Videonystagmography (VNG) is used to test the inner ear and central motor functions to try to determine what is causing your problem with balance or dizziness. This test can confirm if a vestibular (inner ear) disease is the cause of your problems and can also distinguish between unilateral (one ear) and bilateral (both ears) vestibular loss. VNG uses infrared cameras, placed in goggles, to measure your eye movements when presented with different stimuli. This non-invasive test is only mildly uncomfortable and lasts an hour and a half.
This form of testing is becoming the industry standard, taking the place of electronystagmography (ENG). ENG measures eye movements by measuring the mastoid muscles around the eye with electrodes. This proves to be less accurate than measuring with infrared cameras, less comfortable for the patient and less consistent overall.
There are four main parts of the VNG test:
Asking you to follow objects with your eyes that jump from place to place, stand still or move smoothly tests occular mobility. The audiologist will be looking for any slowness or inaccuracies as your eyes try to follow the moving targets. This may indicate a problem in the pathway connecting the vestibular system to the brain or a central or neurological problem.
Your optokinetic nystagmus is measured by having you watch a large, continuously moving image. The audiologist is looking for any slowness or inaccuracies in your ability to follow the target. As with your ocular mobility, any problems with your optokinetic nystagmus can indicate a central or neurological problem or a problem in the pathway connecting the vestibular system to the brain.
Positional nystagmus is measured by moving your head and body into various positions to make sure none create inappropriate eye movements. This test is able to look at your inner ear system and to check if there is fluid buildup in your semi-circular canals.
Caloric testing involves stimulating your inner ears (one at a time) with warm and cold air and then measuring your eye movements. This test is able to confirm if the vestibular system of each ear is working in response to the stimulation. By stimulating one ear at a time, this test is able to distinguish between a unilateral and bilateral loss.