In reference to Electromyographic facial nerve monitoring during parotidectomy for benign lesions does not improve the outcome of postoperative facial nerve function: A prospective two‐center trial

Dear Editor: I agree with Grosheva et al.’s conclusion that electromyographic (EMG) monitoring in parotid surgery does not influence postoperative facial paralysis and their opinion that continuous visual facial observation is still the standard procedure for parotid surgery. In the field of otologic surgery, EMG facial nerve monitoring has been used routinely for a long time. EMG monitoring of the facial or acoustic nerve, which was approved by the National Institutes of Health, can be significantly efficacious for the preservation of facial or acoustic nerve function during acoustic neuroma (AN) or cerebellopontine angle (CPA) tumor surgery. Once the internal auditory canal or CPA is opened, the facial or acoustic nerve is exposed and just adjacent to other nerves. Therefore, EMG monitoring can easily distinguish the facial or acoustic nerve from other nerves. AN or CPA tumor surgery is totally different from that of parotid surgery. The main objective is to distinguish the facial or acoustic nerve from other similar-looking nerves during AN or CPA tumor surgery, and to find them during parotid surgery. I believe that parotid surgery is similar to that of middle ear/mastoid surgery, where the facial nerve passes through the temporal bone, and is coved by overlying bone along most of its course within the tympanic cavity and hidden from the surgeon’s visual field. Some authors suggested that EMG monitoring of the facial nerve could be beneficial for middle ear/mastoid surgery. They pointed out that an otologist, who is employed in academia and is more recently trained, or is an experienced otologic surgeon, tends to use EMG monitoring more frequently. However, many otologists do not advocate mandatory monitoring for middle ear/mastoid surgery. In one report, only 33% of the British Association of Otolaryngologists/ Head and Neck Surgeons regularly used EMG monitoring for mastoidectomies, and 49% used it for tympanomastoidectomy. Why was its utility low in middle ear/mastoid surgery? There may be several reasons why EMGmonitoring is considered less effective than expected for facial nerve monitoring in real situations during middle ear/ mastoid surgery. I believe that one of the main reasons is that an alarm can come too late, or there can be an inappropriate alarm to the surgeon during surgery. A real monitoring system must warn the surgeon of the risk of damage to the facial nerve during mechanical manipulation by microforceps or drilling of the mastoid. It must warn before the facial nerve is exposed or injured. However, although these mechanical stimulations of the facial nerve are extremely important to the surgeon, they rarely provide the alarm. Electrical stimulation can provide a reliable alarm to the surgeon, but it just confirms the visual observation of the facial nerve. I also believe that there are too many bias factors that can affect intraoperative EMG monitoring during the surgery, and it may provide a false positive or negative alarm. Too many false positive or negative alarms can reduce the reliability of EMGmonitoring. I believe that these situations may be similar between middle ear/mastoid surgery and parotid surgery. Therefore, I believe that further study is required to properly evaluate the efficacy of EMG facial nerve monitoring in the field of middle ear/mastoid surgery and parotid surgery. Readers should keep in mind that EMG monitoring does not replace a thorough knowledge of facial nerve anatomy and appropriate surgical skills. Nevertheless, I agree with the opinion supporting EMG monitoring during middle ear/mastoid surgery. The reason is that it may still be useful in avoiding iatrogenic facial nerve injury in appropriate cases, for example, middle ear/mastoid revision surgery. The other reason is that its usage can diminish the likelihood of medicolegal consequences of nonusage.