Videonystagmography (VNG)
.What is Videonystagmography (VNG)?
Videonystagmography (VNG) is a type of diagnostic test that is used to measure and evaluate the response of specific nerve pathways associated with the inner ear. It is often used to diagnose conditions related to the inner ear such as vertigo, dizziness or balance disorders.
Why is VNG performed?
VNG may be performed to detect the causes of balance disorders, dizziness, vertigo, visual disturbances, hearing loss, ringing in the ears, ear pain, and other symptoms associated with the inner ear.
Preparation for VNG
Your doctor or medical provider will provide any instructions prior to the test. However, some general instructions to be aware of include not taking medication that may affect the eye movements, such as sedatives or muscle relaxants, eating lightly beforehand, and wearing loose clothing for the test.
VNG Procedure
The VNG procedure typically takes between 30 minutes and an hour. During the procedure, the patient is typically seated in a chair or reclined on a table. The patient looks at a quick-moving light that follows a circular pattern and the patient must remain still and follow the light. Eye movement is recorded through electrodes placed near the eyes, which detect eye movement velocity and the direction of the eyes.
Types of VNG Tests
VNG tests can range from basic eye movement testing to more comprehensive tests. Some types of VNG tests include:
- Caloric testing – uses warm and cold water in the ear canals to measure eye movements
- Electronystagmography (ENG) – measures the same parameters as VNG, but with more sophisticated instrumentation
- Positional testing – measures eye movements while the head and body are moved in different directions
- Gaze testing – in which the patient focuses on a particular target
Risks of VNG
VNG is generally a safe procedure, with few risks or side effects. Complications can include mild discomfort in the ears from the caloric testing, a temporary increase in dizziness or vertigo, and swelling or irritation of the eyes. Additionally, some patients may experience nausea or vomiting from the movement of the head during positional testing.
When is VNG Performed?
VNG is typically performed after a detailed patient history and physical examination when other tests are either inconclusive or more data is needed for a diagnosis. It may be followed by other tests such as a hearing test or a CT scan to provide more detailed information.