The most common cause of facial weakness which comes on suddenly is referred to as “Bell’s palsy.” This disorder is probably due to the body’s response to a virus: in reaction to the virus the facial nerve within the ear (temporal) bone swells, and this pressure on the nerve in the bony canal damages it. In order to be sure that this is the cause of the facial weakness, and not something else, a special set of questions will be asked. After an examination of the head, neck, and ears, a series of tests may be performed. The most common tests are: ? Hearing Test: Determines if the cause of damage to the nerve has involved the hearing nerve, inner ear, or delicate hearing mechanism. ? Balance Test: Evaluates balance nerve involvement. ? Tear Test: Measures the eye’s ability to produce tears. Eye drops may be necessary to prevent drying of the surface of the eye cornea). ? Imaging: CT (computerized tomography) or MRI (magnetic resonance imaging) determines if there is infection, tumor, bone fracture, or other abnormality in the area of the facial nerve. ? Electrical Test: Stimulates the facial nerve to assess how badly the nerve is damaged. This test may have to be repeated at frequent intervals to see if the disease is progressing.