Continuous monitoring of the recurrent laryngeal nerve

Comprehensive Mapping and Dynamic Monitoring of the Temporal Branch of the Facial Nerve in Complex Cranial Reconstruction Surgery and Revision Cranioplasty

Facial nerve (FN) injury is a significant risk during complex cranial reconstruction surgeries, especially in revision cases where normal anatomy is distorted. The authors introduce a technique to mitigate FN injury, including preoperative FN mapping, intraoperative FN mapping, and continuous FN monitoring. Preoperative mapping uses a handheld ball-tip stimulator to elicit compound muscle action potentials (CMAP) in the frontalis muscle. Needle electrodes are placed above the orbital margin to record responses, starting at the stylomastoid foramen and extending until the entire temporal branch is mapped. Intraoperatively, continuous mapping is achieved using an electrified insulated suction device, allowing dynamic mapping during soft tissue dissection. Continuous monitoring involves placing stimulation electrodes near the stylomastoid foramen and recording CMAP responses from the frontalis and orbicularis oculi/orbicularis oris muscles. The authors tested this technique in 5 patients. The authors successfully mapped the temporal branch of the FN with isolated frontalis CMAP recordings in all patients. Intraoperative FN mapping and continuous monitoring were successfully performed in all cases. Two patients experienced complete cessation of FN CMAPs, which resumed upon loosening the tension on the myocutaneous flap held by fishhooks. One patient showed a 39% decrement in frontalis CMAP that did not recover. Despite these issues, all patients had intact FN function postoperatively and at follow-up. Our technique shows promise in mitigating FN injury during complex cranial reconstruction and cranioplasty revision surgery. Further research with a larger cohort is needed to confirm efficacy and statistical significance.

The weepy cry - short neural signal bursts in intraoperative neuromonitoring

PURPOSE

This study aimed to establish an in-vitro alternative to existing in-vivo systems to analyze nerve dysfunction using continuous neuromonitoring (C-IONM).

METHODS

Three hundred sixty-three recurrent laryngeal nerves (RLN) (N(pigs) = 304, N(cattle) = 59) from food industry cadavers were exposed by microsurgical dissection following euthanasia. After rinsing with Ringer's lactate, they were tempered at 22 °C. Signal evaluation using C-IONM was performed for 10 min at 2 min intervals, and traction forces of up to 2N were applied for a median time of 60 s. Based on their post-traumatic electrophysiological response, RLNs were classified into four groups: Group A: Amplitude ≥ 100%, Group B: loss of function (LOS) 0-25%, Group C: ≥ 25-50%, and Group D: > 50%.

RESULTS

A viable in-vitro neuromonitoring system was established. The median post-traumatic amplitudes were 112%, 88%, 59%, and 9% in groups A, B, C, and D, respectively. A time-dependent further dynamic LOS was observed during the 10 min after cessation of strain. Surprisingly, following initial post-traumatic hyperconductivity, complete LOS occurred in up to 20% of the nerves in group A. The critical threshold for triggering LOS was 2N in all four groups, resulting in immediate paralysis of up to 51.4% of the nerves studied.

CONCLUSION

Consistent with in-vivo studies, RLN exhibit significant intrinsic electrophysiological variability in response to tensile forces. Moreover, nerve damage progresses even after the complete cessation of strain. Up to 20% of nerves with transiently increased post-traumatic amplitudes above 100% developed complete LOS, which we termed the "weepy cry." This time-delayed response must be considered during the interpretation of C-IONM signals.

Effects of Intraoperative Nerve Monitoring Techniques on Voice and Swallowing Disorders after Uncomplicated Thyroidectomy: Preliminary Report of a Bi-Institutional Prospective Study

Background: Voice and swallowing problems are frequently associated with thyroidectomy. Intermittent nerve monitoring (i-IONM) seems to provide a positive effect in reducing its prevalence. The aim of this study was to test the hypothesis that continuous intraoperative nerve monitoring (c-IONM) may reduce the prevalence of these disorders even further than i-IONM. Methods: This 3-arm prospective bi-institutional study compared 179 consecutive patients that underwent thyroidectomy: 56 without IONM, 55 with i-IONM and 67 with c-IONM. Neck dissections and laryngeal nerve palsies were excluded. Two questionnaires (VHI-10 for voice disorders and EAT-10 for swallowing disorders; both validated for Italian language use) were administered before and 1 month after surgery. Statistical significance was analyzed by the chi-squared test. Results: After thyroidectomy, no statistically significant differences were found in the three groups concerning EAT-10. although these symptoms seemed to be influenced by gastro-esophageal reflux. VHI-10 worsened in the “no-IONM” group compared with both i-IONM (p < 0.09, not quite statistically significant) and c-IONM (p < 0.04). Conclusion: Both i- and c-IONM improve voice quality independently of laryngeal nerve integrity. Reduced dissection and particularly restrained manipulation could explain these results, being particularly favorable for c-IONM.

Utility of the continuous intraoperative neuromonitoring in the prevention of the recurrent laryngeal nerve paralysis during thyroid surgery. A prospective observational study

BACKGROUND

The continuous intraoperative neuromonitoring (C-IONM) of the recurrent laryngeal nerve (RLN) could help reducing the incidence of nerve paralysis after thyroid surgery, in comparison with the mere anatomical visualization of the RLN. The objective is to assess the efficacy and utility of C-IONM as a predictive test for recurrent laryngeal nerve paralysis after thyroidectomy.

METHODS

A prospective observational study was performed in 248 patients who underwent thyroid surgery where C-IONM was applied, between September 2018 and December 2019, in a high-volume center. A previous and later laryngoscopy was performed, which allowed to evaluate the reliability of the C-IONM as a predictive test for recurrent paralysis. Sensitivity (SE), specificity (SP), positive predictive value (PPV), negative predictive value (NPV) were studied.

RESULTS

A total number of 171 thyroidectomies, 62 hemithyroidectomies, 15 totalization thyroidectomies and 27 thyroidectomy with cervical dissections were performed. Postoperative laryngoscopy was altered in 40 patients (16.12%). The SE, SP, PPV and NPV values ​​were 65%, 94.7%, 70.2% and 93.4% respectively.

CONCLUSIONS

C-IONM is a safe technique that provides real-time information about anatomical and functional integrity of the RLN and can improve the results of thyroid surgery.

Meta-analysis on continuous nerve monitoring in thyroidectomies

In the last decade, the introduction of continuous intraoperative recurrent laryngeal nerve (RLN) monitoring (C-IONM) has enabled the operator to verify the functional integrity of the vagus nerve-recurrent laryngeal nerve (VN-RLN) axis in real-time. We aim to present the current evidence on C-IONM utility for thyroid surgery by conducting the first meta-analysis on this technique. A systematic review of literature was conducted by two independent reviewers via Ovid in the Medline, EMBASE, and Cochrane reviews databases. The search was limited to human subject research in peer-reviewed articles of all languages published between Jan 1946 and April 2020. Medical subject headings (MeSH) terms utilized were thyroid surgery, thyroidectomies, recurrent laryngeal nerve, vagal nerve, monitor, and stimulation. Thirty-eight papers were identified from Ovid, another six papers were identified by hand-search. A random effect meta-analysis was performed with assessment of heterogeneity using the I² value. A total of 23 papers that investigated the use of continuous vagal nerve monitoring during thyroid surgery were identified. The proportion of nerves at risk (NAR) with temporary RLN paralysis postoperation was 2.26% (95% CI: 1.6-2.9, I²  = 37). The proportion of NAR with permanent RLN palsy postoperation was 0.05% (95% CI: 0.08-0.2, I²  = 0). In this meta-analysis, there is one case of temporary vagal nerve paralysis secondary to VN electrode dislodgement, and a case of hemodynamic instability manifested in bradycardia and hypotension in the initial phase of surgery shortly after calibration. C-IONM is a safe and effective means by which RLN paralyses in thyroid surgery can be reduced.

Intraoperative Neural Monitoring for Early Vocal Cord Function Assessment After Thyroid Surgery: A Systematic Review and Meta-Analysis

Objective This study evaluated the diagnostic accuracies of various forms of intraoperative neural monitoring (IONM) in terms of predicting vocal cord palsy after thyroidectomy. Methods Two authors independently reviewed the six databases (PubMed, the Cochrane database, Embase, the Web of Science, SCOPUS, and Google Scholar) from their dates of inception to March 2021. Intraoperative electromyographic neuromonitoring (IONM) was compared with laryngoscopic detection (the reference method). True-positive, true-negative, false-positive, and false-negative data were extracted from each study. Methodological quality was evaluated using the Quality Assessment of Diagnostic Accuracy Studies ver. 2 tool. Results Twenty-seven prospective or retrospective studies were included. The diagnostic odds ratio for IONM was 152.9623 ([95% confidence interval [75.4249; 310.2085]. The area under the summary receiver operating characteristic curve was 0.966. The sensitivity, specificity, negative predictive value, and positive predictive value were 0.8219 ([0.6862; 0.9069]), 0.9783 ([0.9659; 0.9863]), 0.9943 ([0.9880; 0.9973]), and 0.5523 ([0.4458; 0.6542]), respectively. The correlation between sensitivity and false-positive rate was 0.200, indicating the absence of heterogeneity. Subgroup analysis showed that the diagnostic accuracies of the continuous IONM was higher than those of intermittent IONM, and recent publications (> 2011) was higher than early publication (< 2010). Conclusions As the technology and knowledge of IONM have been accumulated and progressed over the past decades, the predictive value of IONM in postoperative vocal cord palsy has also improved. Moreover, the advances of continuous IONM technology could make a breakthrough in vocal cord evaluation after thyroid surgery.

Superiority of continuous over intermittent intraoperative nerve monitoring in preventing vocal cord palsy

BACKGROUND

Continuous intraoperative nerve stimulation (IONM) with uninterrupted monitoring is likely better than intermittent IONM in preventing vocal cord palsy after thyroid surgery.

METHODS

This was a comparative study of intermittent versus continuous IONM in patients with benign and malignant thyroid disease treated at a tertiary centre over 10 years. Early postoperative and permanent vocal cord palsy rates were estimated. Multivariable logistic regression analysis was used to quantify the contributions of clinical and histopathological variables to early postoperative and permanent vocal cord palsy.

RESULTS

A total of 6029 patients were included, of whom 3139 underwent continuous and 2890 intermittent IONM. Based on nerves at risk (5208 versus 5024 nerves), continuous IONM had a 1·7-fold lower early postoperative vocal cord palsy rate than intermittent monitoring (1·5 versus 2·5 per cent). This translated into a 30-fold lower permanent vocal cord palsy rate (0·02 versus 0·6 per cent). In multivariable logistic regression analysis, continuous IONM independently reduced early postoperative vocal cord palsy 1·8-fold (odds ratio (OR) 0·56) and permanent vocal cord palsy 29·4-fold (OR 0·034) compared with intermittent IONM. One permanent vocal cord palsy per 75·0 early vocal cord palsies was observed with continuous IONM, compared with one per 4·2 after intermittent IONM. Early postoperative vocal cord palsies were 17·9-fold less likely to become permanent with continuous than intermittent IONM.

CONCLUSION

Continuous IONM is superior to intermittent IONM in preventing vocal cord palsy.

Use of intraoperative neural monitoring for prognostication of recovery of vocal mobility and reduction of permanent vocal paralysis after thyroidectomy

INTRODUCTION

The benefits of intraoperative neural monitoring (IONM) of recurrent laryngeal nerve (RLN) on post-thyroidectomy vocal cord palsy (VCP) rates are contentious. We wished to study impact of IONM on permanent VCP after thyroidectomy.

METHODS

Retrospective review of prospective series of 1011 (1539 nerves-at-risk) patients undergoing thyroidectomy without (418, group 1) and with (583, group 2) IONM.

RESULTS

There were three recognized nerve injuries in group 1, vs one in group 2 (P = .3). There were no differences in overall VCP rates. However, patients in group 2 with immediate postoperative VCP had higher likelihood of full recovery than patients in group 1 (55 of 56 vs 23 of 29 patients, P = .01), and lower incidence of total permanent VCP (2 of 917 vs 9 of 647 patients, P = .01).

CONCLUSION

Among patients with immediate postoperative VCP after thyroidectomy, IONM is associated with a higher likelihood of regaining normal vocal function. This may be related to better identification of RLN branching in IONM cases.

Airway Abnormalities in Patients With Congenital Heart Disease: Incidence and Associated Factors

OBJECTIVES

Airway abnormalities complicate the perioperative course of patients with congenital heart disease (CHD), leading to significant morbidity and mortality. The literature describing airway abnormalities in those patients is scarce. This study aimed to determine the incidence of airway abnormalities in CHD patients and identify associated factors, genetic syndromes, and cardiac diagnoses.

DESIGN

Retrospective study conducted after institutional review board approval.

SETTING

Tertiary children's hospital.

PARTICIPANTS

Patients presenting for cardiac diagnostic, interventional, or surgical procedures from 2012 to 2018. A total of 9,495 encounters were reviewed.

EXCLUSION CRITERIA

age >18 years. Methods/Interventions: Age, weight, sex, intubation technique, number of intubation attempts, and difficult intubation (DI) were recorded. Using the International Classification of Diseases, Ninth and Tenth Revisions codes, genetic syndromes, acquired and congenital airway abnormalities, and cardiac diagnoses were identified. Multivariate generalized estimating equations modeling was used to identify independent predictors of airway abnormalities.

RESULTS

A total of 4,797 patients, with 8,657 encounters were included. The median age was 1.3 years (interquartile range [IQR]: 0.2-6.0) and weight was 9.2 kg (IQR: 4.3-19.2), and 55% were male. A total of 16.7% had at least 1 genetic syndrome; 8.5% had congenital airway abnormalities and 9.7% acquired. Incidence of DI was 1.1%. The most common syndromes were Down, 22q11.2 microdeletion, and CHARGE. The most frequent congenital airway abnormalities were laryngomalacia and bronchomalacia, and the most frequent acquired were partial and total vocal cord paralysis.

CONCLUSION

The likelihood of a coexistent airway abnormality should be considered in premature CHD patients, weight <10 kg, and in those with specific cardiac lesions and a concomitant genetic syndrome. Preoperative identification of patients at high risk of airway abnormalities is useful in planning their perioperative airway management.

Predictors and consequences of recurrent laryngeal nerve injury during open thyroidectomy: An American College of Surgeons National Surgical Quality Improvement Project database analysis

BACKGROUND

Recurrent laryngeal nerve (RLN) injury is a serious complication of thyroidectomy. The purpose of this study is to determine the predictors and consequences of RLN injury during thyroidectomy.

METHODS

A retrospective analysis was conducted using the ACS-NSQIP 2016-2017 main and thyroidectomy targeted procedure databases. Data was analyzed by multivariate logistic regression resulting in risk-adjusted odds ratios of RLN injury and morbidity/mortality.

RESULTS

Age ≥65, black race, neoplastic indication, total or subtotal thyroidectomy, concurrent neck surgery, operation time > median, hypoalbuminemia, and anemia were associated with RLN injury. Use of intraoperative nerve monitoring was associated with decreased RLN injuries. RLN injury is a risk factor for overall morbidity, hypocalcemia, hematoma, pulmonary morbidity, readmission, reoperation, and length of stay > median.

CONCLUSION

Several predictors of RLN injury during thyroidectomy are identified, while use of intraoperative nerve monitoring was associated with a decreased risk of RLN injury. RLN injury is associated increased postoperative complications.

Thyroid lobe size predicts risk of postoperative temporary recurrent laryngeal nerve paralysis

OBJECTIVES

In patients who had undergone thyroidectomy in Japan for benign tumor, we determined whether thyroid lobe size correlates with temporary recurrent laryngeal nerve paralysis (T-RLNP).

METHODS

We retrospectively collected medical record data on usage of intraoperative neuromonitoring, laterality of thyroidectomy, amount of bleeding during surgery, duration of surgery, and whether the surgeon was a board certified otorhinolaryngologist as determined by the Oto-Rhino-Laryngological Society of Japan. Thyroid size was measured in preoperative axial computed tomography (CT) images. Receiver operating characteristic (ROC) curve analysis was used to determine the thyroid size that predicted a high risk of T-RLNP or permanent recurrent laryngeal nerve paralysis (P-RLNP).

RESULTS

Of the 146 eligible patients identified, 9 (6.2%) developed T-RLNP and 2 (1.4%) developed P-RLNP. The amount of bleeding during thyroidectomy was significantly greater in T-RLNP patients than in P-RLNP patients. Thyroid sizes in CT images were significantly larger in T-RLNP patients compared to patients who did not develop RLNP (referred to hereafter as N-RLNP). ROC analysis revealed that 1.3% of thyroid lobes with an area of less than 1000.0 mm2, and 9.9% of thyroid lobes with an area of greater than 1000.0 mm2 were at risk for T-RLNP.

CONCLUSION

We presented evidence that thyroid sizes, as measured on preoperative axial CT images, were larger in T-RLNP patients than in N-RLNP patients. Our results indicate a connection between benign thyroid tumor stretch injuries and T-RLNP.

LEVEL OF EVIDENCE

IV.