Introduction
In surgery for benign parotid tumors, the tumor must be completely
removed while ensuring that the facial nerve is preserved. To achieve
this, it is important to understand the positional relationship of the
tumor and the facial nerve before surgery. Delineating the facial nerve
using MRI or ultrasound is generally difficult, but in recent years,
intraoperative facial nerve monitoring (FNM) has been used as an
assistive method 1). Using FNM in parotid surgery provides a more
reliable confirmation of the course of the facial nerve and has led to
reports of reduced frequency of postoperative facial nerve palsy 2, 3)
and a shorter operative time 4). However, some authors have reported
that the use of FNM does not change the rate of postoperative facial
nerve palsy 5, 6). Postoperative facial nerve palsy is the most
important complication in parotid surgery, and even if the facial nerve
can be reliably preserved during surgery, some paralysis is likely to
occur. Even if it is transient, facial nerve palsy can decrease
patients’ quality of life until recovery.
Whether the use of FNM during surgery can predict postoperative facial
nerve palsy is also an interesting question. Maier et al. 7) analyzed
the electromyography recordings of 37 patients who underwent parotid
surgery with intraoperative FNM and reported that it was difficult to
predict postoperative facial nerve palsy despite this assistance.
Meanwhile, Mamelle et al. 8) measured the amplitude of response to
stimulation at the facial nerve trunk before and after tumor resection
in 50 patients who underwent parotid surgery, and reported that it was
significantly lower after resection in patients who developed paralysis
than in those who did not.
Here, we examined a new method for predicting facial nerve palsy after
parotid surgery by using intraoperative FNM.