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Electronystagmography
Definition
Electronystagmography is a test that looks at eye movements to see how well two nerves in the brain are working. These nerves are:
- Acoustic nerve, which runs from the brain to the ears
- Occulomotor nerve, which runs from the brain to the eyes
Alternative Names
ENG
How the Test is Performed
Patches called electrodes, are placed above, below, and on each side of your eyes. They may be sticky patches or attached to a headband. Another patch is attached to the forehead.
The health care provider will deliver cold water or air into each ear at separate times. The patches record eye movements that occur when the inner ear and nearby nerves are stimulated by the water or air. When cold water enters the ear, you should have rapid, side-to-side eye movements called nystagmus.
Next, warm water or air is placed into the ear. The eyes should now move rapidly toward the warm water then slowly away.
Patients may also be asked to use their eyes to track objects, such as flashing lights or moving lines.
The test takes about 90 minutes.
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 dizziness (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 damage to the inner ear from certain medications.
Normal Results
Distinct involuntary eye movements should occur after the warm or cold water or air is placed into your ears.
Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
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:
- Blood vessel disorders with bleeding (hemorrhage), clots, or atherosclerosis of the blood supply of the ear
- Cholesteatoma and other ear tumors
- Congenital disorders
- Injury
- 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
- Rubella
- Some poisons
Additional conditions under which the test may be performed:
Risks
Excessive water pressure inside the ear can injure a previously damaged eardrum, but this rarely occurs. The water part of this test should not be done if your eardrum has been perforated recently, because this can lead to an ear infection.
Considerations
Electronystagmography is a better test than simply watching the eyes after flushing warm or cold water into the ears. It can record movements behind closed eyelids or with the head in a variety of positions.
References
Griggs RC, Jozefowicz RF, Aminoff MJ. Approach to the patient with neurologic disease. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier. 2007: chap 418.
Sanders DB, Howard JF Jr. Neuro-otology: laboratory investigations in diagnosis and management of neuro-otological disorders. In: Bradley WG, Daroff RB, Fenichel GM, Jankovic J, eds. Bradley: Neurology in Clinical Practice. 5th ed. Philadelphia, Pa: Butterworth-Heinemann Elsevier; 2008:chap 40.
Reviewed By: Kevin Sheth, MD, Department of Neurology, University of Maryland School of Medicine, Baltimore, MD. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine;David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
