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Page 4 of 5 Nakamura et al. Mini-invasive Surg 2019;3:29 I http://dx.doi.org/10.20517/2574-1225.2019.28

The sensitivity of f-EMG for neurological deficits was 50% in all cases, 100% for TF-PELD, and 0% for IL-
PELD. The specificity was 95.8%, 100%, and 90.4%, respectively.

DISCUSSION
F-EMG’s effectiveness has been reported for cranial nerve tumor resection and spinal surgery [7-11] . Any
irritation to the nerve, by stretching or compression, causes trains of motor unit potential discharge in
[7]
[8]
the corresponding muscle . F-EMG is reported to have high sensitivity and relatively low specificity .
However, monitoring in real-time would improve specificity when confirming that the related nerve was
[7]
correctly manipulated during surgery . Therefore, application of f-EMG in PELD surgery is considered to
be efficient.

One of the most important complications in TF-PELD is ENR injury, which reportedly occurs at a relatively
high rate of 2%-8.9% under LA [3,4,13-16] . A large LA dosage may increase the risk of ENR injury because of
complete nerve blockage. Furthermore, some patients cannot tolerate surgery because of pain and, thus,
had to be converted to GA on another day. Therefore, we believe that PELD under LA is not necessarily
safe or comfortable for the patient.

In this study, there was one true-positive case with detectable nerve irritation during surgery. This patient
complained of severe numbness without motor deficit after surgery. Train waves appeared when the sleeve
was manipulated by hand. Hence, caution is required during surgery to avoid motor deficits.

Conversely, we carefully monitored f-EMG during IL-PELD while rotating the sleeve when retracting the
dural sac and nerve root. No alarm sounded when performing IL-PELD. However, 2 false-positives were
observed during IL-PELD. An alarm sounded after herniated disc material was removed. F-EMG sensitivity
during IL-PELD was low. Hence, f-EMG may be inappropriate for monitoring the nerve root during IL-
PELD.

F-EMG monitoring cannot detect damage to sensory nerves, but it can potentially prevent injury to motor
and sensory fibers. PELD under GA, without the use of a muscle relaxant with f-EMG monitoring, can
reduce neural injury.

This study was limited by the small number of patients. Therefore, future studies with larger numbers of
patients will be necessary to evaluate the efficacy of f-EMG for PELD.

In conclusion, PELD was performed safely under GA using f-EMG monitoring. Patients who cannot
tolerate pain are good candidates for PELD under GA.

DECLARATIONS
Acknowledgments
The authors would like to thank Enago (www.enago.jp) for the English language review.

Authors’ contributions
Wrote and reviewed the manuscript: Nakamura JI, Setoue T, Hara J

Availability of data and materials
Not applicable.

Financial support and sponsorship
None.