The peripheral nervous system includes nerve trunks, plexuses, ganglia and nerve endings composed of nerve cell bodies and nerve fibers outside the brain and spinal cord. It can be divided into spinal nerve, cerebral nerve and autonomic nerve. Idiopathic facial nerve palsy, also known as facial neuritis or Bell’s palsy, is a peripheral facial palsy caused by nonspecific inflammation of the facial nerve in the stoma. The etiology has not been fully elucidated. Because the bony facial nerve canal can accommodate the facial nerve, once the facial nerve becomes ischemic and edematous, the facial nerve is bound to be compressed. The triggering factors may be wind and cold, viral infection (such as herpes zoster) and autonomic instability, which cause local neurotrophic vasospasm and result in ischemic edema of the nerve. Clinical manifestations 1. The disease can develop at any age, slightly more in males, mostly unilateral, occasionally bilateral, and may be accompanied by pain in the postauricular mastoid area, the ear or the mandibular angle on the paralyzed side at the beginning of the disease. The onset is usually acute, with symptoms peaking within a few hours or 1 to 3 days. 2. Complete paralysis of the expression muscles on one side: the frontal lines disappear, the forehead cannot be frowned, the eye fissure becomes larger, the eyelid cannot be closed or is incompletely closed, and the eyeball on the paralyzed side turns upward when the eye is closed, revealing the white sclera, called Bell’s sign; the nasolabial folds on the affected side become shallow, the corners of the mouth droop, and the corners of the mouth are crooked to the healthy side when the teeth are shown; paralysis of the orbicularis oris muscle makes the air leak when puffing and whistling; paralysis of the buccal muscle makes the food easily stay between the teeth and cheeks on the affected side. If the lesion is above the facial nerve, the ipsilateral loss of taste in the anterior 2/3 of the tongue may occur; if the stapedius muscle branch is damaged, the ipsilateral loss of taste in the anterior 2/3 of the tongue and auditory hypersensitivity may occur; if the lesion is in the geniculate ganglion, in addition to peripheral facial palsy, anterior 2/3 of the tongue and auditory hypersensitivity, there is also pain in the affected mastoid area, decreased sensation in the auricle and external auditory canal, and the appearance of herpes in the external auditory canal or tympanic membrane. Herpes, called Hunt’s syndrome.