A Videonystagmogram (VNG) is the most common audiological test ordered for individuals complaining of dizziness or vertigo. This test records and measures voluntary and involuntary eye movements (the vestibular ocular reflex), specifically nystagmus. Nystagmus is an involuntary back and forth jerking movement of the eyes that occurs when the entire balance system is stimulated. When the vestibular and ocular systems are functioning normally, nystagmus is only rarely seen. For the purpose of testing, nystagmus can be elicited through certain movements or stimulation of the vestibular system (the balance organs of the inner ear). This helps to determine the cause or origin of your dizziness. A VNG evaluates the oculomotor system and the vestibular system. The test takes approximately an hour and a half to complete.
The VNG is comprised of a series of subtests or tasks. There are three main parts:
- Oculomotor Analysis — patients perform various visual tasks that require eye movement
- Positional Testing — patients are placed in various body positions to determine if dizziness develops and to see if nystagmus occurs
- Caloric Stimulation — small amounts of both warm and cool water are introduced into each ear canal to independently stimulate the inner ear vestibular system
Throughout each part of the test, patterns of normal and abnormal eye movements are analyzed. The main purpose is to look for the presence of nystagmus in both the absence and presence of vestibular stimulation, as well as look for symmetry of responses. The analysis allows for determining if the disorder is central, peripheral or systemic.
- Central problems are caused by disturbances in the brain or central nervous system
- Peripheral problems arise from disturbances in the labyrinth (inner ear balance organ)
- Systemic problems are the result of disturbances in the organs and peripheral nerves (nerves outside of the brain or spinal column)
Diagnosis allows your physician to prescribe appropriate treatment options.
PREPARING FOR THE TEST
To achieve the best test results, it is important that you carefully follow the instructions below:
- Wear comfortable clothing and shoes (low-heeled shoes). Female patients may prefer to wear pants. You may want to have a light jacket or sweater with you.
- The face should be washed thoroughly and be clear of any foundation, mascara, eyeliner, and eyeshadow. Makeup can be applied after the test.
- NO coffee, tea or cola after midnight on the day of the test.
- NO solid foods or milk for four (4) hours before the test. Use only SMALL amounts of water when brushing your teeth.
- NO aspirin or medications containing aspirin for two (2) days before the test.
- NO alcoholic beverages or liquid medications containing alcohol for two (2) days before the test.
- DISCONTINUE medications such as allergy pills, decongestants, antihistamines, tranquilizers, sleeping pills, barbiturates, sedatives, pain pills, diet pills, nerve pills, and pills or patches for dizziness one (1) week before your test.
- CONTINUE to take medications for your heart, blood pressure, and diabetes as directed by your physician. If you have any questions about other medications that you are taking, please consult your physician or our office before your test date.
- If you are having severe dizziness, you may want to arrange to have a driver.
Medication can be resumed immediately following the VNG. Your cooperation in following these instructions will greatly improve the quality of your examination.