Facial neuritis, also known as idiopathic facial nerve paralysis or Bell's palsy, is caused by nonspecific inflammation of the facial nerve inside the cranial foramen, leading to peripheral facial paralysis. The exact cause is currently unknown, but it is thought to possibly be related to viral infections of the optic nerve, as well as potentially due to exposure to cold or upper respiratory tract infections. The mechanism of onset involves the bony facial nerve canal, which can only accommodate the facial nerve. However, if the facial nerve becomes ischemic and swollen, it will inevitably lead to nerve compression. Viral infections can lead to local autoimmune responses in the nerves and spasms of the nutrient vessels, resulting in ischemic swelling and facial nerve paralysis.