Intraoperative nerve monitoring during thyroidectomy: evaluation of signal loss, prognostic value and surgical strategy

Surgical Management of Substernal Thyroid Goiters

Substernal thyroid goiters can present with progressive symptoms involving compression of vital structures such as the esophagus, trachea, or large vessels. A multidisciplinary approach is critical when diagnosing and treating these patients. This article discusses patient presentation, workup, and management options for patients with substernal goiter as well as surgical pearls to minimize risk of complications.

Step-by-Step Thyroidectomy-Incision, Nerve Identification, Parathyroid Preservation, and Gland Removal

Thyroidectomy is a surgical procedure to remove part or all of the thyroid gland. Although the general tenets of surgery have remained the same, improvements in techniques, diagnostics, understanding of anatomy, and technology have allowed thyroid surgery to become a standard, effective, and safe surgery. For surgeons undertaking this procedure, it is imperative to have an in-depth knowledge of critical anatomy and a comprehensive understanding of surgical techniques to perform safe and effective surgery. This article aims to provide an overview of surgical techniques that may be applied in both benign and malignant disease settings.

A Prospective Study of Electromyographic Amplitude Changes During Intraoperative Neural Monitoring for Open Thyroidectomy

BACKGROUND

Intraoperative nerve monitoring (IONM) of the vagus and recurrent laryngeal nerve (RLN) enables prediction of postoperative nerve function. The underlying mechanism for loss of signal (LOS) in a visually intact nerve is poorly understood. The correlation of intraoperative electromyographic amplitude changes (EMG) with surgical manoeuvres could help identify mechanisms of LOS during conventional thyroidectomy.

METHODS

A prospective study of consecutive patients undergoing thyroidectomy was performed with intermittent IONM using the NIM Vital nerve monitoring system. The ipsilateral vagus and RLN was stimulated, and vagus nerve signal amplitude recorded at five time points during thyroidectomy (baseline, after mobilisation of superior pole, medialisation of the thyroid lobe, before release at Ligament of Berry, end of case). RLN signal amplitude was recorded at two time points; after medialisation of the thyroid lobe (R1), and end of case (R2).

RESULTS

A total of 100 consecutive patients undergoing thyroidectomy were studied with 126 RLN at risk. The overall rate of LOS was 4.0%. Cases without LOS demonstrated a highly significant vagus nerve median percentage amplitude drop at medialisation of the thyroid lobe (- 17.9 ± 53.1%, P < 0.001), and end of case (- 16.0 ± 47.2%, P < 0.001) compared to baseline. RLN had no significant amplitude drop at R2 compared to R1 (P = 0.207).

CONCLUSIONS

A significant reduction in vagus nerve EMG amplitude at medialisation of the thyroid and the end of case compared to baseline indicates that stretch injury or traction forces during thyroid mobilisation are the most likely mechanism of RLN impairment during conventional thyroidectomy.

Identification of valid anatomical landmarks to locate and protect recurrent laryngeal nerve during thyroid surgery: a cadaveric study

PURPOSE

Recurrent laryngeal nerve (RLN) is the most critical structure in terms of intricacy. Anatomic variations of the nerve may further make thyroid surgery cumbersome. The present study was undertaken to provide comprehensive knowledge about the soundness of commonly used anatomical landmarks such as Berry's ligament (BL), tracheo-esophageal groove (TEG), inferior thyroid artery (ITA), and the midpoint of the posterior border of the thyroid gland in the identification of the nerve intraoperatively.

METHODS

Thirty adult cadavers were dissected to identify the RLN in the neck and to locate it in relation to the aforementioned anatomical landmarks.

RESULTS

The RLN/BL relationship: RLN was most often located superficial to the BL (88.3%), followed by deep to the BL in 8.4%, and piercing the BL in 3.3% of cases, respectively. The RLN/TEG relationship: the RLN was located inside the TEG in most cases (71.7%), followed by RLN lying outside the TEG in 28.3%. Outside the groove, it was most commonly found lateral to the TEG (64.7%). RLN/ITA relationship: the nerve was passing deep to the artery in most of the cases (65%), followed by superficial (30%) and rarely (5%) in-between the branches. RLN/ midpoint posterior border of thyroid relationship: In 57 (95%) cases, RLN was coursing in the area posterior to the midpoint of the posterior border of the gland with an average distance of 4.95 ± 2.23 mm ranging between 2.21 and 12.1 mm.

CONCLUSIONS

Both the BL and TEG are potentially crucial for safeguarding RLN. Although in results, BL turns out to be more consistent than TEG, we propose the utilization of both these anatomical landmarks together for complication-free neck surgeries. Furthermore, the midpoint of the posterior border of the thyroid turns out to be the single most consistent landmark for identifying RLN during partial thyroidectomy.

Transoral and submental thyroidectomy using intraoperative nerve stimulation and indocyanin green fluorescence imaging

There is a recent proliferation of clinical studies about the minimally invasive scarless thyroid surgery. The transoral endoscopic thyroidectomy vestibular approach (TOETVA) carries a great potential for being scarless surgery via a short dissection flap. However, TOETVA has limitations in extracting larger thyroid tumours via the transoral vestibular incision and due to its potential damage to the branches of the mental nerve. The rapidly evolving surgical innovations have now introduced transoral and submental thyroidectomy (TOaST) approach that allows extraction of large thyroid tumours with less flap dissection and minimal postoperative pain. We present a 39-year-old man with a large multinodular goitre. The patient was euthyroid with moderate to severe compression symptoms of difficulty in breathing and swallowing. We performed a TOaST procedure using intraoperative neuromonitoring and indocyanin green fluorescence imaging with an uneventful recovery. This is a first case report from the middle east region that will pave the way to large clinical trials to determine the efficacy and safety of TOaST.

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.

Role of intraoperative neuromonitoring of recurrent laryngeal nerve in thyroid and parathyroid surgery

Objective

To investigate whether intraoperative neuromonitoring (IONM) has a significant advantage in reducing the incidence of recurrent laryngeal nerve (RLN) injury.

Methods

Patients who underwent thyroid and parathyroid surgery from October 2012 to December 2017 at the Center for Thyroid and Breast Surgery of Xuanwu Hospital were retrospectively analyzed. They were divided into the IONM group and visualization alone group (VA group) according to whether IONM was used.

Results

In total, 1696 nerves at risk of injury (IONM group, n = 1104; VA group, n = 592) were included in the analysis. Among the high-risk nerves, permanent damage occurred in no cases in the IONM group but in one case in the VA group. Because the higher proportion of central lymph node metastasis caused difficulties in central cervical lymph node dissection and identification of the RLN, the patients undergoing lateral cervical lymph node dissection in the VA group had a significantly higher risk of postoperative RLN injury (11.76% vs. 0.00%).

Conclusion

IONM technology has advantages in protection of the RLN, especially in high-risk nerves and patients with a high proportion of central lymph node metastasis who require central and lateral cervical lymph node dissection.

A new anesthesia scheme for parathyroidectomy under neuromonitoring: a retrospective cohort study

Background

Parathyroidectomy under nerve monitoring has been carried out for nearly ten years in the China-Japan Union Hospital of Jilin University. We retrospectively evaluated patients' prognosis with secondary hyperparathyroidism (SH) under neuro- and non-neuro-monitored parathyroidectomy anesthesia. The purpose of this study is to summarize and introduce a new anesthesia scheme for parathyroidectomy under nerve monitoring.

Methods

From January 2000 to December 2019, 200 patients with SH in the China-Japan Union Hospital of Jilin University were retrospectively analyzed. Among them, 100 patients underwent parathyroidectomy under neurological monitoring (Group A), and 100 patients underwent parathyroidectomy without neurological monitoring (Group B). The dosage of muscle relaxant, parathyroid hormone (PTH), serum calcium, phosphorus, urea, creatinine, and alkaline phosphatase (ALP) was recorded before surgery (T0), after surgery (T1), at discharge (T2), during skin incision (Ta), at four parathyroidectomies (Tb), and 10 min after total removal. The levels of PTH were measured at four-time points (Tc) and 30 minutes (Td) after complete resection.

Results

After screening and propensity score match (PSM), the data of 92 patients were analyzed. Group A's muscle relaxant dose was significantly less than Group B; the length of hospital stay in Group A was significantly lower than in Group B (P<0.05). The serum calcium levels, phosphorus, urea, and creatinine at T2 in Group A were lower than those in Group B (P<0.05).

Conclusions

Parathyroid nerve monitoring technology combined with preoperative complete anesthesia scheme, anesthesia induction with one time ED95 (95% effective drug dose) cis-atracurium, end breath gas, and sevoflurane maintenance anesthesia under BIS monitoring can improve the prognosis of patients, shorten the length of hospital stay, and is effective and safe.

Comparison of stimulating dissector and intermittent stimulating probe for the identification of recurrent laryngeal nerve in reoperative setting

PURPOSE

Recurrent laryngeal nerve (RLN) paralysis is one of the most devastating complications after thyroidectomy. Thyroid reoperation is a great challenge for surgeons due to anatomical distortion and fibrosis and associated with a higher risk of RLN injury. In this study, we aimed to compare stimulating dissector (SD) with intermittent stimulating probe (ISP) in thyroid reoperations. This study is the first one which compares the impact of different nerve stimulating devices in thyroid reoperations.

METHODS

Included in this randomized prospective study were patients who had a bilateral subtotal thyroidectomy and would undergo a completion thyroidectomy due to a diagnosis of thyroid papillary cancer between January 2015 and January 2017. Patients were divided into two groups as SD group and ISP group. Age, sex, nerve amplitudes, latencies, the first identification time of RLN and complications were compared in both groups.

RESULTS

A total of 32 patients, 16 in both groups, were included in the study. The demographics, nerve signal amplitudes and latencies were similar in both groups (p > 0.05). The mean RLN identification time in the SD group was 17.4 ± 4.3 min, which was significantly shorter than those in the ISP group (mean 21.3 ± 3.9) (p = 0.014).

CONCLUSION

The first identification of RLN in the thyroid reoperations was faster with the use of SD than with the use of the ISP. Since the electromyographic amplitudes of RLN and vagus nerve with using SD were similar to the bipolar ISP, SD can be used safely for thyroid reoperations.

Analyzing the ATA statement on outpatient thyroidectomy using the NSQIP database

INTRODUCTION

The aim of this study is to examine the outcomes of outpatient thyroidectomy per the American Thyroid Association (ATA) statement on this procedure using the American College of Surgeons National Surgical Quality Improvement Project (NSQIP) database.

METHODS

A retrospective study using NSQIP database (2016 2017) comparing outpatient (OP) and inpatient (IP) thyroidectomies based on the ATA statement.

RESULTS

There were 382 inpatient and 628 outpatient thyroidectomies. A vessel sealing device and intraoperative nerve monitoring were more commonly used in OP group. Drain use was less common in OP group. There was no difference in the rate of recurrent laryngeal nerve injury, neck hematoma, or postoperative hypocalcemia within 30 days after surgery. IP group had a higher rate of readmissions (3.4% vs 1.8%, p = 0.004). Logistic regression showed OP surgery was associated with a lower risk of readmission OR 0.38 (CI 0.15-0.97; p = 0.04).

CONCLUSION

The ATA criteria can be used to identify good candidates for outpatient thyroidectomy.

Killian-Jamieson diverticulum safely resected using a manual intraoperative neural monitoring system: a case report

BACKGROUND

Killian-Jamieson diverticulum is a rare pharyngoesophageal diverticulum. The risk of intraoperative injury of the recurrent laryngeal nerve (RLN) is high during surgical resection of Killian-Jamieson diverticulum because the RLN usually runs next to the base of the diverticulum. We present a case of Killian-Jamieson diverticulum that was safely resected with effective use of an intraoperative nerve monitoring (IONM) system with a handheld stimulating probe to prevent RLN injury.

CASE PRESENTATION

A 69-year-old man complaining of dysphagia was diagnosed with Killian-Jamieson diverticulum and underwent open transcervical diverticulectomy. Because the anterior aspect of the diverticulum was expected to be close to the RLN, the accurate location of the RLN was checked during dissection by intermittent stimulation using a handheld probe of the IONM system to avoid mechanical and thermal injury. The diverticulum was transected longitudinally using a linear stapler, and the staple line was buried using absorbable sutures from the distal end. During its closure, RLN was identified very close to the diverticulum stump by IONM, and the upper side of the stump was left unburied to avoid RLN injury. The postoperative course was uneventful and the patient was discharged on postoperative day 7. Postoperative evaluation showed no vocal cord paralysis.

CONCLUSION

IONM may be beneficial during open surgery for Killian-Jamieson diverticulum, which usually protrudes just lateral to the RLN.