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.

Comparison of diffusion ranges at different local anesthetic volumes during superior laryngeal nerve block.

OBJECTIVES: Ultrasound-guided superior laryngeal nerve (SLN) block is a practical and painless approach to avoid the hemodynamic stress response during endotracheal intubation and relieve sore throat after laryngeal surgery. The main purpose of this study was to establish an optimal dosage of local anesthetic when performing SLN block to help anesthetists balance analgesia and side effects. METHODS: Twenty fresh larynx specimens were obtained immediately after resection and then injected with 2-, 3-, 4-, or 5- mL of a lidocaine-blue dye mixture at bilateral SLN puncture sites. Superficial areas of deposited blue dye were measured. Dye leakage and surrounding dyed tissue were recorded. Another 40 patients were included in the ultrasound investigation. Distances between the internal branch of the SLN (iSLN) and adjacent structures were calculated. RESULTS: The dye spread area was greater with the administration of larger doses, especially to the visceral space. A 2- or 3-mL injection of local anesthetic was sufficient to infiltrate the SLN gap. A higher incidence of dye leaking out of the thyrohyoid membrane and anterior epiglottis space was observed; furthermore, there was substantially more dyed hyoid/thyroid cartilage with 4 and 5 mL of injected dye mixture than 2 mL. There was no significant difference between the specimen and ultrasound measurements of for length of iSLN-adjacent structures. CONCLUSIONS: In the Chinese population, 2- or 3- mL of local anesthetic is a safe dose during SLN block. A larger volume could overflow from the cavity to cause complications. The thyrohyoid membrane combined with the superior laryngeal artery is a reliable target for positioning the iSLN during ultrasound-guided regional anesthesia.

Apneic response to fentanyl in adult rats: Role of laryngeal afferents.

Intravenous (systemic) bolus injection of fentanyl (FNT) reportedly induces an immediate vagal-mediated apnea; however, the precise origin of vagal afferents responsible for this apnea remains unknown. We tested whether intralaryngeal (local) application of FNT would also trigger an apnea and whether the apneic response to both local and systemic administration of FNT was laryngeal afferent-mediated. Cardiorespiratory responses to FNT were recorded in anesthetized male adult rats with and without bilateral sectioning of the superior laryngeal nerve (SLNx) or peri-SLN capsaicin treatment (SLNcap) to block local C-fiber signal conduction. Opioid mu-receptor (MOR)-immunoreactivity was detected in laryngeal C- and myelinated neurons. We found that local and systemic administration of FNT elicited an immediate apnea. SLNx, rather than SLNcap, abolished the apneic response to local FNT application though MORs were abundantly expressed in both laryngeal C- and myelinated neurons. Importantly, SLNx failed to affect the apneic response to systemic FNT administration. These results lead to the conclusion that laryngeal afferents' MORs are responsible for the apneic response to local, but not systemic, administration of FNT.

The Impact of Medical Comorbidities on Cough Improvement Following Superior Laryngeal Block.

INTRODUCTION: Chronic refractory cough is defined as cough lasting greater than 8 weeks and with an unclear etiology. Blockade of the internal branch superior laryngeal nerve (iSLN) has been shown to be safe and effective in the treatment of chronic cough. It remains unknown, however, if underlying comorbidities impact patient response to iSLN blockade. METHODS: A total of 44 patients aged 18 years and older were seen at our institution's Laryngology clinics between 2019 and 2022 and treated with iSLN blockade. Patient demographics, comorbidities, and pre- and post-treatment cough severity index (CSI) scores were collected from electronic medical records. Two-tailed independent T tests were used to compare CSI scores between groups with and without 4 underlying comorbidities: GERD, pulmonary history, smoking history, and evidence of vocal fold paresis or asymmetry on stroboscopy. RESULTS: Patients with a history of GERD or smoking and those with evidence of glottic insufficiency had similar improvements in CSI compared to those who did not (22.5 ± 26.4 vs 45.0 ± 47.1, P = .36; 32.7 ± 27.8 vs 29.0 ± 38, P = .85; 41.3 ± 18.8 vs 27.2 ± 37.7, P = .195). Patients with underlying pulmonary conditions had a significantly reduced response to iSLN blockade than did patients without underlying disease (9.85 ± 15.0 vs 47.4 ± 38.1, P = .028). CONCLUSION: Underlying lung pathology may contribute to decreased iSLN blockade efficacy in the treatment of chronic refractory cough from laryngeal hypersensitivity and its treatment is likely necessary for optimal symptom reduction. Characterizing patient comorbidity profiles can help guide patient counseling on expected treatment efficacy.

Continuous electrical stimulation of superior laryngeal nerve inhibits initiation of swallowing in anesthetized rats.

Pharyngeal electrical stimulation (PES) applies electrical stimulation to pharyngeal mucosa (PhM) and represents a useful approach to improve swallowing function in patients with dysphagia. To determine the optimal PES modality to treat dysphagia, the mechanism underlying the effects of PES on swallowing function must be elucidated. In this study, we evaluated how PES and electrical stimulation of the superior laryngeal nerve (SLN) modulate the initiation of swallowing in anesthetized rats. A swallow was evoked by electrical stimulation of the PhM, SLN, and nucleus of the solitary tract (nTS) and pharyngeal mechanical stimulation using a von Frey filament. A swallow was identified by electromyographic bursts in mylohyoid and thyrohyoid muscles. Bilateral SLN transection abolished the swallows evoked by PhM electrical stimulation. PhM and SLN electrical stimulation decreased swallowing frequency in a similar time-dependent manner. Intravenous administration of the GABAA receptor antagonist bicuculine did not affect the time-dependent change in swallowing frequency during SLN electrical stimulation. Continuous SLN electrical stimulation significantly inhibited pharyngeal mechanically and nTS-electrically evoked swallows compared with before and 5 min after stimulation. The present findings suggest that the SLN plays a primary role in PES-evoked swallows. Additionally, continuous SLN electrical stimulation inhibits the initiation of swallowing, and the modulation of central network associated with swallowing might be partially involved in this inhibition.

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.

Superior Laryngeal Nerve Block for Microlaryngoscopic Surgery: A Systematic Review and Meta-Analysis.

OBJECTIVES: To assess the safety and efficacy of superior laryngeal nerve block (SLNB) for microlaryngoscopic surgery (MLS). DATA SOURCES: PubMed, Embase, Web of Science, Ovid Medline, Cochrane Library, CNKI database, VIP database, Wanfang database, and trial registry databases. METHODS: PICOS principles were performed: adults undergoing MLS receiving SLNB compared with no-SLNB in randomized controlled trials were included. Primary outcome included the incidence of severe postoperative sore throat (POST). Secondary outcomes included perioperative mean arterial pressure (MAP) and heart rate (HR), incidence of severe postoperative cough, and anesthesia recovery time. RESULTS: Eleven articles with 728 patients were included. Results indicated that SLNB provides lower incidence of severe POST in post-extubation 30 min (relative ratio [RR] = 0.13; 95% confidence intervals [CIs]: 0.05 ~ 0.34), 2 h (RR = 0.09; 95% CI: 0.02 ~ 0.36), 4-6 h (RR = 0.11; 95% CI: 0.03 ~ 0.41), and 24 h (RR = 0.15; 95% CI: 0.03 ~ 0.83); lower MAP (tracheal intubation: standardized mean difference [SMD] = -1.59; 95% CI: -1.69 to -0.42); suspension laryngoscope insertion: (SMD = -0.98; 95% CI: -1.49 to -0.46); tracheal extubation: (SMD = -0.78; 95% CI:-1.24 to -0.31); post-extubation 5 min: (SMD = -0.95; 95% CI: -1.41 to -0.49); lower HR (tracheal intubation: mean difference [MD] = -9.71; 95% CI: -17.16 to -2.27); suspension laryngoscope insertion: (MD = -8.64; 95% CI: -16.79 to -0.49); tracheal extubation: (MD = -10.13; 95% CI: -17.86 to -2.39); post-extubation 5 min: (MD = -13.44; 95% CI: -22.53 to -4.35); lower incidence of severe postoperative cough in post-extubation 30 min (RR = 0.18; 95% CI: 0.06 ~ 0.57) and 2 h (RR = 0.13; 95% CI: 0.02 ~ 0.69); and shorter anesthesia recovery time (MD = -5.34; 95% CI: -8.81 to -1.86) compared to controls. CONCLUSIONS: SLNB could provide lower incidence of severe POST, more stable perioperative MAP and HR, lower incidence of severe postoperative cough, and shorter anesthesia recovery time for MLS. LEVEL OF EVIDENCE: I Laryngoscope, 134:3437-3446, 2024.

Indications and Short-Term Outcomes for In-Office Therapeutic Superior Laryngeal Nerve Block.

OBJECTIVE: Superior laryngeal nerve (SLN) block consists of injection of steroid and anesthetic at the internal branch of the SLN entry site. Prior case series have demonstrated beneficial effects on neurogenic cough. SLN blocks have also recently shown benefit for paralaryngeal pain. We describe short-term outcomes for multiple symptoms of irritable larynx syndrome (ILS) including neurogenic cough, dysphonia related to laryngeal hypersensitivity, inducible laryngeal obstruction (ILO), paralaryngeal pain, and isolated globus. METHODS: Retrospective review from 2 institutions of patients undergoing a single SLN block for the indications listed. Variables include age, sex, indication(s), known vagus neuropathy, and patient-reported outcomes at short-term follow-up. RESULTS: A total of 209 patients were included (59 males, 150 females; age: 58 ± 13 years). Twenty-six patients (12%) had a history of a vagus nerve injury. Indications included neurogenic cough (n = 149), dysphonia related to laryngeal hypersensitivity (n = 66), paralaryngeal pain (n = 50), ILO (n = 23), and isolated globus (n = 3). Some patients had multiple indications. Significant improvements in patient-reported measures occurred after a single SLN block within 2 to 4 weeks for neurogenic cough (cough severity index; 25.2 ± 11.2 to 19.0 ± 12.8; P < .001), dysphonia (voice handicap index-10; 22.1 ± 12.2-18.0 ± 13.3; P = .005), and ILO (dyspnea index; 21.0 ± 14.9-14.7 ± 15.7; P = .017). Subjective pain improved in 23 of 39 patients with paralaryngeal pain. There was no observed improvement for isolated globus. Presence of known vagal neuropathy or therapy around the time of SLN block did not affect outcome. CONCLUSION: SLN block can be an effective component of treatment for a variety of ILS symptoms. Patients may experience some improvement after 1 injection. LAY SUMMARY: Symptoms of irritable larynx syndrome, such as neurogenic cough, paralaryngeal pain, inducible laryngeal obstruction, and dysphonia related to laryngeal hypersensitivity can be challenging to manage. In-office Superior Laryngeal Nerve blocks can serve as a quick, well tolerated, adjunctive treatment with positive short-term outcomes. LEVEL OF EVIDENCE: 4.

Modulation of the swallowing reflex by stimulation of the gigantocellular reticular nucleus in the rat.

OBJECTIVES: The gigantocellular reticular nucleus (Gi) projects to the nuclues of the solitary tract nucleus (NTS) and the lateral reticular formation (LRF) above the nucleus ambiguus. The swallowing central pattern generator comprises the NTS and the LRF. The present study examined whether stimulation of the Gi affects the swallowing reflex. METHODS: Experiments were performed on urethane-anesthetized rats. The swallowing reflex was evoked by repetitive electrical stimulation of the superior laryngeal nerve and responses were recorded from the mylohyoid muscle on an electromyogram. The Gi was stimulated electrically. In addition, glutamate was injected into the Gi. The Friedman's test, followed by the Wilcoxon signed-rank test with Bonferroni correction, were used to assess the effects of electrical stimulation of the Gi. The Wilcoxon signed-rank test was used to assess the effects of glutamate injection into the Gi. Differences were considered significant at the P < 0.05 level. RESULTS: The number of swallows was significantly increased or decreased by electrical stimulation of the Gi or after injection of glutamate into the Gi. In both electrical stimulation of the Gi and injection of glutamate into the Gi, the onset latency of the first swallow was prolonged when the number of swallows was decreased but showed no change when the number of swallows was increased. CONCLUSIONS: The present results suggest that the Gi is involved in the control of swallowing.

Neurophysiology of the Superior Laryngeal Nerve in an In Vivo Rat Model.

OBJECTIVE: The superior laryngeal nerve (SLN) is fundamental in laryngeal sensation, cough reflex, and pitch control. SLN injury has substantial consequences including altered sensation, aspiration, and dysphonia. To date, in vivo measurement of the SLN remains elusive. The purpose of this study was to assess the feasibility of recording motor and sensory evoked potentials in a rat SLN model. METHODS: Twenty-two rat hemi-laryngeal preparations (n = 11) were obtained from 4-month-old Sprague-Dawley rats and included in this study. Compound motor action potentials (CMAPs) and motor unit number estimation (MUNE) were calculated by stimulating the SLN at the point of medial extension near the carotid artery and by placing a recording electrode on the cricothyroid muscle. Sensory response was determined through stimulation of the SLN and laryngoscopic visualization of a laryngeal adductor reflex (LAR). SLN and cricothyroid muscle cross-sections were stained and histologic morphometrics were quantified. RESULTS: Laryngeal evoked potentials were successfully obtained in all trials. Mean CMAP latency and negative durations were 0.99 ± 0.57 ms and 1.49 ± 0.57 ms, respectively. The median MUNE was 2.06 (IQR 1.88, 3.51). LAR was induced with a mean intensity of 0.69 ± 0.20 mV. Mean axon count, myelin thickness, and g-ratio were 681 ± 192.2, 1.72 ± 0.26, and 0.45 ± 0.04, respectively. CONCLUSIONS: This study demonstrates the feasibility of recording evoked response potentials following SLN stimulation. We hypothesize that this work will provide a tractable animal model to study changes in laryngeal sensation and cricothyroid motor function with aging, neurodegenerative disease, aspiration, or nerve injury. LEVEL OF EVIDENCE: NA Laryngoscope, 134:1778-1784, 2024.

The Role of Bilateral Superior Laryngeal Nerve Block in Managing Refractory Chronic Cough.

OBJECTIVE(S): The aim was to investigate the utilization and efficacy of bilateral superior laryngeal nerve block in patients with refractory chronic cough. METHODS: A retrospective chart review of 164 patients with refractory chronic cough who underwent bilateral SLN block at a single institution between November 2018 and September 2022 was performed. Demographics, comorbidities, and patient-reported outcomes including pre- and postinjection Leicester Cough Questionnaire (LCQ) scores were collected and analyzed. RESULTS: The cohort underwent an average of 2.97 bilateral injections (range 1-22), containing either corticosteroid and local anesthetic or corticosteroid alone. Notably, 116 of 164 of patients reported an average of 67.3% reduction in their symptoms, with the treatment effect lasting 7.60 weeks on average. The average pre- and postinjection LCQ scores were 9.70 and 13.82, respectively. A lower LCQ score represents a greater impairment of health status due to cough, and the minimum important change is 1.3 points between questionnaires. The average improvement on LCQ following bilateral SLN block was 4.11 points for this cohort. CONCLUSION: The use of in-office bilateral SLN block is an effective treatment that can be used alone or in conjunction with oral medications for the treatment of refractory chronic cough. LEVEL OF EVIDENCE: 4 Laryngoscope, 134:1773-1777, 2024.

The Application of Superior Laryngeal Nerve Block for Non-Cough Laryngeal Hypersensitivity.

OBJECTIVE(S): To investigate the effect of superior laryngeal nerve (SLN) block in patients with non-cough complaints relating to laryngeal who have failed conventional medical therapy. METHODS: Retrospective chart review of 46 patients who underwent SLN block for non-cough indications between July 2019 and March 2022 was performed. Demographics, comorbidities, and patient-reported outcomes were collected. The primary diagnoses for this group included: odynophagia, throat pain, cervicalgia, muscle tension dysphonia, globus sensation, hyoid bone syndrome, and Eagle syndrome. RESULTS: The cohort underwent an average of 1.24 bilateral injections (range 0-7) and 0.87 unilateral injections (range 0-4). About 35 of 46 patients reported an average of 51.0% improvement in their symptoms, with the treatment effect lasting 7.60 weeks on average. On subgroup analysis, the patients with spasmodic dysphonia, odynophagia, and hyoid bone syndrome had the best percent improvement on average (75%-77.5%). Patients with globus sensation had the lowest percent improvement on average in response to this therapy, reporting only about 25%. Five patients experienced a mild adverse reaction immediately following injection which resolved spontaneously. CONCLUSION: The use of in-office SLN block for non-cough disorders involving the larynx requires further study with larger sample sizes to better delineate the efficacy of these applications. LEVEL OF EVIDENCE: 4 Laryngoscope, 134:1765-1768, 2024.

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.

Anesthetic management of airway stent placement by rigid bronchoscopy with superior laryngeal nerve block while preserving spontaneous breathing: A case report.

Key Clinical Message: The combination of superior laryngeal nerve block can reduce the respiratory depression that occurs during management under total intravenous anesthesia. Abstract: Anesthetic management of endobronchial stent placement by rigid bronchoscopy requires the maintenance of spontaneous breathing while suppressing upper airway reflexes. The combination of superior laryngeal nerve block (SLNB) can reduce the respiratory depression that occurs during management under total intravenous anesthesia. The patient was diagnosed as having lung cancer with invasion into the right middle bronchus and stenosis of the right main bronchus on chest computed tomography, and emergency airway stent placement was performed. Sedation was initiated with propofol and dexmedetomidine, and ultrasound-guided SLNB was performed after local anesthetic spraying into the oral cavity and trachea. Bucking was minimally controlled during insertion of the rigid bronchoscope. The patient's intraoperative hemodynamics remained stable, and there were no hypoxic events. SLNB can provide the suppression of the upper airway reflex while minimizing effects on spontaneous breathing, and may be useful for achieving balanced anesthesia during rigid bronchoscopy.

Effect of superior laryngeal nerve block in alleviating sore throat after application of i-gel supraglottic airway: a randomized controlled trial.

BACKGROUND: Postoperative sore throat (POST) is a common complaint after supraglottic airway device (SAD) application. Internal branch of the superior laryngeal nerve (iSLN) block has the potential to alleviate POST. The aim of this trial was to explore the effect of iSLN block in alleviating sore throat, as well as to identify the potential risk factors for POST after SAD insertion. METHODS: One hundred thirty-four patients scheduled for elective gynecological surgery were randomized to either group T: tetracaine syrup (1%) for local lubrication on i-gel supraglottic device (n = 67) or group B: i-gel insertion with water based lubricant on it and followed by bilateral iSLN block (ropivacaine, 0.375%, 2 ml for each side) (n = 67). Under ultrasound guidance, iSLN was exposed below thyrohyoid membrane. The primary outcome was the intensity of sore throat at 6 h after surgery. In addition, POST score at 0.5 h and 24 h, the severity of postoperative swallowing discomfort, acoustic analysis and complications were measured. RESULTS: Compared with tetracaine syrup for local lubrication, iSLN block resulted in a reduced intensity of POST at 0.5 h (P = 0.044, OR = 1.99, 95%CI 1.02 to 3.88) and 6 h (P < 0.001, OR = 5.07, 95%CI 2.53 to 10.14) after surgery, as well as less severity of swallowing discomfort (P < 0.001, OR = 2.21, 95%CI 1.63 to 2.99) and cough (P = 0.039, OR = 1.97, 95%CI 1.04 to 3.73). The patients after iSLN block presented lower jitter and shimmer value in acoustic analysis at 6 h after surgery (P < 0.001). CONCLUSIONS: iSLN block was effective in alleviating POST, improving voice function, as well as reducing postoperative swallowing discomfort and coughing. TRIAL REGISTRATION: Chinese Clinical Trial Registry (ChiCTR2000037974) on 8th Sept 2020.

Modified anterior approach versus traditional posterior approach for ultrasound-guided superior laryngeal nerve block in awake endotracheal intubation: a randomized non-inferiority clinical trial.

STUDY OBJECTIVE: This study was undertaken to compare the effect of the modified ultrasound-guided anterior superior laryngeal nerve block (SLNB) with the traditional ultrasound-guided posterior SLNB in providing intubation conditions during awake tracheal intubation (ATI) in patients without difficult airway. DESIGN: Randomized, assessor-blind. Registration number: ChiCTR2200058086. SETTING: West China Hospital of Sichuan University, Chengdu, China. PATIENTS: 104 patients aged 18-65 years, of American Society of Anesthesiologists status I-III, posted for elective general surgery with general endotracheal anesthesia. INTERVENTIONS: The patients were randomized into two groups (modified group, n = 52; traditional group, n = 52). Modified anterior SLNB or traditional posterior SLNB was performed under ultrasound guidance. MEASUREMENTS: The primary outcome was the proportion of acceptable intubation condition (AIC), which was analyzed in both per-protocol (PP) and intention-to-treat (ITT) populations. The prespecified non-inferiority margin was -4.8%. Secondary outcomes included intubation success rate on the first attempt, hemodynamic parameters during ATI, time taken for airway anesthesia and intubation, recall of intubation, patient perception of comfort, and incidence and severity of postoperative complications. MAIN RESULTS: In the PP population, the proportion of AIC in the modified group was 49/49 (100%) and that in the traditional group was 49/49 (100%), absolute difference 0, lower limit of 1-sided 95% CI, -0.3%. In the ITT population, the primary outcomes in the modified and traditional group were 52/52 (100%) and 51/52 (98.1%), respectively, with an absolute difference of 1.9% and a lower limit of 1-sided 95% CI of -1.2%. The non-inferiority of modified ultrasound-guided anterior SLNB was confirmed in both populations. CONCLUSIONS: Among adults without difficult airways during videolaryngoscope-assisted ATI, the modified ultrasound-guided anterior SLNB, compared to the traditional posterior approach, showed a statistically non-inferior effect in terms of providing AIC.

Pathophysiological Mechanisms Underlying Unilateral Vocal Fold Paralysis in Female Patients: An Ultrasonographic Study.

OBJECTIVES: Laryngeal ultrasonography (LUS) has been suggested as an alternative diagnostic tool for unilateral vocal fold paralysis (UVFP). The present study applied LUS and quantitative laryngeal electromyography (LEMG) in female UVFP patients to investigate the pathophysiologic mechanisms of UVFP. METHODS: In this cross-sectional study, vocal fold (VF) length parameters included resting and phonating VF length measured using B-mode LUS, and color Doppler vibrating length (CDVL) measured using the color Doppler mode. RESULTS: Forty female patients with UVFP were enrolled, among whom 11 and 29 were assigned to the thyroarytenoid (TA) muscle+cricothyroid (CT) muscle group (with CT involvement) and the TA (without CT involvement) group, respectively. In the TA group, the turn frequency in thyroarytenoid-lateral cricoarytenoid (TA-LCA) on the paralyzed side, as observed through LEMG, correlated with the VF length during the resting phase (R=0.368, P=0.050) and CDVL values (R=0.627, P=0.000) on the paralyzed side. In the TA+CT group, the turn ratio in the CT muscle correlated with the normalized phonatory vocal length change (nPLC; R=0.621, P=0.041) on the paralyzed side. CONCLUSION: CDVL and nPLC are two parameters that can be utilized to predict the turn frequencies of TA-LCA in UVFP cases without CT involvement, and the turn ratio of CT in cases of UVFP with CT involvement, respectively. The findings suggest that LUS, as a noninvasive tool, can serve as an alternative method for assessing the severity of laryngeal nerve injury and offer valuable insights into the pathophysiology of UVFP.

Revisiting Loré's retrograde thyroidectomy from the perspective of preserving the external branch of the superior laryngeal nerve.

Background: Injury to the external branches of the superior laryngeal nerve (EBSLN) is the main reported cause of inexplicable post-thyroidectomy dysphonia (PTD) without recurrent laryngeal nerve (RLN) injury. Loré proposed a retrograde thyroidectomy (RT) technique in which the superior pole is dissected as a final step after the Berry ligament division, making this approach advantageous for protecting the EBSLN. However, evidence of this protective effect remains insufficient. We aimed to evaluate EBSLN function following RT and conventional thyroidectomy (CT) using postoperative electromyography (EMG). Methods: This is a retrospective cohort study conducted at a single tertiary center. Consecutive patients who had undergone CT or RT were included. Bilateral EMG of the cricothyroid muscle was performed 2-3 months postoperatively in all patients. Patient characteristics, postoperative findings of bleeding events, drain amount, hypocalcemia, calcium replacement, RLN function, and EBSLN function were thoroughly reviewed and compared between the two surgical approaches. Abnormalities in the EMG findings were reported based on the wave configuration, and the results were graded into four categories. Results: Seven hundred and thirty-one consecutive patients who underwent CT (n=341), or RT (n=390) were included, and a total of 1,179 RLNs and EBSLNs were at risk in CT (n=601) and RT (n=578). The CT and RT groups had similar clinical characteristics and surgical data. Two groups presented similar postoperative results for bleeding incidence, drain amount, and hypocalcemia. All RLNs were identified in both groups and their permanent function was preserved. EBSLN was significantly less frequently identified in the surgical field during RT than it was during CT (0.3% vs. 4.2%, respectively; P<0.001). Abnormal rates of postoperative EMG on the EBSLN were significantly lower in the RT group than in the CT group (1.7% vs. 7.8%, respectively; P<0.001), while the CT group presented with a higher grade of abnormal EMG (P<0.001). Conclusions: The RT technique may be beneficial for preserving EBSLN function. Meticulous capsular dissection and appropriate traction of the upper pole facilitated by RT are crucial for decreasing the risk of EBSLN injury, which can be achieved without directly identifying the nerve.

Efficacy of ultrasound guided superior laryngeal nerve block on sedation for delayed extubation in maxillofacial surgery with free flap reconstruction.

OBJECTIVE: Superior laryngeal nerve block (SLNB) is a regional anesthesia technique for addressing airway response. However, SLNB on the efficacy of sedation in patients with delayed extubation is unknown, particularly for maxillofacial surgery (MS). The aim of the study was to assess whether ultrasound guided (UG) SLNB reduces the incidence of moderate to severe cough for delayed extubation in MS with free flap reconstruction. METHODS: 60 patients were randomly assigned to the GEA group (control group) and the SLNB group (UG-SLNB postoperatively, study group). During the initial two postoperative hours, the incidence of moderate and severe cough, agitation, and the number of patients requiring rescue propofol and flurbiprofen were recorded. Additionally, the time spent under the target level of sedation, postoperative hemodynamics, and the total does of propofol during the postoperative 24 h were recorded. RESULTS: The data showed the SLNB group had a significantly lower incidence of moderate to severe cough and agitation (p < 0.05), and a longer sedation time (p < 0.05). The number of patients required rescue propofol and flurbiprofen, as well as the hemodynamic changes, were significantly different between the two groups (p < 0.05). CONCLUSION: The use of UG-SLNB is associated with reduced incidence of postoperative cough. Moreover, SLNB can enhance the efficacy of postoperative sedation with need of fewer agents postoperatively. CLINICAL TRIAL REGISTRATION: ChiCTR2000039982.