The facial nerve is a mixed nerve, the most dominant of which are motor fibers that innervate the facial expression muscles. Anatomically, the facial nerve can be divided into superior motor nucleus segment, motor nucleus segment, cerebellar pontocerebellar horn segment, internal temporal bone segment and external temporal bone segment. Damage to the facial nerve from any cause can lead to facial palsy, where damage above the motor nerve nucleus leads to facial palsy called central facial palsy and damage below the facial nerve nucleus leads to facial palsy called peripheral facial palsy. The most obvious difference between peripheral facial palsy and central facial palsy is the inability to raise the eyebrows and close the eyes. The most common cause of peripheral facial palsy is infection. According to the causative microorganism, it can be divided into viral infection and bacterial infection. Bell’s facial palsy and Hunter’s syndrome are caused by cytomegalovirus and zoster virus, respectively. Bacterial is commonly seen in acute and chronic purulent otitis media. Trauma: Temporal bone fracture is the most common type of trauma causing peripheral facial palsy, followed by ear and parotid surgery, which can also lead to medically induced facial nerve injury. Tumors: These include tumors originating from the facial nerve and tumors surrounding the facial nerve. Common facial nerve tumors include facial nerve sheath tumors, fibromas and hemangiomas. Other tumors include cholesteatoma, middle ear cancer, jugular vein bullae tumor and auditory neuroma. Clinical manifestations】 1. Symptoms (1) Distorted mouth and eye closure disorder: manifested as inability to close the eyes and distorted mouth on the affected side. (2) abnormal tear secretion: tear overflow or no tears may appear on the affected side after facial nerve injury, and crocodile tears may also appear during the recovery period. (3) Taste abnormalities: when the bulbar nerve is involved, the affected side may have abnormal or absent taste in the anterior part of the tongue. (4) Auditory hypersensitivity: When the stapedius muscle is involved, the patient has difficulty tolerating the sudden appearance of strong sound. 2. Physical signs (1) Static manifestations: loss of frontal lines on the affected side, shallow or absent nasolabial folds, low hanging corners of the eyes and mouth. (2) Raised eyebrows: The eyebrows on the affected side cannot be raised. (3) Eye closure: The eyelids on the affected side cannot be closed or are weakly closed. (4) Laughing or showing teeth: When the patient makes a laughing or showing teeth movement, the corners of the mouth move significantly to the healthy side. (5) Cheek puffing: The lips are difficult to close and the affected side shows air. (6) Associative band movement: If the affected side makes eye closing movement, the ipsilateral corner of the mouth will move passively. The cause of the joint band movement is due to the regeneration of nerve fibers in the wrong direction. Diagnosis】 1.Localization diagnosis According to the facial nerve branches, the tear secretion test, stapedius muscle acoustic reflex and taste test were traditionally used to determine the injury site of facial nerve. Nowadays, it has been replaced by imaging examination. 2.Qualitative diagnosis Based on the results of electrophysiological tests, determine the degree of facial nerve injury. Commonly used experiments include nerve electrical excitation test, facial nerve electrogram and electromyography, but clinical practice proves that their application is of little value. The House-Brackmann grading system is commonly used to evaluate the degree of facial palsy and the degree of recovery after surgery.The House-Brackmann grading system classifies facial nerve function into six levels: normal, mild abnormal function, moderate abnormal function, moderate to severe abnormal function, severe abnormal function and complete Paralysis. Treatment】 The treatment of peripheral facial palsy mainly includes non-surgical treatment and surgical treatment. The choice of treatment method is related to the etiology of facial palsy, the timing of the appearance of facial palsy and the degree of facial palsy. Non-surgical treatment includes medication and functional exercise, and commonly used medications include glucocorticoids, antibiotics, antivirals, vitamins, etc. Depending on the degree of facial nerve damage, surgical procedures can be divided into facial nerve decompression, facial nerve anastomosis, facial nerve grafting and sublingual nerve-facial nerve anastomosis. In addition, patients with peripheral facial palsy should pay attention to the protection of the affected cornea.