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Electronystagmography

Definition

Electronystagmography is a test to look at voluntary and involuntary eye movements. It evaluates the acoustic nerve, which aids with hearing and balance.

Alternative Names

ENG

How the test is performed

Patches called electrodes (similar to those used with ECG, but smaller) are placed to above, below, and to the side of each eye. They may be attached by adhesive or by a band around the head. Another electrode is attached to the forehead.

The electrodes record eye movements when a standard caloric stimulation test is done. This test stimulates the inner ear and nearby nerves by delivering cold and warm water to the ear canal at different times. Sometimes, the test is done using air instead of water. Each ear is tested separately.

When cold water enters the ear, it should cause rapid, side-to-side eye movements. The eyes should move away from the cold water and slowly back. Next, warm water is placed into the ear. The eyes should now move towards the warm water then slowly away.

Patients may also be asked to use their eyes to track objects, such as flashing lights.

The electrodes detect the length and speed of eye movements, and a computer records the results.

The test takes about 90 minutes.

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.

How to prepare for the test

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

How the test will feel

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

Why the test is performed

The test is used to determine whether a balance or nerve disorder is the cause of dizziness or vertigo.

Your doctor may order this test if you have dizziness or vertigo, impaired hearing, or suspected toxicity from certain antibiotics.

Normal Values

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

What abnormal results mean

Abnormal results may be a sign of damage to the nerve of the inner ear or other parts of the brain that control eye movements.

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

• Congenital disorders
• Injury
• 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
• Multiple sclerosis
• Movement disorders such as progressive supranuclear palsy

Additional conditions under which the test may be performed:

• Acoustic neuroma
• Benign positional vertigo
• Labyrinthitis
• Meniere's disease

What the risks are

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 your eardrum has been perforated because of the risk of causing ear infection.

Review Date:4/30/2007
Reviewed By:Joseph V. Campellone, M.D., Division of Neurology, Cooper University Hospital, Camden, NJ. Review provided by VeriMed Healthcare Network.

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