Intraoperative neuromonitoring of surgery for benign goiter

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.     

Neuromonitoring in endoscopic and robotic thyroidectomy

Intraoperative neuromonitoring (IONM) has proven effective for intraoperative verification of RLN function in the conventional thyroid surgery. However, no studies have performed a systematic evidence-based assessment of this novel health technology in endoscopic and robotic thyroidectomy. Evidence-based criteria were used in a systematic review of relevant literature for years 2000–2015. Four electronic databases (CENTRAL, MEDLINE, Cochrane and EMBASE) were used to retrieve relevant reports published from January 1, 2000 to September 1, 2016. The search terms included “endoscopic thyroidectomy”, “robotic thyroidectomy”, “IONM”, “continuous IONM (CIONM)”, “neural monitoring”, “recurrent laryngeal nerve monitoring”, and “superior laryngeal monitoring”. The following data were retrieved from eligible studies of patients undergoing endoscopic or robotic thyroidectomy: objective of study, design and setting of study, population, intervention examined, quality of data, follow-up and dropout rate, risk of bias, and outcomes assessed. Of 160 studies retrieved, only 9 (5%) studies used IONM. Eight studies reported 522 nerve at risk (NAR) with IONM. Only three were prospective randomized studies. Reports of IONM endoscopic and robotic procedures included their use for re-surgery and use in both benign and malignant cases. None of the IONM endoscopic procedures involved bilateral palsy. Two studies reported the use of a staged strategy. The rates of recurrent laryngeal palsy were 0–3.6% for transient and 0–0.4% for permanent. Only 30% of the studies performed vagus nerve stimulation, and only 25% performed superior laryngeal nerve monitoring. In addition to the use of IONM as an assistive technology for navigating the anatomy in challenging procedures such as endoscopic and robotic thyroidectomy, IONM has potential use as a routine adjunct to the conventional video-assisted nerve identification in thyroidectomy.     

Systematic review with meta-analysis of studies comparing intraoperative neuromonitoring of recurrent laryngeal nerves versus visualization alone during thyroidectomy

Background

The role of intraoperative neuromonitoring (IONM) of the recurrent laryngeal nerve (RLN) during thyroid surgery is still debatable. The aim of this meta-analysis was to evaluate the potential improvement of IONM versus RLN visualization alone (VA) in reducing the incidence of vocal cord palsy.

Methods

A literature search for studies comparing IONM versus VA during thyroidectomy was performed. Studies were reviewed for primary outcome measures: overall, transient, and permanent RLN palsy per nerve and per patients at risk; and for secondary outcome measures: operative time; overall, transient and permanent RLN palsy per nerve at low and high risk; and the results regarding assistance in RLN identification before visualization.

Results

Twenty studies comparing thyroidectomy with and without IONM were reviewed: three prospective, randomized trials, seven prospective trials, and ten retrospective, observational studies. Overall, 23,512 patients were included, with thyroidectomy performed using IONM compared with thyroidectomy by VA. The total number of nerves at risk was 35,513, with 24,038 nerves (67.7%) in the IONM group, compared with 11,475 nerves (32.3%) in the VA group. The rates of overall RLN palsy per nerve at risk were 3.47% in the IONM group and 3.67% in the VA group. The rates of transient RLN palsy per nerve at risk were 2.62% in the IONM group and 2.72% in the VA group. The rates of permanent RLN palsy per nerve at risk were 0.79% in the IONM group and 0.92% and in the VA group. None of these differences were statistically significant, and no other differences were found.

Conclusions

The current review with meta-analysis showed no statistically significant difference in the incidence of RLN palsy when using IONM versus VA during thyroidectomy. However, these results must be approached with caution, as they were mainly based on data coming from non–randomized observational studies. Further studies including high-quality multicenter, prospective, randomized trials based on strict criteria of standardization and subsequent clustered meta-analysis are required to verify the outcomes of interest.     

Validity of intra-operative neuromonitoring signals in thyroid surgery

Background Although intra-operative neuromonitoring (IONM) is widely used in thyroid surgery, the validity of the received IONM signals are still unknown.Method Prospective collection of data forms in 29 hospitals from 8,534 patients with 15,403 nerves at risk, who underwent surgery for benign and malignant goitre disorders between August 1999 and January 2001. IONM was performed by indirect stimulation via the vagal nerve and by direct recurrent laryngeal nerve (RLN) stimulation in 12,486 cases. IONM signals were compared with early (<14 days) and late (6 months) postoperative vocal cord function findings.Results The transient and permanent RLN palsy rate was 2.8% and 0.7%, respectively. Monitoring of the RLN function was significantly more reliable via the indirect IONM stimulation route than via the direct IONM stimulation route (specificity P<0.05). IONM by indirect stimulation via the vagal nerve reliably excluded postoperative, permanent, vocal cord palsy (specificity 97.6%, negative predictive value 99.6%). However, a changed IONM was insufficient to predict permanent RLN palsy (sensitivity 45.9%, positive predictive value 11.6%). IONM was not associated with increased general morbidity.Conclusions For intra-operative neuromonitoring, indirect stimulation of the RLN is superior to direct stimulation. An intact acoustic IONM signal is highly predictive of intact postoperative RLN function. When the IONM signal is abnormal or absent, a one-stage extensive thyroid resection should be performed only if the surgeon is absolutely convinced that the first RLN is not harmed or a total thyroidectomy is mandatory.     

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??Application of intraoperative neromonitoring during complex thyroid operation SUN Hui,LIU Xiao-li,FU Yan-tao,et al.Division of Thyroid Surgery,China-Japan Union Hospital of Jilin University,Changchun 130033, China Corresponding author: SUN Hui,E-mail:sunhui1229@163.com Abstract Objective Apply the intraoperative neuromonitoring ??IONM?? as an adjunct to avoid recurrent laryngeal nerve (RLN) injury during complex thyroid operation. Methods From March 2009 to July 2009, 132 pations (186 nerves at risk) underwent complex thyroidectomy with the application of IONM. Vagus nerve and RLN were tested respectively before and after resection of thyroid lobe. Video recording of cord mobility was performed routinely pre- and postoperatively. Results In addition to 4 cases with preoperative vocal cord paralysis??182 RLN after resection of thyroid lobe with a clear electromyography(EMG) and 0?? nerves experienced signal loss before closing surgical incision showed normal electrical transduction function. Accurately detect non-RLN in 2 nerves. Conclusion IONM could make RLN identification more reliabe and precise, test the functional integrity of RLN. IONM is a useful adjunct to reduce RLN palsy rate in complex thyroid operation.     

Recurrent laryngeal nerve injury in thyroid surgery: a review

Recurrent laryngeal nerve palsy (RLNP) is an important and potentially catastrophic complication of thyroid surgery. Permanent RLNP occurs in 0.3–3% of cases, with transient palsies in 5–8%. A literature review and analysis of recent data regarding RLNP in thyroid surgery was performed, with particular focus on the identification of high‐risk patients, the role of intraoperative identification and dissection of the nerve, and the role of intraoperative neuromonitoring (IONM) and optimal perioperative nerve assessment. In conjunction with the review, data from the Monash University/Alfred Hospital Endocrine Surgery Unit between January 2007 and October 2011 were retrospectively analysed, including 3736 consecutive nerves at risk (NAR). The current literature and our data confirm that patients undergoing re‐operative thyroid surgery and thyroid surgery for malignancies are at increased risk of RLNP. Intraoperative visualization and capsular dissection of the RLN remain the gold standard for intraoperative care during thyroid surgery for reducing RLNP risk. IONM should not be used as the sole mechanism for identifying and preserving the nerve, although it can be used to aid in the identification and dissection of the nerve, and may aid in nerve protection in high‐risk cases including cancer surgery and re‐operative surgery.     

Intraoperative Neuromonitoring in Thyroid Surgery

Summary 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.     

Sensitivity and Specificity of Intraoperative Recurrent Laryngeal Nerve Stimulation Test for Predicting Vocal Cord Palsy after Thyroid Surgery

INTRODUCTION Recurrent laryngeal nerve (RLN) palsy after thyroidectomy, although infrequently encountered, can decrease quality of life. In addition to the hoarseness that occurs with unilateral RLN palsy, bilateral RLN palsy leads to dyspnea and often to life-threatening glottal obstruction. Therefore, intraoperative awareness of the nerve’s status is of great importance. This study examined the sensitivity and specificity of a palpation technique to detect contraction of the posterior cricoarytenoid muscle (PCA) through the posterior hypopharyngeal wall while the RLN was being stimulated with a disposable nerve stimulator during thyroid surgery (the laryngeal palpation test) to predict postoperative RLN deficits. Methods A total of 2197 RLNs in 1376 patients were identified to be at risk of injury during thyroidectomy performed between July 2003 and August 2004. Postoperative RLN integrity was assessed using direct laryngoscopy or laryngofiberoscopy to visualize vocal fold mobility. Results Altogether, 76 RLNs failed to elicit a PCA contraction in response to nerve stimulation, and 80 cases of temporary vocal cord palsy and 21 cases of permanent vocal cord palsy were recognized on postoperative evaluation. For postoperative vocal cord palsy, the sensitivity and specificity of the laryngeal palpation test were 69.3% and 99.7%, respectively, with a positive predictive value of 92.1% and negative predictive value of 98.5%. For permanent vocal cord palsy, the sensitivity and specificity were 85.7% and 97.3%, respectively, with a positive predictive value of 23.7% and negative predictive value of 99.8%. Conclusions The laryngeal palpation test is not a particularly useful method for predicting the level of RLN function after thyroidectomy. All patients must be examined postoperatively by direct laryngoscopy or laryngofiberoscopy to check vocal cord mobility. Even if there is no contraction of the PCA and we detect vocal cord palsy immediately after surgery, vocal cord palsy often recovers within 1 year when visual preservation of RLN is successful.     

术中神经监测技术在甲状腺手术中的应用与进展

喉返神经损伤是甲状腺手术较常见及最严重的并发症,尤其在复杂甲状腺手术及再次甲状腺手术中,因解剖层次不清、喉返神经解剖变异等所导致的喉返神经损伤机会加大。术中神经监测(IONM)是应用电生理技术监测术中神经功能完整性的一种技术,近年来研究显示,甲状腺手术中喉返神经IONM较常规暴露喉返神经能明显降低暂时性及永久性喉返神经损伤率。笔者就有关喉返神经IONM在甲状腺手术中的应用与进展进行综述。     

Zuverlässigkeit und Konsequenzen des intraoperativen Neuromonitorings in der Schilddrüsenchirurgie

Intraoperative neuromonitoring (IONM) has yielded an increasing effect on thyroid surgery. During IONM, the recurrent laryngeal nerve is stimulated electrically and an acoustically transformed electromyographic signal is derived via either a needle electrode placed in the vocalis muscle or an electrode adjusted to the intubation tube. The IONM is used for identifying and predicting the function of the recurrent laryngeal nerve. Especially under difficult anatomic conditions, IONM has proven a valuable tool for identification of recurrent laryngeal nerves. This can lead to decreased occurrence of nerve palsy rates, as shown in numerous studies. The reliability of the IONM signal (defined as the correlation between intraoperative signal interpretation and postoperative vocal cord function) is reflected by a specificity as high as 98.2%, as shown by German multicenter studies. Thus, normal vocal cord function could be demonstrated postoperatively in over 98.2% of patients with intraoperatively unchanged neuromonitoring signals. If the neuromonitoring signal changed during operation, 39% of the patients suffered from transient vocal cord immobility and 12% had permanent loss of vocal cord function.     

Intraoperatives Neuromonitoring bei Schilddrüsenoperationen

Intraoperative neuromonitoring (IONM) was introduced into thyroid surgery approximately 10 years ago for better identification of recurrent laryngeal nerve palsy. Since then several studies have been performed for evaluation of this new technology. IONM is superior to visual nerve identification alone for prediction of postoperative local cord function. Therefore, in bilateral procedures IONM enables intraoperative decision-making concerning resection of the second side. To avoid misinterpretation of the results of IONM a standardized approach including preoperative and postoperative laryngoscopy and preresection and postresection vagus stimulation is recommended. Trouble-shooting requires systematic checking of the device including control of electrode position (needle or tube electrodes). For expert assessment purposes documentation of the standardized application of IONM is of utmost importance.     

喉返神经隧道解剖法结合神经监测在腔镜甲状腺手术中的应用

目的:探讨喉返神经隧道解剖法结合神经监测在腔镜甲状腺手术中的应用价值。方法:回顾分析2014年11月至2018年12月施行的141例腔镜甲状腺手术,术中均采用喉返神经隧道解剖法结合神经监测技术。其中甲状腺良性结节93例,甲状腺恶性肿瘤48例;行单侧腺叶切除术52例,单侧甲状腺癌根治术44例,双侧甲状腺癌根治术4例,41例部分切除术。结果:140例手术顺利完成,1例因喉返神经横断伤转开放手术行神经对端吻合;术后9例(9/141,6.38%)暂时性神经麻痹,无永久性声音嘶哑患者。结论:腔镜甲状腺手术中采用喉返神经隧道解剖法结合神经监测技术可快速定位喉返神经,降低手术难度,提高手术安全性,利于腔镜甲状腺手术更好地在基层医院推广普及。     

Neuromonitoring and video-assisted thyroidectomy: a prospective, randomized case-control evaluation

Introduction  This study evaluates the role of intraoperative neuromonitoring (IONM) in video-assisted thyroidectomy (VAT) with emphasis given to the identification of recurrent laryngeal nerve (RLN) and external branch of superior laryngeal nerve (EBSLN). Methods  The study was based on a prospectively randomized series comprising 72 standard VAT gasless approaches. In the control group (N = 36), the laryngeal nerves were identified by 30° 5-mm endoscope magnification solely. The standard technique of the IONM group (N = 36) consisted of localizing and monitoring EBSLN, both vagus and RLNs, before and after thyroid resection to prove nerve integrity. Surgical outcomes were mean operative time, nerve representation, incision length, and morbidity. Results  All procedures were performed successfully. There were no instances of equipment malfunction or interference. No permanent complications occurred in either group. The incidences of temporary RLN injury were 2.7% (1 patient) and 8.3% (3 patients) in the IONM and control group, respectively. The EBSLN was identified better in the IONM group: 83.6% versus 42% (p < 0.05). In the IONM group, a negative electromyography (EMG) response indicated an altered function of RLN and stage thyroidectomy was scheduled. Conclusions  This is the first VAT series with a standardized IONM technique. The technical feasibility and safety of IONM in selected patients seem acceptable. Neuromonitoring during VAT is effective in providing identification and function of laryngeal nerves. IONM enables surgeons to feel more comfortable with their approach to VAT. A reduction of rates for postoperative complications could not be demonstrated in the present study. Larger series are needed for further evaluation.     

Intraoperative neuromonitoring for thyroid malignancy surgery: technical notes and results from a retrospective series

This study evaluates the role of intraoperative neuromonitoring (IONM) for thyroidectomy performed in cancer patients with emphasis on postoperative recurrent laryngeal nerve paralysis (RLNP). The study is a retrospective series comprising 76 thyroidectomy alone (control group) versus 76 thyroidectomy with IONM. In the control group the laryngeal nerves have been identified by visualization solely. In the IONM group both vagal nerve and RLN have been localized and monitored during thyroid resection. The main surgical outcome was RLN morbidity. All patients undergo pre- and postoperative laryngeal examination. Overall RLN morbidity was 3.9% in the IONM group and 9.2% in the control group (P < 0.05). There have been two cases of permanent RLNP (2.6%) in the control group and one in the IONM group (1.3%), one case of bilateral RLN injury in the control group. The incidences of temporary RLNP in the IONM group have been 2.6 versus 6.5% in the control group. IONM is an effective procedure in thyroid cancer patients.     

Intraoperative Monitoring of External Branch of the Superior Laryngeal Nerve: Functional Identification,Motor Integrity,and its Role on Vocal Cord Function

ABSTRACT

Purpose: Beside recurrent laryngeal nerve (RLN), protection of the external branch of the superior laryngeal nerve (EBSLN) is required for complication-free thyroid surgery. This study investigates the contribution of intraoperative neuromonitoring (IONM) to identification and motor integrity of the EBSLN. Methods: This prospective study was performed on 245 EBSLNs in 147 patients with thyroid surgery. The rate of visual identification, contribution of IONM to functional localization, the rate and levels of recordable waveform amplitude from vocal cord (VC) movement were determined during surgery. Results: 164 (66.9%) EBSLNs were visually identified and additional 74 branches were functionally identified by IONM. Additional identification rate of IONM was 30.2%. Seven (2.9%) EBSLNs could not be identified during surgery. Cricothyroid muscle (CTM) twitch established functional integrity in 97.1% of EBSLNs. Electrophysiological stimulation of 151 (63.4%) EBSLNs created waveform amplitude >100 µV that mean amplitude level was calculated as 186 µV, and an amplitude >300 µV was recorded in 19 of 151 (12.6%) EBSLNs. Conclusions: In addition to visual identification, surgeons can functionally localize the EBSLN with the assistance of IONM that CTM twitch is a reliable evience for functional integrity of the EBSLN. In the majority of patients, stimulation of the EBSLN creates recordable waveform amplitude thus the EBSLN appears to be a second source of motor innervations for intrinsic laryngeal muscles.     

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

BackgroundBased on current evidence, the benefit of intraoperative nerve monitoring (IONM) in thyroid surgery is equivocal.MethodsAll 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.ResultsIn 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).ConclusionsNationally, IONM is used in nearly two thirds of thyroid surgeries. IONM is associated with a lower risk of recurrent laryngeal nerve injury.     

显露喉返神经在非神经监测与神经监测下单侧甲状腺手术中的临床分析

目的 探讨显露喉返神经在非神经监测与神经监测下单侧甲状腺手术中的临床效果分析.方法 回顾性分析南方医科大学顺德医院2019年1月至2020年11月66例单侧甲状腺手术患者临床资料,根据是否应用喉返神经监测技术分为非神经监测组和神经监测组,每组各33例.非神经监测组钝性分离直接显露喉返神经,神经监测组在神经监测提示下逐步...     

Results of Intraoperative Neuromonitoring in Thyroid Surgery and Preoperative Vocal Cord Paralysis

Background

Systematic studies of intermittent intraoperative neuromonitoring (IONM) have shown that IONM enhances recurrent laryngeal nerve (RLN) identification via functional assessment, but does not significantly reduce rates of vocal cord (VC) paralysis (VCP). The reliability of functional nerve assessment depends on the preoperative integrity of VC mobility. The present study was therefore performed to analyze the validity of IONM in patients with pre-existing VC paralysis.

Methods

Of 8,128 patients, 285 (3.5 %) with preoperative VCP underwent thyroid surgery using standardized IONM of the RLN and vagus nerves (VNs). VC function was assessed by pre- and postoperative direct videolaryngoscopy. Quantitative parameters of IONM in patients with VCP were compared with IONM in patients with intact VC function. Clinical symptoms and surgical outcomes of patients with pre-existing VCP were analyzed.

Results

A total of 244 patients revealed negative, and 41 revealed positive IONM on the side of the VCP. VCP with positive IONM revealed significantly lower amplitudes of VN and RLN than intact VN (p = 0.010) and RLN (p = 0.011). Symptoms of patients with VCP included hoarseness (25 %), dyspnea (29 %), stridor (13 %), and dysphagia (13 %); 13 % were asymptomatic. New VCP occurred in five patients, ten needed tracheostomy for various reasons, and one patient died.

Conclusions

Patients with pre-existing VCP revealed significantly reduced amplitude of ipsilateral VN and RLN, indicating retained nerve conductivity despite VC immobility. Preoperative laryngoscopy is therefore indispensable for reliable IONM and risk assessment, even in patients without voice abnormalities.     

NERVE STIMULATION IN THYROID SURGERY: IS IT REALLY USEFUL?

BACKGROUND: Monitoring of the recurrent laryngeal nerve (RLN) has been claimed in some studies to reduce rates of nerve injury during thyroid surgery compared with anatomical dissection and visual identification of the RLN alone, whereas other studies have found no benefit. Continuous monitoring with endotracheal electrodes is expensive whereas discontinuous monitoring by laryngeal palpation with nerve stimulation is a simple and inexpensive technique. This study aimed to assess the value of nerve stimulation with laryngeal palpation as a means of identifying and assessing the function of the RLN and external branch of the superior laryngeal nerve (EBSLN) during thyroid surgery. METHODS: This was a prospective case series comprising 50 consecutive patients undergoing total thyroidectomy providing 100 RLN and 100 EBSLN for examination. All patients underwent preoperative and postoperative vocal cord and voice assessment by an independent ear, nose and throat surgeon, laryngeal examination at extubation and all were asked to complete a postoperative dysphagia score sheet. Dysphagia scores in the study group were compared with a control group (n = 20) undergoing total thyroidectomy without nerve stimulation. RESULTS: One hundred of 100 (100%) RLN were located without the use of the nerve stimulator. A negative twitch response occurred in seven (7%) RLN stimulated (two bilateral, three unilateral). Postoperative testing, however, only showed one true unilateral RLN palsy postoperatively (1%), which recovered in 7 weeks giving six false-positive and one true-positive results. Eighty-six of 100 (86%) EBSLN were located without the nerve stimulator. Thirteen of 100 (13%) EBSLN could not be identified and 1 of 100 (1%) was located with the use of the nerve stimulator. Fourteen per cent of EBSLN showed no cricothyroid twitch on EBSLN stimulation. Postoperative vocal function in these patients was normal. There were no instances of equipment malfunction. Dysphagia scores did not differ significantly between the study and control groups. CONCLUSION: Use of a nerve stimulator did not aid in anatomical dissection of the RLN and was useful in identifying only one EBSLN. Discontinuous nerve monitoring by stimulation during total thyroidectomy confers no obvious benefit for the experienced surgeon in nerve identification, functional testing or injury prevention.     

Intraoperative electrophysiological monitoring of the recurrent laryngeal nerve in thyroid gland surgery--a prospective study

INTRODUCTION: In the last few years the use of intraoperative electrophysiological monitoring of the recurrent laryngeal nerve (RLN) in thyroid gland surgery has become more and more important. PATIENTS AND METHOD: In a prospective study 223 nerves at risk in 116 patients were monitored with the Neurosign(R)100 (Fa. Magstim Ltd., UK). We used intramuscular needle electrodes inserted into the vocal muscle through the conic ligament. Practicability, complications, acceptance and predictive value of the method were documented. Recurrent nerve palsy rate and complications were compared with a control group operated upon without monitoring. RESULTS: The intraoperative delay using this method was on average 8.9 minutes. There were problems with monitoring equipment avoiding use in 6.4 %. In 2 cases (1.7 %) an accidental lesion of endotracheal tube cuff was found related to malpositioning of the needle and in 7.7 % a hematoma of the vocal cords was observed. 73.3 % of the surgeons accepted the method to identify and control the nerve integrity. False-positive and false-negative signals may occur. In cases of a final real stimulus response a regular vocal cord motility was found in 95 %. If a nerve conduction block was noted an immobility of ipsilateral vocal cord was diagnosed postoperatively in 50 %. There was no decrease in transient recurrent palsy rate using monitoring (10.7 % vs. 9.6 % without monitoring) but in permanent paralysis (1.8 % vs. 3.0 %). CONCLUSIONS: It may be concluded that intraoperative electrophysiological monitoring of the RLN is a simple and accepted method with low complications reducing the incidence of permanent RLN palsy rate. We found the monitoring especially useful for operations of recurrent goiter and carcinomas of the thyroid gland as well as for learning thyroid gland surgery.