Intraoperative Neuromonitoring: Evaluating the Role of Continuous

Intraoperative Neuromonitoring:

Evaluating the Role of Continuous

IONM and IONM Techniques

for Emerging Surgical and

Percutaneous Procedures

Catherine McManus

and Jennifer Hong Kuo

Department of Surgery, Columbia University Irving Medical Center, New York, NY, United States

Intraoperative nerve monitoring (IONM) is a tool used during thyroid surgery to assist in the

identiﬁcation of the recurrent laryngeal nerve (RLN). Multiple IONM systems that exist for

thyroide ctom y require intubation with an end otracheal tube. Given that one of the

advantages of thermal ablation procedures, such as radiofrequency ablation, is that

they can be done safely without the use of general anesthesia, nerve monitoring systems

that utilize cutaneous surface electrodes have been developed, though are not widely

available in the United States. This article will review the use of IONM for RFA including the

cutaneous surface electrode system.

Keywords: radiofrequency ablation, thyroid, intraoperative nerve monitoring (IONM), recurrent laryngeal nerve,

recurrent laryngeal nerve injury

INTRODUCTION

Thyroidectomy is a technically delicate surgery involving highly detailed anatomy. The recurrent

laryngeal nerve (RLN) is the most important structure at risk during these operations (Figure 1).

Traditionally, the gold standard for protecting the nerve is identifying it through careful dissection

before proceeding with the removal of the thyroid gland. The importance of deﬁnitively identifying

the nerve in order to preserve it was highlighted in the 1950s by Riddell and colleagues (1). Since

that report, nerve visualization, anatomical knowledge, and surgeons’ experience have been the

most important tools for protecting the RLN and still serve as the standard of care. However, despite

cautious RLN visual identiﬁcation, RLN nerve injury can still occur because of anatomical variation,

surgeon inexperience, and difﬁcult situations including a large goiter, revision surgery and invasive

malignancy. Although the rate of injury to the nerve has been reported to be relatively low (<1%–

5%), especially when performed by high-volume surgeons (2, 3) postoperative compromise of voice

quality may diminish the patient’s quality of life and trigger litigation for malpractice (4). To help

reduce the incidence of dysfunction, intraoperative neural monitoring (IONM) was introduced in

the 1970s and has become an increasingly popular adjunct in thyroidectomy (2).

Frontiers in Endocrinology | www.frontiersin.org March 2022 | Volume 13 | Article 8081071

Edited by:

Loredana Pagano,

University of Turin, Italy

Reviewed by:

Erivelto Martinho Volpi,

Centro de referencia no ensino do

diagno

stico por imagem (CETRUS),

Brazil

*Correspondence:

Catherine McManus

[email protected]

Specialty section:

This article was submitted to

Thyroid Endocrinology,

a section of the journal

Frontiers in Endocrinology

Received: 03 November 2021

Accepted: 10 February 2022

Published: 30 March 2022

Citation:

McManus C and Kuo JH

(2022) Intraoperative

Neuromonitoring: Evaluating

the Role of Continuous IONM

and IONM Techniques for

Emerging Surgical and

Percutaneous Procedures.

Front. Endocrinol. 13:808107.

doi: 10.3389/fendo.2022.808107

MINI REVIEW

published: 30 March 2022

doi: 10.3389/fendo.2022.808107

DIFFERENT IONM

The most widely used IONM systems facilitate RLN

identiﬁcation and mapping of the anatomic course of the nerve

and uses passive monitoring, in which the presence and quality

of the interrogation signal conﬁrms neural integrity, and loss of

signal at any point caudal to an injury indicates a nonfunctioning

nerve or technical issues. In its ﬁrst iteration, IONM used needle

electrodes inserted through the cricothyroid membrane into the

vocal muscle and an intermittent nerve stimulation is conducted

with a hand-held monopolar probe that stimulated the RLN,

enabling recording the electrophysiological response signal.

Currently, most IONM systems involve monopolar hand-held

probes that intermittently stimulate the nerve through surface or

incorporated electrodes on the endotracheal tube and records the

electrophysiological response signal (Figure 2). Most systems

also allow for continuous nerve stimulation, with a clip electrode

mounted on the vagus nerve and surface electrodes afﬁxed to the

endotracheal tube recording the electrophysiological response

signal (5).

An alternative form of c ontinuous IONM relies on an

electromyogra phic endo tracheal tu be (EMG-ETT) alone to

elicit a laryngeal adductor reﬂex (LAR), which allows for

continuous monitoring of the RLN and VN function (6–8).

Irritation to the RLN or VN (i.e. due to traction, compression,

heat) results in transient or permanent LAR amplitude declines

with permanent LAR loss correlating with postoperative vocal

fold paralysis (6, 7). Similar to intraoperative neuromonitoring

techniques that use direct nerve stimulation (6, 7), an amplitude

decline >50% is considered signiﬁcant and warrants corrective

actions by the surgeon such as cessation of dissection, relaxation

of tissues, and warm irrigation (9). The biggest advantage of this

technique is the lack of neural electrodes required.

Both intermittent and continuous IONM allow for

differentiation between segmental loss of signal (LOS; type 1)

and diffuse LOS (type 2), whereas conti nuous IONM offers

provides real-time intraoperative feedback of nerve signals.

This facilitates instant detection and release of a distressed

nerve can minimize RLN injury. For documentation purposes,

the electromyographic recordings can be printed out from the

system and ﬁled with the patient’s clinical chart. Both IONM

modalities inform the surgical treatment plan and provide

strategic direction regarding the need for staged thyroidectomy

in the event of deﬁnitive LOS on the ﬁrst side of the

operation (9).

EFFICACY OF IONM

The efﬁcacy of IONM has been studied extensively, including

several large-scale multi-institutional trials, both prospective and

retrospective, with conﬂicting results. There is some evidence to

suggest that IONM decreases both transient and permanent RLN

injury (10, 11), only transient RLN injury (11, 12 ), or only

permanent RLN injury (13). In contrast, other researchers

found no substantial reduction of permanent RLN injury (14),

or both transient and permanent RLN injuries (15–17). A 2017

review of 8 meta-analyses conﬁrmed no observable reduction in

transient or permanent RLN injury. 740 Routine use of IONM

during total thyroidectomy was not found to be cost-effective

compared with visual identiﬁcation alone, though a 2017 study

showed that IONM was potentially cost effective in preventing

bilateral RLN dysfunction (18).

Although selective use of IONM by many specialties is

common in the United States, IONM has become the standard

of care in many countries and is endorsed by the German

FIGURE 1 | Anatomy of the Recurrent Laryngeal Nerves.

McManus and Kuo IONM for RFA

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Association of Endocrine Surgeons (19) and the Australian

College of Surgeons (20) as a valuable adjunct to

RLN visualization.

CHALLENGES WITH IONM AND

THERMAL ABLATION

Introduced in the early 2000s, thermal ablation (TA) procedures,

such as radiofrequency ablation (RFA) and laser ablation (LA),

are increasingly used to treat benign thyroid nodules (21, 22).

Short-term studies (<1 to 2 years) showed that TA is effective and

safe for the treatment of cosmetic or symptomatic benign

nodules, resulting in a reduction in nodule volume of 50% to

80% (23–25). These procedures can be performed under local or

general anesthesia. Although RFA appears to be a relatively safe

procedure, the potential for injury to the vagus (VN) and

recurrent laryngeal nerves (RLN) exists. Similar to RLN injuries

incurred during open thyroidectomy, the incidence of thermal

injury to either of these nerves during RFA is low, ~1%, but can

result in temporary or permanent vocal fold immobility, vocal

hoarseness, aspiration and/or dysphagia (26, 27). However, there

is limited objective data on the risk of nerve injury during RFA,

such as pre and post RFA laryngeal examinations or feedback

from a nerve monitor, which has limited the direct comparison of

rates of nerve injury with RFA and thyroidectomy.

The vast majority of these thermal ablation procedures are

performed under local anesthesia, which precludes the use of

current, FDA approved IONM systems in the United States.

IONM for thermal ablation procedures is not only logistically

difﬁcult, it is also not essential if providers use appropriate

techniques to reduce the risk of thermal injury. Excellent

understanding of the sonographic anatomy of the neck,

including potential aberrant anatomy s uch as a medially

positioned vagus nerve, is required and the concept of a

‘danger triangle’ adjacent to the posteromedial thyroid capsule

has been proposed (Figure 3). It is generally recommended to

leave a cuff of unablated thyroid tissue immediately adjacent to

this region (21, 22, 28, 29). Widely adopted technical concepts

such as the trans-isthmic approach and moving-shot technique

are advocated in order to decrease the risk of thermal injury

(Figure 4). Another strategy utilized to decrease the risk of nerve

injury is hydrodissection, speciﬁcally if the nodule abuts the

lateral capsule and the vagus nerve takes an aberrant medial

position. Hydrodissection involves a pre-ablation injection of 5%

dextrose to create space between the lateral thyroid and the

medial vagus to allow for ablation of the lateral most part of

the nodule (30). In addition, having the patient speak during the

course of the procedure may alert the interventionalist of a

possible injury if a change in the quality of the voice is

detected. However, despite these precautions, injury to the

laryngeal nerves by virtue of their proximity to the target tissue

remains a real risk.

SUMMARY OF IONM STUDIES AND

THERMAL ABLATION

In 2021, Sinclair et al. conducted a prospective single institution

study to evaluate whether the recurrent laryngeal nerve was

affected during RFA of thyroid nodules using continuous

intraoperative nerve monitoring (30). Inclusion criteria

FIGURE 2 | An example of a IONM system. Adhesive electrodes are applied to an endotracheal tube and the blue and red wires are connected to a nerve

monitoring system. One needle wire (white) is inserted into the deltoid muscle, a green lead wire sticker is applied to the forehead, and the single red wire connects

to a handheld monopolar probe that is used to stimulate the recurrent laryngeal nerve.

McManus and Kuo IONM for RFA

Frontiers in Endocrinology | www.frontiersin.org March 2022 | Volume 13 | Article 8081073

consisted of symptomatic thyroid nodules with elevated cosmetic

and symptom scores and two ﬁne needle aspiration biopsies that

demonstrated Bethesda II cytology. All patients underwent a pre

procedure laryngoscopy. This was followed by induction of general

anesthesia with placement of a monitored electromy ography

endotracheal tube (NI M EMG-ETT). An electrical stimuli

consisting of 1-3 rectangular pulses at a 3-20 mA intensity with a

1-2 ms interstimulus interval and duration of 0.5-1ms was applied

to the laryngeal muco sa t hrough electrodes on the ETT

contralateral to the RLN at risk to elicit a laryngeal adductor

reﬂex (LAR). The LAR was then recorded by the electrodes on

the ipsilateral side of the RLN at risk. All posterior nodules were

treated with a max of 40 W and the amplitude was continuously

monitored throughout the ablation procedure. The surgeon was

FIGURE 3 | ‘Danger Triangle’ housing the recurrent laryngeal nerve (permission to reprint from Taewoong Medical USA).

FIGURE 4 | Trans-isthmic approach and moving shot technique used in thermal ablation. (Permission to reprint from Taewoong Medical USA).

McManus and Kuo IONM for RFA

Frontiers in Endocrinology | www.frontiersin.org March 2022 | Volume 13 | Article 8081074

careful to not breach the posterior capsule of the thyroid and was

notiﬁed if there was a decrease >50% from baseline, at which point

the procedure was stopped to allow amplitude to recover. Patients

then underwent a post procedure laryngoscopy.

A total of 10 patients participated in the study consisting of 20

nodules total. There was no signiﬁcant change in the LAR during

the ablation (no patient experienced a >50% decline in LAR

amplitude), no ablation needed to be halted to allow for nerve

recovery, and pre and post procedure laryngoscopies were

similar. The largest decrease in amplitude was 25% in one

patient, which recovered rapidly upon repositioning the

electrode using the moving shot technique. Based on this

study, it is difﬁcult to determine whether the advantages of

continuous nerve monitoring with open surgery (providing

feedback of possible impending injury) would also be

advantageous in RFA or whether the moving shot technique is

protective on its own. The authors concluded that RFA was safe

as long as the posterior capsule was not breached by the ablation

zone and the power was less than 40 W.

Given that most RFA procedures are performed using local

anesthesia, alternative forms of nerve monitoring that do not

require the placement of an endotracheal tube have also been

investigated. Lin et al. conducted a retrospective cohort study of

patients who underwent ultrasound- guided RFA of thyroid

nodules between 2/2019 to 8/2019 using neuromonitoring with

cutaneous electrodes (31). Inclusion criteria consisted of having a

symptomatic nodule (discomfort, compressive symptoms,

foreign body sensation), beni gn cytology on ﬁne-needle

aspiration, no BRAF mutation, normal thyroid function tests,

and normal movement of the vocal cords on laryngoscopy. The

primary endpoint of the study was to determine the feasibility

of using neuromonitoring with cutaneous surface electrodes

during ultrasound guided RFA of thyroid nodules, which was

deﬁned as the ability to obtain nerve stimulation. The secondary

end point was achievement of technical success, deﬁned as

correlation between the ﬁnal EMG signal and post procedure

laryngoscopy results.

For nerve monitoring, Ambu Neuroline 715 single-patient

surface electrodes were placed on the skin anterior to the left and

right laminas of the thyroid cartilage (recording electrodes) and

on the upper arm (grounding electrodes). A 22-gauge nerve

stimulation needle (Stimuplex D; B. Braun, Melsungen,

Germany) was attached to a saline syringe and set at 100ms

and 4Hz to be used as both a stimulation probe and for

hydrodissection. The NIM Nerve monitoring System version

3.0 (Medtronic, Minneapolis, MN, ISA) was used to record

electromyograms (EMGs) with an event threshold of 100 mV.

The nerve stimulation needle was inserted under ultrasound

guidance between the common carotid artery and the internal

jugular vein at the level of the lower pole of the thyroid to

stimulate the vagus nerve using a 3.0 mA current (“V1”). A

robust initial EMG goal was deﬁned as obtaining an amplitude

>500 mV. Once the vagus nerve was identiﬁed, hydrodissection

with normal saline was performed between the carotid sheath

and thyroid gland. The stimulation probe was used to detect the

course of the laryngeal nerve along the posterior aspect of the

thyroid. If no signal was detected, normal saline was injected to

create a plane between the posterior thyroid and the RLN. RFA

was performed with a power ranging between 30-50 W. After

ablation, the nerve stimulation needle was again inserted into the

carotid sheath to obtain a ﬁnal vagus EMG (“V2”) with a 3.0 mA

current. The ﬁnal EMG (V2) was categorize d as normativ e

baseline (absolute amplitude of the signal is not <50% and the

growth of its latency is <10% of the initial baseline), impending

adverse EMG (amplitude decrease >50% and a latency increase

10% of the initial baseline), or loss of signal (normal vocal cord

movement on pre procedure laryngoscopy with a subsequent low

(<100 mV) or absent EMG response). For either the impending

adverse EMG or loss of signal events, cold liquid was injected

posterior to the thyroid gland and into the tracheoesophageal

groove and stimulations were performed every 5 minutes to

monitor for recovery, which was deﬁned as reaching an absolute

amplitude of >50% of the baseline. Patients underwent post

procedure laryngoscopy one day after the procedure and RLN

injury was conﬁrmed if there was abnormal vocal cord activity.

Patients had 6 month follow up with a 10 cm visual analog scale,

cosmetic score, and calculation of the volume reduction

ratio (VRR).

A total of 16 patients satisﬁed inclusion and exclusion criteria

consisting of 20 nodules. Nerve stimulation was achieved before

and after the procedure for all 20 vagus nerves among the 16

patients and 16 of the 20 nerves had a robust initial EMG (>500

mV). There was a signiﬁcant difference in the mean response

amplitude between V1 (612.7 +/- 130 m V) and V2 (592.7 +/-

127.3 mV), p<0.05. However, there was no signiﬁcant difference

between the response latencies of V1 and V2. No patients were

categorized as impending adverse EMG or loss of signal. All 20

nerves had a post EMG that correlated with the post

laryngoscopy results and there were no instances of injury to

the recurrent laryngeal nerve.

At the 6 month follow up, the maximum nodule lesion size

decreased from 2.49 +/- 0.73 cm to 1.47 +/- 0.44 cm (p<0.05) and

the VRR was 68.5 +/- 21.5%. Furthermore, the mean symptom

score decreased from 3.6 +/- 0.7 to 1.2 +/- 0.4 (p<0.05) and the

mean cosmetic score decreased from 3.4 +/- 0.5 to 1.6 +/- 0.6

(p<0.05). There were no complications related to nerve

monitoring or RFA including hematoma, tracheal or

esophageal injury, skin burn, or lidocaine toxicity.

The authors concluded that using cutaneous electrodes for

RLN monitoring during RFA was feasible and safe. However, the

authors also recognize the limitations of this study including the

retrospective nature, small sample size, lack of a control group

and the ability of this technique to only provide intermittent

nerve monitoring (before and after the procedure). Furthermore,

similar to the study by Sinclair, et al, the use of the nerve monitor

among these 16 patients did not alter the procedure to prevent a

potential nerve injury. Due to the low rate of nerve injury,

detecting whether nerve monitoring signiﬁcantly impacts the

rate of nerve injury for RFA will require a much larger sample

size than prior studies.

McManus and Kuo IONM for RFA

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CONCLUSION

Intraoperative nerve monitoring has been widely accepted as a

useful adjunct to visual identiﬁcation of the nerve during

thyroidectomy. However, most IONM systems require the use

of an endotracheal tube to allow for continuous or intermittent

nerve monitoring. Such nerve monitoring systems can be used to

perform thermal ablation procedures such as RFA, however the

procedure must be done under general anesthesia. Consequently,

there is a role for nerve monitoring systems that employ

cutaneous surface electrodes, allowing for the RFA procedure

to be done under local anesthesia. Similar to surgery, protection

of the recurrent laryngeal and vagus nerves during RFA requires

a thorough understanding of neck anatomy and the ability to

infer the course of the RLN and vagus nerves using sonography.

AUTHOR CONTRIBUTIONS

All authors listed have made a substantial, direct, and intellectual

contribution to the work, and approved it for publication.

REFERENCES

1. Riddell VH. Injury to Recurrent Laryngeal Nerves During Thyroidectomy; a

Comparison Between the Results of Identi ﬁcation and Non-Identiﬁcation in

1022 Nerves Exposed to Risk. Lancet (Lond Engl) (1956) 271:638–41. doi:

10.1016/S0140-6736(56)92333-9

2. Schneider R, Machens A, Lorenz K, Dralle H. Intraoperative Nerve

Monitoring in Thyroid Surgery —Shifting Current Paradigms. Gland Surg

(2020) 9:S120. doi: 10.21037/gs.2019.11.04

3. Sosa JA, Bowman HM, Tielsch JM, Powe NR, Gordon TA, Udelsman R. The

Importance of Surgeon Experience for Clinical and Economic Outcomes

From Thyroidectomy. Ann Surg (1998) 228:320–30. doi: 10.1097/00000658-

199809000-00005

4. Abadin SS, Kaplan EL, Angelos P. Malpractice Litigation After Thyroid

Surgery: The Role of Recurrent Laryngeal Nerve Injuries, 1989–2009.

Surgery (2010) 148:718–23. doi: 10.1016/j.surg.2010.07.019

5. Sedlma ier A, Steinmuller T, Hermanns M, Nawka T, Weikert S, Sadlmaier

B, et al. Continuous Versus Intermittent Intraoperative Neuromonitoring in

Complex Benign Thyroid Sur gery: A R etrospective Analysis and

Prospective Follow-Up. Clin Otolaryngol (2019) 44:1071–9. doi: 10.1111/

coa.13446

6. Sinclair CF, Te

llez MJ, Tapia OR, Ulkatan S, Deletis V. A Novel Methodology

for Assessing Laryngeal and Vagus Nerve Integrity in Patients Under General

Anesthesia. Clin Neurophysiol (2017) 128:1399–405. doi: 10.1016/

j.clinph.2017.03.002

7. Sinclair CF, Te

llez MJ, Ulkatan S. Continuous Laryngeal Adductor Reﬂex

Versus Intermittent Nerve Monitoring in Neck Endocrine Surgery.

Laryngoscope (2021) 131:230–6. doi: 10.1002/lary.28710

8. Sinclair CF, Te

llez MJ, Tapia OR, Ulkatan S. Contra lateral R1 and R2

Components of the Laryngeal Adductor Reﬂex in Humans Under General

Anesthesia. Laryngoscope (2017) 127:E443–8. doi: 10.1002/lary.26744

9. Schneider R, Randolph G. International Neural Monitoring Study Group

Guideline 2018 Part I: Staging Bilateral Thyroid Surgery With Monitoring

Loss of Signal. Wiley Online Libr (2018) 128:S1–17. doi: 10.1002/lary.27359

10. Bai B, Chen W. Protective Effects of Intraoperative Nerve Monitoring

(IONM) for Recurrent Laryngeal Nerve Injury in Thyroidectomy: Meta-

Analysis. Sci Rep (2018) 8:1–11. 2018 81. doi: 10.1038/s41598-018-26219-5

11. KP W, KL M, CK W, BH L. Systematic Review and Meta-Analysis on Intra-

Operative Neuro-Monitoring in High-Risk Thyroidectomy. Int J Surg (2017)

38:21–30. doi: 10.1016/j.ijsu.2016.12.039

12. Yang S, Zhou L, Lu Z, Ma B, Ji Q, Want Y. Systematic Review With Meta-

Analysis of Intraoperative Neuromonitoring During Thyroidectomy. Int J

Surg (2017) 39:104

–13. doi: 10.1016/j.ijsu.2017.01.086

13. Sun W, Liu J, Zhang H, Zhang P, Wang Z, Dong W, et al. A Meta-Analysis of

Intraoperative Neuromonitoring of Recurrent Laryngeal Nerve Palsy During

Thyroid Reoperations. Clin Endocrinol (Oxf) (2017) 87:572–80. doi: 10.1111/

cen.13379

14. Lombardi CP, Carnassale G, Damiani G, Acampora A, Raffaelli M, De Crea C,

et al. ‘The Final Countdown’: Is Intraoperative, Intermittent Neuromonitoring

Really Useful in Preventing Permanent Nerve Palsy? Evidence From a Meta-

Analysis. Surgery (2016) 160:1693–706. doi: 10.1016/j.surg.2016.06.049

15. Malik R, Linos D. Intraoperative Neuromonitoring in Thyroid Surgery: A

Systematic Review. World J Surg (2016) 40:2051–8. doi: 10.1007/s00268-016-

3594-y

16. Pisanu A, Porceddu G, Podda M, Cois A, Uccheddu A. Systematic Review

With Meta-Analysis of Studies Comparing Intraoperative Neuromonitoring

of Recurrent Laryngeal Nerves Versus Visualization Alone During

Thyroidectomy. J Surg Res (2014) 188:152–61. doi: 10.1016/j.jss.2013.12.022

17. Sanabria A, Ramirez A, Kowalski L, Silver CE, Shaha A, Owen R, et al.

Neuromonitoring in Thyroidectomy: A Meta-Analysis of Effectiveness From

Randomized Controlled Trials. Eur Arch Otorhinolaryngol (2013) 270:2175–

89. doi: 10.1007/s00405-013-2557-2

18. Henry BM, Graves MJ, Vikse J, Sanna B, Pekala P, Walocha JA, et al. The

Current State of Intermittent Intraoperative Neural Monitoring for

Prevention of Recurrent Laryngeal Nerve Injury During Thyroidectomy:

A PRISMA-Compliant Systematic Review of Overlapping Meta-Analyses.

Langenbeck’sArchSurg(2017) 402:663–73. doi: 10.1007 /s00423-017-

1580-y

19. Dralle H, Lorenz K, Schabram P, Mushold TJ, Dotzenrath C, Goretzki PE,

et al. Intraoperative Neuromonitoring in Thyroid Surgery. Recommendations

of the Surgical Working Group for Endocrinology. Chirurg (2013) 84:1049–

56. doi: 10.1007/s00104-013-2656-z

20. Serpell J, Sidhu S, Vallance N, Panizza B, Randolph G. Consensus Statement

on Intra-Operative Electrophysiological Recurrent Laryngeal Nerve

Monitoring During Thyroid Surgery. ANZ J Surg (2014) 84:603–4. doi:

10.1111/ans.12590

21. Kim JH, Baek JH, Lim HK, Ahn HS, Baek SM, Choi YJ, et al. 2017 Thyroid

Radiofrequency Ablation Guideline: Korean Society of Thyroid Radiology.

Korean J Radiol (2018) 19:632–55. doi: 10.3348/kjr.2018.19.4.632

22. Papini E, Monpeyssen H, Frasoldati A, Hegedüs L, Karger S. 2020 European

Thyroid Association Clinical Practice Guideline for the Use of Image-Guided

Ablation in Benign Thyroid Nodules. Eur Thyroid J (2020) 9:172–85. doi:

10.1159/000508484

23. Cho J, Hwan Baek J, Chung SR, Choi YJ, Lee JH. Long-Term Results of

Thermal Ablation of Benign Thyroid Nodules: A Systematic Review and

Meta-Analysis. Endocrinol Metab (2020) 35:339– 50. doi : 10.3803/

EnM.2020.35.2.339

24. Kim HJ, Cho SJ, Baek JH, Suh CH. Efﬁcacy and Safety of Thermal Ablation for

Autonomously Functioning Thyroid Nodules: A Systematic Review and

Meta-Analysis.

Eur Radiol (2021) 31:605–15. doi: 10.1007/s00330-020-

07166-0

25. Trimboli P, Castellana M, Sconﬁenza LM, Virili C, Pescatori LC, Cesareo R,

et al. Efﬁcacy of Thermal Ablation in Benign Non-Functioning Solid Thyroid

Nodule: A Systematic Review and Meta-Analysis. Endocrine (2020) 67:35–43.

doi: 10.1007/s12020-019-02019-3

26. Sharma RK, Kuo JH. Complications of RFA for Thyroid Nodules: Prevention

and Management. Curr Otorhinolaryngol Rep (2021) 9:79–86. 2021 91. doi:

10.1007/s40136-020-00322-6

27. Baek JH, Lee JH, Sung JY, Bae Y, Kim KT, Sim J, et al. Complications

Encountered in the Treatment of Benign Thyroid Nodules With US-Guided

Radiofrequency Ablation: A Multicenter Study. Radiology (2012) 262:335–42.

doi: 10.1148/radiol.11110416

McManus and Kuo IONM for RFA

Frontiers in Endocrinology | www.frontiersin.org March 2022 | Volume 13 | Article 8081076

28. Jeong W K, Baek JH, Rhim H, Kim Y S, Kwak MS, Jeong HJ, et al.

Radiofrequency Ablation of Benign Thyroid Nodules: Safety and Imaging

Follow-Up in 236 Patients. Eur Radiol (2008) 18:1244–50. doi: 10.1007/

s00330-008-0880-6

29. Deandrea M, Sung JY, Limone P, Mormile A, Garino F, Ragazzoni F, et al.

Efﬁcacy an d Safet y of Radiofrequency Ablation Versus Observation for

Nonfunctioning Benign Thyroid Nodules: A Randomized Controlled

International Collaborative Trial. Thyroid (2015) 25:890–6. doi: 10.1089/

thy.2015.0133

30. Sinclair CF, Te

llez MJ, Pela

ez-Cruz R, Dı

az-Baamonde A, Ulkatan S.

Continuous Neuromonitoring During Radiofrequency Ablation of Benign

Thyroid Nodules Provides Objective Evidence of Laryngeal Nerve Safety. Am

J Surg (2021) 222:354–60. doi: 10.1016/j.amjsurg.2020.12.033

31. Lin E, Lin S, Fu J, Lin F, Luo Y, Hong X, et al. Neural Monitoring During

Ultrasound-Guided Radiofrequency Ablation of Thyroid Nodules. Int J

Hyperthermia (2020) 37:1229–37. doi: 10.1080/02656736.2020.1778109

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