Figure 1: The method of high frequency ultrasonography examination in longitudinal planes in the study. The patient is relaxed lying on his back on the examination bed with his face and neck fully exposed. Turn the head to the other side of the check. Below the earlobe, the probe is oblique to the direction of the osseous external auditory canal, and the facial nerve with high and low echoes can be scanned in the triangular region surrounded by the three points of the osseous external auditory canal, mastoid process, and parotid gland. Along the direction of nerve path, the probe is probed to the part before entering the parotid gland, namely, the diameter of the nerve trunk near the end face after exiting the stem milk foramina (a,b,c)