A VNG is the most common vestibular dizziness test ordered. It tests how well the semicircular canals in the inner ear are working. The acronym VNG stands for Videonystamography which essentially means that a video system is monitoring your eye movements to see if they ‘beat’ back and forth.
VNG
In addition to VNG testing, your audiologist may complete other balance tests. A series of balance tests were designed to provide more information regarding the source of your dizziness/vertigo/imbalance and to guide treatment. Because good balance requires the coordination of inner ear function, vision and proprioception (muscle and joint sensation, strength and flexibility), each of these components is important.
The testing is designed to measure these individually, as well as how they work together to help you maintain your balance. There are four main components to the tests:
What are VNG and Rotary Test Looking For?
A VNG test looks for how a portion of the inner ear known as the vestibular system processes rotation and accretion and relays that information to the brain.
It is very important that both ears give the same amount of information to the brain otherwise the brain does not know which ear to trust and results in dizziness (usually vertigo, a spinning sensation) or lightheadedness.
What To Expect At The VNG Test Appointment
How Long Does It Take?
Most appointments last for around 90 minutes but if an entire vestibular battery is needed it may take up to 3 hours. Here’s a breakdown of that time frame and what to expect:
- 20 minutes: Typically, the first 20 minutes of your appointment the audiologist is going to take a detailed case history.
- 20-30 minutes: A typical hearing exam (though may have been done at a previous appointment, saving you a little time.)
- 10 minutes: 10 minutes will be used to test the set up which includes placing moderately heavy goggles over your eyes and calibrating them to your pupils.
- 20 minutes for oculomotor testing
- 15 minutes for positional testing
- 30 minutes for caloric testing
- A subset of test that also may be included in the appointment
- 20 minutes Computerized Dynamic Posturography
- 20 minutes for Vestibular-evoked Myogenic Potential Test (VEMP)
- 3 minutes for High Frequency Headshake Test
- 30 minutes for Rotational Chair Test (Sinusoidal Harmonic Acceleration and Chair Rotation Trapezoidal test)
- 10 minutes for Static Subjective Visual Vertical Test
Below is a detailed description of what each part of the appointment is like and what it includes:
Vestibular Case History
The audiologist is likely to spend significant time in getting a very thorough case history from you on everything about your dizziness. The more detailed and thorough the answers that you provide the easier their job will be in determining if and where the vestibular problem occurs.
Same Case History Question You May Be Asked
Do you ever have any of the following sensations?Spinning in circles? Falling to one side? World spinning around you?
I. The following refer to a typical dizzy spell:
Do the dizzy spells come in attacks?
How often?
How long?
Date of first spell?
Are you free from dizziness between attacks?
Does your hearing change with an attack?
Are you dizzy mainly when you sit or stand up quickly?
Are you more dizzy in certain positions?
Are you nauseated during an attack?
Are you dizzy even when lying down?
Have you had a recent cold or flu preceding recent dizzy spells?
Have you had fullness, pressure or ringing in your ears?
Have you had pain or discharge in your ear of recent onset?
Have you had trouble walking in the dark?
Are you better if you sit or lie perfectly still?
II. The following refer to other sensations you may have:
Do you black out or faint when dizzy?
Have you had:
Severe or recurrent headaches?
Any double or blurry vision?
Numbness in your face or extremities?
Weakness or clumsiness in arms or legs?
Slurred or difficult speech?
Difficulty swallowing?
Tingling around your mouth?
Spots before your eyes?
Jerking of arms or legs?
Seizures?
Confusion or memory loss?
Recent head trauma? (if yes, please explain)
III. The following refers to habits and lifestyle: Is there added stress to your life recently Is your dizziness related to:
Moments of stress?
Overwork or exertion?
Do you feel lightheaded or have a swimming sensation are dizzy?
Do you find yourself breathing faster or deeper when excited or dizzy?
Did you recently change eyeglasses?
Have you ever had a weakness or faintness a few hours after eating?
Do you drink coffee? How much?
Do you drink tea?
Do you drink soft drinks?
Do you drink alcohol?
Do you smoke?
IV. Past medical
Have you taken Meclizine or any other medication to suppress your dizziness? Did it help
Family history:
Any family history of:
High blood pressure?
Low blood pressure?
Diabetes?
Low blood sugar?
Thyroid disease?
Asthma?
What Will Happen With Each Vestibular Test?
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.
What Is Ocularmotor Testing?
Essentially, they have you stare at a screen and instruct you to follow a dot moving around a screen. Sometimes the dot jumps from point to point and sometimes the dot moves slowly back and forth around the screen.
A computer is tracking your precise eye movement via the googles that you wear and can analyzed if your eyes move as they should. This test is easy to complete and goes quickly. Any abnormality found in these tests would indicate that you have a central processing (your brain) issue.
What Are Positional Vestibular Tests Like?
The purpose of positional testing is to detect an imbalance in resting afferent activity in static positions and the ability to visually suppress that response.
Essentially, they lay you in various positions such as on your back, on your back with your head to your right/left, on your right/left side.
Then do additional tests called a Dix Hallpike Maneuver to assess for BPPV (Benign Paroxysmal Positional Vertigo). In this test you start by sitting up looking over your shoulder with the goggles on.
You then lay back and your head slightly hangs off the table. If this makes you dizzy your eyes will beat and indicate that you have BPPV. This is the most common vestibular problem and the easiest one to fix using the Epley maneuvers.
What is Caloric Testing?
This is the test that no one likes because the audiologist intentionally make you feel like you are spinning. However, It is also the test that provides the most information. This test has you lay back on a table that is tilted up at 30 degrees at a comfortable position.
While you lay in the dark goggles they change the temperature in one of your ear canals. This is usually done by blowing air into your ear but can also be done with water.
Typically, air blows in your ear for 60 seconds and you may start to feel like you are spinning. The recording last for 2 minutes following
What is happening is that the temperature change in your ear is starting a convection current (remember heat always rises) in the semicircular canal and your vestibular system is telling your brain that you are rotating. Each ear is tested 2 times, once with cold air and once with hot air.
Also, during the test, your audiologist by turn on a light for 10 seconds in the goggles for you to look at. This fixation light is identifying if your visual system can override the vestibular system.
To add more fun to the experience, while you are feeling like you are spinning, the audiologist needs to task your brain. The can do this with a simple conversation with you or they will ask questions to get you thinking. My favorite way of this was asking patients to name all the states that they can think of that start with any given letter. No one cares if you get the answer right or not but just that your brain stays active.
This would be the end of most VNG or ENG appointment. However, if they are doing a full and complete battery of vestibular tests, they may also do some of the exams below.
Subset of tests that also may be included in the appointment
What is Computerized Dynamic Posturography?
This test’s main purpose is to monitor the patient’s ability to utilize and integrate somatosensory, vestibular, and visual response inputs. This is done by you standing on a platform. You will be in a harness that will insure that you will not fall.
The test is comprised of 6 subtests to evaluate the patient’s abilities. Subtests 1-3 involve a stable platform and subtests 4-6 involve a platform that moves depending on the patient’s postural sway. Subtests 1 and 4 are completed with the eyes open, 2 and 5 are completed with the eyes closed, and 3 and 6 are completed with vision disturbed.
Additionally, they may measure your reactions to when the platform moves forwards or
What is Vestibular-evoked Myogenic Potential Test (VEMP)?
The purpose of this test is to determine if the saccule, one portion of the otolith organ, as well as the inferior vestibular nerve and central connections, are intact and functioning normally.
It is completed by presenting a 95dB tone unilaterally which evokes a myogenic response from the sternocleidomastoid muscle. The patient is tested while
Absent bilateral VEMPs are not necessarily indicative of pathology in patients over the age of 60 years old.
What are Rotational Chair Test (Sinusoidal Harmonic Acceleration and Chair Rotation Trapezoidal test)?
Similar to Caloric testing, rotational chair tests look to see how much your vestibular system assess rotation. The advantage of rational chair testing is that it can be done at varying speeds while caloric only measures rotation at a very low speed.
This is completed in a dark room with a chair that rotates a patient at speeds and direction controlled by the computer. Portions of these tests may induce a sensation of disorientation or spinning, but the effects should be brief and temporary.
Some patient’s do fine with rotational chair testing but others sometimes feel sick during it. If you like amusement park rides you will probably feel fine but if not the audiologist will give you breaks in between tests to insure that you do not get sick.
For this series of test, you are put into a circular room that has a chair in the center of it. You get harnessed into the chair to limit your body from moving and then your head is put in braces to ensure that it
You also wear goggles over your eyes similar to the caloric testing and wear headphones with
There are a few different types of tests that are done. The first is the SHA test which stands for Sinusoidal Harmonic Acceleration. Basically, the chair rotates you back and forth like you are in a washing machine. They start very slow and do a series of 6 different speed until they go fast enough that you actually do feel like you are in a true washing machine
The purpose of the SHA test is to characterize the function of the vestibular ocular reflex over a range of frequencies from .01 to 2.0 with no visual stimulus.
The second rotary chair test is called the step test or the chair rotation trapezoidal test. In this start rotating at a fixed speed. Overtime (1-2 minutes) you feel as if you are not spinning anymore because the vestibular system doesn’t sense a change in speed. And then the chair suddenly stops and you feel like you are spinning back in the opposite direction.
This test typically competes for two different times at two different speeds. Slow at 60 degrees/sec and fast at 240 degrees/sec.The primary purpose of the 60/sec test is to estimate the system time constants, the degree of decay of the slow component eye velocity (VOR) over time. Time constants are abnormal if <10 seconds or >30 seconds. If 240/sec testing is completed, this assesses asymmetry. Asymmetry greater than 30% is considered abnormal. This asymmetry should also correlate with any asymmetry seen on caloric testing.
A third rotational chair test that they may do is the Vestibular-Visual Interaction (Visual Suppression Test and Visual Enhancement Test). The purpose of
What is Static Subjective Visual Vertical Test?
This is a test of otolith function, specifically utricle function. In it a person is shown a line on the wall and are given controls to move the tilt of the line. They are instructed to position the line so that it is straight vertically. There is of course no other visual stimulus present. The results are considered normal if the line is set within +/-2.5 degrees of true vertical.
Getting The Results
In this 1-3 hour of testing that you just completed there is a lot of data collected and it has to be analyzed by the audiologist before they offer you results. Often, they will not give you results for a few days. Other times, if the problem is obviously or if all results were within normal limits they may be able to give their interpretation immediately.
The audiologist should tell you before you leave their plan in when you should expect results either from them or the physician that ordered the exam and what the next step in your medical care process to expect.
Instructions to Follow Prior to Testing
Your audiologist is likely to give you specific instructions to follow prior to test VNG and other vestibular tests. It is very important to follow all instructions that give you. Typically, instructions that they give would be.
Prior to testing it is very important you observe certain instructions. If you do not follow the below listed instructions, it can cause inaccurate and unreliable results and/or your appointment may need to be rescheduled. Please comply with the following:
- Stop all medications for dizziness at least 48 hours prior to testing.
- If possible, stop anti-anxiety, sleep, and allergy medications at least 48 hours prior to testing (see list below). DO NOT STOP TAKING MEDICATIONS FOR HIGH BLOOD PRESSURE, SEIZURES, DIABETES, OR OTHER DISORDERS. If unsure, please consult your physician.
- Do not eat for four hours prior to the test because some of the testing may make you dizzy or nauseous. If you must eat for health reasons, please eat lightly. You will be more comfortable during the test with an empty stomach.
- Your face should be thoroughly washed and clean of make-up of any kind.
- Dress comfortably.
- Please arrange for a ride home from this appointment, if possible, as driving ability may be compromised following testing.
You will not have the results of your testing immediately. A follow-up appointment will be made for you after your testing for you to discuss the results with an audiologist or a physician.
These are examples of medications you should not take 48 hours prior to testing, as they can influence your body’s response to the testing, providing misinformation about your problem:
Anti-Anxiety medications, (if approved by prescribing physician) including:
- Valium/Diazepam
- Ativan/Lorazepam
- Compazine
- Xanax
Anti-Vertigo or Motion Sickness medications, including:
- Antivert/Meclizine/Bonine
- Valium
- Phenergan
- Dramamine
- Compazine
- Marezine
- Vontrol
- Scopolamine (Transderm Patch)
Allergy Medications, including:
- Antihistamines (Diphenhydramine, Chlor-trimeton, Dimetane, Disophrol, Benadryl, Actifed, Teldrin, Triaminic, Seldene or any over the counter cold remedy)
Do not stop taking medications for high blood pressure, seizures, diabetes, or other disorders. If unsure, please consult your physician prior to stopping medicine.
