Predicting postoperative facial dysfunction by using facial nerve
monitoring during parotid surgery
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.