The facial nerve is a motor (movement) nerve that enters the face through the parotid gland in the cheek and branches to the muscles of facial expression. These include eye closure, smiling and lips. Causes of parotid nerve disease include tumours which may be benign or cancerous as well as trauma and infection including viral infection. Occasionally the facial nerve will be weak without an obvious cause and often resolves by itself. It is sometimes aided by treatment with anti-inflammatory steroid medications and sometimes antiviral medications. Other underlying causes may need to be treated and rehabilitation is often required with some surgical techniques if the facial nerve remains weak over a long period of time.