The facial nerve, also known as cranial nerve VII, originates in the brainstem and controls the many muscles of the face and the anterior part of the tongue. It is responsible for the taste sensation on the front part of the tongue and the performance of facial expressions such as smiling, closing the eyes, and grimacing. Injury or damage to the facial nerve can result in the development of facial nerve palsy. This condition causes paralysis to the structures this nerve commonly innervates.
There are many factors that can lead to the development of facial nerve palsy. Some cases occur at birth, because of deficits in the brain due to an inherited disease, or caused by complications during delivery. Other causes include trauma to the head; infections from bacteria and viruses, such as otitis media and encephalitis; and metabolic diseases, like diabetes mellitus and hypertension. A growing tumor or cancer in the brain can also impinge and cause injury to the facial nerve.
Symptoms seen in patients with facial nerve palsy usually include paralysis on one side of the face, difficulty in closing one eye, a droop in the eyebrow, difficulty eating, and the impairment of the sense of taste. The ear may also be affected, with some patients observing an increased sensitivity to sounds and pain in the affected ear. A common example of facial nerve palsy is Bell's palsy, a condition of unknown cause characterized by the sudden onset of paralysis on one side of the face. Another example is Ramsay Hunt syndrome, which often presents with facial paralysis and hearing problems.
In cases of facial paralysis, a neurologist, a doctor who specializes in diseases of the nervous system, will evaluate the symptoms to look for a cause. A thorough history about the patient is usually taken, including previous infections and head trauma which may have occurred. Physical and neurological examinations are often done to assess the extent of facial nerve palsy. Laboratory studies, such as complete blood count (CBC) and test for blood sugar, are also usually requested to rule out other causes. Computed tomography (CT) scans and magnetic resonance imaging (MRI) of the head can also be helpful in the evaluation of the condition.
Treatment and management of facial nerve palsy often depends on the cause of the injury. Surgical procedures are usually done when penetrating trauma or tumors in the brain are the primary cause. Other management may include physical and speech therapy, reconstructive surgery, and use of medications.