Predicting postoperative facial
dysfunction by using facial nerve monitoring during parotid surgery
A short running title: predicting of post-operative facial dysfunction
The authors have no funding, financial relationships, or conflicts of
interest to disclose.
Abstract
Objectives : To investigate a method for predicting
postoperative facial nerve palsy during parotid surgery using facial
nerve monitoring.
Design and setting : This was a prospective study of diagnostic
tests performed from 2015 to 2018.
Participants: We included adult patients who were underwent
parotid surgery.
Main outcome measure: We assessed prediction for postoperative
facial nerve palsy by using intraoperative facial nerve monitoring,
comparing between facial nerve trunk stimulation before and after tumor
resection and between stimulation in the facial nerve trunk and each
branch by using facial nerve monitoring. The amplitude response ratio
(ARR) was calculated for the nerve trunk before/after surgery (ARR1) and
for the trunk/periphery (ARR2). We compared these data in each group. In
addition, we then examined the correlation between ARR and time to
recovery of paralyzed branches.
Results: A total of 113 patients were included. Among the 113
patients, 372 branches of 93 patients did not develop facial nerve palsy
and were classified as group A. Among 20 patients who developed
paralysis, 51 branches without paralysis were classified as group B, and
29 branches with paralysis were classified as group C. In patients with
postoperative facial nerve palsy, the potential of the main stimulus was
lower after removal than before removal. Similarly, the main trunk
stimulation was lower than the peripheral stimulation after tumor
extraction. When cut-off values for ARR1 and ARR2 were set to 0.63 and
0.55, respectively, the accuracy of postoperative facial nerve palsy
diagnosis was 91.7% and 96.0%, respectively.
Conclusion: Using FNM during parotid surgery enables easy
prediction of postoperative facial nerve palsy.
Key points:
- Using FNM during parotid surgery enables easy prediction of
postoperative facial nerve palsy.
- In the cases without postoperative facial palsy, trunk stimulation
potential and peripheral stimulation were equivalent.
- In the cases with facial nerve palsy, the trunk stimulation potential
was significantly lower than that of peripheral nerve stimulation.
- Comparison of trunk and peripheral stimulation potentials was more
effective than comparison of trunk stimulation potentials before and
after tumor removal.
- Intraoperative nerve monitoring was ineffective in predicting the
recovery period of postoperative facial nerve palsy.