The causes of facial paralysis include brain diseases and facial nerve damage. Facial paralysis is medically known as facial nerve palsy, which refers to the loss of facial muscle movement caused by damage to the facial nerve, which may result in the loss of frontal lines, inability to close the eyelids, crooked corners of the mouth, shallow nasolabial folds, and drooping of the corners of the mouth. Facial paralysis can be divided into central facial paralysis and peripheral facial paralysis. 1. Central facial nerve palsy: The main causes of central facial nerve palsy are cerebrovascular diseases, such as cerebral infarction and cerebral hemorrhage, followed by tumors and intracranial infections, such as viral encephalitis, which can damage the central nerves and lead to facial paralysis. 2. Peripheral facial nerve palsy: Peripheral facial nerve palsy is related to cold, infection, trauma and other factors. Among them, cold is the most common cause of peripheral facial nerve palsy, because the body’s resistance decreases after being exposed to cold and wind, which can easily lead to viral attack on the facial nerve, resulting in inflammation and swelling of the facial nerve, causing facial paralysis. Localized infections and trauma are also common, such as otitis media, mumps and tooth extraction. Once the sudden weakness of facial muscles and crooked corners of the mouth occurs, it is necessary to consult a doctor in a timely manner and standardize the diagnosis and treatment, so as to avoid delaying the condition.