Dr. LOU KIN HENG

1. Intra-operation nerve
monitoring (IONM)
Application
General Surgery
IC: LOU KIN HENG
2023/04/14
1

2. Incidence of nerve palsy
Recurrent laryngeal nerve palsy
Thyroid surgery 1-2%
Thyroid cancer surgery 4-8%
2

3. • External
branch of
superior
laryngeal
nerve
• Recurrent
laryngeal
nerve
3

4. External
branch of
superior
laryngeal
nerve
4

5. 5

6. 6

7. 7

8. 8

9. Recurrent laryngeal nerve monitoring (RLNM)
9

10. Recurrent laryngeal nerve monitoring (RLNM)
10

11. 11

12. Algorithm of RLNM
12

13. 13

14. Thyroidectomy
• Over the last century, from a dangerous and bloody undertaking to a
safe operation with favorable outcomes.
Benign and malignant conditions:
Thyroid nodules Hyperthyroidism Obstructive or substernal goiter
Differentiated (papillary or
follicular) thyroid cancer
Medullary thyroid cancer Anaplastic thyroid cancer
Metastases to the thyroid Primary thyroid lymphoma
Vocal fold dysfunction (VFD): temporary rate 9.8%, permanent rate 2.3% (meta analysis, 2009, over 25,000 patients)
14

15. Recommendation 2: The preoperative physical examination
should include voice assessment. (Strong recommendation, moderate-
quality evidence)
• Patients with preoperative hoarseness or voice changes
• Patients with history of prior neck or mediastinal surgery, both thyroid and nonthyroid
• Patients with extrathyroidal extension of tumor posteriorly
• Patients with bulky lymphadenopathy in the central compartment or jugular chain
15

16. Laryngeal assessment
• Auditory assessment
• Mirror examination
• Transcutaneous laryngeal ultrasound
• Flexible laryngoscopy
• Video laryngo stroboscopy
16

17. Intraoperative Events cause VFD
• Intubation -> vocal fold laceration, hematoma, edema or rupture;
Arytenoid dislocation;
formation of chronic granuloma or polyp
• Thermal or traction-related nerve trauma (use of energy devices too
close to a nerve; unintentional clamping, ligation or transection);
• Nerve transection (intentional or rarely unintentional)
Excessive traction on the RLN or a thermal event are common mechanisms leading to paresis or paralysis and
May not always be recognized intraoperatively.
17

18. Intraoperative Assessment of Nerve
Function
• Traditional methods –
intraoperative visualization and
knowledge of the normal and
variant RLN anatomy.
• Recurrent Laryngeal nerve
monitoring –
preoperative planning
significant expertise
avoidance of neuromuscular
blockade after anesthetic induction
18

19. Challenging operations
• Reoperation with adhesion tissue, difficult anatomy
• Resection of large or substernal goiter, suspect RLN dislocation
• Resection of locally advanced thyroid cancer with central LN resection
• Unilateral VCD, lobectomy with the opposite side
19

20. 20

21. Result of IONM application
Total RLN injury Transient injury Permanent injury
Overall meta-analysis + + +
Subgroup – bilateral
operation
+ + +
Subgroup – malignancy
operation
+ + -
Subgroup – reoperation - - -
Subgroup – operation
volume
+ + +
+ significant reduce the nerve injury; - no significant reduce the nerve injury
21

22. Summary
• Laryngeal assessment is needed before thyroidectomy
• IONM can help surgeon easily to identification and preservation of
nerve, especially in re-operation case, substernal goiter, cancer and
vocal fold dysfunction case.
22

23. 23

24. 24

25. 25

26. 26

27. 27

28. 28

29. Types of
thyroidectomy
29

30. 30

31. 31