Both of these test the vestibular system (balance system) of the inner ear to determine if your dizziness/loss of balance is caused by an inner ear abnormality.
When undergoing the VNG test, you are wearing a pair of goggles over your eyes used to monitor and record eye movement. During the ENG test, instead if wearing goggles, you have sticker electrodes placed around your eyes and forehead to record eye movements.
The type of test you have will depend on the type of equipment and protocol of the clinic where your testing is taking place. One way is not better than the other, they just utilize different ways of recording information.
While testing may vary slightly from clinic to clinic, there are 4 main parts to a VNG/ENG test.
1. Sensory organization testing
During the testing you will be asked to walk or stand in various conditions. With eyes open and closed and on different surfaces. This is used to determine how well your sensory systems are working together to maintain balance.
It is unlikely that you will feel dizzy during this part of the test but you may lose your balance.
2. Ocular motor testing
During this portion of the testing you will be asked to follow a light with your eyes. The light will be moving across a bar in front of your, or inside the goggles. The light will be moving quickly in different directions.
This part of the test may make you slightly dizzy.
3. Positioning/Positional testing
With assistance from your test proctor, you will be asked to move your head and body in a series of positions. This includes head movements up and down, side to side, and body movements sitting up, laying down, and turning on your side. You will be instructed on whether to open or close your eyes during the movements, while your eyes are being recorded.
During this part of the test, you may experience dizziness and/or vertigo. This is more likely to occur if your initial symptoms of dizziness are triggered by movement.
4. Caloric testing
This portion of the testing is usually done at the end. You will be laying on your back while cool and warm air or water is delivered to your ear canal, one at a time, warm in each ear followed by cool in each ear.
This is a very important part of the testing that will stimulate each vestibular system, right ear and left ear, and compare the response between the ears. It helps to determine whether the vestibular organs are functioning properly and whether one system is significantly weaker than the other.
The air or water will stay in your ear for about 1 minute each time. Once it is removed, your eye movements will be recorded for an additional minute. It is important to follow the instruction of the test proctor during this time as to whether your eyes should remain opened or closed in order to avoid the need for repeat testing.
During this portion of the test, it is likely that you will experience dizziness and vertigo. This will only remain for a few minutes following each ear stimulation. It is normal to be dizzy during caloric testing.
Total VNG/ENG test time is about an hour
Below is a video example of what you will experience during a VNG test with your Audiologist.
Prior to testing, you may be given a list of restrictions to follow.
Certain medications, such as Vestibular Suppressants, Antihistamines/Decongestants, and Diuretics, must be avoided for 48 hours prior to testing. Other medications such as pain medications, Sedatives, Antidepressants, Tranquilizers, and other recreational drugs must be avoided prior to testing if possible.
You may also be asked to limit yourself to a light meal immediately prior to testing, avoid caffeine and alcohol, and not wear contact lenses or mascara during testing. These restrictions will help to ensure accurate and comprehensive test results so proper diagnosis can be made.
Results and alternative tests
Results of the VNG/ENG test will help to determine if the dizziness is caused by an inner ear abnormality. If the test results clearly indicate an inner ear issue, diagnosis can be made and treatment options recommended.
If results indicate normal or inconclusive results, alternative tests may be recommended to determine the cause of the dizziness.