What is a VNG?
This test has been ordered by your doctor to test the inner ear that is part of the balance system. The test measures eye muscle movements, and your doctor can learn a lot about how your inner ear is working from this. This test may be ordered for any of the following symptoms:
- Off balance
- Hearing loss
- Ringing in the ears (‘tinnitus’)
- Pressure or fullness in the ears or head
How Do I Prepare for the Test? 48 hours before the test
It is important that you don’t drink any alcohol and stop taking certain medications 48 hours before the test, as they could affect the results.
If possible, stop taking the following:
- allergy pills
- sleeping pills
- cold pills
- alcoholic drinks
- pain pills
- dizziness pills
- anti-nausea pills
Continue to take all of your other medications.
The Day of the Test:
- Do not put any makeup or creams on or around the eyes.
- Eat a light breakfast or lunch, depending on the time of your test.
- It’s best not to wear contact lenses – wear glasses if you have them.
- The test takes 1 to 1 ½ hours, so plan on being here for about 2 hours.
- You may want to bring someone with you who can drive you home, in case you don’t feel up to it.
What Happens During the Test?
You will sit in a reclining chair, facing a wall with a small white light on it and a pair of goggles will be placed over your eyes, they will be adjusted to fit you firmly but comfortably.
- First you will be asked to watch the light while you do a number of different eye movement tests.
- A head shaking test will be done, unless you suffer from neck or back problems.
- You will then be tested in each of the following positions: Sitting, lying down, head to the right, head to the left, lying on your right side, lying on your left side.
- Finally, a tiny tube will direct warm and cool air into your ear. Each ear is stimulated for 60 seconds with cool air, and for 60 seconds with warm air.
You may experience dizziness during the last part of the test but this is a normal reaction and will gradually go away after about 2 minutes. If you suffer from motion sickness there is a small chance you might feel nauseated.
What Happens After the Test?
You should not be left with any side effects. If you have any questions feel free to call us at 817 641-3750
Electrocochleography is a complex hearing test designed to record the electrical activity of the cochlea, a part of the inner ear. This test is commonly done to diagnose a condition called Meniere’s Disease. The ECOG is performed by placing an electrode that consists of a wire, wick, or a sponge into the ear canal as close as possible to the eardrum. The ear is then stimulated with a loud tone burst. These tone bursts are transformed into vibrations in the middle ear, your ear does this naturally and automatically all the time. The vibrations are turned into electrical impulses in the inner ear and are recorded and measured using computer software.
The main objective of this test is to magnify and record wave-1 of the 5-waves present in a evoked potential study to detect the summating potential which is located on the shoulder of wave-1. The results of an ECOG test are reported in an SP/AP ratio. Calculating the SP/AP ratio in electrocochleography requires the interpreting audiologist to identify the peak of the SP wave.
The results are then compared to established patterns typical of normal hearing and to data from Meniere’s patients. Hydrops (Ménières) is suggested when the ratio is greater than 35%, although most audiologists and technicians today say 50% is a more reliable number due to noise common during the test.
Vestibular Myogenic Potential: VEMP
VEMP stands for “vestibular evoked myogenic potential.” This study takes approximately 45 minutes and evaluates a different function of the vestibular/auditory system not tested by the VNG or ABR tests. Vestibular Evoked Myogenic Potential (VEMP) testing has become a well-established test to determine the integrity of the saccule in the inner ear. The purpose of this test is to determine if the saccule, a part of an inner ear organ called the otolith, and the VIIIth nerve are intact and functioning normally. The VEMP test has been gaining popularity for patients with symptoms of Meniere’s Disease.
The VEMP testing procedure consists of placing electrodes to the middle third of the front neck muscles (sternocleidomastoids) and the forehead. With the patient laying back, the patient is instructed to hold their head up with no support surface using their front neck muscles. Tone bursts or loud clicks are then repetitively presented to each ear and generally 3 sessions of acoustic stimulation per ear. Patients are instructed to tense their neck muscles during acoustic stimulation, and relax between bursts. If the patient does not activate their neck muscles during stimulation, no VEMP is produced.
The tone bursts stimulates the saccule, which then traverses the vestibular nerve (VIIIth) and the ganglion to reach the vestibular nucleus in the lower part of the brainstem. From there, impulses are sent to the neck muscles via the medial vestibulospinal tract (MVST) and the leg muscles via the lateral vestibulospinal tract (LVST). The electrode that is placed near the sternum is used as a reference during the test, and the forehead electrode serves as a ground. The myogenic potentials are amplified using the computer equipment and then averaged to represent the most accurate testing data. The response evoked in the neck electrode is averaged and presented as a VEMP.