Facial nerve paralysis is a common problem that involves the paralysis of any structures innervated by the facial nerve. The pathway of the facial nerve is long and relatively convoluted, so there are a number of causes that may result in facial nerve paralysis. The most common is Bells palsy, a disease of unknown cause that may only be diagnosed by exclusion of identifiable serious causes. Signs and symptoms
Facial nerve paralysis is characterised by facial weakness, usually only in one side of the face, with other symptoms possibly including loss of taste, hyperacusis and decreased salivation and tear secretion. Other signs may be linked to the cause of the paralysis, such as vesicles in the ear, which may occur if the facial palsy is due to shingles. Symptoms may develop over several hours. : 1228  Acute facial pain radiating from the ear may precede the onset of other symptoms. : 2585

Causes
Bells palsy
Bells palsy is the most common cause of acute facial nerve paralysis. There is no known cause of Bells palsy, although it has been associated with herpes simplex infection. Bells palsy may develop over several days, and may last several months, in the majority of cases recovering spontaneously. It is typically diagnosed clinically, in patients with no risk factors for other causes, without vesicles in the ear, and with no other neurological signs. Recovery may be delayed in the elderly, or those with a complete paralysis. Bells palsy is often treated with corticosteroids.
The VI cranial nerve, which controls lateral eye movement, is also affected, so people with Moebius syndrome cannot form facial expression or move their eyes from side to side. Moebius syndrome is extremely rare, and its cause or causes are not known. Facial piercings, namely eyebrow piercings or tongue piercings, can in very rare cases cause damage to the facial nerve. Diagnosis
A medical history and physical examination, including a neurological examination, are needed for diagnosis. The first step is to observe what parts of the face do not move normally when the person tries to smile, blink, or raise the eyebrows. If the forehead wrinkles normally, a diagnosis of central facial palsy is made, and the person should be evaluated for stroke. Otherwise, the diagnosis is peripheral facial palsy, and its cause needs to be identified, if possible. Ramsey Hunts syndrome causes pain and small blisters in the ear on the same side as the palsy. Otitis media, trauma, or post-surgical complications may alternatively become apparent from history and physical examination. If there is a history of trauma, or a tumour is suspected, a CT scan or MRI may be used to clarify its impact. Blood tests or x-rays may be ordered depending on suspected causes.