Videonystagmography (VNG) test records involuntary eye movements, called nystagmus, during visual tracking of objects and vestibular (balance part of inner ear) stimulation to obtain information about the balance system. Briefly, the balance system has input from:
- The balance part of the inner ear for gravitational and movement changes;
- Visual system for orientation to the surroundings, and
- Muscle and skin to maintain postural control.
Since the visual system is involved with maintaining balance, influencing eye movements can be utilized to evaluate some aspects of the balance system. Sometimes this information can confirm balance dysfunction and localize the area of deficiency in the balance system.
WHAT TO EXPECT:
Special goggles will be placed on your head. VNG measures the movements of the eyes directly through infrared cameras placed inside the goggles. There will be no pain, injections or needles.
There are three basic parts to the test:
- Oculomotor Tests – In a darkened room, you will be asked to have your eyes follow lights that move across a light bar in a rightward and leftward direction, standing still or jumping from place to place. An abnormality in these tests may indicate a central problem, or problem in the pathway connecting the vestibular system to the brain.
- Positional Tests – Your eye movements will be monitored with closed and open goggles after being placed in various body positions. If nystagmus is present in one or more of the body positions it may mean that displaced debris is floating in the fluid of one of the semicircular canals of the inner ear.
- Caloric Tests – Both ears are irrigated one at a time with cool and then warm air. Nystagmus (eye movements) will be elicited by the temperature change of the air in the middle ear adjacent to the tympanic membrane, which in turn stimulate the inner ear to respond. Again your eye movements will be monitored using infrared goggles to make sure that both of your ears respond to stimulation of the air calorics. This test can localize if there is a decreased vestibular response in one or both ears.
PLEASE TAKE THE FOLLOWING PRECAUTIONS
- Please do not eat for four hours before the test. No caffeine the day of the test.
- No alcohol for 48 hours prior to testing.
- No antivert (Meclizine), sedatives, tranquilizers, antidepressants or similar types of medications for 48 hours prior to testing.
- No face or eye make-up.
After your physician reviews the VNG along with your physical examination and other tests, he will be able to make recommendations regarding further tests, diagnosis, and or treatment.