MedlinePlus Medical Encyclopedia: Electronystagmography

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Electronystagmography

Contents of this page:
Alternative names Definition How the test is performed How to prepare for the test How the test will feel	Why the test is performed Normal Values What abnormal results mean What the risks are Special considerations

Alternative names

ENG

Definition Return to top

Electronystagmography records involuntary eye movements. The test is used to determine whether ear nerve damage is the cause of dizziness or vertigo. Damage to the nerve of the inner ear is one of the more common causes of vertigo.

How the test is performed Return to top

Metal electrodes (similar to those used with ECG, but smaller) are placed to the side, above, and below each eye. They may be attached by adhesive or by a band around the head. A "ground" electrode is attached to the forehead. These electrodes record eye movements relative to the position of the ground electrode.

A standard caloric stimulation test is performed, with cold or hot water instilled into the ear canal. Each ear is tested separately. The duration and velocity (speed) of eye movements that occur when the inner ear is stimulated are recorded by the electrodes.

The test takes about 90 minutes. It is performed by an audiologist and interpreted by an ENT specialist.

How to prepare for the test Return to top

No preparation is necessary. Check with your health care provider if you are taking any medications.

For infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:

Infant test or procedure preparation (birth to 1 year)
Toddler test or procedure preparation (1 to 3 years)
Preschooler test or procedure preparation (3 to 6 years)
Schoolage test or procedure preparation (6 to 12 years)
Adolescent test or procedure preparation (12 to 18 years)

How the test will feel Return to top

There is minimal discomfort. Some people find cold water in the ear uncomfortable. Brief vertigo may occur during the test.

Why the test is performed Return to top

This test is used to determine if ear nerve damage is a cause of dizziness or vertigo. Damage to the vestibular portion of the acoustic nerve (the nerve of the inner ear) is one of the more common causes of vertigo.

Electronystagmography is performed to evaluate the acoustic nerve, which provides hearing and helps with balance. This test may be recommended when the person is experiencing dizziness or vertigo, when there is impaired hearing, with suspected toxicity from certain antibiotics, and when psychologic causes of vertigo are suspected.

Electronystagmography provides exact measurements of eye movements rather than the objective observation of standard caloric stimulation. It can record behind closed eyelids or with the head in a variety of positions.

Normal Values Return to top

Distinct involuntary eye movements should occur after instillation of cold or hot water into the ear canal.

What abnormal results mean Return to top

If the expected eye movements do not occur, there may be some damage to the nerve of the inner ear.

Any disease or injury that damages the acoustic nerve can cause vertigo. This may include:

Congenital disorders
Trauma
Rubella
Blood vessel disorders with hemorrhage (bleeding), clots, or atherosclerosis of the blood supply of the ear
Cholesteatoma and other ear tumors
Some poisons
Medications that are toxic to the ear nerves, including aminoglycoside antibiotics, some antimalarial drugs, loop diuretics, and salicylates

Additional conditions under which the test may be performed:

What the risks are Return to top

A risk is associated with the caloric stimulation part of the test. Excessive water pressure can injure a previously damaged eardrum, but this rarely occurs. Caloric stimulation should not be performed if the eardrum is perforated because of the risk of causing ear infection.

Special considerations Return to top

This test is an adjunct to a caloric stimulation test.

Update Date: 5/12/2003

Updated by: Elaine T. Kiriakopoulos, M.D., M.Sc., Department of Neurology, Beth Israel Deaconess Medical Center, Harvard University, Boston, MA. Review provided by VeriMed Healthcare Network.

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