Videonystagmography (VNG) is a test of your balance system. An extensive evaluation is required at times to determine the cause of dizziness or unsteadiness. The tests necessary to diagnose your problem have been determined by our doctor at the time of examination, and may include detailed hearing and balance tests. The object of this evaluation is to be certain that there is no serious disease, and to try to pinpoint the exact site of the problem. This lays the ground work for effective medical or surgical treatment by your doctor.
VNG is a method of recording eye movements that uses digital video image technology to determine eye position. During the testing, patients wear specialized goggles which block all outside light while a small infrared video camera in the goggles records the eye movements. Once the eye movement information is recorded, it is then analyzed by medical personnel and a computer to determine if signs of a balance disorder are present.
During the VNG, eye movements are recorded while performing various head movements as well. This helps to determine the presence of positional vertigo, which Charnond identified as the most common balance disorder. He explained that positional vertigo occurs when the head is put into a particular position which elicits dizziness.
The cause of most balance disorders is the shifting of tiny particles located in the inner ear. Charnond explained that the shifting of these particles causes the dizziness felt by the patients suffering from vertigo and other balance disorders.
The test battery consists of three parts: oculomotor evaluation, positional/positioning testing, and caloric stimulation of the vestibular system. The comparison of results obtained from these sub-tests of the VNG helps to determine if the balance disorder is peripheral or central. If the inner ear is determined to be the cause of the vertigo or dizzy sensation, this peripheral disorder will have recommendations and treatment. If the disorder is central then your physician will determine if additional testing is warranted.
In the case of the most common inner ear disorder, BPPV (Benign Paroxysamal Positional Vertigo), balance rehabilitation may be used. BPPV is caused by false stimulation of the sensors in the vestibular canals. The false stimulation is caused by tiny particles called canaliths, which have fallen out of place in the inner ear.
A balance rehabilitation procedure called Canalith Repositioning Therapy (CRT) is designed to reposition or realign the canaliths. The CRT procedure involves a series of head maneuvers, manipulations and excercies to reposition the canaliths. Successful in 80% of cases; often just one session relieves symptoms.
The test protocol indiciates that ceratin medications not be taken 24-48 hours before the test. Specifically, medications used to control dizziness symptoms such as Meclizine or Antivert, prescription pain pills, Valium, tranquilizers, or sleeping pill should be avoided. Other types of medications that could affect the test outcome include stong cold pills, allergy pills and antihistamines. Alcoholic beverages should also be avoided 24 hours before the test
How does VNG Work?
VNG is a complete diagnostic system for recording, analyzing and reporting involuntary eye movements, called nystagmus, using video imaging technology. Hi-tech video goggles with infrared cameras are worn while you look or lie in different positions.
There are four main parts to the VNG. The saccade test evaluates rapid eye movements. The tracking test evaluates movement of the eyes as they follow a visual target. The positional test measures dizziness associated with positions of the head. The caloric test measures responses to warm and cold water circulated through a small, soft tube in the ear canal. The cameras record the eye movements and display then on a video/computer screen. This allows the examiner to see how the eyes move which is very helpful in assessing balance system health
In order to achieve the best test results, you should carefully follow these instructions:
- Your ears must be clean.
- Contact lenses should NOT be worn three days prior to testing or on the test day. Glasses should be worn during the three days and during the test.
- Wear flat or low-heeled shoes.
- Wash your face thoroughly. (Creams, lotions and make-up should NOT be used.)
- No solid foods or milk for 2 to 4 hours before the test.
- No coffee, tea, cola, or caffeine after midnight on the day of the test.
- No aspirin or medication containing aspirin for two days before the test.
- No alcoholic beverages or liquid medication containing alcohol for two days before testing.
- Please dress comfortably.
Certain medications or substances can influence the body’s response to the test, giving a useless or even false result. Please continue to take heart, high blood pressure and anticonvulsant medications. Questions about other medications should be discussed with your doctor.
Do not drink coffee, tea, soda or any beverage containing caffeine or alcohol within 24 hours of the test.
Do not eat or smoke for 3 hours before the test.
The following medications must not be taken for at least 3 days (72 hours) before the test:
- Alcohol in any quantity: Including beer, wine and cough medicines containing alcohol
- Anti-nausea medication: Dramamine, Compazine, Bonine, Marezine, Phernergan, Thorazine, etc.
- Anti-vertigo medication: Antivert, Meclizine, etc.
- Tranquilizers: Valium, Librium, Atarax, Vistaril, Equanil, Miltown, Triavil, Serax, Etrafon, etc.
- Sedatives: Nembutal, Seconal, Dalmane, Doriden, Placidyl, Qualude, Butisol, or any other sleeping pills
- Narcotics and Barbiturates.
- Phenobarbital, Codeine, Demerol, Benadryl, Actifed, Teldrin, Triaminic, any over-the-counter cold remedies, etc.
- Antihistamines: Chlortrimeton, Dimetane, Disophrol, Benadryl, Actifed, Teldrin, Triaminic, or any over-the-counter cold remedies, etc.