Electronystagmogram (ENG)

An electronystagmogram (ENG) measures normal eye movement and involuntary rapid eye movements called nystagmus. It also checks the muscles that control eye movements. ENG checks how well the eyes, inner ears, and brain help you keep your balance and position (such as when you change from lying down to standing).

ENG is done to help see whether there is damage or a problem in how the inner ear, brain, or nerves connecting them work. These problems may cause dizziness, vertigo or loss of balance.

Nystagmus occurs normally when the head is moved. However, nystagmus without moving your head or nystagmus that does not go away may be caused by conditions that affect the inner ear, brain, or the nerves connecting them.

During ENG, electrodes are attached to the face near the eyes to record eye movements. The movements are recorded on graph paper. A series of recordings is done.

• Baseline recordings are taken with your head at rest.
• More recordings are done:
  • While you move your head up and down, left and right.
  • While you look at a moving object.
  • After warm or cold water (or air) is placed inside your ears.

An electronystagmogram (ENG) is done to:

• Find where the problem is in the inner ear, brain, or nerves connecting them that is causing dizziness, vertigo, or a loss of balance.
• Find any damage to structures or nerves in the inner ear, brain, or nerves connecting them.

For 2 to 5 days before the test, you will be asked to stop taking:

• Medicines that help your vertigo.
• Sedatives and tranquilizers.
• Drinks with alcohol.
• Foods that contain caffeine, such as coffee, tea, cola, and chocolate.

Your doctor may ask you to eat a light meal or not eat for 3 to 4 hours before the test, because the test can cause nausea and vomiting.

Do not wear facial makeup during the test so the electrodes can attach to the skin.

If you normally wear glasses, contact lens, or hearing aids, bring them to the test.

If you have a neck or back problem, tell your doctor, so your neck and back will be protected during the test.

An electronystagmogram (ENG) may be done in a hospital or in a doctor's office by a doctor or hearing specialist (audiologist).

Before the test begins, your eyes and ears will be checked. Any earwax in your ear canal will be removed.

Five electrodes will be attached with a special paste to your face. You will be in a dark room for the test. The test may have six parts.

• To find the right settings for the measuring tool, you will follow a moving point of light with only your eyes. You should not move your head during this part of the test.
• Readings will be taken with your eyes closed. You may be given a mental task to do, such as an arithmetic problem, during this part of the test. Readings will be taken while you look straight ahead and to each side.
• Readings will be taken while your eyes follow the back-and-forth movement of a pendulum.
• Readings will be taken while you follow a series of moving objects out of your line of vision. As each object leaves your line of vision, you will be asked to look immediately at the next moving object.
• Readings will be taken while you move your head from side to side and up and down. You may be asked to move your body (as well as your head) into different positions.
• Near the end of the test, your eye movements may be recorded while cool and warm water is placed inside your ears. In some cases, warm and cool air may be blown gently into your ears instead of using water. This part of the test is called the caloric test and may be done without using electrodes near your eyes. The caloric test is not done if you have a perforated eardrum, because water used in the caloric test can get into the middle ear and lead to infection. The caloric test can be done with air instead of water, but if the eardrum is perforated, the caloric test may not be done at all.

The test may take 60 to 90 minutes.

You may feel weak, dizzy, or nauseated during an electronystagmogram. You may feel as if you are going to fall down during the test, but don't worry, the doctor or audiologist will make sure you do not fall. These feelings will go away when the test is done.

If you are having the test because you have dizziness or vertigo, you may find that the test causes your condition to be worse for a short time.

During the caloric test, you may feel nauseous and may vomit. You may need to lie down until the nausea and vomiting or vertigo pass.

An electronystagmogram may cause vomiting. There is a small chance of causing a neck or back problem to get worse during the test because of the quick body movements that are done.

An electronystagmogram (ENG) measures normal eye movement and involuntary rapid eye movements called nystagmus. It also checks the muscles that control eye movements. ENG checks how well the eyes, inner ears, brain, and nerves connecting them, help you keep your balance and position (such as when you change from lying down to standing). Results are recorded as normal or abnormal.

Normal

Test results are normal if there are no abnormal involuntary eye movements during the test. Some nystagmus occurs normally when you turn your head.

Results of the caloric test are normal if involuntary eye movements have normal direction and intensity.

Abnormal

Test results are abnormal if there is nystagmus with head-turning that does not go away in a specific or normal length of time. The results of the caloric test are abnormal if there are fewer eye movements or no eye movement during the test. Abnormal results may:

• Find damage to nerves or structures in the ear or the brain that affect balance.
• Mean Ménière's disease, multiple sclerosis, or labyrinthitis is present or a brain disease is present or that you have had a stroke.

Reasons you may not be able to have the test or why the results may not be helpful include:

• Taking some medicines, such as stimulants (including caffeine), depressants, sedatives, and medicines to help vertigo.
• Too many movements of the head or other eye movements, such as blinking.
• Not being able to do what is asked during the test. Medical conditions that affect attention, poor eyesight, or cause sleepiness can affect the test results.

• At some centers, you cannot have an electronystagmogram if you have a pacemaker because the tool that measures eye movements can affect pacemaker function.
• Because an electronystagmogram cannot find some inner ear problems, a normal result does not mean an inner ear condition is not present.
• To check for hearing loss or tinnitus, other tests such as audiometry or a brain stem auditory evoked response (BAER) test may be done. If a tumor or stroke is suspected in a certain part of the brain, a CT scan or MRI may be used to confirm the diagnosis. For more information, see the medical tests Hearing Tests, CT Scan of the Head and Face, and Magnetic Resonance Imaging (MRI) of the Head.

Other Works Consulted

• Chernecky CC, Berger BJ, eds. (2004). Laboratory Tests and Diagnostic Procedures, 4th ed. Philadelphia: Saunders.

• Fischbach FT, Dunning MB III, eds. (2004). Manual of Laboratory and Diagnostic Tests, 7th ed. Philadelphia: Lippincott Williams and Wilkins.

• Pagana KD, Pagana TJ (2006). Mosby’s Manual of Diagnostic and Laboratory Tests, 3rd ed. St. Louis: Mosby.