Electronystagmography (ENG)
(Electrooculography)
Procedure Description
What is electronystagmography?
Electronystagmography (ENG) is used to evaluate people with vertigo (a false sense of spinning or motion that can cause dizziness) and certain other disorders that affect hearing and vision. Electrodes are placed at locations above and below the eye to record electrical activity. By measuring the changes in the electrical field within the eye, ENG can detect nystagmus (involuntary rapid eye movement) in response to various stimuli. If nystagmus does not occur upon stimulation, a problem may exist within the ear, nerves that supply the ear, or certain parts of the brain.
Videonystagmography (VNG)
What is videonystagmography?
Videonystagmography (VNG) is also used to evaluate people with vertigo and dizziness. However, instead of attaching electrodes to detect nystagmus, video analysis is done to detect abnormalities. This is the preferred method of testing because it can give your doctor a more accurate reading in most cases. This method also takes less time for setup and is more comfortable for the patient.
Different types of VNG/ENG tests:
The ENG is actually a battery of tests that may include one or more of the following measurements:
- Calibration test: involves following a light about 6 to 10 feet away with your eyes. This test measures ocular dysmetria (a condition in which movements of the pupil of the eye overshoot their target).
- Gaze nystagmus test: involves staring at a fixed light placed either to the center or side as you are seated or lying down. This test measures how well you can fix your gaze upon an object without your eyes moving involuntarily.
- Pendulum-tracking test: as its name suggests, measures how well you can follow a light with your eyes as it moves like the pendulum of clock.
- Optikinetics test: measures 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: involves moving your head and perhaps your whole body as opposed to 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.
- Air caloric test: involves introducing warm or cool air into the ear canal so that it touches the tympanic membrane. If no problem exists, your eyes will move involuntarily to this stimulus.
The ENG/VNG is used to detect 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.
The test may be performed if an individual is experiencing unexplained dizziness, vertigo, or hearing loss. Additional conditions in which ENG/VNG may be performed are acoustic neuroma, labyrinthitis, and Ménière’s disease.
There may be other reasons for your physician to recommend an ENG/VNG.
ENG/VNG is associated with minimal risks. Some people may experience dizziness or nausea during the test.
ENG should not be used in individuals with pacemakers because the equipment may interfere with pacemaker function; however, VNG may be used instead without harm.
Back or neck problems may be aggravated by rapid changes in position required for the test.
The air caloric test may produce mild discomfort.
There may be other risks depending upon your specific medical condition. Be sure to discuss any concerns with your physician prior to the procedure.
Certain factors or conditions may interfere with ENG/VNG. These include, but are not limited to, the following:
- earwax
- impaired vision
- frequent blinking
- certain medications, such as sedatives, tranquilizers, and antivertigo medications
Your physician or audiologist will explain the procedure to you and offer you the opportunity to ask any questions that you might have about the procedure.
Please do NOT wear any eye or face makeup on the day of the test.
You may eat a light meal four hours before the test.
Avoid consuming caffeine and alcohol for 24 to 48 hours before the test.
Discontinue taking sedatives, tranquilizers, antivertigo, and any other medications as instructed by your physician before the test.
Clean your ears of excessive earwax. Before the ENG/VNG, your ears will be examined for the presence of wax, inflammation, or other problems that may interfere with the test.
If you wear eyeglasses and/or a hearing aid, bring them with you to the test.
If you wear contact lenses, then it is preferred that you wear your contact lenses instead of your glasses during the test.
An ENG/VNG may be performed on an outpatient basis or as part of your stay in a hospital. Procedures may vary depending on your condition and your physician's practices.
Generally, the ENG/VNG follows this process:
- If there is wax in the ear, it will be removed.
- Before positioning the electrodes, areas of the skin on your face will be cleaned with an alcohol-saturated cotton pad and allowed to air-dry. (This does not apply for VNG)
- A paste will be used to attach the electrodes. One electrode will be positioned in the center of your forehead, and the other electrodes will be positioned above the eyebrow and below the eye in a way that allows you to close your eyes. Electrodes may also be placed to the side of each eye. (This does not apply for VNG)
- Depending on the type of test being performed, you may be asked to look up, down, or to the side or move your head and/or entire body. You may also be asked to close your eyes, which does not hinder the recording of eye movement.
- For caloric testing, air will be introduced to the ear while eye movements are recorded.
- The electrical activity detected by the electrodes will be fed into a recorder, which amplifies the signal and charts it so that your physician can interpret the results.
Once the test is complete, the electrodes (if used) will be removed and the electrode paste washed off. You may be instructed to avoid rubbing your eyes to avoid spreading the electrode paste.
You will be observed for any signs of weakness, dizziness, and nausea, and may need to lie down or sit for a few minutes to recover.
Your physician will inform you as to when to resume any medications you stopped taking before the test.
Your physician may give you additional or alternate instructions after the procedure, depending on your particular situation.
Frequently Asked Questions about ENG/VNG
Q. Does it hurt?
A. Generally there is no pain, although you may become dizzy during parts of the test.
Q. What conditions are being evaluated?
A. See above discussion.
Useful links about ENG
The content provided here is for informational purposes only, and was not designed to diagnose or treat a health problem or disease, or replace the professional medical advice you receive from your physician. Please consult your physician with any questions or concerns you may have regarding your condition.
This page contains links to other Web sites with information about this procedure and related health conditions. We hope you find these sites helpful, but please remember we do not control or endorse the information presented on these Web sites, nor do these sites endorse the information contained here.
Acoustic Neuroma Association
American Academy of Neurology
American Tinnitus Association
Brain Injury Association
National Brain Tumor Foundation
National Institute of Neurological Disorders and Stroke
National Institutes of Health (NIH)
National Library of Medicine
Vestibular Disorders Association
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