Abstract
To prevent postoperative facial nerve paralysis in parotid gland surgery, we investigated surgical techniques using two cases of parotid gland tumors. The surgery was performed while observing the surgical field on a magnified screen with a 4K3D video microscope （ORBEYE exoscope） and measuring facial nerve functions with intermittent/continuous nerve monitoring systems （NIM VitalTM）.
As a result, after exposing the facial nerve branches from the surrounding connective tissue, direct operation on the nerve and indirect external force on the branches by moving the tumor （blood removal operation by gauze compression） caused nerve injury. In addition, operation of the descending branch caused damage not only to this branch, but also to the ascending branch that was not directly treated. As a result, detachment of some branches exerted external force on the branch network of the facial nerve including the main trunk and other branches and led to their nerve paralysis. Therefore, it is conceivable that large tumors, deep lobe tumors, and bleeding-prone tumors, which require surgeons to perform frequent nerve traction and extension operations during surgery, are risk factors for post-operative facial nerve palsy.
The current study was conducted using only two cases; it is necessary to study more cases by the real-time monitoring used in this study and to analyze the surgical technique more accurately. Eventually, it is desirable for surgeons to acquire the skills needed to preserve nerves without costly monitoring.
