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ELECTRONYSTAGMOGRAM (ENG)

Test Overview

An electronystagmogram (ENG) measures involuntary rapid eye movements called nystagmus and evaluates the muscles controlling eye movements. ENG evaluates how well the eyes, inner ears, and brain help you maintain balance and a sense of position (such as when changing from lying down to a standing position).

ENG is done to help determine whether damage to the structures or nerves in the inner ear or brain is causing dizziness or vertigo.

Nystagmus occurs normally when the head is moved. However, spontaneous or prolonged nystagmus may be associated with certain conditions that affect the nerves or structures of the inner ear or brain.

During ENG, electrodes are attached to the face near the eyes to detect eye movements. The signals from the electrodes are recorded on graph paper. ENG involves a series of recordings.

  • Baseline readings are taken with the head at rest.
  • Additional readings are taken:
    1. While the head is moved in different positions (up and down, left and right).
    2. While looking at a moving object.
    3. After warm or cold water (or air) is placed inside the ears.
Why It Is Done

An electronystagmogram (ENG) is done to:

  1. Determine a possible point of origin for dizziness or vertigo.
  2. Locate, determine the extent, and monitor the progress of damage to structures or nerves in the inner ear or brain.
  3. Evaluate hearing loss in one ear (unilateral) with unknown cause.
How To Prepare

Before the test, you will be asked to stop taking:

  1. Medications that reduce vertigo.
  2. Sedatives and tranquilizers.
  3. Drinks containing alcohol.
  4. Stimulants, including foods that contain caffeine (such as coffee, tea, cola, and chocolate).
Your health professional may advise you to eat only a light meal or not eat for several hours before the procedure, because the procedure may cause nausea and vomiting. Do not wear facial makeup during the test because it can interfere with attaching the electrodes to the skin.
If you normally wear glasses, contact lenses, or hearing aids, bring them to the test. If you have a neck or back condition, tell your health professional before the test so that precautions can be taken to prevent worsening of your problem.

How It Is Done

Before testing begins, your eyes and ears will be examined. Any earwax blocking your ear canal will be removed.
Five electrodes will be attached with an adhesive to the skin of your face. You will be tested while seated in a darkened room. The test may have up to six parts.

  1. To determine the proper settings for the measuring instrument, you will follow a moving point of light with only your eyes. You should not move your head during this part of the test.
  2. Readings will be taken while your eyes are closed. You may be given a mental task to do (such as an arithmetic problem) during this part of the test. Also, readings will be taken while you gaze straight ahead and to each side.
  3. Readings will be taken while your eyes follow the back-and-forth movement of a pendulum.
  4. 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.
  5. 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.
Toward the end of the test, your eye movements may be monitored 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 testing is called the caloric test and may be done without using electrodes to detect the eye movements. 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.
Testing may take up to 90 minutes.

How It Feels

You may become weak, dizzy, or nauseated during an electronystagmogram. You may feel as though you are going to fall down during testing. Care will be taken to make sure that you do not fall. The effects of the test are temporary.
The level of discomfort caused by an electronystagmogram depends on the reason for having the test. If you are having the test done due to periods of dizziness or vertigo, you may find that the test causes your condition to worsen temporarily.
During the caloric testing, you may feel nauseated and may vomit. You may need to lie down until the nausea and vomiting or vertigo pass.

Risks

An electronystagmogram may cause vomiting. There is a slight risk of causing a neck or back condition to worsen because of the quick body movements that are done during the test. If you have a neck or back condition, tell your health professional before the test so that precautions can be taken to prevent worsening of your problem.

Results

An electronystagmogram (ENG) is a test that measures involuntary rapid eye movements called nystagmus. ENG evaluates how well the eyes, inner ears, and brain help you maintain balance and a sense of position (such as when changing from lying down to a standing position). Results are recorded as normal or abnormal.

Normal

Test results are normal if there are no abnormal involuntary eye movements during testing. Normally, some nystagmus may be expected with head-turning. 
Results of the caloric test are normal if involuntary eye movements have normal direction and intensity.

Abnormal

Test results are abnormal if there is prolonged nystagmus or vertigo with head-turning. The results of the caloric test are abnormal if there are decreased eye movements or an absence of eye movements. Abnormal results may:

  1. Identify and locate some kinds of brain damage or damage to nerves or structures in the ear that affect balance.
  2. Suggest a stroke, Méniere’s disease, otosclerosis, multiple sclerosis, or labyrinthitis.
What Affects The Test

Factors that can interfere with your test and the accuracy of the results include:

  1. Some medications, such as stimulants (including caffeine), depressants, sedatives, and medications to relieve vertigo.
  2. Excess movements of the head or other movements, such as blinking,
  3. The inability to cooperate and focus. Medical conditions that affect attention, poor eyesight, and excessive sleepiness can affect test results.
What To Think About
  1. At some health care facilities, you cannot have an electronystagmogram if you have a pacemaker because the instrument that measures the eye movements can affect pacemaker function.
  2. The caloric test creates an abnormal situation that the ear would not normally experience. In some cases, this can make the results difficult to interpret.
  3. Because an electronystagmogram cannot detect some inner ear problems, a normal result does not completely rule out an inner ear condition.
  4. To evaluate hearing loss or tinnitus, other tests, such as audiometry may be done. If a tumor or stroke is suspected in a certain part of the brain, a CT scan or MRI scan may be used to confirm the diagnosis.
Credits:
Author: Jan Nissl, RN, BS
Primary Medical Reviewer: Renee M. Crichlow, MD – Family Medicine
Specialist Medical Reviewer: Colin Chalk, MD, CM, FRCPC – Neurology