喉返神经的解剖显露在甲状腺手术中的价值

目的 探讨甲状腺手术喉返神经（RLN）的解剖特点和方法，以减少神经的损伤。方法 回顾分析2000年1月-2005年10月256例甲状腺手术的临床资料，常规显露RLN201例（211条），不显露RLN55例，并对RLN解剖特点、损伤情况和预防进行分析。结果 显露RLN者暂时性损伤率为1．00％（2／201），无永久性损伤；未显露者暂时性损伤率为7．27％（4／55），永久性损损伤率为3．64％（2／55），两组暂时性损伤率之间和永久性损伤率之间经统计学处理差异均有统计学意义（P〈0．05）。“非返性喉下神经”发生率为0．95％（2／211）；67．30％（142／211）RLN在入喉前有分支，59．24％（125／211）的RLN位于甲状腺下动脉的深面，30．81％（65／211）位于动脉的浅面，5．68％（12／211）穿行于动脉的分叉处，4．27％（9／211）与动脉无关。结论 RLN的行程过程中解剖关系较为复杂；甲状腺手术中有计划显露RLN可以预防其损伤。     

全麻甲状腺手术中的喉返神经实时监控

目的评价术中实时监控技术在预防喉返神经医源性损伤中的实际意义和应用前景.方法自2002年11月至2005年5月在40例全麻甲状腺手术中对喉返神经功能进行术中实时监控.全部采用气管插管式电极,同步进行全麻与术中监控.在7例腺叶切除手术中主动探测解剖喉返神经,搜寻探测到喉返神经5例,其他类型的手术中均没有解剖暴露喉返神经.结果39例患者术后喉返神经功能保持完好,1例术中即发生左侧喉返神经麻痹.40例均满意记录到声带非同步性自发喉肌肌电图波,刺激显露和探测到的12例喉返神经,均能诱发喉肌同步肌电图反应波.最小刺激电流强度阈值为0.08～0.35 mA,平均最小电刺激阈值为0.25 mA,适宜刺激电流范围为0.2～1.0 mA.结论喉返神经术中实时监控技术具有灵敏度高、准确性强和稳定性好的特点,可以在术中提供神经受刺激的同步信息,起到早期预警的作用.该技术的应用可以减少医源性喉返神经损伤,预防严重并发症的发生.术中可以不用预先解剖喉返神经,提高手术安全性.     

甲状腺手术解剖喉返神经对其损伤的预防作用

目的：探讨甲状腺手术中解剖喉返神经对预防喉返神经损伤的作用。方法：回顾性分析我科1993年1月～2005年5月手术治疗的甲状腺病变患者517例,解剖喉返神经组（解剖组）163例187侧,未解剖喉返神经组（未解剖组）354例438侧。未解剖组按常规甲状腺手术保护喉返神经行走区的神经。解剖组于甲状腺下极下方离气管食管间沟0～1cm处先找到喉返神经,顺其向上解剖;或先找到喉返神经入喉处,顺其向下解剖。边解剖喉返神经边切除甲状腺病变,解剖长度视甲状腺病变而定。结果：解剖组喉返神经部分解剖123侧,全程解剖64侧,除2例甲状腺癌已侵犯喉返神经术前已有声带麻痹外,无一例发生医源性喉返神经损伤。未解剖组发生喉返神经损伤3例3侧,喉返神经损伤发生率为0．7％,明显高于解剖组,差异有统计学意义（P〈0．01）。结论：甲状腺手术中解剖喉返神经对喉返神经损伤有预防作用。解剖喉返神经的长度视病变大小及部位而定。远离气管食管间沟的良性病变可不解剖喉返神经。     

Vagus nerve stimulation: quality control in thyroid and parathyroid surgery

This paper describes the use of the Neurosign 100 Nerve Monitor and vagus nerve stimulation in the identification and assessment of the integrity of the recurrent laryngeal nerve (RLN) during thyroid and parathyroid surgery. Vocal fold function was assessed pre- and post-operatively in all patients undergoing thyroid and parathyroid surgery. The nerve monitor, used in association with endotracheal electrodes, was used to confirm correct RLN identification and demonstrate its integrity at the completion of surgery. There were 21 unilateral and 19 bilateral neck explorations. In these 40 patients, 57 of 59 RLNs were identified. The nerve monitor demonstrated RLN continuity in all but one case (equipment failure: electrode misplacement) after initial identification. Vagus nerve stimulation was performed in 21 patients without adverse sequelae. Damage to the RLN was identified in one of these patients, in whom direct RLN stimulation close to the larynx had failed to indicate discontinuity. Post-operatively this patient had a transient unilateral vocal fold palsy. The use of the Neurosign 100 Nerve Monitor is no substitute for meticulous surgery. Stimulation of the vagus nerve may be a more sensitive means of assessing RLN integrity during thyroid and parathyroid surgery than stimulation of the RLN itself. Confirmation of RLN integrity allows the surgeon to proceed with confidence to the contralateral side of the neck during hazardous bilateral explorations.     

Spontaneous laryngeal reinnervation after recurrent laryngeal or vagus nerve injury

OBJECTIVES: The status of innervation in patients with laryngeal paralysis is somewhat controversial. Electromyographic activity has been frequently documented in the laryngeal muscles of patients with laryngeal paralysis, and animal experiments report a strong propensity for reinnervation after laryngeal nerve injury. However, a study of intraoperative electromyography performed in patients during reinnervation surgery failed to document activity with stimulation of the recurrent laryngeal nerve (RLN). Noting the long-observed differences in the symptoms of patients with vagus nerve injury and those with RLN injury, I hypothesized that reinnervation is influenced by the site of nerve injury. METHODS: Cats were sacrificed at various intervals after resection of 1 cm of either the RLN or the vagus nerve, without any attempt to repair the nerve. RESULTS: Four months after RLN resection, distal nerve biopsy revealed unmyelinated axons scattered through fibrous tissue. By 6 months, myelinated axons were organized, and electromyographic and histologic examination showed preferential reinnervation of the thyroarytenoid muscle. After vagotomy, the RLN was fibrotic and no axons were present. Both the thyroarytenoid and posterior cricoarytenoid muscles were fibrotic and had no electromyographic activity. CONCLUSIONS: The results confirm the strong propensity for laryngeal reinnervation after RLN injury, but not after vagus nerve injury. Preferential reinnervation of adductor muscles may account for a medial position of the paralyzed vocal fold.     

Incidence of vocal cord paralysis with and without recurrent laryngeal nerve monitoring during thyroidectomy

OBJECTIVE: To compare the incidence of postoperative vocal cord paresis or paralysis in a cohort of patients who underwent thyroidectomy with and without continuous recurrent laryngeal nerve (RLN) monitoring by a single senior surgeon. We hypothesize that continuous RLN monitoring reduces the rate of nerve injury during thyroidectomy DESIGN: Retrospective medical chart review. SETTING: Academic tertiary care medical center. PATIENTS: A total of 684 patients (1043 nerves at risk) who underwent thyroid surgery under general anesthesia. MAIN OUTCOME MEASURE: Incidence of vocal cord paresis or paralysis in patients who underwent thyroid surgery with continuous RLN monitoring vs those undergoing surgery without continuous RLN monitoring. RESULTS: The incidence of unexpected unilateral vocal cord paresis based on RLNs at risk was 2.09% (n = 14) in the monitored group and 2.96% (n = 11) in the unmonitored group. This difference was not statistically significant. The incidence of unexpected complete unilateral vocal cord paralysis was 1.6% in each group. Two of the 5 paralyses in the unmonitored group and 7 of the 11 paralyses in the monitored group had complete resolution. CONCLUSIONS: Monitoring of the RLN does not appear to reduce the incidence of postoperative temporary or permanent complete vocal cord paralysis. There appeared to be a slightly lower rate of postoperative paresis with RLN monitoring, but this difference was not statistically significant.     

Warning criterion to predict recurrent laryngeal nerve injury with percentage reduction of the amplitude of V2/R2d in neuromonitoring thyroidectomy

ObjectiveTo evaluate the contribution of amplitude reduction compared vagal stimulation at the end of thyroid dissection (V2) to the most distal RLN stimulation during thyroidectomy in predicting postoperative vocal cords paralysis (VCP).MethodsPatients with intact preoperative RLN function who underwent monitored thyroidectomy between August 2017 and April 2018 were included. We routinely tested the exposed RLN at the lowest proximal end (R2p signal) and the most distal end near the laryngeal entry point (R2d signal), and then routinely detected the vagal nerve at the horizontal plane of the inferior pole of thyroid with 2mA stimulation current. The cut-off value was calculated with Receiver Operating Characteristic curve. Rates of specificity, sensitivity, negative predictive value, positive predictive value (PPV) for V2/R2d and R2p/R2d were compared.ResultsPercentage reduction of the amplitude of V2/R2d ranged from 34.8% to 76.7%. Twenty-two (1.5%) nerves developed temporary VCP, in which one nerve with VCP showed no significant amplitude reduction at the end of the surgery. There was no permanent or bilateral VCP. Sensitivity, specificity, PPV, NPV, and accuracy for the amplitude reduction of V2/R2d> 60% were 95.5%, 99.8%, 99.9%, 98.2%, respectively, for R2p/R2d were 99.5%, 99.2%, 63.6%, 99.9%, 97.7%, respectively.ConclusionPercentage reduction of the amplitude of V2/R2d is a reliable and practical warning criterion for RLN injury. When the amplitude reduction> 60% surgeons should consider the possibility of postoperative VCP and correct some surgical maneuvers.     

改良Miccoli术中喉返神经的显露及损伤预防

目的：探讨甲状腺改良Miccoli术中解剖显露喉返神经的方法及预防喉返神经损伤的临床意义。方法：回顾性分析218例行甲状腺改良Miccoli术患者的资料，均在内镜直视下寻找喉返神经并进一步显露直至人喉处，行甲状腺次全切或腺叶全切除。结果：218例患者手术均获成功，无中转开放手术。术中均成功显露颈段喉返神经并保护之。术中、术后病理证实结节性甲状腺肿185例，甲状腺腺瘤8例，甲状腺乳头状微小癌25例。2例甲状腺乳头状微小癌及1例有鼻咽癌放疗史的患者，术后出现暂时性声嘶，3个月内声带活动恢复正常。结论：甲状腺改良Miccoli术中解剖显露喉返神经是该手术顺利进行的关键，是预防喉返神经损伤的有效方法。     

Recurrent laryngeal nerve monitoring in thyroid and parathyroid surgery: the University of Michigan experience

OBJECTIVES/HYPOTHESIS: Intraoperative monitoring of the recurrent laryngeal nerve (RLN) is finding increasing acceptance during thyroidectomy. Recently, a laryngeal surface electrode was introduced to enable another form of noninvasive monitoring of the RLN. The present report examines the University of Michigan experience with RLN monitoring using the postcricoid surface electrode. STUDY DESIGN: All patients undergoing partial or total thyroidectomy or parathyroidectomy from January 1999 to July 2001 were considered candidates for the study. Audiologists trained in intraoperative electrophysiological techniques performed all of the monitoring. METHODS: Data collected on each patient included 1) stimulation threshold for a laryngeal compound muscle action potential on initial RLN identification, 2) stimulation threshold of the laryngeal compound muscle action potential on completion of the procedure, and 3) flexible fiberoptic evaluation of the larynx at the initial postoperative visit and at the 3-month follow-up visit. The average duration of follow-up was 9.8 months with a range of 3 to 60 months. RESULTS: The average minimum current required for stimulation on first identification of all nerves was 0.57 mA (+/-0.48 mA). After completion of the procedure a mean threshold level of 0.42 mA (+/-0.55 mA) was obtained during direct RLN stimulation. Post-dissection stimulation of the RLN on the side of tumor dissection was 0.92 mA (+/-0.65 mA) compared with a stimulation threshold of 0.76 mA (+/-0.57 mA) for the nontumor side. CONCLUSIONS: Electromyographic monitoring of the RLN using a postcricoid surface electrode provides a safe, simple, and effective method for intraoperative monitoring during thyroid or parathyroid surgery. Further, evoked electromyography confirms RLN integrity at the conclusion of surgery.     

Recurrent laryngeal nerve monitoring during cricotracheal resection

Cricotracheal resection has been advocated in the management of severe subglottic stenosis. One of the possible complications of this procedure is injury to the recurrent laryngeal nerve (RLN). We describe a new technique in which electrodes are placed directly through the thyroid cartilage to monitor the RLN intraoperatively. Nine cats' left vocal cords were monitored, and 3 cats had unilateral vocal cord injury postoperatively: 1 right cord and 2 left cords. Even though this technique was efficacious, our ability to monitor the RLNs was difficult secondary to difficulty interpreting the nerve monitor's wave morphologies. The future use of RLN nerve monitoring during cricotracheal resection will depend upon the ability to distinguish true stimulation from artifact. Monitoring of the RLN could be beneficial in patients with previous operations for subglottic stenosis.     

喉返神经与甲状腺下动脉及其分支的显微解剖关系研究

目的探讨甲状腺术区喉返神经与甲状腺下动脉及分支的显微解剖关甲状腺手术中喉返神经保护提供解剖学参考。方法对69例(80侧)头颈肿瘤患者甲状腺区的喉返神经和甲状腺下动脉及分支进行显微解剖及观测。结果 38.0%(30/79)的喉返神经在入喉前分为前、后两支,59.5%(47/79)的甲状腺下动脉存在二级分支,40.5%(32/79)的甲状腺下动脉存在三级分支。51.9%(41/79)的甲状腺下动脉二、三级分支与喉返神经相夹持、勾绕或小段伴行,其中24.1%(19/79)的甲状腺下动脉二、三级分支发出明确与喉返神经相勾绕或平行伴行的分支直至入喉处。结论甲状腺下动脉二、三级分支于近入喉处与喉返神经解剖关系密切,是甲状腺手术中喉返神经损伤的主要责任血管。     

The utility of evaluating true vocal fold motion before thyroid surgery

OBJECTIVE: The objective of this study was to evaluate the utility of screening laryngoscopic examination in evaluating vocal fold (VF) mobility before thyroid surgery. METHODS: The authors conducted a retrospective chart review of 340 patients who have undergone thyroid surgery from January 1998 to June 2005 and had preoperative laryngoscopy by mirror, fiberoptic, or videostroboscopic examination. Reports of preoperative voice change or complaint and reports of preoperative VF examination, including the method of examination, were recorded. For patients with VF motion impairment, reports of the intraoperative condition of the recurrent laryngeal nerve (RLN), preoperative diagnosis based on fine needle aspiration, and final postoperative histopathologic examination results were recorded. RESULTS: Twenty-two patients were found to have preoperative VF motion impairment, of which seven (32%) patients were asymptomatic with no detectable subjective or objective voice problems. This differs significantly from the hypothesis that patients with VF motion impairment are always symptomatic (P=.009). Using voice symptoms as a screening test to predict VF motion impairment in 340 patients reveals that the sensitivity was 68%, specificity was 91%, positive predictive value (PPV) was 31%, and negative predictive value (NPV) was 98%. Among the 22 patients with preoperative VF motion impairment, five (72%) of the seven asymptomatic patients had benign, slowly progressive disease on their final histopathology reports. Six of these asymptomatic patients had their preoperative VF evaluation by fiberoptic examination, whereas one patient had indirect mirror laryngoscopy. Of 22 patients with preoperative VF motion impairment, five (22.5%) patients had abnormal VF mobility contralateral to the thyroid lesion on their preoperative evaluation, and only two of them had nerve injury reported after a previous thyroid surgery. This result differs significantly from the hypothesis that impaired mobility is ipsilateral to the side of the lesion (P=.05). CONCLUSIONS: Patients without voice complaints can have VF motion impairment. Patients can also have VF motion impairment contralateral to the thyroid lesion. Preoperative VF examination helps counsel patients appropriately about the risks of surgery and helps outline a plan for the extent of surgery while minimizing the medicolegal ramifications of iatrogenic RLN injury.     

A novel method in predicting immediate postoperative facial nerve function post acoustic neuroma excision.

To determine whether the percentage calculated by dividing the amplitude of postexcision direct facial nerve stimulus responses (at pontomedullary junction) by the amplitude of distal ipsilateral transcutaneous (stylomastoid region) maximal stimulus responses and response amplitude progression by increasing stimulus intensities have predictive value for determining normal or near-normal (House-Brackmann Grade 1 or 2) immediate postoperative facial nerve function. STUDY DESIGN: Intraoperative recordings of three muscle groups: 1) frontalis, 2) orbicularis oculi, and 3) orbicularis oris. Postexcision direct facial nerve stimulation at the pontomedullary junction and transcutaneous maximal facial nerve stimulation at the ipsilateral stylomastoid region and their associated response amplitudes were recorded. SETTING: Tertiary referral center. PATIENTS AND METHODS: Patients who underwent acoustic neuroma surgery from January 2004 to March 2006 with intraoperative facial nerve monitoring and an intact facial nerve after tumor excision were included. Recordings were available for 38 patients. RESULTS: With a stimulus intensity of 0.3 mA at the root exit zone, there was an 81% positive predictive value in patients that exhibited a compound action potential of greater than 20% of maximum (sensitivity, 81%). This increased to 93% when the compound action potential was greater than 50% of maximum. When the amplitude increase was greater than 5 microV, there was a 77% positive predictive value (sensitivity, 87%). CONCLUSION: The percentage of the response amplitude of direct facial nerve stimulation at the pontomedullary junction when compared with the maximum response amplitude of ipsilateral transcutaneous stimulation at the stylomastoid foramen is a good predictor of normal to near-normal immediate postoperative facial nerve function. Progression of amplitude response also seems to be a good predictor of normal to near-normal immediate postoperative facial nerve function.     

甲状腺手术中解剖喉返神经的意义

目的:探讨甲状腺手术中解剖喉返神经的意义及预防喉返神经损伤的方法.方法:回顾性分析230例行甲状腺手术患者的资料,所有患者均在全身麻醉下进行,行单侧腺叶切除术109例,单侧腺叶加峡部切除术59例,甲状腺次全切除术44例,甲状腺全切除术18例.术中常规解剖显露喉返神经;根据术中病变情况决定手术切除范围,手术前后分别进行喉镜观察声带活动情况.结果:解剖暴露喉返神经共292条(右侧156条,左侧136条);位于气管食管沟内走行者134条,偏离者158条;神经位于下动脉深面通过197例(67.5%),神经位于动脉浅面通过60例(20.5%).神经在动脉分支之间通过24例(8.2%),神经分支与动脉分支交叉穿过者11例(3.8%).喉返神经入喉前分支者185条(63.4%),未分支直接入喉者107条(36.6%).术后8例出现声音嘶哑,经过治疗7例恢复,1例经6个月后对侧声带超越代偿嘶哑改善,无永久性声音嘶哑和呼吸困难.结论:甲状腺手术中解剖喉返神经是防止术后喉返神经损伤的有效方法.     

Intraoperative recurrent laryngeal nerve monitoring in revision thyroidectomy

Recurrent laryngeal nerve (RLN) palsy is one of the most important complications after thyroid and parathyroid surgery. There is controversy in the literature regarding whether or not intraoperative nerve monitoring decreases the risk of injury. We report our experience using Nerve Integrity Monitoring (NIM) system in cases of revision thyroidectomy, providing clear indications for its use. A series of 97 patients who underwent revision thyroidectomy with and without intraoperative NIM alternately was evaluated. There were 121 RLN patients at risk. Use of NIM during revision thyroidectomy was not statistically significant compared to revision operation without monitoring (p value = 0.059). Furthermore, comparison of operative times either with or without NIM showed that use of NIM led to statistically significant prolonged operation time (p value <0.001). There is no strict indication to use RLN monitoring during thyroid surgery, especially as there is no statistical evidence that the use of this technique decreases the incidence of RLN palsy, although there is a trend especially in difficult revision cases.     

Laryngeal mask anesthesia with intraoperative laryngoscopy for identification of the recurrent laryngeal nerve during thyroidectomy

OBJECTIVES/HYPOTHESIS: A critical step in thyroidectomy involves definitive identification of the recurrent laryngeal nerve (RLN). Using the laryngeal mask airway, identification of the RLN can be facilitated by stimulation of the nerve while monitoring vocal cord movement with a fiberoptic laryngoscope. We present this technique as an effective and safe means to identify the RLN during thyroid surgery, with significant advantages over existing techniques in appropriately selected patients. STUDY DESIGN: Retrospective case series. METHODS: We performed thyroidectomy on 8 patients (13 RLN identifications) in which laryngeal mask airway anesthesia with fiberoptic laryngoscopy was used to identify the RLN. Results are reviewed with regard to postoperative vocal cord function, as well as intraoperative and postoperative courses with laryngeal mask airway anesthesia. RESULTS: In all 13 cases in which the RLN was sought, it was definitively identified by witnessing brisk vocal cord movement on a video screen with stimulation of the RLN. No patient had postoperative vocal cord paresis or paralysis. Overall recovery from laryngeal mask airway anesthesia was uneventful and had advantages when compared with general anesthesia with endotracheal intubation. CONCLUSIONS: Laryngeal mask airway anesthesia with intraoperative fiberoptic laryngoscopy to identify the RLN is effective and safe in carefully selected patients. Advantages include decreased postoperative throat discomfort, absence of coughing during emergence from anesthesia, and elimination of the possibility of vocal cord mobility impairment secondary to RLN ischemia from the endotracheal tube balloon. In addition, this technique is applicable in operations besides thyroid surgery, in which definitive identification of the RLN is indicated.     

Intraoperative nerve monitoring reduces recurrent laryngeal nerve injury in geriatric patients undergoing thyroid surgery

Objective: This research was aimed to investigate whether the intraoperative nerve monitoring (IONM) can reduce the incidence of recurrent laryngeal nerve (RLN) injury in geriatric patients undergoing thyroid surgery.

Methods: This retrospective cohort study included 522 geriatric patients undergoing thyroid surgery between January 2013 and June 2016 in the Sun Yat-sen Memorial Hospital. Patients with IONM during the surgery (n?=?340) were compared with patients without IONM (n?=?212). RLN injury was verified by direct or indirect laryngoscope and relative factors for injury would be retrospectively analyzed.

Results: The use of IONM group showed significant reduction in both total and transient RLN injury incidence, when compared with that in control group (1.76 versus 4.72%, p?=?.01 and 1.32 versus 3.67%, p?=?.03, respectively). However, the permanent RLN injury incidence did not show difference between the two groups (p?=?.3).

Conclusions: Our finding showed the use of IONM resulted in significantly reduction in RLN injury incidence. The technology of IONM is safe and convenient to detect, track and monitor the complete function of RLN and to provide the guidance for the surgeons during the thyroid surgery in geriatric patients, who are at high risk of RLN injury.     

喉返神经解剖在甲状腺手术中的意义

目的探讨甲状腺术中解剖喉返神经(recurrent laryngeal nerve,RLN)在预防神经损伤中的作用。方法回顾分析174例甲状腺肿瘤,84例术中常规解剖喉返神经,90例按传统方法对喉返神经行径区进行保护,未解剖喉返神经。结果解剖喉返神经组神经暂时性损伤1例,无永久性损伤病例,总损伤率为1.2%;未解剖喉返神经组暂时性损伤3例,永久性损伤3例,总损伤率为6.7%,经统计学处理(x2检验),差异有统计学意义(P<0.05)。结论甲状腺手术中解剖喉返神经能减少喉返神经的损伤,但术者需充分掌握神经行径的解剖特点,术中正确地辨认喉返神经。     

Value of recurrent laryngeal nerve monitoring in the operative strategy during total thyroidectomy and parathyroidectomy

ObjectiveThe purpose of this study was to assess the role of recurrent laryngeal nerve (RLN) monitoring in the operative strategy during total thyroidectomy and parathyroidectomy. Due to the risk of serious respiratory complications of bilateral recurrent nerve paralysis, two-stage surgery may be considered in the case on negative stimulation of the first side.Patients and methodsThis prospective study was conducted in 100 consecutive patients between May 2007 and March 2011. Translaryngeal monitoring was performed. When stimulation of the RLN on the first side dissected was negative, dissection of the other side was deferred to avoid the risk of bilateral RLN paralysis.ResultsThe main surgical indications were thyroid carcinoma (34%), Graves’ disease (27%), multinodular goitre (27%) and parathyroid hyperplasia (9%) with seven cases of redo surgery. Four RLN identified on the first side gave a negative response to stimulation and surgery to the other side was therefore deferred. Transient unilateral RLN paralysis was observed in these four patients and two cases of RLN paralysis were observed among patients with positive RLN stimulation. Among the 96 contralateral RLNs tested, two were not visualized (one case of transient RLN paralysis, one case of permanent RLN paralysis), two gave a negative response to stimulation (two cases of permanent RLN paralysis) and 92 gave a positive response to stimulation (nine cases of transient RLN paralysis, including two cases associated with transient paralysis of the first side, and one case of permanent RLN paralysis). The incidence of RLN paralysis by nerve was 9.6% for transient RLN paralysis and 2% for permanent (unilateral) RLN paralysis.ConclusionWhen bilateral RLN dissection is planned, RLN monitoring is particularly useful to limit the risk of bilateral RLN paralysis. Two-stage thyroidectomy, following functional recovery of the damaged RLN, can therefore be proposed. The risk of bilateral RLN paralysis was avoided in four patients, while transient bilateral RLN paralysis was observed in two patients despite positive stimulation.     

Innervation of the paralyzed laryngeal muscles by phrenic motoneurons. A quantitative study by light and electron microscopy.

In the cat, inspiratory opening of the paralyzed glottis recovered after unilateral or bilateral reinnervation of the posterior cricoarytenoid (PCA) muscles by phrenic axons. The morphometric analysis of the regenerated recurrent laryngeal nerves (RLNs), showed that proliferation was abundant; 4 months after the nerve anastomosis, more than 500 myelinated axonal branches repopulated the RLNs. The mean diameter of motor axons (3.5 to 5.0 microns) was lower than in normal phrenic and RLN (8 to 10 microns), and the mean internode length was about half that of the normal RLN. Histochemical examination of the PCA muscle revealed that muscle fiber composition (44% type I and 56% type II muscle fiber) was fairly similar to that of normal PCA. The contraction time of the reinnervated muscles was as long as 60 msec at the time of movement recovery, but it shortened to 25 to 30 msec when the reinnervation time increased. These anatomical and functional results support the choice of the phrenic nerve for laryngeal reinnervation.