What Is Electronystagmography Used For?

cross section of inner ear
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Electronystagmography, also known by the acronym “ENG”, is a common diagnostic used to test for problems related to the inner ear. More specifically, ENG testing evaluates the function of:

  • Oculomotor nerve (3rd cranial nerve) – controls most of the eye movements
  • Vestibulocochlear nerve (8th cranial nerve) – transmits sound and balance information to the brain
  • Semicircular canals of the inner ear – canals, lined with microscopic hairs and a fluid known as endolymph, that provide positional information related to balance to the brain via the vestibulocochlear nerve.

    Electronystagmography involves measuring nystagmus (involuntary eye movement) throughout four phases of the test:

    • Calibration test
    • Tracking test
    • Positional test
    • Caloric test

    Electronystagmography – Calibration Test

    During the calibration portion of the electronystagmography test (done in an upright position), you will have small electrodes placed next to your eyes to record eye movements. Another version of this test, videonystamography, uses goggles instead of electrodes. The calibration test not only sets up the testing calibration for the rest of the test but also evaluates your rapid eye movement, also known as saccades.

    Electronystagmography -- Tacking Test

    The calibration and tracking portion of the test can also be lumped into a category referred to as oculomotor battery tests. This combination of testing evaluates the movement of your eyes and is also performed in an upright position. During the tracking portion of the electronystagmography test, your ability to accurately and smoothly follow a target will be assessed (smooth pursuit testing).

    Your ability to change from tracking to having steady focus on a target will also be assessed (optokinetic testing).

    Electronystagmography – Positional Test

    For the positional testing portion of the test, you will be asked to lie down. Once appropriately positioned, you will be assisted in turning you head and neck in a variety of angles to assess your inner ear function.

    One of the tests to be performed is the Dix-Hallpike maneuver which is usually indicative of benign paroxysmal positional vertigo (BPPV).

    Electronystagmography – Caloric Test

    The last part of the electrostagmography test is the caloric test. During this part of the exam, you will be laying back at an angle, while both cool and warm air or water are inserted into the ear canal through a small tube. The physician will be evaluating an automatic eye response that occurs under these conditions. Under normal conditions, the cold air/water will cause the eyes to turn towards the same ear and warm air/water will cause the eyes to turn towards the opposite ear. When nystagmus is present, the opposite will occur: cold air/water will cause the eyes to turn toward the opposite ear, while warm air/water will cause the eyes to turn towards the same ear.

    What Should I Do to Prepare for an Electrostagmography Test?

    Before preparing for this test, be sure to discuss specific instructions with your physician.

    Often you will be asked to stop any medications being prescribed to treat vertigo or nystagmus. However if you are symptomatic even with these medications, your physician may want you to continue taking them before the exam. Medications like meclizine, compazine, or librium may decrease the accuracy of results by limiting the nystagmus identified during the exam. Alcohol, sedatives, and narcotics can also skew the results.

    You should also avoid eating for approximately three hours before the test. The meal prior to the exam should also be light. You should also avoid wearing contacts during the exam. If you require corrective lenses, you should wear glasses during the exam.

    What Are Diagnoses That May Be Tested With Electrostagmography?

    Some of the reasons you may be having vertigo/nystagmus issues that may be tested with electrostagmography include but not limited to (listed by effectiveness of ENG for testing choice):

    For tips on how to manage vertigo read my article How to Manage Peripheral Vertigo.

    Sources:

    Furman, J.M. & Barton, J.JS. (2014). Evaluation of the patient with Vertigo. Accessed: May 31, 2015 from http://www.uptodate.com

    U.S. National Library of Medicine. (2013). Electronystagmography. Accessed: May 31, 2015 from http://www.nlm.nih.gov/medlineplus/ency/article/003448.htm

    American Hearing Research Foundation. (2012). Vestibular Testing. Accessed: May 31, 2015 from http://american-hearing.org/disorders/vestibular-testing/#eng

    Purves D, Augustine GJ, Fitzpatrick D, et al., editors. Neuroscience. 2nd edition. Sunderland (MA): Sinauer Associates; 2001. Types of Eye Movements and Their Functions. Accessed: May 31, 2015 from http://www.ncbi.nlm.nih.gov/books/NBK10991/

    Peltier, J. (201). Testing Vestibular Function. The University of Texas Medical Branch, Department of Otolaryngology. Accessed: May 31, 2015 from http://www.utmb.edu/otoref/grnds/Vestibular-051214/Vestibular-slides-051214.pdf

    Weill Cornell Medical College. (n.d.) Electronystagmography (ENG)/Videonystagmography (VNG) Testing. Accessed: May 31, 2015 from http://cornellent.org/healthcare_services/hearing/eng.html

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