundamental principles of exposure and dissection that have evolved over decades remain the basis of our surgical approach and must continue to do so.

Intraoperative trans-laryngeal ultrasound (LUSG) of the vocal cord is a novel method of confirming the recurrent laryngeal nerve (RLN) integrity during thyroid and neck surgery.

BACKGROUND: Eliciting a normal electromyography signal has been the usual method to confirm the functional integrity of the recurrent laryngeal nerve during intraoperative nerve monitoring. Given that oscillations of the vocal cord can be detected with trans-laryngeal ultrasound when the ipsilateral recurrent laryngeal nerve is stimulated with the endotracheal tube in situ, we aimed to compare the accuracy and cost of this novel method with the conventional electromyography method. METHODS: Consecutive patients who underwent elective thyroid, parathyroid or neck dissection procedures were included. The NIM-Neuro 3.0 system was used. Endotracheal tube-based surface electrodes were utilized for electromyography signal recording. Standard anesthetic technique was adopted. Recurrent laryngeal nerve integrity was verified by both detection methods (laryngeal ultrasound and electromyography) independently. Vocal cord function was validated by flexible direct laryngoscopy postoperatively. For each method, concurrence with flexible direct laryngoscopy was defined as "true-positive" or "true-negative," based on the presence or absence of vocal cord paresis. Accuracy was calculated as the sum of all true positives and negatives divided by the total of nerves-at-risk. The cost of each method was calculated. RESULTS: One hundred and four patients were eligible. Total number of nerves-at-risk was 155. Based on flexible direct laryngoscopy findings, the test sensitivity, specificity, positive predictive value, and negative predictive value of intraoperative laryngeal ultrasound were 75.0%, 99.3%, 85.7%, and 98.6%, respectively, while those of electromyography were 87.5%, 98.0%, 70.0%, and 99.3%, respectively. The prognostic accuracy in laryngeal ultrasound versus electromyography was comparable (98.1% vs 97.4%). The cost of the laryngeal ultrasound per operation was less than electromyography ($82 vs $454). CONCLUSION: Laryngeal ultrasound has a similar detection accuracy to electromyography during intraoperative nerve monitoring. Apart from being a cheaper alternative, laryngeal ultrasound may be useful when there is unexplained loss of electromyography signals during surgery and may play a role in the intraoperative nerve monitoring troubleshooting algorithm.

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.

Intraoperative nerve monitoring is associated with a lower risk of recurrent laryngeal nerve injury: A national analysis of 17,610 patients.

BACKGROUND: Based on current evidence, the benefit of intraoperative nerve monitoring (IONM) in thyroid surgery is equivocal. METHODS: All patients who underwent planned thyroid surgery in the 2016-2018 ACS NSQIP procedure-targeted thyroidectomy dataset were included. Multivariable regression analyses were performed to examine the association between nerve monitoring and recurrent laryngeal nerve (RLN) injury while adjusting for patient demographics, extent of surgery, and perioperative variables. RESULTS: In total, 17,610 patients met inclusion criteria: 77.8% were female, and the median age was 52 years. IONM was used in 63.9% of cases. Of the entire cohort, 6.1% experienced RLN injury. Cases with IONM use had a lower rate of RLN injury compared to those that did not use IONM (5.7% vs. 6.8%, p = 0.0001). After adjustment, IONM was associated with reduced risk of RLN injury (OR 0.69, 95% CI 0.59-0.82, p < 0.0001). CONCLUSIONS: Nationally, IONM is used in nearly two thirds of thyroid surgeries. IONM is associated with a lower risk of recurrent laryngeal nerve injury.

New operative surgical concept of two fascial layers enveloping the recurrent laryngeal nerve.

BACKGROUND: Avoiding recurrent laryngeal nerve (RLN) injury is aided by a precise anatomical understanding of the RLN before entry into the larynx where it is at greatest risk. METHODS: A literature review and study of 977 RLNs at operation have been used to describe the last 2 cm of the anatomical course of the extralaryngeal RLN. RESULTS: The tertiary branches of the inferior thyroid artery pass in a superficial vascular fascial layer anterolateral to the RLN. The tubercle of Zuckerkandl and the superior parathyroid glands lie within this superficial vascular fascial covering layer. The RLN lies on a deeper layer of more fibrous tissue, the ligament of Berry. In all 977 RLNs, the RLN was sandwiched between an anterolateral vascular layer and a medial layer, the ligament of Berry. CONCLUSIONS: The site of greatest risk during thyroidectomy to the RLN is in the 2-cm course of the extralaryngeal nerve above the trunk of the inferior thyroid artery where tension forms an artificial genu of the nerve. Once the superficial vascular fascial and Berry's ligament layers are released, the nerve falls back into the tracheoesophageal groove and adopts a serpiginous appearance, indicating completeness of the dissection of the lobe from the lateral trachea and division of the ligament of Berry.