Ansa Cervicalis External Branch Anastomosis to Restore High Tone Voice in Thyroid Surgery.

OBJECTIVES: Injury to the external branch of the superior laryngeal nerve (EBSLN) causes low-pitch voice and voice fatigue, particularly in female subjects, and available treatments are limited. Here, we assess a novel surgical procedure to restore a high-tone voice: ansa cervicalis to EBSLN anastomosis (A-E anastomosis). METHODS: Between November 2012 and April 2022, 13 patients (12 female) underwent unilateral EBSLN resection and A-E anastomosis, while 20 (16 female) underwent EBSLN resection during thyroid surgery. Patients (4494 women and 1025 men) with normal laryngoscopy scheduled for thyroid surgery served as normal controls. Phonatory function was examined using a Phonation Analyzer PA-1000 preoperatively and intermittently postoperatively. RESULTS: In patients who underwent A-E anastomosis, high-tone voice pitch decreased significantly postoperatively (673.9-471.5 Hz, p = 0.047), with restoration achieved within 5 months. The mean voice pitch in female patients who underwent A-E anastomosis, EBSLN resection, and controls were 580.4, 522.8, and 682.0 Hz, respectively, indicating a significant decrease in EBSLN resection patients than controls (p = 0.002). The (mean - 1SD) of high-tone voice pitch in female controls was 497 Hz; exceeding this may indicate recovery to a high-tone voice. Overall, 73% (8/11) of A-E anastomosis patients exceeded this value, which was marginally larger than the 43% (6/14) who underwent EBSLN resection. Data on male subjects are limited. There were no cases of adverse functional or cosmetic events. CONCLUSIONS: A-E anastomosis, a novel simple procedure, restored high-tone voice to some extent without any adverse events and thus warrants further investigation. LEVEL OF EVIDENCE: 3 Laryngoscope, 134:3868-3873, 2024.

Is identification and dissection of the external laryngeal nerve necessary during thyroidectomy? A prospective study.

BACKGROUND: Compared to the recurrent laryngeal nerve, the EBSLN (or external laryngeal nerve) is less studied in terms of its course and relationship with the thyroid gland. This is a prospective intraoperative study designed to identify the anatomical variations of the EBSLN in relation to the IPC, the superior thyroid pedicle, and the point where the nerve crosses the STA. Additionally, the study aims to propose a technical procedure for its preservation. METHODS: We conducted a prospective study of 50 patients (total of 100 nerves) undergoing total thyroidectomy at the Department of Surgery 'B' in Ibn Sina Hospital, Rabat. Intraoperatively, the EBSLN was visually identified and preserved before ligating the superior thyroid vessels. Each nerve was categorized using established classification systems. RESULTS: The overall pooled EBSLN identification rate was 82%. Cernea type IIa (nerves crossing the STA less than 1 cm above the upper edge of the superior thyroid pole) and Friedman type II (nerves piercing the lower fibers of the IPC) were the most prevalent (64% and 44%, respectively). Kierner type IV (nerves crossing the branches of the STA immediately above the upper pole of the thyroid gland) was represented in 27% of cases. CONCLUSION: A better understanding of surgical anatomy of the neck allows for better results of thyroidectomy by preserving the external and recurrent laryngeal nerves.

Assessment of different classification systems for predicting the risk of superior laryngeal nerve injury during thyroid surgery: a prospective cohort study.

Background: A multitude of anatomical variations have been noted in the external branch of the superior laryngeal nerve (EBSLN). In this study, intraoperative neuromonitoring (IONM) was used to assess the potential value of the different classical EBSLN classifications for predicting the risk of EBSLN injury. Methods: In total, 136 patients with thyroid nodules were included in this prospective cohort study, covering 242 nerves at risk (NAR). The EBSLN was identified by observing the cricothyroid muscle twitch and/or typical electromyography (EMG) biphasic waveform. The EBSLNs were classified by Cernea classification, Kierner classification, and Friedman classification, respectively. The EMG parameters and outcomes of vocal acoustic assessment were recorded. Results: The distribution of Cernea, Kiernea, and Friedman subtypes were, respectively, Cernea 1 (40.9%), Cernea 2A (45.5%), Cernea 2B (10.7%), Kierner 1 (40.9%), Kierner 2 (45.5%), Kierner 3 (10.7%), Kierner 4 (2.9%) and Friedman 1 (15.7%), Friedman 2 (33.9%), Friedman 3 (50.4%). The amplitudes of EBSLN decreased significantly after superior thyroid pole operation, respectively, in Cernea 2A (193.7 vs. 226.6µV, P=0.019), Cernea 2B (185.8 vs. 221.3µV, P=0.039), Kierner 2 (193.7vs. 226.6µV, P=0.019), Kierner 3 (185.8 vs. 221.3µV, P=0.039), Kierner 4 (126.8vs. 226.0µV, P=0.015) and Friedman type 2 (184.8 vs. 221.6µV, P=0.030). There were significant differences in Fmax and Frange for Cernea 2A (P=0.001, P=0.001), 2B (P=0.001, P=0.038), Kierner 2 (P=0.001), Kierner 3 (P=0.001, P=0.038), and Friedman 2 (P=0.004, P=0.014). In the predictive efficacy of EBSLN injury, the Friedman classification showed higher accuracy (69.8% vs. 44.3% vs. 45.0%), sensitivity (19.5% vs. 11.0% vs. 14.0%), and specificity (95.6% vs. 89.9% vs. 89.9%) than the Cernea and Kierner classifications. However, the false negative rate of Friedman classification was significantly higher than other subtypes (19.5% vs. 11.0% vs. 14.0%). Conclusion: Cernea 2A and 2B; Kierner 2, 3, and 4; and Friedman 2 were defined as the high-risk subtypes of EBSLN. The risk prediction ability of the Friedman classification was found to be superior compared to other classifications.

Intraoperative cricothyroid muscle electromyography may contribute to the monitorization of the external branch of the superior laryngeal nerve during thyroidectomy.

Background: In thyroid surgery, both the recurrent laryngeal nerve (RLN) and external branch of the superior laryngeal nerve (EBSLN) should be preserved for maintaining the vocal cord functions. We aimed to evaluate whether EMG of the CTM applied after the superior pole dissection provided additional informative data to the IONM via ETT or not, regarding the EBSLN function. Methods: The prospectively collected data of the patients, who have undergone thyroidectomy with the use of IONM for the exploration of both the RLN and EBSLN between October 2016 and March 2017, were evaluated retrospectively. Patients over 18 years of age with primary thyroid surgery for malignant or benign thyroid disease, and whom were applied CTM EMG with a needle electrode after the completion of thyroidectomy were included in the study. In the study, each neck side was evaluated as a separate entity considering the EBSLN at risk. Results: The data of 41 patients (32 female, 9 male) (mean age, 46.7 + 9.1; range, 22-71) were evaluated. Sixty seven EBSLNs out of 26 bilateral and 15 unilateral interventions were evaluated. With EBSLN stimulation after the superior pole dissection, positive glottic EMG waveforms via ETT were obtained in 45 (67.2%) out of 67, and the mean glottic amplitude value was 261 + 191 µV (min-max: 116-1086 µV). Positive EMG responses via the CTM EMG were achieved from all of the 67 EBSLNs (100%) with stimulation using a monopolar probe at the most cranial portion above the area of divided superior pole vessels. The mean value of CTM amplitudes via CTM EMG obtained with EBSLN stimulation was 5268 + 3916 µV (min-max:1215 -19726 µV). With EBSLN stimulation, the mean CTM EMG amplitude was detected significantly higher than the mean vocal cord amplitude (p<0.0001). The CTM EMG provided more objective quantifiable data regarding the EBSLN function (100% vs 67,2%, p<0.001). Conclusion: In addition to the IONM via ETT, intraoperative post-dissection CTM EMG via needle electrode is a safe, simple and applicable method that may provide significant additional informative data to IONM with ETT by obtaining and recording objective quantitative data related to the EBSLN function.

Visual identification and neuromonitoring vs. no sighting the external branch of the superior laryngeal nerve in thyroid surgery: a randomized clinical trial.

To evaluate the incidence of external branch of the superior laryngeal nerve (EBSLN) injuries after thyroid surgical procedures with or without the functional and visual identification of the EBSLN before ligation at the superior thyroid pole. Patients with papillary thyroid carcinoma (PTC) enrolled from a single tertiary referral academic medical center were assigned to functional and visual identification of EBSLN group (study group) or no identification of EBSLN group (controlled group). The main outcome measures were the incidence of EBSLN injury detected by the intraoperative neuromonitoring and Voice Handicap Index-10 (VHI-10) and Impairment Index-5 (VII-5) valuation questionnaires. Postoperative complications were recorded. A total of 140 (50.4%) patients were enrolled in study group and 138 (49.6%) in controlled group. In the study group, 110 (39.3%) EBSLNs were direct visual recognized and 170 (60.7%) nerves were visually identified with the help of neuromonitoring. Three patients in the study group and two patients in the controlled group were diagnosed with vocal cord paralysis. Six (4.4%) patients in the identification group and 37 (27.2%) patients in the no identification group presented no response from the stimulation of sternothyroid-laryngeal triangle. The VII-5 scores of the study group were significantly higher than those of the controlled group at one and three months postoperatively (P = 0.024 and P = 0.034). With significant lower scores of VII-5 and VHI-10, functional and visual identification of EBSLN might be necessary during thyroid surgery to protect the structural integrity and motor activity of the nerve.

Effect of mouse nerve growth factor combined with the exposure of the external branch of superior laryngeal nerve on voice changes after thyroidectomy: a prospective non-randomized controlled trial.

Background: The superior laryngeal nerve (SLN) injury may also affect vocal fold function and voice quality. It is efficient yet simple approach to expose the external branch of the superior laryngeal nerve (EBSLN). Neurotrophic agent mouse nerve growth factor (mNGF) to treat patients after thyroid surgery, and found it had significant efficacy in improving the voice of patients. However, the potential effectiveness and safety of mNGF combined with EBSLN were unclear. Methods: In this study, 96 patients who suffered from hoarseness after thyroidectomy at Hangzhou First People's Hospital between January 2018 and October 2019 were screened and divided into the control group and the observation group by patients' choice. In the control group, the SLN was not exposed. In the observation group, the SLN was exposed. The mNGF treatment was administered for observation group once a day at 20 µg each time for 4 weeks. The data of acoustic voice indicators was analysis by univariate analyses. Patients in both groups were followed up for more than 6 months. The rate of SLN damage was compared between two groups. Results: The baseline clinical characteristics of the two groups showed no statistic difference. The results showed that the fundamental frequency was significantly lower 1 month after surgery than 3 days after surgery in both groups. The fundamental frequency perturbation, shimmer, maximum phonation time, highest fundamental frequency, and dysphonia severity index in 1 month after surgery were significantly higher than they were 3 days after surgery (all P<0.001). There was no significant difference in the postoperative harmonic-to-noise ratio between the 2 groups (P=0.426). Conclusions: MNGF combined with the exposure and protection of the EBSLN effectively may prevent voice damage after thyroid surgery.

Can we routinely identify the external branch of the superior laryngeal nerves with neural monitoring?: a prospective report on 176 consecutive nerves at risk.

The external branch of the superior laryngeal nerve (EBSLN) provides motor function to the cricothyroid muscle (CTM). EBSLN damage produces changes in voice quality and projection. Intraoperative neuromonitoring (IONM) in thyroid surgery aims to optimize EBSLN control during dissection. We prospectively collected the data of 88 consecutive patients who underwent total thyroidectomy with IONM from July 2019 to December 2019. IONM was offered in the intermittent mode of application. We routinely searched for the EBSLN electromyographic (EMG) signal before (S1) and after (S2) dissection of the superior vascular peduncle. In the absence of the EMG signal, we observed the CTM twitch. We identified 141 (80%) S1 EMG signals, while we recorded the CTM twitch in 15 cases (8.5%). In 20 (11.3%) cases, we were unable to identify the EMG signal. Analysing the S2 results, we found loss of EBSLN signal in 11/141 cases (7.8%) identified with IONM in pre-dissection stimulation. Among the 20 cases without pre-dissection identification (we had not identified the external branch of the superior laryngeal nerve or the muscle twitch), in the post-dissection evaluation, we confirmed the loss of signal in 17 of 20 cases, equal to 85% (p < 0.001). Our data clearly show that intraoperative stimulation and recognition of EBSLN, performed before any dissection manoeuvre to the superior vascular thyroid pole, leads to a much higher rate of nerve conservation.

Simple technique to preserve the external branch of the superior laryngeal nerve during thyroidectomy: Clinical practicability of an attachable nerve stimulator.

OBJECTIVE: This study aimed to demonstrate the usefulness of an attachable magnetic nerve stimulator for preservation of the external branch of the superior laryngeal nerve (EBSLN) during thyroidectomy. METHODS: We retrospectively analyzed 120 female patients, of which 60 underwent thyroidectomy with an attachable magnetic nerve stimulator (magnetic group) and the remaining 60 underwent thyroidectomy with a conventional method without EBSLN identification (control group). For both groups, objective and subjective voice parameters were investigated on the day before surgery and at 2 weeks and 2 months after surgery. RESULTS: In the magnetic group, a magnetic nerve stimulator was used to ligate only the site without cricothyroid muscle (CTM) twitching, and thyroid surgery was successfully performed without damage to the EBSLN. In the control group, objective voice parameters, including fundamental frequency, voice range profile (VRP), highest VRP (VRP-H), and maximal phonation time, and the subjective thyroidectomy-related voice questionnaire score were significantly decreased at 2 months after surgery compared to preoperative values. Compared to the control group, the magnetic group did not show a significant decrease in the objective VRP and VRP-H at 2 months after surgery. CONCLUSION: The use of metallic surgical instruments with an attachable magnetic nerve stimulator may provide surgeons with real-time feedback on CTM twitching feedback and EBSLN status. Compared to direct EBSLN identification during thyroidectomy, this is a simple, easy, and noninvasive method for EBSLN preservation that is useful, especially for less-experienced surgeons.

Intraoperative Neuromonitoring in Thyroid and Parathyroid Surgery.

Background: It has been reported that the incidence of recurrent laryngeal nerve (RLN) injury is higher in an operational procedure in the thyroid and parathyroid region. Elevating voice pitch is achieved by the cricothyroid contraction, which in turn is innervated by the external branch of the superior laryngeal nerve (EBSLN). Due to the subtle nature and clinical variability of EBSLN damage, diagnosis may be difficult. The use of intraoperative neuromonitoring (IONM) as a supplement to enhance surgical identification in thyroid and parathyroid operation appeared to have collected momentum with operators. Methods: IONM clinical usage rationale, efficiency, and safety profile are discussed in this overview in thyroid and parathyroid surgery. Results: IONM usage incurred numerous skepticisms in decreasing the frequency of EBSLN or RLN injury. However, a recent article has shown the efficacy and benefits of using IONM in thyroid and parathyroid procedures. IONM facilitates the recognition of RLN and EBSLN, verifies its functional integrity, localizes the site of a nerve injury, and gives postsurgical function feedback. This technique has been successful in reducing rates of bilateral laryngeal paralysis, with the elevated safety profile for surgical patients. Conclusions: It is recommended using IONM in all thyroidectomies and in high-risk parathyroidectomies.

Endoscopic thyroidectomy versus traditional open thyroidectomy for identification of the external branch of the superior laryngeal nerve.

AIM: To explore the anatomical features of the external branch of the superior laryngeal nerve (EBSLN) and determine an effective approach for its preservation during endoscopic thyroidectomy (ET). METHODS: From January 2017 to December 2018, a total of 405 consecutive patients with thyroid disease were retrospectively analyzed. These patients were divided into the ET group and the open thyroidectomy (OT) group according to the surgical approaches. There were 195 cases in the ET group including 43 males and 152 females, and 210 cases in the OT group including 65 males and 145 females. The dissection process of EBSLN, detection rate, distribution of identification methods of the EBSLN and rate of voice change were recorded. RESULTS: There were 205 EBSLNs detected under direct vision in ET group for a detection rate of 88.0%, while 158 EBSLNs were detected under direct vision in OT group for a detection rate of 58.1%. But with the assistant of intraoperative neuromonitoring (IONM), the number of EBSLNs detected visually reached up to 220 in ET group and 226 in OT group, respectively, for a visual detection rate of 94.4% and 83.1%, respectively. There were significant difference in the rate of direct visual identification, total visual identification with IONM. Stratified risk estimation indicated that the tumor size and location were risk factors for the direct visual dissection of EBSLN. Stratified analysis by tumor size indicated that when tumor diameter was ≤ 4 cm, the incidence of vocal cord fatigue and total vocal changes in ET group was significantly lower than that in OT group. CONCLUSIONS: Recognition and exposure of the EBSLN can be facilitated by the magnification and focusing function of high-definition endoscopy and the advantage of a 30° variable angle. Full exposure of the sternothyroid-laryngeal triangle and fine dissection along the superior thyroid vessels is beneficial for recognizing the EBSLN.

Factors Influencing the Relationship of the External Branch of the Superior Laryngeal Nerve with the Superior Pole Vessels of the Thyroid Gland.

OBJECTIVES: In a thyroidectomy, the external branch of the superior laryngeal nerve (EBSLN) is a potential risk during the superior pole dissection due to its close anatomical relationship with the superior thyroid artery and its highly variable anatomy. In this study, we aimed to evaluate the relationship of EBSLN with the superior pole considering Cernea classification and the factors affecting this relationship. METHODS: The data of thyroidectomized 126 patients (95 female, 31 male) with 200 neck sides (mean age of 45.6±12.1 years) using intraoperative neuromonitoring (IONM) for the EBSLN exploration were evaluated retrospectively. During the superior pole dissection, the EBSLN course was classified according to Cernea classification after being confirmed with IONM. It was defined as a large goiter in the case of the thyroid lobe volume being >50 cc. The factors influencing the presence of type 2b, which has the highest risk of injury, were evaluated using logistic regression analysis. RESULTS: Of the 200 EBSLNs evaluated, 52 (26%) were type 1, 134 (68%) were type 2a, and 14 (7%) were type 2b. The mean volumes of the resected thyroid lobes were 22±25 cc (min-max: 2-136), 23±20 cc (3-163), and 39±24 cc (3-65) in type 1, 2a and 2b, respectively, which was significantly higher in type 2b (p=0.035). Presence of large goiter rates were 5.8% (n=3), 8.2% (n=11), 64.3% (n=9) in type 1, 2a, and 2b, respectively, and was significantly higher in type 2b (p=0.0001). There was no significant difference between EBSLN Cernea types concerning age, sex, nerve side, presence of cancer and hyperthyroidism. In logistic regression analysis, large goiter was the only independent factor associated with Cernea type 2b. In case of a lobe volume greater than 50 cc, the probability of type 2b presence was approximately 25 times higher (p<0.001, odds ratio: 25.262). CONCLUSION: Type 2b course of EBSLN is more common in large goiters, and it is 25 times more likely to be seen in the presence of a lobe volume over 50 cc. Thus, it should be considered that the probability of this high-risk course is significantly higher in large goiters.

Anatomía topográfica del nervio laríngeo superior: importancia quirúrgica en las tiroidectomías / Topographic anatomy of the upper laryngeal nerve: surgical importance in thyroidectomies

En las cirugías sobre la glándula tiroides se ha prestado mucha atención al manejo del nervio laríngeo inferior y de las glándulas paratiroides, no así del ramo lateral del nervio laríngeo superior, el cual es satélite del pedículo vascular superior de la glándula tiroides. El manejo del polo superior de la glándula tiroides requiere de un conocimiento acabado de su anatomía topográfica del área y está determinada por sus relaciones más importantes, dadas por el citado nervio y la arteria tiroidea superior principalmente. En este trabajo se pretende estudiar estas relaciones en base a la disección meticulosa del triángulo laringo-esternotiroideo ("Triángulo de Joll") de 25 cadáveres adultos formolizados. Como hallazgo relevante se informa que los "nervios en riesgo", según la clasificación de Cernea, que se basa en una distancia menor a un centímetro en el entrecruzamiento del nervio con la arteria tiroidea superior con respecto al polo superior de la glándula tiroides, es del 52 % para el lado derecho y 44 % para el lado izquierdo del cuello. El origen bajo de la arteria a nivel de la bifurcación carotídea se presenta asociada a un mayor número de "nervios en riesgo" en el lado izquierdo. Según el punto de penetración del ramo lateral del nervio laríngeo superior en el músculo constrictor inferior de la faringe se establece la clasificación de Friedman, muy útil sobre todo en cirugías ayudadas por la neuroestimulación. En esta clasifiacción los "nervios en riesgo" son aquellos que transcurrren superficial al músculo, mientras que los "nervios protegidos" serían aquellos que perforan el músculo en su porción superior. En este trabajo los "nervios en riesgo" se presentaron del lado izquierdo en el 56 % de los casos y del derecho en el 60 %, mientras que los "nervios protegidos" en el 24 % y 16 %, respectivamente.

In surgeries on the thyroid gland, much attention has been given to the management of the inferior laryngeal nerve and parathyroid glands, but not the external branch of the given by the aforementioned nerve and the superior thyroid artery. This paper intends to study these relationships based on the meticulous dissection of the larynx-sternothyroid triangle ("Joll triangle") of 25 formolized adult corpses. As a relevant finding, it is reported that the " nerves at risk" according to the Cernea classification, which is based on the distance less than one centimeter at the intersection of the nerve with the superior thyroid artery with respect to the upper pole of the gland, is 52 % for the right side and 44 % for the left side of the neck. The low origin of the artery at the level of the carotid bifurcation is associated with a greater number of "nerves at risk" on the left side. According to the penetration point of the external branch of the superior laryngeal nerve in the inferior pharyngeal constrictor muscle, the Friedman classification is established, very useful especially in surgeries aided by neurostimulation. In this classification the "nerves at risk" are those that run superficially to the muscle, while the protected nerves would be those that pierce the muscle in its upper part. In tis work, the "nerves at risk" presented on the left side in 56 % of the cases and the right side in 60 %, while those "protected" in 24 % and 16 % respectively.

New placement of recording electrodes on the thyroid cartilage in intra-operative neuromonitoring during thyroid surgery.

OBJECTIVE: During thyroid surgery, extreme caution is needed not to harm the recurrent laryngeal nerve and to avoid vocal cord palsy. Intra-operative neuromonitoring became increasingly popular as an adjunct to the gold standard of visual identification of the recurrent laryngeal nerve (RLN). Electromyographic (EMG) responses are normally recorded by electrodes attached to the endotracheal tube. Alteration in position can lead to false loss of signal. We developed thyroid cartilage electrodes that can be fixed directly onto the thyroid cartilage. STUDY DESIGN: Prospective clinical cohort METHODS: Thyroid surgery with intra-operative neuromonitoring using both endotracheal tube-based electrodes and thyroid cartilage electrodes was performed in 25 patients undergoing thyroid surgery. EMG data were collected and reported as median and interquartile ranges (IQR), and the results were compared with the x Wilcoxon signed-rank test for paired measurements. RESULTS: After stimulating vagal nerve (VN), recurrent laryngeal nerve (RLN) and external branch of the superior laryngeal nerve (EBSLN), significantly higher EMG amplitudes were measured before and after thyroid resection for the thyroid cartilage (TC) electrodes, in all comparisons except for the right VN. At the level of the left EBSLN, median amplitude of 560 mV (IQR 190-1050) before and 785 mV (IQR 405-3670) after resection was noted. At the level of the right EBSLN, median amplitude of 425 µV (IQR 257-698) before and 668 mV (IQR 310-1425) after resection was noted. Median amplitudes of 760 mV (IQR 440-1180) and 830 mV (IQR 480-1490) were noted at the left RLN, median amplitudes of 695 mV (IQR 405-1592) and 1078 mV (IQR 434-1895) were noted at the right RLN. CONCLUSION: Thyroid cartilage electrodes appear to be a feasible and reliable alternative for endotracheal electrodes.

The Impact of Post-thyroidectomy Paresis on Quality of Life in Patients with Nodular Thyroid Disease.

OBJECTIVE: To investigate the impact of postoperative paresis on disease-specific quality of life (DSQoL) after thyroidectomy in patients with benign nodular thyroid disease. STUDY DESIGN: Observational study. SETTING: University hospital. SUBJECTS AND METHODS: Patients were evaluated before and 3 weeks and 6 months after surgery in an individual prospective cohort study using videolaryngostroboscopy (VLS), voice range profile, voice handicap index (VHI), multidimensional voice program, maximum phonation time (MPT), and auditory perceptual evaluation. Changes in DSQoL were assessed by the Thyroid-specific Patient-Reported Outcome measure. Cohen's effect size was used to evaluate changes. RESULTS: Sixty-two patients were included, 55 of whom completed all examinations. Three weeks after surgery, a blinded VLS examination showed signs of paresis of either the recurrent laryngeal nerve or the external branch of the superior laryngeal nerve (RLN/EBSLN) in 13 patients (24%). A paresis corresponded to a 12 ± 28 point increase in VHI (P = .002) and was associated with a significant 4.3 ± 7.5 semitone decrease in the maximum fundamental frequency (P < .001) and a 5.3 ± 8.2 dB reduction in maximum intensity. Further, it was associated with a 4.5 ± 11.2 second reduction in MPT (P = .001) and an increase of 0.40 ± 1.19 in grade, 0.42 ± 1.41 in roughness, and 0.36 ± 1.11 in breathiness. Signs of postoperative RLN/EBSLN paresis correlated with an 11.0-point (P = .02) poorer improvement in goiter symptoms at both 3 weeks and 6 months after surgery. CONCLUSION: Signs of RLN/EBSLN paresis after thyroidectomy were associated with less pronounced improvement in goiter symptoms in patients with thyroid nodular disease. However, thyroidectomy was associated with an overall improved DSQoL by 6 months after surgery.

Identification of the External Branch of the Superior Laryngeal Nerve during Thyroid Surgery.

AIM: To compare the level of intra-operative identification of external branch of the superior laryngeal nerve (EBSLN) through classical conventional clinical methods of prevention against those applying intraoperative neuromonitoring (IONM). MATERIALS AND METHODS: The study included 102 patients with interventions on the thyroid gland performed in the surgical clinics of St George University Hospital and the Department of Special Surgery of Plovdiv Medical University. All operative procedures were performed by the standard technique of capsular dissection and IONM. RESULTS: Of all 102 thyroid procedures 87 (85.3%) patients underwent total thyroidectomy and 15 (14.7%) had unilateral thyroid lobectomy. One hundred fifty-five (82.01%) out of 189 expected EBSLN were identified and investigated intraoperatively when trying to identify visually EBSLN by the so called classical (conventional) methods of prevention. With the use of IONM, 181 (96.76%) EBSLN were correctly identified. Compared to the preliminary results of visual identification - 155/189 (82.01%) EBSLN, the degree of identification of EBSLN through IONM reached 96.76% which is a statistically significant difference (P <0.05) Conclusion: The use of IONM during thyroid resection significantly improves the degree of identification of EBSLN compared to conventional means of prevention. Routine use of IONM in surgical interventions on the thyroid gland will be beneficial for more secure identification and prevention of EBSLN.

The role of intraoperative neurological monitoring in identifying the external branch of superior laryngeal nerve / 中国肿瘤临床

Recurrent laryngeal nerve injury during thyroid surgery has captured the attention of all thyroid surgeons,but protection of the external branch of the superior laryngeal nerve(EBSLN)is often ignored.Injury to the EBSLN can cause hoarseness,sound fatigue, decreased frequency range,and other symptoms.Many difficulties exist in identifying the EBSLN;therefore,most surgeons are unable to perform routine exposure and protection of the EBSLN during operation for thyroid cancer.Intraoperative neurological monitoring has the potential to identify EBSLN and evaluate its functional integrity.Revealing EBSLN routinely,along with neurological monitoring during thyroid surgery can significantly reduce the incidence of postoperative neurological injury and improve operation safety.

Contribution of intraoperative neuromonitoring to the identification of the external branch of superior laryngeal nerve.

OBJECTIVE: We evaluated the contribution of intraoperative neuromonitoring to the visual and functional identification of the external branch of the superior laryngeal nerve. MATERIAL AND METHODS: The prospectively collected data of patients who underwent thyroid surgery with intraoperative neuromonitoring for external branch of the superior laryngeal nerve exploration were assessed retrospectively. The surface endotracheal tube-based Medtronic NIM3 intraoperative neuromonitoring device was used. The external branch of the superior laryngeal nerve function was evaluated by the cricothyroid muscle twitch. In addition, contribution of external branch of the superior laryngeal nerve to the vocal cord adduction was evaluated using electromyographic records. RESULTS: The study included data of 126 (female, 103; male, 23) patients undergoing thyroid surgery, with a mean age of 46.2±12.2 years (range, 18-75 years), and 215 neck sides were assessed. Two hundred and one (93.5%) of 215 external branch of the superior laryngeal nerves were identified, of which 60 (27.9%) were identified visually before being stimulated with a monopolar stimulator probe. Eighty-nine (41.4%) external branch of the superior laryngeal nerves were identified visually after being identified with a probe. Although 52 (24.1%) external branch of the superior laryngeal nerves were identified with a probe, they were not visualized. Intraoperative neuromonitoring provided a significant contribution to visual (p<0.001) and functional (p<0.001) identification of external branch of the superior laryngeal nerves. Additionally, positive electromyographic responses were recorded from 160 external branch of the superior laryngeal nerves (74.4%). CONCLUSION: Intraoperative neuromonitoring provides an important contribution to visual and functional identification of external branch of the superior laryngeal nerves. We believe that it can not be predicted whether the external branch of the superior laryngeal nerve is at risk or not and the nerve is often invisible; thus, intraoperative neuromonitoring may routinely be used in superior pole dissection. Glottic electromyography response obtained via external branch of the superior laryngeal nerve stimulation provides quantifiable information in addition to the simple visualization of the cricothyroid muscle twitch.

Innervation of the human posterior cricoarytenoid muscle by the external branch of the superior laryngeal nerve.

BACKGROUND: The posterior cricoarytenoid muscle is the abductor muscle for the vocal cords and is innerved by the recurrent laryngeal nerve (RLN). The purpose of this study was to present our determination if the external branch of the superior laryngeal nerve (SLN) contributes to the motor innervation of the posterior cricoarytenoid muscle. METHODS: We performed electromyographies (EMGs) via needle electrodes on 47 posterior cricoarytenoid muscles from 28 patients during thyroidectomy (9 lobectomies and 19 total thyroidectomies) with intraoperative neural monitoring. The RLN, vagus nerve, and external branch of the SLN were stimulated intraoperatively and the responses were evaluated by EMG. RESULTS: Positive EMG responses were obtained from 16 (34%) of 47 posterior cricoarytenoid muscles after external branch of the SLN stimulation. The EMG of the posterior cricoarytenoid muscle was unilaterally positive in 8 of 19 patients (42%) with total thyroidectomy, and 2 of 19 patients (10.5%) were bilaterally positive. CONCLUSION: The external branch of the SLN contributes to the ipsilateral posterior cricoarytenoid muscle innervation in one-third of the cases. This contribution is usually unilateral, but is occasionally bilateral.

Innervation of the human cricopharyngeal muscle by the recurrent laryngeal nerve and external branch of the superior laryngeal nerve.

PURPOSE: The major component of the upper esophageal sphincter is the cricopharyngeal muscle (CPM). We assessed the contribution of the laryngeal nerves to motor innervation of the CPM. METHODS: We performed an intraoperative electromyographic study of 27 patients. The recurrent laryngeal nerve (RLN), vagus nerve, external branch of the superior laryngeal nerve (EBSLN), and pharyngeal plexus (PP) were stimulated. Responses were evaluated by visual observation of CPM contractions and electromyographic examination via insertion of needle electrodes into the CPM. RESULTS: In total, 46 CPMs (24 right, 22 left) were evaluated. PP stimulation produced both positive visual contractions and electromyographic (EMG) responses in 42 CPMs (2080 ± 1583 µV). EBSLN stimulation produced visual contractions of 28 CPMs and positive EMG responses in 35 CPMs (686 ± 630 µV). Stimulation of 45 RLNs produced visible contractions of 37 CPMs and positive EMG activity in 41 CPMs (337 ± 280 µV). Stimulation of 42 vagal nerves resulted in visible contractions of 36 CPMs and positive EMG responses in 37 CPMs (292 ± 229 µV). Motor activity was noted in 32 CPMs by both RLN and EBSLN stimulation, 9 CPMs by RLN stimulation, and 3 CPMs by EBSLN stimulation; 2 CPMs exhibited no response. CONCLUSIONS: This is the first study to show that the EBSLN contributes to motor innervation of the human CPM. The RLN, EBSLN, or both of the nerves innervate the 90, 75, and 70 % of the CPMs ipsilaterally, respectively.

The electrophysiology of thyroid surgery: electrophysiologic and muscular responses with stimulation of the vagus nerve, recurrent laryngeal nerve, and external branch of the superior laryngeal nerve.

OBJECTIVES/HYPOTHESIS: Correlation of physiologically important electromyographic (EMG) waveforms with demonstrable muscle activation is important for the reliable interpretation of evoked waveforms during intraoperative neural monitoring (IONM) of the vagus nerve, recurrent laryngeal nerve (RLN), and external branch of the superior laryngeal nerve (EBSLN) in thyroid surgery. STUDY DESIGN: Retrospective chart review. METHODS: Data were reviewed retrospectively for thyroid surgery patients with laryngeal nerve IONM from January to December, 2015. EMG responses to monopolar stimulation of the vagus/RLN and EBSLN were recorded in bilateral vocalis, cricothyroid (CTM), and strap muscles using endotracheal tube-based surface and intramuscular hook electrodes, respectively. Target muscles for vagal/RLN and EBSLN stimulation were the ipsilateral vocalis and CTM, respectively. All other recording channels were nontarget muscles. RESULTS: Fifty surgical sides were identified in 37 subjects. All target muscle mean amplitudes were significantly higher than in nontarget muscles. With vagal/RLN stimulation, target ipsilateral vocalis mean amplitude was 1,095.7 µV (mean difference range = -814.1 to -1,078 µV, P < .0001). For EBSLN stimulation, target ipsilateral CTM mean amplitude was 6,379.3 µV (mean difference range = -6,222.6 to -6,362.3 µV, P < .0001). Target muscle large-amplitude EMG responses correlated with meaningful visual or palpable muscular responses, whereas nontarget EMG responses showed no meaningful muscle activation. CONCLUSIONS: Target and nontarget laryngeal muscles are differentiated based on divergence of EMG response directly correlating with presence or absence of visual and palpable muscle activation. Low-amplitude EMG waveforms in nontarget muscles with neural stimulation can be explained by the concept of far-field artifactual waveforms and do not correspond to a true muscular response. The surgeon should be aware of these nonphysiologic waveforms when interpreting and applying IONM during thyroid surgery. LEVEL OF EVIDENCE: 4 Laryngoscope, 127:764-771, 2017.