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
- 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
- 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
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
- 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
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