There are many causes of facial palsy, including infections, neurological diseases, congenital diseases, tumors, trauma, and systemic diseases, all of which can cause facial palsy to varying degrees. 1, Bell facial palsy Bell facial palsy is an acute onset, idiopathic unilateral complete or incomplete peripheral facial nerve palsy. The incidence of Bell facial palsy is 20-30/100,000 people, accounting for 60-75% of patients with unilateral facial palsy from various causes, with no difference in incidence between men and women. The incidence is highest, and both sides of the facial nerve are equally likely to develop Bell’s facial palsy. The cause of Bell facial palsy is unclear, and the cause of some cases of Bell facial palsy may be related to diabetes mellitus and ischemia caused by vascular sclerosis, which is also the reason for the higher incidence in the elderly, but most opinions believe that herpes simplex virus type I infection is the possible cause of Bell facial palsy. Herpes simplex virus DNA was detected in 11 of 14 patients with Bell facial palsy, but not in Hunter syndrome and other neurological diseases. Medically induced facial palsy Medically induced facial nerve injury is one of the medically prone complications of middle ear, mastoid and other temporal bone surgeries, and medically induced facial nerve injury includes both unavoidable and accidental injuries. Accidental facial nerve injury during middle ear and mastoid surgery is a serious complication of ear surgery and is an event that every ear surgeon tries to avoid. Familiarity with temporal bone anatomy, good professional training and practical experience are necessary to avoid accidental facial nerve injury, and facial nerve monitoring is a useful technique to avoid accidental facial nerve injury during surgery, but it cannot replace anatomical knowledge and experience. The facial nerve should be positioned according to the relationship and distance between the facial nerve and the fixed anatomical landmarks of the middle ear. The vertical line at the junction of the posterior middle 1/3 of the horizontal semicircular canal is the posterior edge of the vertical segment of the facial nerve, while the arc of the upper edge of the short angle of the anvil is the anterior edge of the vertical segment of the facial nerve, and the facial nerve is basically at the same depth as the horizontal semicircular canal; the horizontal segment of the facial nerve is located under the short process of the anvil, and the anterior edge of the rongeur of the horizontal semicircular canal is 30° upward in front The facial nerve is located below the short process of the anvil and travels 30° upward at the anterior edge of the horizontal hallux valgus. It is located at the junction of tympanic membrane tension and relaxation, and travels along the tympanic sulcus to the lateral side of the long process of the anvil and the medial side of the hamate neck. 3.Temporal bone fracture Cranial trauma is often accompanied by temporal bone fracture, and temporal bone fracture is often combined with peripheral facial paralysis, and the manifestation of temporal bone fracture varies widely depending on the mechanism of injury. However, based on the relationship between the direction of the fracture line and the long axis of the temporal bone cone, temporal bone fractures can be broadly classified as longitudinal fractures, transverse fractures and mixed fractures. If the fracture line is parallel to the back of the temporal bone cone, it is classified as a longitudinal fracture, and if it is perpendicular to the back of the cone, it is classified as a transverse fracture. In longitudinal fractures, the fracture line usually passes above the external auditory canal, the middle ear, and reaches the rupture hole via the eustachian tube and the internal carotid canal, which can cause tympanic membrane perforation, interruption of the auditory chain, conductive deafness and middle ear bleeding. In longitudinal fractures, due to the pulling effect of the superficial large nerve of the rock, it often causes injury to the knee ganglion area of the facial nerve, and in addition, due to the interruption of the auditory chain, the horizontal segment of the facial nerve is injured by the severe displacement of the anvil bone. Longitudinal fractures account for approximately 80% of temporal bone fractures. About 20% of these can cause facial nerve injury. For incomplete facial palsy, it can be observed, while for complete facial palsy that occurs immediately, facial nerve decompression should be considered if the nerve degeneration exceeds 90% within two weeks of facial nerve injury and no motor unit potentials are recorded on facial electromyography. If a violent impact is suffered in the occipital region of the skull, it can easily lead to a transverse fracture of the temporal bone, where the fracture line is perpendicular to the back of the temporal bone rock and extends from the foramen magnum to the foramen ovale. Because the fracture line of a transverse fracture is perpendicular to the rock cone, it often crosses the ear envelope and damages the inner ear, causing sensorineural deafness and vertigo, and the fracture line crosses the facial nerve canal and causes facial nerve injury, although transverse fractures account for only 20% of temporal bone fractures, they cause Since the fracture line does not pass through the tympanic membrane and external auditory canal, the tympanic membrane is usually intact and the ear canal does not bleed, but blood often accumulates in the lower tympanic chamber. Facial nerve tumor The incidence of facial nerve tumor is low. Primary tumors of the facial nerve can be derived from Chewang cell tumor, fibroblasts of the inner nerve membrane, and fibroblasts of the outer nerve membrane. The clinical manifestations are diverse, mainly with slow or sudden unilateral peripheral facial nerve palsy. It is easily misdiagnosed clinically as an inflammatory disease of the facial nerve. The clinical manifestations depend on the response of the nerve to compression and infiltration; the location of the tumor and its effect on adjacent anatomical structures, such as the cochlea and the auditory chain; and the type of histopathology. Small hemangiomas can present with severe facial palsy, while facial nerve sheath tumors sometimes present with facial palsy symptoms when the tumor is relatively large. The typical clinical presentation of facial nerve tumors is a progressive facial nerve palsy, which can be intermittent and may be mistaken for “recurrent Bell’s palsy”. Facial nerve tumors originating from the vagus segment are most likely to present with cochlear and vestibular symptoms, such as tinnitus, sensorineural deafness, and vertigo. Tumors involving the vertical segment of the facial nerve can affect the activity of the auditory chain and result in conductive hearing loss. Imaging is the main tool for facial nerve tumors. In patients with facial nerve palsy, high-resolution thin CT scan bone window slices complemented with MRI imaging can improve the accuracy of facial nerve lesion diagnosis. CT shows facial nerve sheath tumors mostly with distending changes and neural tube defects. Facial nerve fibroma mainly shows thickening of the facial nerve canal and walking in the facial nerve bone canal. Magnetic resonance imaging can show all facial nerve travel pathways and show the extension of facial nerve tumors from the mastoid to the parotid gland.