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Comparative Analysis of Intraoperative Nerve Monitoring (IoNM) with Conventional Thyroidectomy: A 10-Case Study
*Corresponding author: Kavitha Prakash Palled, Department of Head Neck Oncology and Skull Base Surgery, BGS Apollo Hospital Mysore, Karnataka, India. kavitharaxith@gmail.com
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Received: ,
Accepted: ,
How to cite this article: Palled KP, Comparative Analysis of Intraoperative Nerve Monitoring (IoNM) with Conventional Thyroidectomy: A 10-Case Study. Kartanaka J Surg. doi: 10.25259/KJS_14_2024.
Abstract
Objectives:
To evaluate the effectiveness of intraoperative nerve monitoring (IoNM) in reducing recurrent laryngeal nerve (RLN) injury and improving surgical outcomes compared to conventional thyroidectomy.
Material and Methods:
This study at BGS Apollo Hospital, Mysore, included 20 patients (ten with IoNM, ten conventional) from January to July 2023. Outcomes assessed were RLN injury, hypocalcemia, operative time, hospital stay, and vocal cord function.
Results:
RLN Injury: IoNM group had 10% temporary RLN injuries and no permanent injuries, versus 30% temporary and 10% permanent injuries in the conventional group.
Hypocalcemia: Transient hypocalcemia occurred in 20% of the IoNM group and 40% of the conventional group.
Operative Time and Hospital Stay: IoNM cases had a slightly longer operative time (110 min) but shorter hospital stay (2.2 days) compared to the conventional group (95 min and 3.1 days).
Vocal Cord Function: IoNM group showed minimal voice changes and normal vocal cord mobility, while 40% of the conventional group experienced significant voice issues.
Conclusion: IoNM significantly reduces RLN injury and improves recovery, despite a minor increase in operative time. IoNM is recommended for enhancing outcomes in thyroid surgery.
Keywords
Intraoperative Nerve Monitoring (IoNM)
Thyroidectomy
Recurrent Laryngeal Nerve (RLN) Injury
Hypocalcemia
INTRODUCTION
Thyroidectomy, the surgical removal of the thyroid gland, is a fundamental procedure for addressing both benign and malignant thyroid conditions. The complexity of thyroid surgery lies in the proximity of critical structures, particularly the recurrent laryngeal nerve (RLN), which is vital for vocal cord function. Injury to the RLN during thyroidectomy can result in severe postoperative complications, such as vocal cord paralysis and compromised voice quality, which significantly impact a patient’s quality of life.
Recurrent Laryngeal Nerve Injury
The RLN is at high risk of injury during thyroidectomy due to its intricate anatomical course. Damage to this nerve can lead to temporary or permanent vocal cord paralysis, manifesting as voice hoarseness, breathiness, and difficulties with phonation. The incidence of RLN injury remains a critical measure of surgical quality and is a major concern for both surgeons and patients.
Intraoperative Nerve Monitoring (IoNM)
IoNM has emerged as a sophisticated technique designed to enhance nerve preservation during thyroid surgery. By providing real-time feedback on the functional status of the RLN, IoNM enables surgeons to identify and protect the nerve more effectively. This technology involves the use of electrodes and a nerve stimulator to monitor nerve function continuously throughout the procedure. The goal of IoNM is to reduce the risk of nerve injury by alerting the surgeon to potential issues before they result in permanent damage.
Study Rationale
This study aims to provide a detailed comparison of outcomes between IoNM-guided and conventional thyroidectomy. By analyzing key metrics such as RLN injury rates, hypocalcemia incidence, operative time, and postoperative recovery, we seek to evaluate the efficacy of IoNM in enhancing surgical safety and patient outcomes. Our findings are intended to contribute to evidence-based practices and potentially set new standards for thyroid surgery, promoting improved patient care and surgical precision.
Objective
To evaluate the efficacy of IoNM in reducing postoperative complications and improving surgical outcomes compared to conventional thyroidectomy, aiming for an evidence-based assessment to drive improvements in global thyroid surgery practices.
MATERIAL and METHODS
Study DesignLocation: BGS Apollo Hospital, Mysore
Period: January 2023 to July 2023
Sample Size: 20 patients (ten cases each in IoNM and conventional groups)
Group A (IoNM): ten patients underwent thyroidectomy with IoNM
Group B (Conventional): ten patients underwent conventional thyroidectomy without IoNM
Inclusion CriteriaPrimary thyroid surgery
Benign and malignant thyroid conditions
Exclusion CriteriaRecurrent thyroid surgeries
Patients with preoperative RLN palsy or vocal cord dysfunction
Parameters Assessed
Incidence of RLN injury (temporary and permanent)
Transient and permanent hypocalcemia
Operative time
Hospital stay duration
Postoperative vocal cord function
RESULTS
The analysis focuses on key outcome variables in the two groups [Table 1]
| Metric | IoNM group | Conventional group |
|---|---|---|
| Temporary RLN Injury (%) | 10 | 30 |
| Permanent RLN Injury (%) | 0 | 10 |
| Transient Hypocalcemia (%) | 20 | 40 |
| Operative time (minutes) | 110 | 95 |
| Hospital stay (days) | 2.2 | 3.1 |
| Voice deterioration (%) | 0 | 40 |
| Recovery time (Vocal Cord) (days) | 2–3 | 10–15 |
RLN: Recurrent Laryngeal Nerve, IoNM: Intraoperative Nerve Monitoring.
1. Recurrent Laryngeal Nerve Injury
The incidence of RLN injury in the two groups showed a notable difference:
In the IoNM group, only 10% of cases presented with temporary RLN injury, while none of the patients had permanent RLN damage.
In contrast, the Conventional thyroidectomy group experienced significantly higher rates of RLN injury, with 30% of patients having a temporary injury and 10% suffering from permanent RLN damage [Figure 1].
- Incidence of RLN injury.
This marked reduction in both temporary and permanent RLN injuries highlights the efficacy of intraoperative nerve monitoring in reducing the risk of nerve damage during thyroid surgeries.
2. Hypocalcemia Rates
Hypocalcemia, a common complication following thyroidectomy, was also examined.
The IoNM group showed a transient hypocalcemia rate of 20%, while the Conventional group had a higher rate of 40% [Figure 2].
- Hypocalcemia rates.
This data supports the idea that IoNM not only assists in safeguarding nerves but may also contribute indirectly to reducing postoperative complications like hypocalcemia, likely due to better overall surgical precision and reduced inadvertent injury to the parathyroid glands.
3. Operative Time and Hospital Stay
The mean operative time in the IoNM group was slightly higher at 110 min compared to 95 min in the Conventional group [Figure 3]. This increase can be attributed to the additional steps involved in setting up and using intraoperative nerve monitoring.
- Operative time and hospital stay.
However, the hospital stay and recovery time for patients in the IoNM group was significantly shorter, averaging 2.2 days, while the conventional group averaged 3.1 days.
Although the IoNM technique requires additional operative time, the benefit of a shorter hospital stay translates into quicker recovery and reduced healthcare costs.
4. Vocal Cord Assessment and Voice Outcomes
Detailed voice analysis was conducted postoperatively for each patient, measuring vocal cord function and acoustic voice quality:
In the IoNM group, the postoperative acoustic analysis showed little to no significant changes in voice quality for most patients. All patients in this group retained normal vocal cord mobility post-surgery, with only minor temporary changes in voice detected in some cases.
The Conventional group, however, showed significant deterioration in voice quality, with hoarseness and reduced vocal cord mobility observed in 40% of patients [Table 2]. Recovery time for voice issues and vocal cord function was also notably longer in the conventional group, averaging 10–15 days, compared to 2–3 days in the IoNM group.
| Patient ID | Surgical method | Preoperative acoustic analysis (Hz) | Postoperative acoustic analysis (Hz) | Voice quality changes | Vocal cord mobility (post-surgery) | Recovery time (days) |
|---|---|---|---|---|---|---|
| 001 | IoNM | 225 | 220 | No significant changes | Normal | 2 |
| 002 | IoNM | 250 | 245 | Slight improvement | Normal | 2 |
| 003 | Conventional | 230 | 270 | Hoarseness observed | Reduced mobility | 10 |
| 004 | IoNM | 240 | 235 | No significant changes | Normal | 3 |
| 005 | Conventional | 235 | 265 | Hoarseness observed | Reduced mobility | 14 |
| 006 | IoNM | 220 | 225 | No significant changes | Normal | 2 |
| 007 | Conventional | 245 | 275 | Hoarseness observed | Partial immobility | 12 |
| 008 | IoNM | 210 | 215 | Slight improvement | Normal | 3 |
| 009 | Conventional | 230 | 280 | Hoarseness observed | Reduced mobility | 15 |
| 010 | IoNM | 225 | 220 | No significant changes | Normal | 2 |
IoNM: Intraoperative nerve monitoring.
This table summarizes vocal cord outcomes post-surgery based on detailed acoustic voice analysis. As seen, patients in the IoNM grousp tend to have more stable postoperative voice quality with faster recovery compared to the conventional thyroidectomy group.
DISCUSSION
1. Recurrent Laryngeal Nerve Injury
The RLN injury rate in the IoNM group was significantly lower compared to the conventional group. Temporary RLN injury occurred in 10% of patients with IoNM versus 30% in the conventional group. Permanent RLN injury was entirely absent in the IoNM group, while 10% of conventional cases reported permanent injury. This reduction aligns with major studies showing IoNM significantly enhances nerve identification and protection.[1]
Studies like that of [2] have demonstrated that IoNM improves the surgeon’s ability to visually identify the RLN and reduces the incidence of permanent vocal cord paralysis. Additionally, IoNM provides feedback on whether the nerve is functioning properly during the procedure, allowing for immediate corrective actions if nerve irritation or injury occurs.
2. Hypocalcemia
Transient hypocalcemia was observed in 20% of IoNM patients versus 40% in conventional cases. Although IoNM is not directly involved in parathyroid preservation, improved visualization during surgery may lead to better parathyroid identification and preservation. Permanent hypocalcemia was not reported in either group, consistent with findings in recent literature.[3]
Research by[4] and others has supported this view, showing that the adoption of precision techniques such as IoNM not only improves nerve preservation but can also lower secondary complications, including transient hypocalcemia.
3. Operative Time
The IoNM group had a slightly longer operative time (mean 110 ± 10 min) compared to the conventional group (mean 95 ± 8 min). The marginal increase in operative time with IoNM is due to the time needed for nerve monitoring setup. However, this additional time is justified by the substantial reduction in complications and improved outcomes.
4. Hospital Stay and Postoperative Recovery
Patients in the IoNM group had shorter hospital stays (2.2 ± 0.5 days) compared to conventional patients (3.1 ± 0.6 days), which reflects faster recovery and fewer complications. Postoperative voice issues were also markedly lower in the IoNM group, highlighting its value in enhancing patient quality of life post-thyroidectomy.[5]
A study by[6] confirmed that although the use of IoNM slightly increases the upfront surgical cost, it reduces the overall cost due to fewer complications and shorter hospital stays.
5. Voice Outcomes and Vocal Cord Function
Detailed postoperative assessments of vocal cord function and voice quality revealed striking differences between the two groups. None of the patients in the IoNM group reported significant changes in voice quality or vocal cord mobility after surgery, while 40% of the patients in the conventional group experienced postoperative voice deterioration. Hoarseness, partial vocal cord immobility, and delayed recovery of voice were more common in the conventional group.
This finding highlights the role of IoNM in nerve preservation and voice protection, which is critical in thyroid surgery. Patients who experience RLN damage often face long-term voice issues, which can significantly impact their quality of life. IoNM offers an added layer of safety by allowing the surgeon to monitor nerve function and avoid inadvertent injury during critical phases of dissection. Studies by[7, 8] also emphasize the importance of IoNM in preventing voice complications, particularly in patients undergoing more complex surgeries, such as total thyroidectomies or revision surgeries.[9]
LIMITATIONS
Despite the promising results, there are several limitations to this study that should be acknowledged:
Small Sample Size: The study was conducted with a relatively small sample size of 20 patients (10 in each group), which may not provide a comprehensive representation of the general population undergoing thyroid surgery. Larger, multi-centre studies are needed to validate these findings.
Short-Term Follow-Up: The follow-up period was relatively short, primarily focusing on immediate postoperative complications like RLN injury and hypocalcemia. Long-term outcomes, including permanent voice changes, recurrence of thyroid disease, and late-onset complications, were not assessed.
Learning Curve for IoNM: The study did not account for the surgeon’s learning curve with IoNM. Surgeons who are new to the technology may require additional time to become proficient, which could affect operative times and outcomes. Future studies should consider stratifying results based on the surgeon’s experience with IoNM
CONCLUSION
IoNM offers substantial advantages over conventional thyroidectomy, particularly in reducing RLN injury and improving postoperative outcomes. While there is a slight increase in operative time, this is offset by improved safety and faster patient recovery. Based on these findings and supported by a growing body of international research, we advocate for the broader use of IoNM in thyroid surgeries, especially in complex cases where RLN preservation is critical.
Author Contributions
I was solely responsible for the conception, design, and execution of the study. I conducted all the research, data collection, and analysis independently. The writing, editing, and finalization of the manuscript were carried out entirely by me, who also handled the submission process, revisions, and communication with the journal. All aspects of the work, from idea formulation to publication, were completed by me.
Ethical approval
Institutional Review Board approval is not required for retrospective analysis.
Declaration of patient consent
Patient’s consent not required as patients identity is not disclosed or compromised.
Conflicts of interest
There are no conflicts of interest.
Use of Artificial Intelligence (AI)-Assisted Technology for manuscript preparation
The authors confirm that there was no use of artificial intelligence (AI)-Assisted Technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.
Financial support and sponsorship
Nil
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