Electronystagmography (ENG)

What is electronystagmography?

Your healthcare provider can use electronystagmography (ENG) to evaluate vertigo and certain other hearing and vision disorders. Vertigo is a false sense of spinning or motion that can cause dizziness. Your eyes and sense of vision are a major part of your sense of balance.

For this test, your healthcare provider places electrodes above and below the eye. The electrodes record electrical activity of the muscles that control eye movement. An ENG measures the changes in the electrical field in the eye. An ENG can then find uncontrolled (involuntary) rapid eye movement (nystagmus) in response to certain stimuli. If this eye movement doesn't occur when stimulated, you may have a problem within the ear. Or you may have a problem with the nerves that supply the ear, or certain parts of the brain.

The ENG is actually a series of tests that may include 1 or more of these measurements:

• Calibration test. For this test, you follow a light with your eyes. This test checks for ocular dysmetria, a condition that causes the pupils to overshoot their target.

• Gaze nystagmus test. For this test, you stare at a fixed light placed to either the center or the side as you are seated or lying down. This test measures how well you can fix your gaze at an object without your eyes moving involuntarily.

• Pendulum-tracking test. For this test, you follow a light with your eyes as it moves like a clock's pendulum.

• Optokinetics test. This checks your ability to follow a light. The light moves quickly across and out of your field of vision and back again while you keep your head still.

• Positional test. For this test, you move your head and perhaps your whole body, not just your eyes. For example, you may be told to turn your head quickly to one side. Or you may be asked to sit up quickly after you have been lying down. The amount of eye motion that results from this activity is recorded.

• Water caloric test. This test places warm or cool water into the ear canal with a syringe. The water touches the tympanic membrane. If no problem exists, your eyes will move involuntarily to this stimulus. Your provider may use air instead of water as the stimulus for this test. This is more likely if you have a damaged tympanic membrane.

Why might I need an ENG test?

Your healthcare provider uses ENG to find disorders of the peripheral vestibular system, the parts of the inner ear that interpret balance and spatial orientation, or the nerves that connect the vestibular system to the brain and the muscles of the eye.

You may have this test if you have unexplained dizziness, vertigo, or hearing loss. These are symptoms, not a diagnosis. The ENG may help find the exact cause of your symptoms. Possible causes include:

• Acoustic neuroma. A tumor of the nerve that controls sound and balance.

• Labyrinthitis. Inflammation and infection of the inner ear, often caused by a virus. It may affect hearing and balance.

• Usher syndrome. A rare congenital disorder that causes hearing and vision loss.

• Ménière disease. This is when you have too much fluid in the inner ear. It can affect hearing and balance.

If a known sore (lesion) exists, an ENG can find the actual site. There may be other reasons for your healthcare provider to advise an ENG.

What are the risks of an ENG test?

There are very few risks with ENG. Some people may have dizziness or nausea during the test.

ENG should not be used if you have a pacemaker. The equipment may interfere with pacemaker function.

The quick changes in position needed for the test may make back or neck problems worse.

The water caloric test may cause mild discomfort. If you have been previously diagnosed with a perforated tympanic membrane, you should not have the water caloric part of the ENG test.

There may be other risks depending on your specific health condition. Discuss any concerns with your healthcare provider before the procedure.

Certain factors or conditions may interfere with ENG. These include:

• Earwax

• Impaired vision

• Frequent blinking

• Certain medicines, such as sedatives, tranquilizers, and antivertigo medicines

How do I get ready for an ENG test?

• Your healthcare provider will explain the procedure to you and you can ask any questions that you might have about the procedure.

• You may be asked to sign a consent form that gives your permission to do the procedure. Read the form carefully and ask questions if something isn't clear.

• Follow any directions you are given for not eating or drinking before the test.

• Tell your healthcare provider of all medicines (prescribed and over-the-counter), vitamins, and herbal supplements that you take.

• Stop taking sedatives, tranquilizers, and any other medicines as instructed by your healthcare provider before the test.

• Carefully clean your ears of excessive earwax. Before the ENG, your ears will be checked for wax, inflammation, or other problems that may interfere with the test.

• If you wear glasses or a hearing aid, bring them with you to the test.

• Arrange for someone to drive you to and from the procedure.

• Based on your health condition, your healthcare provider may request other specific preparation.

What happens during an ENG test?

You may have an ENG on an outpatient basis. This means you go home the same day. Or it may be done as part of a hospital stay. These tests are generally done in a room with low lighting. Procedures may vary depending on your condition and your healthcare provider's practices.

Generally, the ENG follows this process:

1. Your healthcare provider will remove any wax in your ear.

2. Before placing the electrodes, your healthcare provider will clean areas of the skin on your face with an alcohol-saturated cotton pad and let them air dry. 

3. Your provider will use a paste to attach the electrodes. They will place an electrode in the center of your forehead. Another electrode will be placed above the eyebrow and below the eye. You will still be able to close your eyes. You may also have electrodes on the side of each eye.

4. Depending on the type of test being done, you may be asked to look up, down, or to the side. Or you may be asked to move your head or entire body. You may also be asked to close your eyes. This won't interfere with recording your eye movement.

5. For caloric testing, your provider will put either air or water into the ear. This is done while recording your eye movements.

6. A recorder finds the electrical activity from the electrodes. The recorder amplifies the signal and charts so that your provider can interpret the results.

What happens after an ENG test?

Once the test is done, your provider will remove the electrodes and wash off the electrode paste. Don't rub your eyes to prevent spreading the electrode paste.

Your provider will watch you for any signs of weakness, dizziness, and nausea. You may need to lie down or sit for a few minutes to recover.

Your healthcare provider will tell you when to start taking any medicines you stopped taking before the test.

Your healthcare provider may give you other instructions after the procedure, depending on your particular situation.

You may also have a videonystagmography. This is a test that also finds eye movement. But it uses video cameras instead of electrodes.

Next steps

Before you agree to the test or procedure make sure you know:

• The name of the test or procedure

• The reason you are having the test or procedure

• What results to expect and what they mean

• The risks and benefits of the test or procedure

• What the possible side effects or complications are

• When and where you are to have the test or procedure

• Who will do the test or procedure and what that person’s qualifications are

• What would happen if you did not have the test or procedure

• Any alternative tests or procedures to think about

• When and how will you get the results

• Who to call after the test or procedure if you have questions or problems

• How much you will have to pay for the test or procedure