Recurrent laryngeal nerve management in thyroid surgery: consequences of routine visualization, application of intermittent, standardized and continuous nerve monitoring

Intraoperative neuromonitoring during thyroidectomy does not decrease vocal cord palsy risk, but the cumulative experience of the surgeon may

PURPOSE

To evaluate the influence of intraoperative neuromonitoring (IONM) on vocal cord palsy (VCP) rates and assess the temporal trends in VCP rates.

METHODS

The subjects of this retrospective study were patients who underwent thyroidectomy for thyroid cancer between March, 2014 and June, 2022, at a university hospital in Korea. We compared VCP rates between the non-IONM and IONM groups and analyzed the risk factors for VCP and VCP rates over time.

RESULTS

A total of 712 patients were included in the analysis. The rates of transient and permanent VCP did not differ significantly between the non-IONM and IONM groups. Transient VCP occurred in 4.6% and 4.3% patients (p = 0.878) and VCP was permanent in 0.7% and 0.4% patients (p = 0.607) in the non-IONM and IONM groups, respectively. Among the nerves at risk, transient damage occurred in 2.8% and 3.0% patients (p = 0.901), and permanent damage occurred in 0.4% and 0.3% (p = 0.688), respectively. Multivariate analysis revealed no significant risk factors for VCP. There was a significant decreasing trend in VCP rates over time as the cumulative number of cases increased (p = 0.017).

CONCLUSIONS

IONM did not reduce the risk of VCP significantly. However, the declining trend of VCP rates suggests that the surgeon's experience may mitigate VCP risk.

Does the Use of Intraoperative Neuromonitoring during Thyroid and Parathyroid Surgery Reduce the Incidence of Recurrent Laryngeal Nerve Injuries? A Systematic Review and Meta-Analysis

Injury to the recurrent laryngeal nerve (RLN) can be a devastating complication of thyroid and parathyroid surgery. Intraoperative neuromonitoring (IONM) has been proposed as a method to reduce the number of RLN injuries but the data are inconsistent. We performed a meta-analysis to critically assess the data. After applying inclusion and exclusion criteria, 60 studies, including five randomized trials and eight non-randomized prospective trials, were included. A meta-analysis of all studies demonstrated an odds ratio (OR) of 0.66 (95% CI [0.56, 0.79], p < 0.00001) favoring IONM compared to the visual identification of the RLN in limiting permanent RLN injuries. A meta-analysis of studies employing contemporaneous controls and routine postoperative laryngoscopy to diagnose RLN injuries (considered to be the most reliable design) demonstrated an OR of 0.69 (95% CI [0.56, 0.84], p = 0.0003), favoring IONM. Strong consideration should be given to employing IONM when performing thyroid and parathyroid surgery.

A Prospective Study of Electromyographic Amplitude Changes During Intraoperative Neural Monitoring for Open Thyroidectomy

BACKGROUND

Intraoperative nerve monitoring (IONM) of the vagus and recurrent laryngeal nerve (RLN) enables prediction of postoperative nerve function. The underlying mechanism for loss of signal (LOS) in a visually intact nerve is poorly understood. The correlation of intraoperative electromyographic amplitude changes (EMG) with surgical manoeuvres could help identify mechanisms of LOS during conventional thyroidectomy.

METHODS

A prospective study of consecutive patients undergoing thyroidectomy was performed with intermittent IONM using the NIM Vital nerve monitoring system. The ipsilateral vagus and RLN was stimulated, and vagus nerve signal amplitude recorded at five time points during thyroidectomy (baseline, after mobilisation of superior pole, medialisation of the thyroid lobe, before release at Ligament of Berry, end of case). RLN signal amplitude was recorded at two time points; after medialisation of the thyroid lobe (R1), and end of case (R2).

RESULTS

A total of 100 consecutive patients undergoing thyroidectomy were studied with 126 RLN at risk. The overall rate of LOS was 4.0%. Cases without LOS demonstrated a highly significant vagus nerve median percentage amplitude drop at medialisation of the thyroid lobe (- 17.9 ± 53.1%, P < 0.001), and end of case (- 16.0 ± 47.2%, P < 0.001) compared to baseline. RLN had no significant amplitude drop at R2 compared to R1 (P = 0.207).

CONCLUSIONS

A significant reduction in vagus nerve EMG amplitude at medialisation of the thyroid and the end of case compared to baseline indicates that stretch injury or traction forces during thyroid mobilisation are the most likely mechanism of RLN impairment during conventional thyroidectomy.

Effects of Intraoperative Nerve Monitoring Techniques on Voice and Swallowing Disorders after Uncomplicated Thyroidectomy: Preliminary Report of a Bi-Institutional Prospective Study

Background: Voice and swallowing problems are frequently associated with thyroidectomy. Intermittent nerve monitoring (i-IONM) seems to provide a positive effect in reducing its prevalence. The aim of this study was to test the hypothesis that continuous intraoperative nerve monitoring (c-IONM) may reduce the prevalence of these disorders even further than i-IONM. Methods: This 3-arm prospective bi-institutional study compared 179 consecutive patients that underwent thyroidectomy: 56 without IONM, 55 with i-IONM and 67 with c-IONM. Neck dissections and laryngeal nerve palsies were excluded. Two questionnaires (VHI-10 for voice disorders and EAT-10 for swallowing disorders; both validated for Italian language use) were administered before and 1 month after surgery. Statistical significance was analyzed by the chi-squared test. Results: After thyroidectomy, no statistically significant differences were found in the three groups concerning EAT-10. although these symptoms seemed to be influenced by gastro-esophageal reflux. VHI-10 worsened in the “no-IONM” group compared with both i-IONM (p < 0.09, not quite statistically significant) and c-IONM (p < 0.04). Conclusion: Both i- and c-IONM improve voice quality independently of laryngeal nerve integrity. Reduced dissection and particularly restrained manipulation could explain these results, being particularly favorable for c-IONM.

Surgical tips and techniques to avoid complications of thyroid surgery

Objectives

Surgery of the thyroid takes place in a body part with complicated anatomy and several vital physiologic functions. Thyroidectomy is rarely associated with mortality but can be followed by significant complications, (i.e. hypoparathyroidism, hemorrhage, upper airway obstruction, laryngeal nerve injuries and thyrotoxic storm). This review aims to indicate surgical tips and techniques to sustain a low level of complications.

Content

MEDLINE database (PubMed) platform was used as a search engine and the articles related to the topic were selected using the keywords combination "thyroid surgery and complications".

Summary and Outlook

The most common complication of total thyroidectomy with an occurrence ranging between 0.5 and 65% is hypoparathyroidism. Damage to recurrent laryngeal nerves can be temporary or permanent, unilateral or bilateral; bilateral lesion is associated with severe episodes of breathlessness. Thus, intraoperative monitoring of nerve function is essential to prevent damage. Ιn addition, hematoma formation can lead to breathing difficulties due to airway obstruction; preventive hemostasis during surgery is essential. The surgeon must have a complete anatomical understanding of not only the normal anatomy of the central visceral compartment of the neck, but also the common variations of the laryngeal nerves and parathyroid glands in order to keep the complication rate at a very low level.

Anatomy and motor function of extra-laryngeal branching patterns of the recurrent laryngeal nerve; an electrophysiological study of 1001 nerves at risk

INTRODUCTION

Safe thyroid surgery depends on a deep knowledge of human neck anatomy, including the recurrent laryngeal nerve (RLN). Anatomic variations such as extra-laryngeal terminal branching (ETB) are common.

PATIENTS AND METHODS

We studied the ETB pattern of 1001 RLNs at risk in 596 patients. We identified and exposed the location of division points on the cervical part of bifid RLN. The function of nerve branches was assessed through intraoperative nerve monitoring (IONM).

RESULTS

Bifid RLNs was identified in 39.6% of patients. The nerve-based prevalence of ETB was 28.5%. The prevalence of ETB for the right and left RLN was 21.8% and 35.5%, respectively (p < 0.001). The location of the division point was found in the middle, distal, and proximal segments in 48.8%, 33.3%, and 18% of bifid RLNs, respectively. Electrophysiological monitoring revealed motor functions in all anterior and in 7% of posterior branches. The rate of injury was 0.4%, and 1.1% in single trunk and bifid nerves, respectively (p = 0.360), and 3.9% in nerves with proximal branching (p = 0.084).

CONCLUSIONS

The ETB prevalence is high and showing division points in different cervical segments of the RLN. All anterior branches and some posterior branches contain motor fibers. Knowledge and awareness of these anatomic and functional variations are mandatory for every thyroid surgeon to avoid misidentification and misinterpretation of human RLN anatomy.

Time to Revisit a Low-Cost Alternative? Palpation Assessment Nerve Monitoring (PANM) for Recurrent Laryngeal Nerve to Predict Postoperative Vocal Cord Function-a Validation Study Using an In-House Neuromonitoring Device

Neuromonitoring has proved to be a useful technique in reducing nerve injury during thyroid surgery; however, costs continue to limit its use in resource-constrained settings. This study was done to assess the functional integrity of the recurrent laryngeal nerve (RLN) during thyroid surgery using palpation assessment of posterior cricoarytenoid muscle twitch in response to RLN stimulation. Between August 2016 and July 2017, 24 patients with 47 nerves at risk (NARs) underwent thyroid surgery with visual identification and testing of 44 RLNs. The functional integrity of the RLN was checked by stimulation of the RLN. Intraoperative assessment showed 100% sensitivity and positive predictive value in predicting postoperative vocal cord function. The postoperative vocal cord assessment confirmed all 44 nerves tested to be normally functioning. The mean (standard deviation) peak-to-peak amplitude and latency of the CMAP were 0.889 (0.740)/1.336 (1.660) mV and 2.295 (0.319)/2.217 (0.393) ms for left/right side NARs, respectively, with no statistically significant difference (P > 0.05). Palpation assessment of the posterior cricoarytenoid muscle provides a simple and reliable technique for confirming integrity of the RLN. Combining palpation assessment with CMAP from the inferior constrictor muscle may help reduce potential false negative results. With the use of our in-house built device which is significantly cheaper than the commercial ones, this could be considered a low-cost alternative to current established techniques.

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.

Anatomical, Functional, and Dynamic Evidences Obtained by Intraoperative Neuromonitoring Improving the Standards of Thyroidectomy

The use of intraoperative neuromonitoring (IONM) is getting more common in thyroidectomy. The data obtained by the usage of IONM regarding the laryngeal nerves’ anatomy and function have provided important contributions for improving the standards of the thyroidectomy. These evidences obtained through IONM increase the rate of detection and visual identification of recurrent laryngeal nerve (RLN) as well as the detection rate of extralaryngeal branches which are the most common anatomic variations of RLN. IONM helps early identification and preservation of the non-recurrent laryngeal nerve. Crucial knowledge has been acquired regarding the complex innervation pattern of the larynx. Extralaryngeal branches of the RLN may contribute to the motor innervation of the cricothyroid muscle (CTM). Anterior branch of the extralaryngeal branching RLN has always motor function and gives motor branches both to the abductor and adductor muscles. In addition, up to 18% of posterior branches may have adductor and/or abductor motor fibers. In 70–80% of cases, external branch of superior laryngeal nerve (EBSLN) provides motor innervation to the anterior 1/3 of the thyroarytenoid muscle which is the main adductor of the vocal cord through the human communicating nerve. Furthermore, approximately 1/3 of the cases, EBSLN may contribute to the innervation of posterior cricoarytenoid muscle which is the main abductor of ipsilateral vocal cord. RLN and/or EBSLN together with pharyngeal plexus usually contribute to the motor innervation of cricopharyngeal muscle that is the main component of upper esophageal sphincter. Traction trauma is the most common reason of RLN injuries and constitutes of 67–93% of cases. More than 50% of EBSLN injuries are caused by nerve transection. A specific point of injury on RLN can be detected in Type 1 (segmental) injury, however, Type 2 (global) injury is the loss of signal (LOS) throughout ipsilateral vagus-RLN axis and there is no electrophysiologically detectable point of injury. Vocal cord paralysis (VCP) develops in 70–80% of cases when LOS persists or incomplete recovery of signal occurs after waiting for 20 min. In case of complete recovery of signal, VCP is not expected. VCP is temporary in patients with incomplete recovery of signal and permanent VCP is not anticipated. Visual changes may be seen in only 15% of RLN injuries, on the other hand, IONM detects 100% of RLN injuries. IONM can prevent bilateral VCP. Continuous IONM (C-IONM) is a method in which functional integrity of vagus-RLN axis is evaluated in real time and C-IONM is superior to intermittent IONM (I-IONM). During upper pole dissection, IONM makes significant contributions to the visual and functional identification of EBSLN. Routine use of IONM may minimalize the risk of nerve injury. Reduction of amplitude more than 50% on CTM is related with poor voice outcome.

Introducing routine intraoperative nerve monitoring in a high-volume endocrine surgery centre: a health technology assessment

We sought to analyse the effect of the introduction of intraoperative nerve monitoring (IONM) in our routine surgical practice and to provide a circumstantial analysis of direct costs of IONM in total thyroidectomy and of indirect costs associated with vocal fold palsy, as centred in the health care system of Italy. We retrospectively compared outcomes of 232 total thyroidectomies performed between November 2017 and October 2019, respectively, before (109 TT-Group A) and after (123 TT-Group B) adopting IONM technology in November 2018. We analysed the costs of IONM per procedure and rate and costs of vocal fold palsy events (temporary and permanent). Overall, there were 61 thyroid cancers (32 in Group B) and 171 multinodular goitres (91 in Group B). We recorded 5 cases of vocal fold palsy (4.6%-4 transient, 1 permanent) in Group A and none in Group B (p = 0.016). IONM consumables cost 219 eur per case. Healthcare and social cost of Vocal fold palsy ranged between 3200 eur (function recovery < 1 month postoperatively) and over 32,000 eur (permanent event). When only direct costs are considered, IONM can hardly be cost effective. In this study, cost of IONM implementation was offset by the absence of complications attributable to recurrent laryngeal nerve dysfunction.

Superiority of continuous over intermittent intraoperative nerve monitoring in preventing vocal cord palsy

BACKGROUND

Continuous intraoperative nerve stimulation (IONM) with uninterrupted monitoring is likely better than intermittent IONM in preventing vocal cord palsy after thyroid surgery.

METHODS

This was a comparative study of intermittent versus continuous IONM in patients with benign and malignant thyroid disease treated at a tertiary centre over 10 years. Early postoperative and permanent vocal cord palsy rates were estimated. Multivariable logistic regression analysis was used to quantify the contributions of clinical and histopathological variables to early postoperative and permanent vocal cord palsy.

RESULTS

A total of 6029 patients were included, of whom 3139 underwent continuous and 2890 intermittent IONM. Based on nerves at risk (5208 versus 5024 nerves), continuous IONM had a 1·7-fold lower early postoperative vocal cord palsy rate than intermittent monitoring (1·5 versus 2·5 per cent). This translated into a 30-fold lower permanent vocal cord palsy rate (0·02 versus 0·6 per cent). In multivariable logistic regression analysis, continuous IONM independently reduced early postoperative vocal cord palsy 1·8-fold (odds ratio (OR) 0·56) and permanent vocal cord palsy 29·4-fold (OR 0·034) compared with intermittent IONM. One permanent vocal cord palsy per 75·0 early vocal cord palsies was observed with continuous IONM, compared with one per 4·2 after intermittent IONM. Early postoperative vocal cord palsies were 17·9-fold less likely to become permanent with continuous than intermittent IONM.

CONCLUSION

Continuous IONM is superior to intermittent IONM in preventing vocal cord palsy.

[Maximum dose of continuous infusion of mivacurium for thyroid surgery under total intravenous anesthesia: a sequential trial of monitoring neurological function in 30 patients]

OBJECTIVE

To investigate the maximum dose of continuous mivacurium infusion for intraoperative neuromonitoring (IONM) and observe the adverse reactions during thyroid surgery under total intravenous anesthesia (TIVA).

METHODS

Thirty patients undergoing IONM during thyroid surgery received continuous infusion of mivacurium at the initial rate of 14.97 μg · kg^-1 · min^-1. The infusion rate was adjusted in the next patient based on the response of the previous patient in IONM. The depth of anesthesia was maintained with propofol and remifentanil during the surgery. The EC₅₀ and 95%CI of mivacurium were calculated with Brownlee's up- and-down sequential method. During the operation, body movement and skin flushing of patient was monitored, and the mean arterial pressure (MAP) and heart rate (HP) were recorded immediately (T₀) and at 5 min (T₁) after injection of muscle relaxant for anesthesia induction, immediately (T₂) and at 10 min (T₃) and 20 min (T₄) after initiation of intraoperative infusion of the muscle relaxant.

RESULTS

The EC₅₀ for continuous infusion of mivacurium without affecting IONM was 18.9 μg · kg^-1 · min^-1(95%CI: 17.3-20.5 μg · kg^-1 · min^-1) during thyroid surgery under TIVA. One patient (3.3%) developed transient facial skin redness after induction. Intubation difficulties or body motions occurred in none of the patients during the surgery. Pair-wise comparison showed no significant variations in MAP or HR of the patients at the 5 time points (P>0.05).

CONCLUSIONS

In patients undergoing thyroid surgery under TIVA, the EC₅₀ for continuous infusion of mivacurium is 18.9 μg · kg^-1 · min^-1 (95%CI: 17.3-20.5 μg · kg^-1 · min^-1), which does not affect IONM or causes serious adverse reactions during the operation.

Influence of rocuronium on achieving optimal vagal stimulation during intraoperative nerve monitoring in thyroid surgery

BACKGROUND

In the present study we determine the feasibility of intraoperative neuromonitoring following the administration of a nondepolarizing neuromuscular blocking agent during thyroid operations, as well as the influence of rocuronium on the achievement of optimal vagal stimulation during intraoperative neuromonitoring in thyroid surgery. We further investigate whether accelerometry is a reliable approach to obtaining an ipsilateral vagus signal prior to recurrent laryngeal nerve dissection.

METHODS

Included in the study were 61 thyroidectomized patients whose demographic data, indications, type of surgery, vagus, and recurrent nerve values before and after resection were obtained. We created five groups of patients based on the twitch values recorded during ipsilateral vagus stimulation prior to the recurrent laryngeal nerve dissection: (1) <10%, (2) 11-25%, (3) 26-50%, (4) 51-75% and (5) >75%.

RESULTS

The average electromyography amplitudes of the vagus nerve prior to the determination of the recurrent laryngeal nerve for each group were 552 μV, 463 μV, 543 μV, 513 μV and 551 μV, respectively. No difference between the groups was observed in this regard (p > 0.05).

CONCLUSION

It can be expected that as soon as the effects of neuromuscular blockers on the peripheral muscles begin to abate, it will be possible to obtain the ipsilateral vagus signal prior to recurrent laryngeal nerve dissection at the desired levels. It can be concluded from this study that accelerometry using the pollicis muscle is an unreliable tool for the interpretation of the proper electromyography signals of the vagus nerve prior to the determination of the recurrent laryngeal nerve.

Role of intraoperative recurrent laryngeal nerve monitoring for pediatric thyroid surgery: Comparative analysis

BACKGROUND

The data on the advantages of intraoperative nerve monitoring (IONM) during pediatric thyroid surgeries are limited. We aimed to study the role of IONM by comparing between children who underwent thyroid surgery with and without IONM.

METHODS

A retrospective study of all children who underwent thyroid surgery between 2001 and 2019.

RESULTS

The study included 113 patients with 183 recurrent laryngeal nerve (RLN) at risk. Transient paralysis rate was more than 5-fold lower in the IONM group compared to the control group (1.5% vs 8%; P = .114). Permanent paralysis was documented only in the control group (2.5% vs 0%; P = .552). Children <10 years and those who underwent central neck dissection had significantly higher rates of RLN injury.

CONCLUSIONS

IONM was associated with decreased rate of RLN injury during pediatric thyroid surgery and should be considered especially in children under 10 years of age and those undergoing concomitant central neck dissection.

Use of intraoperative neural monitoring for prognostication of recovery of vocal mobility and reduction of permanent vocal paralysis after thyroidectomy

INTRODUCTION

The benefits of intraoperative neural monitoring (IONM) of recurrent laryngeal nerve (RLN) on post-thyroidectomy vocal cord palsy (VCP) rates are contentious. We wished to study impact of IONM on permanent VCP after thyroidectomy.

METHODS

Retrospective review of prospective series of 1011 (1539 nerves-at-risk) patients undergoing thyroidectomy without (418, group 1) and with (583, group 2) IONM.

RESULTS

There were three recognized nerve injuries in group 1, vs one in group 2 (P = .3). There were no differences in overall VCP rates. However, patients in group 2 with immediate postoperative VCP had higher likelihood of full recovery than patients in group 1 (55 of 56 vs 23 of 29 patients, P = .01), and lower incidence of total permanent VCP (2 of 917 vs 9 of 647 patients, P = .01).

CONCLUSION

Among patients with immediate postoperative VCP after thyroidectomy, IONM is associated with a higher likelihood of regaining normal vocal function. This may be related to better identification of RLN branching in IONM cases.

[Modern thyroid surgery - the surgeon's endocrine-surgical understanding and his responsibility for the extent of surgery and complication rate]

Die hohe Qualität der Schilddrüsenchirurgie impliziert ein endokrin-chirurgisches Verständnis des Operateurs mit dem Ziel einer bestmöglichen Ergebnisqualität. Das beinhaltet ein befundadäquates Resektionsausmaß und eine möglichst niedrige Komplikationsrate. Der Chirurg sollte frühzeitig in die Operationsindikation eingebunden sein und auch selbst die Diagnostik, speziell den Schilddrüsen- und Halslymphknotenultraschall, sowie die Interpretation der Schnittbild- und nuklearmedizinischen Verfahren beherrschen. Im Besonderen sollte er über zeitgemäße Radikalitätsprinzipien in der Chirurgie Bescheid wissen.

Bei der gutartigen Struma ist eine individualisierte Operationsstrategie anzuwenden: Solitärknoten können auch einer gewebeschonenden Knotenresektion unterzogen werden. Bei multinodulärer Knotenstruma ist nicht zwingend eine totale Thyreoidektomie notwendig, die Vermeidung eines permanenten Hypoparathyreoidismus hat Priorität. Bei Rezidivstrumen ist oft die einseitige Operation des dominanten Befundes zu bevorzugen. Auch besteht zunehmend der Trend, die Indikation zur Entfernung der Schilddrüsenlappen seitengetrennt zu stellen. Die Basedow Struma erfordert eine Thyreoidektomie. Auch die hypertrophe Thyreoiditis Hashimoto kann eine Operationsindikation darstellen.

Die Radikalitätsprinzipien bei maligner Struma haben sich ebenfalls deutlich gewandelt als auch die strenge Indikation zur Radiojodtherapie. Das gilt speziell für papilläre Mikrokarzinome und minimal invasive follikuläre Tumortypen. Selbst bei medullären Schilddrüsenkarzinom stehen die Radikalitätsprinzipien im Hinblick auf synchrone oder metachrone laterale Halsdissektion in Diskussion.

Der Hypoparathyreoidismus stellt derzeit das Hauptproblem in der radikalen Schilddrüsenchirurgie dar. Recurrensparese und Nachblutung sind durch die subtile Operationstechnik selten geworden. Spezielle extrazervikale Operationszugänge sind nach wie vor in der Erprobungsphase und unter strengen Studienbestimmungen nur Zentren vorbehalten. Die Radiofrequenzablation stellt für gewisse Läsionen wie Zysten und autonome Adenome bei chirurgischer Kontraindikation ein alternatives Ablationsverfahren dar.

Intraoperative Neuromonitoring in Thyroid Surgery: An Efficient Tool to Avoid Bilateral Vocal Cord Palsy

OBJECTIVES

This study aimed to analyze the effects of intraoperative neuromonitoring (IONM) on the prevalence of vocal cord palsy (VCP) in thyroid surgery.

METHODS

Data from 493 patients (839 nerves at risk [NAR]) who underwent thyroid surgery between July 2014 and May 2016 were retrospectively evaluated. The patients were divided into 2 groups: Group 1 (G1) consisted of patients who underwent surgery without IONM, whereas group 2 (G2) consisted of patients who underwent surgery with IONM. The surgical techniques were identical, and experienced surgeons performed the procedures in both groups. Intraoperative neuromonitoring was performed in compliance with the International Neural Monitoring Guidelines.

RESULTS

In total, 211 patients (170 female, 41 male) with 360 NAR were included in G1, and 282 patients (220 female, 62 male) with 479 NAR were included in G2. The number of VCP per NAR in G1 and G2 was 33 (9.2%) and 27 (5.6%), respectively (P = .005). The number of transient VCP per NAR in G1 and G2 was 27 (7.5%) and 23 (4.8%; P = .230), respectively. The number of permanent VCP per NAR in G1 and G2 was 6 (1.7%) and 4 (0.8%; P = .341), respectively. Bilateral VCP was detected in 4 (2.7%) patients in G1, whereas there was no patient with bilateral VCP in G2 (P = .033).

CONCLUSIONS

Intraoperative neuromonitoring may decrease the incidence of total VCP and prevent the development of bilateral VCP, which has unfavorable results for both patients and health-care professionals.

A Surgical Mouse Model for Advancing Laryngeal Nerve Regeneration Strategies

Iatrogenic recurrent laryngeal nerve (RLN) injury is a morbid complication of anterior neck surgical procedures. Existing treatments are predominantly symptomatic, ranging from behavioral therapy to a variety of surgical approaches. Though laryngeal reinnervation strategies often provide muscle tone to the paralyzed vocal fold (VF), which may improve outcomes, there is no clinical intervention that reliably restores true physiologic VF movement. Moreover, existing interventions neglect the full cascade of molecular events that affect the entire neuromuscular pathway after RLN injury, including the intrinsic laryngeal muscles, synaptic connections within the central nervous system, and laryngeal nerve anastomoses. Systematic investigations of this pathway are essential to develop better RLN regenerative strategies. Our aim was to develop a translational mouse model for this purpose, which will permit longitudinal investigations of the pathophysiology of iatrogenic RLN injury and potential therapeutic interventions. C57BL/6J mice were divided into four surgical transection groups (unilateral RLN, n = 10; bilateral RLN, n = 2; unilateral SLN, n = 10; bilateral SLN, n = 10) and a sham surgical group (n = 10). Miniaturized transoral laryngoscopy was used to assess VF mobility over time, and swallowing was assessed using serial videofluoroscopy. Histological assays were conducted 3 months post-surgery for anatomical investigation of the larynx and laryngeal nerves. Eight additional mice underwent unilateral RLN crush injury, half of which received intraoperative vagal nerve stimulation (iVNS). These 8 mice underwent weekly transoral laryngoscopy to investigate VF recovery patterns. Unilateral RLN injury resulted in chronic VF immobility but only acute dysphagia. Bilateral RLN injury caused intraoperative asphyxiation and death. VF mobility was unaffected by SLN transection (unilateral or bilateral), and dysphagia (transient) was evident only after bilateral SLN transection. The sham surgery group retained normal VF mobility and swallow function. Mice that underwent RLN crush injury and iVNS treatment demonstrated accelerated and improved VF recovery. We successfully developed a mouse model of iatrogenic RLN injury with impaired VF mobility and swallowing function that can serve as a clinically relevant platform to develop translational neuroregenerative strategies for RLN injury.

Methodological Quality of Systematic Reviews of Intraoperative Neuromonitoring in Thyroidectomy: A Systematic Review

Importance

Systematic reviews and meta-analyses are considered the best evidence for clinical decision making. Many reviews of intraoperative neuromonitoring (IONM) in thyroidectomy have conflicting results, owing in large part to methodological quality.

Objective

To assess the methodological quality and the causes of heterogeneous results of systematic reviews that compare routine IONM vs visual identification of the recurrent laryngeal nerve (RLN) in patients undergoing thyroidectomy.

Data Sources

A systematic search was performed of MEDLINE (PubMed), Embase, the Cochrane Library, LILACS (Literatura Latino Americana e do Caribe em Ciências da Saúde), Web of Science, and Google from January 1, 1968, through June 30, 2018. Data were analyzed from July 17 to November 30, 2018.

Study Selection

Studies that mentioned performance of a systematic review/meta-analysis during the search period.

Data Extraction and Synthesis

Data including study characteristics, type of patients, numbers of nerves at risk, and temporary and definitive RLN paralysis by group were extracted. Data about methodological characteristics, type of statistical analysis and summary estimator, endorsement of systematic review/meta-analysis guidelines, heterogeneity, publication bias, funding, conflict of interest, and statistical analysis were also recorded. The methodological quality was measured with the AMSTAR2 (A Measurement Tool to Assess Systematic Reviews) tool by 2 independent evaluators.

Main Outcomes and Measures

Methodological quality.

Results

The search identified 13 systematic reviews that included patients who underwent open or minimally invasive thyroidectomy, second operations, and a mixture of low- and high-risk procedures. The mean compliance with the AMSTAR2 overall criteria was 53% (range, 11%-83%); with critical criteria, 71% (range, 50%-94%). The percentage of nerves at risk from RCTs was 4.8%. The mean (SD) crude rate of definitive RLN paralysis was 0.81% (0.22%; median, 0.75% [range, 0.53%-1.30%]) in the monitoring group and 1.14% (0.56%; median, 0.96% [range, 0.57%-2.56%]) in the control group.

Conclusions and Relevance

A substantial number of systematic reviews of IONM in thyroidectomy have conflicting results, but their mean methodological quality is critically low. Design of a systematic review should comply with methodological standards and recommendations to offer relevant and practical information for decision making.

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.

A Review of Methods for the Preservation of Laryngeal Nerves During Thyroidectomy

The recurrent laryngeal nerve (RLN) provides motor innervation to the abductor and adductor muscles of the vocal cord, whereas the external branch of the superior laryngeal nerve (EBSLN) provides motor innervation to the cricothyroid muscle, which is the tensor muscle of the vocal cord. Both the RLN and the EBSLN are anatomically close to the thyroid and are therefore at risk of injury during thyroidectomy. These 2 laryngeal nerves must be carefully preserved during surgery to ensure that the function of the vocal cord is not impaired. Currently, complete exposure of the RLN during thyroidectomy is accepted as the gold standard method for the preservation of RLN. Sufficient knowledge of surgical anatomy, clinical experience, and meticulous surgical techniques are key factors in the identification and safe dissection of the RLN. During a thyroidectomy, the RLN can be identified using four different approaches, depending on the type of thyroid growth and choice of the surgeon: There are lateral, inferior, superior, and medial approaches.

The lateral approach is the most commonly used technique in primary thyroid surgery. The RLN is usually found by dissection around the inferior thyroid artery at the level of the middle lobe of the thyroid. RLN is generally found at the site of its entry into the neck region devoid of scar formation when the inferior approach is used especially in cases with secondary surgery. The superior approach is recommended for patients with an huge goiter or large substernal goiter. In this approach, the upper pole of the thyroid is first released and then pulled forward and laterally, and the RLN is exposed on the nerve’s entry point (NEP), into the larynx, under the cricopharyngeus muscle. The medial approach is preferred for patients with substernally or retropharyngeally enlarged goiters. In this approach, the isthmus is first dissected and divided, and then the isthmus and the medial part of the lobe are dissected away from the trachea to reveal the anterolateral part of the trachea. The fibers between the lateral aspect of the second or third tracheal rings and the thyroid, and the fibers of the Berry ligament are gradually dissected cranially, to allow RLN to enter into the field of view lateral to the trachea. The preservation of the anatomical integrity of the RLN does not indicate that its functional integrity is also preserved. IONM is a tool for the functional assessment of RLN, and so this method is an addition to visually identifying RLN, which is the gold standard. IONM significantly contributes to visual identification of the RLN, determination of its anatomical variations, intraoperative recognition of RLN injury, prevention of bilateral vocal cord paralysis, and detection and preservation of electrical activity in the nerve in patients with preoperative vocal cord paralysis.

Although there is no standardized method for the preservation of the EBSLN, 3 methods have been defined during the release of the upper pole of the thyroid. These methods involve dividing the branches of the superior thyroidal artery one by one on the capsule without visually identifying the EBSLN, searching and visually identifying the EBSLN before the dissection of the upper pole vessels, or detecting the EBSLN and dissecting the upper pole under the guidance of IONM. IONM also significantly contributes to the detection and confirmation of the EBSLN and dissection and preservation of the upper pole of the thyroid gland.

Protective Effects of Intraoperative Nerve Monitoring (IONM) for Recurrent Laryngeal Nerve Injury in Thyroidectomy: Meta-analysis

Recurrent laryngeal nerve (RLN) injury is an intractable complication of thyroidectomy. Intraoperative nerve monitoring (IONM) was designed to prevent RLN injury. However, the results concerning the protective effect of IONM on RLN injury are still controversial. We searched all eligible databases from 1980 to 2017. Meta-analysis was performed to evaluate the effect of IONM on RLN injury. Sensitivity analysis was also conducted to check the stability of our results. There were 34 studies included in the analysis. Overall analysis found a significant decrease in total injury (RR = 0.68, 95%CI: 0.55 to 0.83), transient injury (RR = 0.71, 95%CI: 0.57 to 0.88), and permanent injury (RD = −0.0026, 95%CI: −0.0039 to −0.0012) with IONM. Subgroup analysis found IONM played a preventive role of total, transient and permanent injury in patients undergoing bilateral thyroidectomy. IONM also reduced the incidence of total and transient injury for malignancy cases. Operations with IONM were associated with fewer total and transient RLN injuries in operation volume < 300 NARs per year and fewer total and permanent RLN injuries in operation volume ≥ 300 NARs per year. The application of IONM could reduce the RLN injury of thyroidectomy. Particularly, we recommend routine IONM for use in bilateral operations and malignancy operations.

Effect of nerve monitoring on complications of thyroid surgery

OBJECTIVE:

The most frequent and critical complications of thyroid surgery are recurrent laryngeal nerve palsy and hypocalcemia. In first years of the 21st century, intraoperative neuromonitoring (IONM) was introduced as a new technique to avoid the recurrent laryngeal nerve (RLN) injury. However, the role and the benefits of IONM are still controversial. In this study, we aimed to compare the postoperative complication rates during thyroid surgery with IONM usage (Group 1) and conventional direct visual technique without IONM usage (Group 2).

METHODS:

We conducted retrospective review of all patients undergoing thyroid surgery in Lütfiye Nuri Burat State Hospital General Surgery Department between 2014 and 2016 years. Patients have been classified in to two groups: Group 1 and 2.

RESULTS:

Overall, 191 patients were included in the study; Group 1 comprised 79 patients and Group 2 comprised 112 patients. Unilateral RLN paralysis was observed in 7 patients in Group 1 (8.9%) and 15 patients in Group 2 (13.4%) without any significant difference between the groups (p=0.368). Hypocalcemia was encountered in 5 patients (6.3%) in Group 1 and 18 patients (16.1%) in Group 2; this difference was statistically significant (p=0.045). Other complications (such as hematoma and suture reaction) were not significantly different. Operation time was found to be significantly shorter in Group 1 (Mean time, 93.08 min) than in Group 2 (116.54 min) (p=0.03).

CONCLUSION:

Proven effect of IONM on RLN paralysis is still controversial. However, easy identification of RLN, which gives more confidence to surgeon, and shorter operation time may be factors to lower hypocalcemia rates.

Approach to thyroid carcinoma in pregnancy

Thyroid carcinoma is the first cancer found in general population and the second diagnosed during pregnancy following the breast one. Diagnostic and therapeutic approaches to thyroid malignancy in pregnant women pose several and serious issues to the physicians. Even if there is no consensus about the surgical treatment of thyroid carcinomas during pregnancy, a large number of women undergo surgery over the world. The best surgical and anesthesiological treatment should be chosen after reaching a consensus between surgeons, anesthesiologists, obstetrics, and the patients. From 2000 to 2016, 18 pregnant patients underwent thyroidectomy under local anesthesia (cervical plexus block) combined with conscious sedation using benzodiazepines and opiates with ultrashort duration of action. Our 15-year experience on the thyroidectomies performed using the cervical plexus block combined with conscious sedation confirms that this combined technique offers a safe chance to defeat cancer also during pregnancy. Application of hypnosis could be an interesting alternative approach to pharmacological sedation in patients who would avoid intravenous drugs.

Transoral thyroidectomy: limitations, patients' safety, and own experiences

For patients undergoing thyroidectomy, the minimally invasive aspect and the cosmetic advantage of the procedure seem to be important factors in surgery. Studies in cadaver and animals have shown that different endoscopic techniques can be performed in a safe and successful way. In the evolution of thyroid surgery, for many endocrine surgeons, the transoral approach seems to be the next step. Even if such procedures are more and more frequently applied in patients, these procedures are far from being generally implemented in routine surgery. In this study, we report on our own experience and considerations in the process of finding a sublingual endoscopic transoral way to the endoscopic transoral thyroidectomy. We describe our failures, risk assessment and compare that with the available literature on transoral sublingual and vestibular thyroid surgery. The access itself needs to be further refined, and even more suitable and better adapted instruments need to be developed, so that optimal and safe results that meet all requirements on endocrine surgery can be achieved. A learning curve at the risk of patients' lives should be avoided. Furthermore, a combination of transoral endoscopic non-transoral techniques might be a useful safer, but more traumatising alternative for implementation. The sublingual access seems to be less invasive than the vestibular access. For a sublingual single-access routine surgery, better instruments are needed. Only in highly specialized centres for endocrine and endoscopic surgery, transoral thyroidectomy should be performed.