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.
For this test, your healthcare provider places electrodes above and below the eye to record electrical activity. By measuring the changes in the electrical field within the eye, ENG can detect involuntary rapid eye movement (nystagmus) in response to certain stimuli. If it does not occur when stimulated, you may have a problem within the ear, nerves that supply the ear, or certain parts of the brain.
The ENG is actually a series of tests that may include one or more of the following 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 of the eye to overshoot their target.
Gaze nystagmus test. For this test, you stare at a fixed light placed to either the center or 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 pendulum of a clock.
Optokinetics test. This checks your ability to follow a light as it 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 instructed 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 involves introducing warm or cool water into the ear canal with a syringe so that it 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, especially 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 responsible for sound and balance)
- Labyrinthitis (inflammation of the inner ear, often caused by a virus)
- Usher syndrome (a congenital disorder that causes hearing loss)
- Meniere's disease (excess fluid in the inner ear that can affect hearing and balance)
If a known lesion exists this test can identify the actual site. There may be other reasons for your healthcare provider to recommend an ENG.
What are the risks of ENG tests?
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 because the equipment may interfere with pacemaker function.
Rapid changes in position required for the test may aggravate back or neck problems.
The water caloric test may cause mild discomfort. If you have been previously diagnosed with a perforated tympanic membrane, you should not undergo the water caloric portion of the ENG test.
There may be other risks depending on your specific medical condition. Be sure to discuss any concerns with your healthcare provider before the procedure.
Certain factors or conditions may interfere with ENG. These include:
- Impaired vision
- Frequent blinking
- Certain medicines, such as sedatives, tranquilizers, and anti-vertigo 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 is not clear.
- You may be asked to avoid eating for at least four hours before the test.
- Avoid caffeine and alcohol for 24 to 48 hours before the test.
- Tell your healthcare provider of all medicines (prescribed and over-the-counter) and herbal supplements that you take.
- Discontinue 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 examined for the presence of wax, inflammation, or other problems that may interfere with the test.
- If you wear eyeglasses or a hearing aid, bring them with you to the test.
- Based on your medical condition, your healthcare provider may request other specific preparation.
What happens during an ENG test?
You may have an ENG on an outpatient basis or as part of a hospital stay. Procedures may vary depending on your condition and your doctor's practices.
Generally, the ENG follows this process:
- Your healthcare provider will remove any wax in your ear.
- Before positioning 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.
- Your provider will use a paste to attach the electrodes. He or she will position an electrode in the center of your forehead, and the other above the eyebrow and below the eye in a way that allows you to close your eyes. You may also have electrodes on the side of each eye.
- Depending on the type of test being done, you may be asked to look up, down, or to the side or move your head or entire body. You may also be asked to close your eyes, which does not hinder the recording of eye movement.
- For caloric testing, your provider will introduce either air or water to the ear while he or she records eye movements.
- A recorder detects the electrical activity from the electrodes. The recorder amplifies the signal and charts so that your healthcare provider can interpret the results.
What happens after the 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 avoid 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 resume any medicines you stopped taking before the test.
Your healthcare provider may give you other instructions after the procedure, depending on your particular situation.
Before you agree to the test or the 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 will you have to pay for the test or procedure