Traction Injury of Recurrent Laryngeal Nerve During Thyroidectomy

Study on the Influencing Factors of Short-Term Recovery of Neurological Symptoms after Carotid Body Tumor Resection

OBJECTIVE

To compare the differences in the short-term recovery from neurological symptoms (SRN) (≤ 6 months) and clinical characteristics of patients with different Shamblin classifications carotid body tumor (CBT) resection and to analyze the risk factors affecting SRN after surgery.

METHODS

Patients who underwent CBT resection between June 2018 and September 2022 were recruited. Perioperative factors and indicators of the nature of the tumor were recorded. The risk factors affecting SRN after CBT resection were analyzed using logistic regression analysis.

RESULTS

Eighty-five patients (43.86 ± 12.7 years, 46 females) were included, 40 (47.06%) of whom exhibited SRN. Univariate logistic regression showed that preoperative symptoms, surgical side, bilateral posterior communicating artery (PcoA) opening, some indicators of tumor size, operative/anesthesia time, and Shamblin III classification were correlated with postoperative neurological prognosis (all p < 0.05). After adjusting for confounders, preoperative symptoms (OR, 5.072; 95% CI 1.027-25.052; p = 0.046), surgical side (OR, 0.025; 95% CI 0.003-0234; p = 0.001), bilateral PcoA opening (OR, 22.671; 95% CI 2.549-201.666; p = 0.005), distance from the tip of the C2 dens to the superior aspect (dens-CBT) (OR, 0.918; 95% CI 0.858-0.982; p = 0.013) and Shamblin III classification (OR, 28.488; 95% CI 1.986-408.580; p = 0.014) were correlated with postoperative neurological symptom recovery.

CONCLUSION

Preoperative symptoms, surgical side (right), bilateral PcoA opening, a short dens-CBT and Shamblin III classification are risk factors affecting SRN after CBT resection. Early resection is recommended for small-volume CBTs without neurovascular compression or invasion to obtain SRN.

The Feasibility Study of Intraoperative RLN Monitoring Using Cricothyroid Membrane-Inserted Needle Electrodes During Thyroid Surgery

OBJECTIVE

This study evaluated the feasibility, stability, safety, and economy of cricothyroid membrane (CM)-inserted needle electrodes for recurrent laryngeal nerve monitoring.

STUDY DESIGN

Parallel and controlled study.

SETTING

Clinical research center for thyroid diseases of Shaanxi province.

METHODS

A total of 64 patients in the needle electrodes group (104 recurrent laryngeal nerves [RLNs]) and 44 patients in the endotracheal tube (ETT)-based electrodes group (80 RLNs) underwent monitored thyroidectomy. The evoked electromyography (EMG) signals detected by the 2 electrodes were recorded and analyzed. The changes in EMG during Berry's ligament traction and tracheal displacement were compared. All patients underwent preoperative and postoperative laryngoscopy within 1 week.

RESULTS

Both electrodes successfully recorded typical evoked laryngeal EMG waveforms from RLNs. The needle electrodes recorded relatively higher amplitudes and similar latencies compared to ETT-based electrodes. The evoked EMG signals attributed to needle electrodes could accurately predict the function of RLNs with 100% sensitivity and specificity. The reduction in the recorded amplitudes attributed to needle electrodes was higher than that observed with ETT-based electrodes during Berry's ligament traction or trachea displacement, whereas a similar increase in the latencies was recorded in the 2 groups. Particularly, Berry's ligament traction was more likely to lead to EMG amplitude reduction and latency prolongation. The needle electrodes group recorded 2 cases of minor bleeding on the CM. The needle electrodes were more cost-effective than ETT-based electrodes.

CONCLUSION

The CM-inserted needle electrodes are feasible, stable, safe, and economical for RLN monitoring, and they provide an alternative novel intraoperative neural monitoring format for thyroid surgeons.

Advantages of Intraoperative Neuromonitoring Over Direct Visualization of the Recurrent Laryngeal Nerve During Thyroidectomy

BACKGROUND

The well-recognized risk of injury to the recurrent laryngeal nerve (RLN) during thyroidectomy has instigated various preventive measures. One such measure involves directly visualizing the RLN, but this is not always feasible in practice. A more recent approach involves using intraoperative neuromonitoring to identify and preserve the RLN. This study aims to evaluate the effectiveness of intraoperative neuromonitoring compared to single visualization of the RLN in averting nerve injury.

METHODS

We conducted a retrospective, observational, and descriptive study on a cohort of 218 patients. A Chi-square test was employed to determine the influence of intraoperative neuromonitoring on the incidence of nerve injury, with P < 0.05 considered statistically significant. We used Jamovi software version 2.3.18 to analyze the data.

RESULTS

Of the 218 patients, intraoperative neuromonitoring was used in 150 (68.8%) cases; none of which resulted in nerve injury. Conversely, 68 (31.2%) patients underwent surgery without the use of neuromonitoring, with two (2.9%) patients in this group experiencing nerve injury (p=0.037). In comparison, the risk of nerve injury was 0% in the group monitored intraoperatively and 2.94% in the group that did not undergo intraoperatively neuromonitoring. Further, the relative risk of complications was 0.66% in patients operated with neuromonitoring, while it was 5.88% in the group operated without neuromonitoring, thus demonstrating a clinically significant protective against vasculonervous complications.

CONCLUSION

The results advocate for the use of intraoperative neuromonitoring, whenever available, as it is a safe method for significantly decreasing the incidence of RLN injury during thyroidectomy compared with only visualization.

The Role of Primary Repair of the Recurrent Laryngeal Nerve during Thyroid/Parathyroid Surgery in Vocal Outcomes-A Systematic Review

Recurrent laryngeal nerve (RLN) injury is a well and long-known complication of thyroid and parathyroid surgery that significantly affects the quality of life of patients. Despite the advances in surgical techniques and technology, it still occurs in clinical practice either as temporary paresis or as permanent paralysis of the corresponding vocal cord. The purpose of the current systematic review is to examine the value of intraoperative repair of the RLN in voice restoration. A systematic review of the existing literature was conducted using PubMed, Scopus, Cochrane Library, and Google Scholar databases according to the PRISMA guidelines. The systematic review resulted in 18 studies, which met the inclusion criteria. An improvement in phonatory function and voice quality was observed in all these studies after immediate RLN reconstruction (not always statistically significant). This improvement appears to be comparable to or even higher than that achieved with other methods of repair, and in some cases, the improvement approaches levels found in normal subjects. Intraoperative RLN reconstruction is not widely used in clinical practice, but the evidence so far makes it a viable and safe alternative to traditional techniques with better long-term results, as it prevents the occurrence of atrophy of the vocal cord and should be considered in the operating room if possible.

Intraoperative Neuromonitoring and Optical Magnification in the Prevention of Recurrent Laryngeal Nerve Injuries during Total Thyroidectomy

Background and Objectives: Recurrent laryngeal nerve (RLN) paralysis is a fearful complication during thyroidectomy. Intraoperative neuromonitoring (IONM) and optical magnification (OM) facilitate RLN identification and dissection. The purpose of our study was to evaluate the influence of the two techniques on the incidence of RLN paralysis and determine correlations regarding common outcomes in thyroid surgery. Materials and Methods: Two equally sized groups of 50 patients who underwent total thyroidectomies were examined. In the first group (OM), only surgical binocular loupes (2.5×−4.5×) were used during surgery, while in the second group (IONM), the intermittent NIM was applied. Results: Both the operative time and the length of hospitalization were shorter in the OM group than in the IONM group (median 80 versus 100 min and median 2 versus 4 days, respectively) (p < 0.05). The male patients were found to have a five-fold higher risk of developing transient dysphonia than the females (adjusted OR 5.19, 95% IC 0.99−27.18, p = 0.05). The OM group reported a four-fold higher risk of developing transient hypocalcemia than the IONM group (OR 3.78, adjusted OR 4.11, p = 0.01). Despite two cases of temporary bilateral RLN paralysis in the IONM group versus none in the OM group, no statistically significant difference was found (p > 0.05). No permanent RLN paralysis or hypoparathyroidism have been reported. Conclusions: Despite some limitations, our study is the first to compare the use of IONM with OM alone in the prevention of RLN injuries. The risk of recurrent complications remains comparable and both techniques can be considered valid instruments, especially if applied simultaneously by surgeons.

Selective Electrical Surface Stimulation to Support Functional Recovery in the Early Phase After Unilateral Acute Facial Nerve or Vocal Fold Paralysis

This article addresses the potential clinical value of surface electrical stimulation in the acute phase of denervation after the onset of facial nerve or recurrent laryngeal nerve paralysis. These two nerve lesions are the most frequent head and neck nerve lesions. In this review, we will work out several similarities concerning the pathophysiology features and the clinical scenario between both nerve lesions, which allow to develop some general rules for surface electrical stimulation applicable for both nerve lesions. The focus is on electrical stimulation in the phase between denervation and reinnervation of the target muscles. The aim of electrostimulation in this phase of denervation is to bridge the time until reinnervation is complete and to maintain facial or laryngeal function. In this phase, electrostimulation has to stimulate directly the denervated muscles, i.e. muscle stimulation and not nerve stimulation. There is preliminary data that early electrostimulation might also improve the functional outcome. Because there are still caveats against the use of electrostimulation, the neurophysiology of denervated facial and laryngeal muscles in comparison to innervated muscles is explained in detail. This is necessary to understand why the negative results published in several studies that used stimulation parameters are not suitable for denervated muscle fibers. Juxtaposed are studies using parameters adapted for the stimulation of denervated facial or laryngeal muscles. These studies used standardized outcome measure and show that an effective and tolerable electrostimulation of facial and laryngeal muscles without side effects in the early phase after onset of the lesions is feasible, does not hinder nerve regeneration and might even be able to improve the functional outcome. This has now to be proven in larger controlled trials. In our view, surface electrical stimulation has an unexploited potential to enrich the early therapy concepts for patients with unilateral facial or vocal fold paralysis.

Intraoperative EMG recovery patterns and outcomes after RLN traction-related amplitude decrease during monitored thyroidectomy

OBJECTIVES

Traction injury is the most common type of recurrent laryngeal nerve (RLN) injury in thyroid surgery. Intraoperative neuromonitoring (IONM) facilitates early detection of adverse electromyography (EMG) effect, and this corrective maneuver can reduce severe and repeated nerve injury. This study aimed to evaluate intraoperative patterns and outcomes of EMG decrease and recovery by traction injury.

METHODS

644 patients received nerve monitored thyroidectomy with 1142 RLNs at risk were enrolled. Intermittent IONM with stimulating dissecting instrument (real-time during surgical procedure) and trans-thyroid cartilage EMG recording method (without electrode malpositioning issue) were used for nerve stimulation and signal recording. When an EMG amplitude showed a decrease of >50% during RLN dissection, the surgical maneuver was paused immediately. Nerve dissection was restarted when the EMG amplitude was stable.

RESULTS

44/1142 (3.9%) RLNs exhibited a >50% EMG amplitude decrease during RLN dissection and all (100%) showed gradual progressive amplitude recovery within a few minutes after releasing thyroid traction (10 recovered from LOS; 34 recovered from a 51-90% amplitude decrease). Three EMG recovery patterns were noted, A-complete EMG recovery (n=14, 32%); B-incomplete EMG recovery with an injury point (n=16, 36%); C-incomplete EMG recovery without an injury point (n=14, 32%). Patients with postoperative weak or fixed vocal cord mobility in A, B, and C were 0(0%), 7(44%), and 2(14%), respectively. Complete EMG recovery was found in 14 nerves, and incomplete recovery was found in another 30 nerves. Temporary vocal cord palsy was found in 6 nerves due to unavoidable repeated traction.

CONCLUSION

Early detection of traction-related RLN amplitude decrease allows monitoring of intraoperative EMG signal recovery during thyroid surgery. Different recovery patterns show different vocal cord function outcomes. To elucidate the recovery patterns can assist surgeons in the intraoperative decision making and postoperative management.

Micropatterned Poly(D,L-Lactide-Co-Caprolactone) Conduits With KHI-Peptide and NGF Promote Peripheral Nerve Repair After Severe Traction Injury

Severe traction injuries after stretch to peripheral nerves are common and challenging to repair. The nerve guidance conduits (NGCs) are promising in the regeneration and functional recovery after nerve injuries. To enhance the repair of severe nerve traction injuries, in this study KHIFSDDSSE (KHI) peptides were grafted on a porous and micropatterned poly(D,L-lactide-co-caprolactone) (PLCL) film (MPLCL), which was further loaded with a nerve growth factor (NGF). The adhesion number of Schwann cells (SCs), ratio of length/width (L/W), and percentage of elongated SCs were significantly higher in the MPLCL-peptide group and MPLCL-peptide-NGF group compared with those in the PLCL group in vitro. The electromyography (EMG) and morphological changes of the nerve after severe traction injury were improved significantly in the MPLCL-peptide group and MPLCL-peptide-NGF group compared with those in the PLCL group in vivo. Hence, the NGCs featured with both bioactive factors (KHI peptides and NGF) and physical topography (parallelly linear micropatterns) have synergistic effect on nerve reinnervation after severe traction injuries.

Correlation between Electrophysiological Change and Facial Function in Parotid Surgery Patients

This observational study investigated intraoperative electrophysiological changes and their correlation with postoperative facial expressions in parotidectomy patients with visual confirmation of facial nerve (FN) continuity. Maximal electromyography(EMG) amplitudes of the facial muscles corresponding to temporal, zygomatic, buccal and mandibular branches were compared before/after FN dissection, and facial function at four facial regions were evaluated before/after parotidectomy in 112 patients. Comparisons of 448 pairs of EMG signals revealed at least one signal decrease after FN dissection in 75 (67%) patients. Regional facial weakness was only found in 13 of 16 signals with >50% amplitude decreases. All facial dysfunctions completely recovered within 6 months. EMG amplitude decreases often occur after FN dissection. An amplitude decrease >50% in an FN branch is associated with a high incidence of dysfunction in the corresponding facial region. This study tries to establish a standard facial nerve monitoring (FNM) procedure and a proper facial function grading system for parotid surgery that will be useful for the future study of FNM in parotid surgery.

Anatomical, Functional, and Dynamic Evidences Obtained by Intraoperative Neuromonitoring Improving the Standards of Thyroidectomy

The use of intraoperative neuromonitoring (IONM) is getting more common in thyroidectomy. The data obtained by the usage of IONM regarding the laryngeal nerves’ anatomy and function have provided important contributions for improving the standards of the thyroidectomy. These evidences obtained through IONM increase the rate of detection and visual identification of recurrent laryngeal nerve (RLN) as well as the detection rate of extralaryngeal branches which are the most common anatomic variations of RLN. IONM helps early identification and preservation of the non-recurrent laryngeal nerve. Crucial knowledge has been acquired regarding the complex innervation pattern of the larynx. Extralaryngeal branches of the RLN may contribute to the motor innervation of the cricothyroid muscle (CTM). Anterior branch of the extralaryngeal branching RLN has always motor function and gives motor branches both to the abductor and adductor muscles. In addition, up to 18% of posterior branches may have adductor and/or abductor motor fibers. In 70–80% of cases, external branch of superior laryngeal nerve (EBSLN) provides motor innervation to the anterior 1/3 of the thyroarytenoid muscle which is the main adductor of the vocal cord through the human communicating nerve. Furthermore, approximately 1/3 of the cases, EBSLN may contribute to the innervation of posterior cricoarytenoid muscle which is the main abductor of ipsilateral vocal cord. RLN and/or EBSLN together with pharyngeal plexus usually contribute to the motor innervation of cricopharyngeal muscle that is the main component of upper esophageal sphincter. Traction trauma is the most common reason of RLN injuries and constitutes of 67–93% of cases. More than 50% of EBSLN injuries are caused by nerve transection. A specific point of injury on RLN can be detected in Type 1 (segmental) injury, however, Type 2 (global) injury is the loss of signal (LOS) throughout ipsilateral vagus-RLN axis and there is no electrophysiologically detectable point of injury. Vocal cord paralysis (VCP) develops in 70–80% of cases when LOS persists or incomplete recovery of signal occurs after waiting for 20 min. In case of complete recovery of signal, VCP is not expected. VCP is temporary in patients with incomplete recovery of signal and permanent VCP is not anticipated. Visual changes may be seen in only 15% of RLN injuries, on the other hand, IONM detects 100% of RLN injuries. IONM can prevent bilateral VCP. Continuous IONM (C-IONM) is a method in which functional integrity of vagus-RLN axis is evaluated in real time and C-IONM is superior to intermittent IONM (I-IONM). During upper pole dissection, IONM makes significant contributions to the visual and functional identification of EBSLN. Routine use of IONM may minimalize the risk of nerve injury. Reduction of amplitude more than 50% on CTM is related with poor voice outcome.

The area under the waveform of electromyography for monitoring the external branches of the superior laryngeal nerve during thyroid surgery

Background

Injuries to the external branches of the superior laryngeal nerve (EBSLN) are difficult to identify during thyroidectomy. Monitoring the low amplitudes of the EBSLN during surgery has proven to be complicated. Therefore a new parameter, the area under the waveform (AUW), was designed to improve monitoring efficiency. The aim of this study was to determine the effectiveness of using AUW to monitor the EBSLN during thyroidectomy.

Methods

A total of 927 patients and 927 recurrent laryngeal nerves (RLN) and EBSLNs who underwent monitored unilateral thyroidectomy were included. Standardized intraoperative neuromonitoring procedures were followed. RLN injuries were confirmed using stroboscopic laryngoscopy after surgery. EBSLN injuries were identified by means of observing changes in cricothyroid muscle (CTM) twitches when stimulated. Amplitude and AUW changes were assessed using statistical analysis. The correlations between AUW and amplitude were verified using the ratio of the two parameters to determine any decreases that were observed in the number of nerve injury cases. The receiver operating characteristic (ROC) curve was used to estimate the prediction of nerve injury.

Results

The overall injury rates of the RLN and EBSLN were 3.56% and 2.05%, respectively. The AUW for the RLN and EBSLN presented linear correlations with amplitude. In the RLN injury cases, no significant difference was observed between the two parameters (P>0.05). In the cases with EBSLN injuries, the AUW decreased 64.5%±14.1%, on average, which was a greater decrease compared to that observed for amplitude 49.7%±22.2% (P<0.0001). The summary of the EBSLN injury prediction included, amplitude vs. AUW, AUC: 0.918 vs. 0.994; P<0.0001, and Youden's index: 31.54% vs. 49.58%.

Conclusions

The AUW demonstrated consistency with the change in amplitude, and the observed changes were significant. The use of the AUW allowed successful predictions for both RLN and EBSLN nerve injuries. Also, the sensitivity of AUW was greater than amplitude for predicting EBSLN injuries.