Do you ever get dizzy when you’re getting out of bed? Ever become nauseous when looking down from a great height? Have you felt like the world is moving even if you’re not?
It’s a common sensation, and it’s known as vertigo. Perhaps the most famous example is Jimmy Stewart’s character in the Alfred Hitchcock film “Vertigo,” who faints while merely climbing a stepladder.
But it’s hard to diagnose. It’s usually related to inner ear problems. But your doctor needs to figure out what’s triggering those problems -- be it disease, trauma, or a virus.
That’s where electronystagmography comes in.
ENG is a series of sensory tests for your eyes and ears. Your doctor puts electrodes above and below your eyes and measures your reactions to light, motion, depth perception, and the effect of fluids in your ear canals. Ideally, the tests will isolate the things causing the vertigo.
When Would My Doctor Order an ENG?
Vertigo is fairly common but a challenge to treat. Sometimes it simply goes away. Other times, it comes back randomly. This is true particularly for people with a condition called Meniere’s disease, a disorder of the inner ear.
Used to detect even slight movements in your eyes, ENG is a key tool in diagnosing vertigo and other “vestibular” issues – that is, things related to balance, movement, the inner ear, and the nerves sending messages to the brain. The tests may be able to locate physical signs of the ailment.
Your doctor may ask for an ENG If you’re having symptoms of vertigo, including:
How to Prepare
Before the tests, you’ll probably be asked to do the following:
- Tell your doctor what medications you’re on. She may ask you to stop taking them for 72 hours before the test.
- Cut out caffeine and alcohol. No drinking or coffee for 48 hours before an ENG.
- No food. Most doctors recommend avoiding eating for at least 4 hours beforehand.
- Clean your ears. Earwax and ear blockages can skew results, so a medical assistant may flush your ear canals before the procedure if they aren’t clear.
- Set up a ride for afterward. That’s usually good advice for many medical procedures, just in case you don’t feel up to driving.
You usually can go home after your ENG, though the test may also be given during a hospital stay. The test takes up to 90 minutes.
What Happens During an ENG?
So now it’s time for your ENG. You’re probably a little hungry, you may be weary, and you could be a tad nervous. What can you expect?
The procedure actually involves several tests. Before starting, your doctor will clean your forehead, temples, and cheeks with alcohol. Then she’ll attach electrodes to those areas with a paste.
In some testing facilities, instead of electrodes, you may be fitted with a binocular camera that looks like virtual-reality goggles. Tests done with this system are known as videonystagmography, or VNG. These devices capture your eye movements on video and can measure them just as well as electrodes.
The tests include:
The calibration test: Using only your eyes, you’ll be asked to follow a light about 6 to 10 feet away or look back and forth between dots on a wall. This test measures ocular dysmetria, a condition in which your pupils have trouble judging distances to targets.
The tracking test: Also known as the gaze nystagmus test, this is similar to the sobriety test police give. But in an ENG, you’re usually seated or lying down. (Nystagmus is a condition in which your eyes twitch out of your control.) In this test, you try to stare at a fixed light, which is set straight ahead of you or at an angle, without moving your eyes around.
There are two related tracking tests:
- One is the pendulum-tracking test. In it, you follow a light that moves back and forth like a pendulum without moving your head.
- The other is an optokinetics test, in which you follow several moving objects without turning your head. The objects may travel at high speeds and go in and out of your field of vision.
The positional test: Now it’s time for you to move your head.
Often your doctor will ask you to perform what’s called the Dix-Hallpike maneuver. While seated on a table, you’ll turn your head to one side and quickly lay back so your head -- supported by your doctor -- is about 20 degrees below the table’s surface. You’ll stay there for 30 seconds, then sit upright again. You’ll repeat it with your head to the opposite side.
Your doctor will note the effect on your eyes.
The water caloric test: As you recline, your doctor will inject a stream of cool or warm water in one ear, then the other. (Air is sometimes used.) If you’re not affected by vertigo, your eyes should jerk reflexively.
Your doctor may not do every test. If you have neck or back problems, she may suggest something else.
What Do the Results Mean?
After the electronystagmography series is done, your doctor will take off the electrodes (or camera device) from your face. If you’re dizzy, you may be asked to lie down for a few minutes.
Then it’s time to go over the data and figure out what it all means.
ENG is great at recognizing inner ear disorders -- and since the inner ear regulates balance, it can be key to diagnosing a variety of ailments.
If the ENG diagnoses a form of vertigo, your doctor will suggest actions that may include physical therapy, surgery, or medication for vestibular (or balance-related) disorders.