Feng Yu Chiang

Continuous monitoring of the recurrent laryngeal nerve in thyroid surgery: a critical appraisal

BACKGROUND AND PURPOSEnIntraoperative neuromonitoring (IONM) contributes in several ways to recurrent laryngeal nerve (RLN) protection. Notwithstanding these advantages, surgeons must be aware that the current, intermittent, mode of IONM (I-IONM) has relevant limitations. To overcome these I-IONM limitations, a continuous IONM (C-IONM) technology has been proposed.nnnMETHODSnA PubMed indexed literature review of the current limitations of I-IONM is presented and a commentary about C-IONM is provided presenting the preliminary results of research on this topic.nnnMAIN FINDINGSnI-IONM, despite the advantages it produces, presents some important limitations; to overcome these drawbacks a C-IONM technology has been introduced.nnnCONCLUSIONSnRLN traction injury is still the most common cause of RLN injury and is difficult to avoid with the application of I-IONM in thyroid surgery. C-IONM is useful to prevent the imminent traction injury by detecting progressive decreases in electromyographic amplitude combined with progressive latency increases. C-IONM seems to be a technological improvement. Likely, C-IONM by vagal nerve stimulation should enhance the standardization process, RLN intraoperative information, documentation, protection, training, and research in modern thyroid surgery. Although C-IONM is a promising technology at the cutting edge of research in thyroid surgery, we need more studies to assess in an evidence-based way all its advantages.

Severity of Recurrent Laryngeal Nerve Injuries in Thyroid Surgery

BackgroundFew studies in the literature have reported recovery data for different types of recurrent laryngeal nerve injuries (RLNIs). This study is the first attempt to classify RLNIs and rank them by severity.MethodsThis prospective clinical study analyzed 281 RLNIs in which a true loss of signal was identified by intraoperative neuromonitoring (IONM), and vocal cord palsy (VCP) was confirmed by a postoperative laryngoscope. For each injury type, the prevalence of VCP, the time of VCP recovery, and physical changes on nerves were analyzed. Additionally, different RLNI types were experimentally induced in a porcine model to compare morphological change.ResultsThe overall VCP rate in at-risk patients/nerves was 8.9/4.6xa0%, respectively. The distribution of RLNI types, in order of frequency, was traction (71xa0%), thermal (17xa0%), compression (4.2xa0%), clamping (3.4xa0%), ligature entrapment (1.6xa0%), suction (1.4xa0%), and nerve transection (1.4xa0%). Complete recovery from VCP was documented in 91xa0% of RLNIs. Recovery time was significantly faster in the traction group compared to the other groups (pxa0<xa00.001). The rates of temporary and permanent VCP were 98.6 and 1.4xa0% for traction lesion, 72 and 28xa0% for thermal injury, 100 and 0xa0% for compression injury, 50 and 50xa0% for clamping injury, 100 and 0xa0% for ligature entrapment, 100 and 0xa0% for suction injury, and 0 and 100xa0% for nerve transection, respectively. Physical changes were noted in 14xa0% of RLNIs in which 56xa0% of VCP was permanent. However, among the remaining 86xa0% IONM-detectable RLNIs without physical changes, only 1.2xa0% of VCP was permanent. A porcine model of traction lesion showed only distorted outer nerve structure, whereas the thermal lesion showed severe damage in the inner endoneurium.ConclusionsDifferent RNLIs induce different morphological alterations and have different recovery outcomes. Permanent VCP is rare in lesions that are visually undetectable but detectable by IONM. By enabling early detection of RLNI and prediction of outcome, IONM can help clinicians plan intra- and postoperative treatment.

Prospective study of vocal fold function after loss of the neuromonitoring signal in thyroid surgery: The International Neural Monitoring Study Group's POLT study.

Intraoperative neuromonitoring identifies recurrent laryngeal nerve (RLN) injury and gives prognostic information regarding postoperative glottic function. Loss of the neuromonitoring signal (LOS) signifies segmental type 1 or global type 2 RLN injury. This study aimed at identifying risk factors for RLN injury and determining vocal fold (VF) function initially and 6 months after definitive LOS.

Recurrent laryngeal nerve safety parameters of the Harmonic Focus during thyroid surgery: Porcine model using continuous monitoring.

The Harmonic Focus (HF) is one of the most popular energy‐based devices. The aim of this study was to provide recurrent laryngeal nerve (RLN) functional data that define the safety parameters of the HF during thyroidectomy.

Recurrent laryngeal nerve management in thyroid surgery: consequences of routine visualization, application of intermittent, standardized and continuous nerve monitoring.

The objective is to compare the consequences of routine visualization (RV) and the application of intermitted (I-IONM), standardized (S-IONM), and continuous monitoring (C-IONM) of recurrent laryngeal nerve (RLN) management. RV includes that 698 RLNs managed solely with visual identification. In a second period 777, RLNs were handled by the I-IONM. The third period 768 RLNs monitoring was performed according to the standards. C-IONM via VN stimulation included 626 RLNs. The following issues were analyzed and compared per each period study: RLN identification rate, branching detection, assessment of NRLN, intraoperative recognizable nerve damage, stage thyroidectomy rate, transient or definitive lesions, bilateral nerve palsy, and recovery time. Significance for nerve identification rate was achieved (pxa0=xa00.03) when the statistical analysis was applied between RV vs. S-IONM and C-IONM. Extralaryngeal bifurcation was identified in 21, 44, 43, and 46 of RLN dissected, respectively, per period (pxa0=xa00.005). The incidence of paralysis in identified and unidentified RLN was 3.8xa0% (107/2806) and 82xa0% (52/63), respectively. Rates of temporary/permanent RLNP were 16.7/1.7, 5/1.1, 4.5/1, and 3.1/0xa0% per period study, respectively (pxa0=xa00.07). Recognizable intraoperatively nerve damage was, respectively, 15, 45, 100, and 100xa0% for period study (pxa0=xa00.03). The recovery of injured nerves was significantly faster in C-IONM group. S-IONM and C-IONM cumulate 40-stage procedures. The standardized technique, guidelines adherences, and C-IONM allowed to (1) increase RLN identification; (2) reduce the severity of injuries in terms of (a) reset bilateral RLNP, (b) faster recovery time, and (c) lower definitive RLNP; (3) gather detection of branching and NRLN; (4) recognize nerve stress; and (5) cumulate stage procedures.

Impact of positional changes in neural monitoring endotracheal tube on amplitude and latency of electromyographic response in monitored thyroid surgery: Results from the Porcine Experiment.

The purpose of this study was to evaluate electromyography (EMG) amplitude and latency changes during tube dislocation in monitored thyroid surgery, which may be observed without recurrent laryngeal nerve injury.

Traction injury of the recurrent laryngeal nerve: Results of continuous intraoperative neuromonitoring in a swine model

Recurrent laryngeal nerve (RLN) palsy is the most serious complication after thyroidectomy. However, little is known about the degree of traction injury that causes loss of signal. The purpose of this study was to evaluate traction injuries in the swine RLN using continuous intraoperative neuromonitoring (IONM) and determine the traction power that results in loss of signal.

Continuous intraoperative neuromonitoring in thyroid surgery: Safety analysis of 400 consecutive electrode probe placements with standardized procedures

Continuous intraoperative neuromonitoring (C‐IONM) is a new technology and it is appropriate to analyze its safety.

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

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.

Vocal cord paralysis predicted by neural monitoring electrophysiologic changes with recurrent laryngeal nerve compressive neuropraxic injury in a canine model.

Recurrent laryngeal nerve (RLN) injury is a known complication of thyroid/parathyroid surgery. Intraoperative nerve monitoring (IONM) has been used to gain more information regarding the functional status of the RLN intraoperatively; however, the electromyography (EMG) parameters of RLN after nontransection neuropraxic compressive injury remain unknown.