Abstract
Background
Eliciting a normal electromyography signal has been the usual method to confirm the
functional integrity of the recurrent laryngeal nerve during intraoperative nerve
monitoring. Given that oscillations of the vocal cord can be detected with trans-laryngeal
ultrasound when the ipsilateral recurrent laryngeal nerve is stimulated with the endotracheal
tube in situ, we aimed to compare the accuracy and cost of this novel method with
the conventional electromyography method.
Methods
Consecutive patients who underwent elective thyroid, parathyroid or neck dissection
procedures were included. The NIM-Neuro 3.0 system was used. Endotracheal tube-based
surface electrodes were utilized for electromyography signal recording. Standard anesthetic
technique was adopted. Recurrent laryngeal nerve integrity was verified by both detection
methods (laryngeal ultrasound and electromyography) independently. Vocal cord function
was validated by flexible direct laryngoscopy postoperatively. For each method, concurrence
with flexible direct laryngoscopy was defined as “true-positive” or “true-negative,”
based on the presence or absence of vocal cord paresis. Accuracy was calculated as
the sum of all true positives and negatives divided by the total of nerves-at-risk.
The cost of each method was calculated.
Results
One hundred and four patients were eligible. Total number of nerves-at-risk was 155.
Based on flexible direct laryngoscopy findings, the test sensitivity, specificity,
positive predictive value, and negative predictive value of intraoperative laryngeal
ultrasound were 75.0%, 99.3%, 85.7%, and 98.6%, respectively, while those of electromyography
were 87.5%, 98.0%, 70.0%, and 99.3%, respectively. The prognostic accuracy in laryngeal
ultrasound versus electromyography was comparable (98.1% vs 97.4%). The cost of the
laryngeal ultrasound per operation was less than electromyography ($82 vs $454).
Conclusion
Laryngeal ultrasound has a similar detection accuracy to electromyography during intraoperative
nerve monitoring. Apart from being a cheaper alternative, laryngeal ultrasound may
be useful when there is unexplained loss of electromyography signals during surgery
and may play a role in the intraoperative nerve monitoring troubleshooting algorithm.
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Article info
Publication history
Published online: July 30, 2021
Accepted:
May 4,
2021
Identification
Copyright
© 2021 Elsevier Inc. All rights reserved.
