The role of intraoperative neuromonitoring of recurrent laryngeal nerve during thyroidectomy: a comparative study on 1000 nerves at risk

BACKGROUND: The role of intraoperative neuromonitoring of recurrent laryngeal nerve (RLN) during thyroidectomy has not been well established. The present study evaluates whether RLN injury can be reduced by the application of this technique during thyroidectomy in a single center. METHODS: Of 1000 RLNs that were at risk of injury in 639 consecutive patients who underwent thyroidectomy, the outcome of 501 RLNs with the use of neuromonitoring was compared with that of 499 nerves that were operated by routine identification only. The incidences of RLN paralysis were compared between the 2 groups and the assigned risk subgroups. RESULTS: Postoperative palsy was identified in 47 RLNs (4.7%), with complete recovery in 37 of 44 RLNs (84%) without documented injury. The overall incidence of postoperative RLN paralysis was significantly higher during thyroidectomy for malignancy (P = .025) and secondary thyroidectomy (P = .017). There was no significant difference in postoperative, transient, and permanent paralysis rates between the neuromonitoring and control groups. In subgroup analysis, the postoperative RLN palsy rate was higher during reoperative thyroidectomy (19% vs 4.6%; P = .019) in the control group but not in the neuromonitoring group (7.8% vs 3.8%; P > .05). CONCLUSION: Neuromonitoring of the RLN during thyroid surgery could not be demonstrated to reduce RLN injury significantly, compared with the adoption of routine RLN identification. However, its application can be considered for selected high-risk thyroidectomies.     

Course of the recurrent laryngeal nerve relative to the inferior thyroid artery and the suspensory ligament of Berry.

An awareness of the surgical anatomy and the possible dispositions of the recurrent laryngeal nerve (RLN) is very helpful in avoiding its injury during thyroidectomy. The relationship of the RLN to the inferior thyroid artery (ITA) and the suspensory ligament of Berry were studied in 172 patients undergoing thyroidectomy. One hundred and ninety one nerves were identified, 109 on the right and 82 on the left. Most nerves, both on the right (82.6%) as well as on the left (85.4%) ran either posterior or between the branches of the inferior thyroid artery. The majority of nerves were found within 3 mm from Berry's ligament. The relationship of the recurrent laryngeal nerve to the inferior artery and to the ligament of Berry does not follow a constant anatomical pattern. Nevertheless these structures have a quite close relationship to the nerve in the majority of cases.     

Intraoperative neurophysiology testing of the recurrent laryngeal nerve: plaudits and pitfalls

BACKGROUND: Electrode-imbedded endotracheal tubes allow continuous intraoperative assessment of vocal cord function when connected to an electromyographic (EMG) response monitor. Whether this device enhances or hinders the identification and preservation of the recurrent laryngeal nerve (RLN) is unclear. METHODS: The utility of continuous intraoperative neurophysiology testing (INT) of RLNs was evaluated prospectively in 100 patients undergoing 103 thyroid or parathyroid operations, involving 185 RLNs. The initial experience with 93 RLNs was compared with the subsequent 92 RLNs. RESULTS: Overall, 97.8% of RLNs were identified intraoperatively: 1.6% visually only, 2.2% nerve stimulator only, and 94% both. There was 1 transected RLN (1.1%) in each study group. The EMG monitor could not alert the surgeon to prevent these injuries. Overall, there were 14 instances of nonfunction of visually intact RLNs (7.6%), at some point during the operation and 4 resulting in temporary paralysis (2.2%). There were 8 instances of altered RLN function (4.3%) with no altered vocal cord function postoperatively. The nerve stimulator aided dissection of the RLN in 17 instances (9.2%). There were 7 episodes (3.8%) of equipment dysfunction that hampered surgical dissection. Between study groups there was significantly increased use of the nerve stimulator to first identify the location of the RLN before visual confirmation: 4 of 93, initial group versus 25 of 92, latter group (P < .001). CONCLUSIONS: INT aids the anatomic identification of the RLN only when a positive EMG response occurs. A negative EMG response can indicate a non-nerve structure, altered function of the RLN, or equipment setup malfunction. INT cannot necessarily prevent RLN transection.     

甲状腺手术中常规显露喉返神经的意义

目的 探讨甲状腺手术中常规显露喉返神经(RLN)对保护神经的作用.方法 回顾性分析2009年至2010年间连续实施的232例甲状腺切除手术患者的资料.手术均由同一组医师实施,方式为甲状腺腺叶切除或全切除术,术中常规显露喉返神经.结果 共行腺叶切除181例,甲状腺全切除51例.术中解剖喉返神经280根(98.9%).术后10例患者(3.6%)出现声音嘶哑,其中7例术中证实了喉返神经的完整性,但声带检查出现患侧运动障碍,均在术后2个月内发音恢复正常.另外3例为术中离断性神经损伤并行即刻吻合者,在术后4个月内声音均恢复正常.结论 甲状腺手术中常规显露喉返神经是预防喉返神经永久性损伤的有效方法.     

甲状腺手术中常规显露喉返神经的意义

目的 探讨甲状腺手术中常规显露喉返神经(RLN)对保护神经的作用.方法 回顾性分析2009年至2010年间连续实施的232例甲状腺切除手术患者的资料.手术均由同一组医师实施,方式为甲状腺腺叶切除或全切除术,术中常规显露喉返神经.结果 共行腺叶切除181例,甲状腺全切除51例.术中解剖喉返神经280根(98.9%).术后...     

Surgical anatomy of the recurrent laryngeal nerve revisited.

OBJECTIVES: Previous anatomic studies of the recurrent laryngeal nerves (RLNs) have described the variability in the course of the RLN. The anatomy of the nerve appears more constant along its distal segment near the cricothyroid joint, which is our surgical approach to the initial identification of the nerve. Understanding the topographical anatomy of the nerve in this region facilitates quick and safe nerve identification. The surgical topographical anatomy of the nerve in this region has not been studied in detail, which is the focus of this study. METHODS: A total of 278 RLNs in 190 patients were dissected during thyroidectomy and/or parathyroidectomy. The course of the nerve was recorded, paying particular attention to the directional course along its distal portion. The angle in which it coursed in relationship to a line paralleling the tracheoesophageal groove was determined. RESULTS: All 278 nerves were identified. Seventy-eight percent of the right-sided nerves coursed between 15 and 45 degrees, and 77% of the left-sided nerves coursed between 0 and 30 degrees. It appears that the nerve is more likely to travel at a more obtuse angle with right-sided RLNs and in patients with a low-lying cricoid. There was no permanent postoperative RLN palsy, and the incidence of temporary palsy was 1%. CONCLUSIONS: Approaching the nerve along its distal portion is safe and effective. The surgical topographical anatomy in this region is described in detail. Some of the potential advantages of identifying the nerve more distally include less chance of disrupting the blood supply to the inferior parathyroid gland, dissection along a shorter portion of the nerve, and less variability of the nerve.     

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.     

喉返神经的显露在甲状腺癌根治术中的意义

目的探讨喉返神经的显露在甲状腺癌根治性手术中的意义。方法回顾分析2003年7月至2006年12月间186例主动显露喉返神经的甲状腺癌根治手术病例资料。结果186例甲状腺癌均施行甲状腺全切或近全切除术。术中均成功显露双侧喉返神经,其中1例右侧非返喉下神经。喉返神经永久性损伤1例,暂时性损伤1例,永久损伤率为0．54％。结论甲状腺癌根治术中应常规在甲状腺下动脉周围寻找喉返神经,主动显露喉返神经不仅可减少喉返神经损伤的发生率,并可提高甲状腺癌手术的彻底性。     

甲状腺手术行喉返神经解剖显露的临床分析

目的探讨甲状腺术中喉返神经的解剖及显露的临床意义,以减少喉返神经损伤。方法回顾性分析965例甲状腺手术患者的临床资料,所有手术均在全嘛下进行并常规显露喉返神经,手术切除范围由病变情况决定,并对喉返神经解剖特点、损伤情况进行分析。结果共解剖显露喉返神经1052条,其中右侧721条,左侧331条,包括双侧87条;采用上方入路解剖86条,侧方661条,下方305条;右侧喉返神经位于气管食管沟内走行者461条,偏离者260条;左侧位于气管食管沟内走行者285条,偏离者46条;喉返神经入喉前有分支者687条（65．3％）,未分支直接人喉者365条（34．7％）;喉不返神经2条;解剖神经平均用时（6．7±0．54）min;术后神经暂时性损伤11例,永久性损伤2例,均于6个月后对侧声带代偿,嘶哑改善。结论熟悉喉返神经的解剖,灵活运用不同的解剖入路,常规解剖显露神经,是避免喉返神经损伤的有效方法。     

Predictors and consequences of recurrent laryngeal nerve injury during open thyroidectomy: An American College of Surgeons National Surgical Quality Improvement Project database analysis

BackgroundRecurrent laryngeal nerve (RLN) injury is a serious complication of thyroidectomy. The purpose of this study is to determine the predictors and consequences of RLN injury during thyroidectomy.MethodsA retrospective analysis was conducted using the ACS-NSQIP 2016–2017 main and thyroidectomy targeted procedure databases. Data was analyzed by multivariate logistic regression resulting in risk-adjusted odds ratios of RLN injury and morbidity/mortality.ResultsAge ≥65, black race, neoplastic indication, total or subtotal thyroidectomy, concurrent neck surgery, operation time > median, hypoalbuminemia, and anemia were associated with RLN injury. Use of intraoperative nerve monitoring was associated with decreased RLN injuries. RLN injury is a risk factor for overall morbidity, hypocalcemia, hematoma, pulmonary morbidity, readmission, reoperation, and length of stay > median.ConclusionSeveral predictors of RLN injury during thyroidectomy are identified, while use of intraoperative nerve monitoring was associated with a decreased risk of RLN injury. RLN injury is associated increased postoperative complications.     

A device for the intraoperative identification of the recurrent laryngeal nerve in piglets

The recurrent laryngeal nerve (RLN) is one of the most frequently injured nerves in head and neck surgery. Routine identification of the RLN during thyroid surgery has reduced the injury rate from 10% to less than 4%. Difficulty in identification of the RLN contributes to this surgical morbidity. Devices previously used for intraoperative identification of the RLN have failed to achieve the simplicity and reliability necessary for clinical use. This animal study uses a simple double-ballooned endotracheal tube and pressure transducer system, which assists intraoperative RLN identification through nerve stimulation and graphic documentation of vocal fold (VF) motion. Iatrogenic injury is demonstrated by a dampened stimulation-pressure tracing. The RLNs of three piglets were injured and examined, and the degree of injury was correlated with perioperative nerve stimulation patterns. The piglet proved to be an adequate model for laryngeal research. An FDA-approved multi-institutional prospective human study using this system of identification of the RLN is in progress.     

Does Extralaryngeal Branching Have An Impact on the Rate of Postoperative Transient or Permanent Recurrent Laryngeal Nerve Palsy?

Background  This prospective study assessed the prevalence of the extralaryngeal branching of the recurrent laryngeal nerve (RLN) and its impact on the incidence of postoperative transient or permanent RLN palsy. Methods  Total or hemithyroidectomy was performed in 115 patients, with a total of 195 RLNs displayed. The RLN extralaryngeal branches were routinely identified and preserved. The postoperative course of each patient was evaluated. Outcomes of patients with and without branching RLN were compared. Results  In all, 36 of 195 (18.5%) nerves showed extralaryngeal branching: 27 cases (25.5%) on the right and 9 on the left side (10.1%; p = 0.0088).Trifurcation of the RLN was identified in two dissections (1%). Bilateral bifurcations were observed in 3 of 80 (3.7%) patients. We reported four (2.1%) unilateral permanent RLN palsies, eight cases of unilateral transient nerve palsy (4.1%), and one bilateral transient RLN injury (0.6%). The comparative analysis of postoperative outcomes between branched and nonbranched RLNs revealed that the anatomical variation was more frequently associated both with unilateral permanent RLN palsy (relative risk, 13.25; 95% confidence interval, 1.42–123.73; p = 0.0204) and unilateral transient RLN palsy (relative risk, 7.36; 95% confidence interval, 1.84–29.4; p = 0.0061). The only case of bilateral transient RLN injury was associated with a nonrecurrent inferior laryngeal nerve. Conclusions  Branched RLNs represent a risk factor both for transient and permanent nerve palsy after surgery. Awareness of this anatomical variation and its routine investigation are essential during thyroid surgery to limit its relevant impact on postoperative RLN injury rate.     

甲状腺手术中显露喉返神经以避免喉返神经损伤的临床意义

目的探讨甲状腺手术中显露喉返神经(RLN)对预防RLN损伤的临床意义。方法回顾性分析2006年9月至2011年8月期间我院行甲状腺全切除术和次全切除术1 723例患者的临床资料,其中行显露RLN术式914例,共显露RLN 1 203条;行不显露RLN术式809例,共行1 013侧甲状腺腺叶切除手术。比较术后RLN损伤情况及术后6个月声带恢复情况。结果显露组与不显露组RLN损伤发生率分别为0.91%(11/1 203)和2.07%(21/1 013),2组比较差异有统计学意义(P<0.05)。术后随访6个月,显露组与不显露组分别有0例和13例(61.9%,13/21)永久性RLN损伤,2组比较差异有统计学意义(P<0.01)。结论在甲状腺全切除和次全切除术中,显露并注意保护RLN能最大程度地避免RLN损伤,尤其是永久性RLN损伤。     

术中神经监测技术在复杂甲状腺手术中的应用

目的 探讨应用术中神经监测技术（intra operative neuromonitoring,IONM）,以减少复杂甲状腺手术喉返神经损伤。方法 吉林大学中日联谊医院甲状腺外科2009年3~7月对132例复杂甲状腺手术病人,共186支高风险喉返神经行术中神经监测。在甲状腺切除前后分别探测迷走神经及喉返神经肌电信号。甲状腺手术前后常规检查声带活动度。结果 除术前声带麻痹4例,余182支喉返神经均可在甲状腺切除后测得明显肌电信号,未发生缝合切口前神经肌电信号消失,提示神经电传导功能良好。精确检出非返性喉返神经2例。结论 术中喉返神经监测使喉返神经显露更加便捷,更加确切,并可验证喉返神经功能完整性。在高风险、复杂甲状腺术中应用神经监测是降低喉返神经损伤率的一种重要辅助措施。     

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.     

Continuous laryngeal nerve integrity monitoring during thyroidectomy: does it reduce risk of injury?

OBJECTIVE: To determine if continuous laryngeal nerve integrity monitoring (NIM) during thyroidectomy is associated with a decreased risk of postoperative recurrent laryngeal nerve (RLN) injury. STUDY DESIGN AND SETTING: Retrospective cohort study of 165 patients who underwent thyroidectomy at a resident teaching institution between 1999 and 2002. The control group had 120 nerves at risk (NAR) whereas the NIM group consisted of 116 NAR. Primary outcome measures included postoperative RLN paralysis, paresis, and total injury rates. RESULTS: RLN paralysis occurred in 2.54% NAR in the control group and 0.86% in the NIM group [relative risk (RR) = 0.34, 95% confidence interval (CI95) = 0.04-3.27, P = 0.62]. Temporary RLN paresis occurred in 4.24% NAR in the control group and 3.45% in the NIM group (RR = 0.9, CI95 = 0.23-3.55, P = 0.89). Total RLN injury occurred in 6.78% NAR in the control group and 4.31% in the NIM group (RR = 0.66, CI95 = 0.21-2.09, P = 0.48). When compared to all other NAR, advanced T-stage malignancy was associated with a significantly increased risk of RLN paresis (T4 RR = 9.0, CI95 = 2.56-31.67, P = 0.0006; T3+T4 RR = 7.5, CI95 = 2.17-25.86, P = 0.0001) but not paralysis. NIM did not significantly reduce the risk of RLN paresis in the advanced T-stage subset (T3+T4 RR = 0.36, CI95 = 0.04-3.0, P = 0.59). CONCLUSION: There were no statistically significant differences in RLN paralysis, paresis, or total injury rates between control and NIM groups, even in subsets with advanced T-stage and increased baseline risk. Advanced T-stage is a significant predictor of RLN paresis in this cohort.     

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.     

腔镜甲状腺手术喉返神经的显露技巧

目的:探讨腔镜甲状腺手术中喉返神经的显露技巧。方法:回顾分析56例腔镜甲状腺近全/全切除术的临床资料,总结腔镜手术中喉返神经的显露入路及方法。结果:53例手术获得成功,3例因术中冰冻病理报告为甲状腺乳头状癌而中转开放行患侧颈部淋巴结改良清扫术。手术时间平均125.3 min,其中23例经腺体下极入路,20例经峡部向气管食管沟入路;13例经甲状软骨下角入路。术后住院期间及出院后3个月随访,患者均无声音嘶哑。结论:腔镜甲状腺手术中剖显喉返神经是安全、可行的,可避免喉返神经损伤。     

Extralaryngeal bifurcation of the recurrent laryngeal nerve: a common variation

Extralaryngeal bifurcation and trifurcation of the recurrent laryngeal nerve (RLN) is not well described in anatomical texts. This significant anatomical variation is important because prevention of vocal cord paralysis requires preservation of all branches of the RLN. The aim of this study was to examine the prevalence of extralaryngeal bifurcation of the RLN seen during thyroid/parathyroid surgeries. All patients undergoing total thyroidectomy, hemithyroidectomy and parathyroidectomy (excluding all minimally invasive procedures) carried out by a single endocrine surgeon from November 2003 to December 2004 were included. Operative data obtained prospectively included the location of the nerve, number of branches and the distance in millimetres from the inferior border of the cricothyroid to the point of bifurcation. A total of 213 (right = 114, left = 99) RLN in 137 patients were studied. Seventy-seven (36%) nerves bifurcated or trifurcated before entry into the larynx. Bifurcations were more common on the right (43%) than on the left (28%) (P = 0.05). Trifurcations were seen in eight nerves, seven on the right and one on the left (P = 0.05). Bilaterally branched RLN were observed in 14 (18%) of 77 patients undergoing a bilateral procedure. One non-RLN was identified on the right. The median distance from the cricothyroid to the point of division was 18 mm on the right and 13 mm on the left. Extralaryngeal division of the RLN is a common anatomical variant occurring more frequently on the right. Unseen branches of the RLN are at risk of injury during surgery. Therefore, great care is required following presumed identification of the RLN to ensure that there are no other unidentified branches.     

Evolution of Nerve Injury with Unexpected EMG Signal Recovery in Thyroid Surgery Using Continuous Intraoperative Neuromonitoring

Background

Intermittent intraoperative neuromonitoring cannot prevent preparative surgical damage or predict imminent recurrent laryngeal nerve (RLN) damage with subsequent development of loss of electromyogram (EMG) signal during thyroid surgery. In case the nerve is stressed, i.e., from traction near the ligament of Berry, the nerve injury is only detected after it has occurred, not allowing the surgeon to correct the mechanical maneuver and salvage nerve function intraoperatively.

Methods

The unusual clinical scenario of sacrifice of a tumor-infiltrated RLN was used to study real-time evolution of RLN injury caused by mechanical distention. The ipsilateral vagus nerve (VN) was continuously stimulated with a new stimulation probe, and changes in EMG response were correlated with the varying levels of stretch and traction.

Results

Mechanical traction induced an intermittent depression of EMG amplitudes as a sign of impaired propagation of axon potentials or synaptic transmission. Prolonged mechanical stress caused a long-lasting depression of EMG response. When the mechanical distention was relieved, neurotransmission was gradually restored, with reappearance of singular muscle depolarization of full magnitude interspersed between the barely detectable deflections in the EMG recording. These responses of full amplitude appeared with increasing frequency, until the regular continuous EMG pattern was completely restored.

Conclusions

Only continuous VN stimulation serves to detect early changes in EMG response that indicate imminent danger to RLN functional integrity and alerts the surgeon to immediately correctable surgical actions, thus possibly preventing nerve damage or transforming damage into a reversible event.