A VNG (videonystagmography) test helps diagnose disorders of the inner ear and parts of the brain that control balance. It’s most commonly used to find the cause of vertigo, dizziness, and balance problems by tracking your eye movements with infrared cameras. The conditions it can identify range from benign positional vertigo to nerve inflammation, fluid buildup disorders, and even tumors on the balance nerve.
Conditions a VNG Test Can Identify
The VNG is designed to evaluate your vestibular system, the network of structures in your inner ear and brain responsible for balance and spatial orientation. The specific conditions it helps diagnose include:
- Benign paroxysmal positional vertigo (BPPV), the most common cause of vertigo in adults. BPPV happens when tiny calcium crystals in your inner ear slip out of place, sending confusing signals about head movement. The VNG’s positioning test can trigger the characteristic eye-jerking pattern that points to this diagnosis.
- Meniere’s disease, a disorder caused by excess fluid buildup in the inner ear. It produces vertigo alongside hearing loss, ringing in the ears, and a feeling of fullness in the affected ear.
- Vestibular neuritis, inflammation of the nerve that carries balance signals from your inner ear to your brain. It’s typically caused by a viral infection and produces severe vertigo and nausea.
- Labyrinthitis, a related condition where deeper structures of the inner ear become inflamed, usually after a cold or flu. It causes dizziness and temporary hearing loss, and sometimes resolves on its own.
- Acoustic neuroma, a usually noncancerous tumor that grows on the nerves involved with hearing and balance. It can cause hearing loss, tinnitus, and dizziness.
Abnormal VNG results can also point to problems in the brain itself, particularly areas that help control balance. This means the test serves as a screening tool for both peripheral problems (inner ear) and central problems (brain and brainstem).
How the Test Works
You wear goggles fitted with infrared cameras that track your eye movements in a dark room. The darkness is intentional: it prevents you from visually “locking on” to objects, which would mask the involuntary eye movements the test is trying to detect. These involuntary eye movements, called nystagmus, are the key data point. The pattern, direction, and speed of nystagmus tell your provider where the problem is coming from.
The test has three main parts, each targeting a different aspect of your vestibular and neurological function.
Oculomotor Testing
This portion asks you to follow a moving target with your eyes. It measures how accurately and smoothly your eyes track objects, and how quickly your eyes jump to a new target (saccades). Healthy eyes reach a target in about 200 to 250 milliseconds. Eyes that consistently undershoot or overshoot the target can indicate cerebellar or brainstem dysfunction. Smooth pursuit, the ability to track a slowly moving object, also degrades naturally with age but declines more noticeably with neurodegenerative conditions, certain medications, or lesions in specific brain areas.
Positional Testing
Your provider moves your head and body into different positions while the cameras record your eye movements. This is the portion that’s most useful for diagnosing BPPV. When displaced calcium crystals are floating in the wrong part of your inner ear canal, changing head position triggers a burst of nystagmus with a recognizable pattern. The direction of the eye jerking and the brief delay before it starts help confirm the diagnosis and identify which ear canal is affected.
Caloric Testing
Warm and cool air (or water) is gently delivered into each ear canal, one at a time. The temperature change stimulates the inner ear and should produce a predictable nystagmus response. By comparing the strength of the response between your left and right ears, your provider can detect whether one side is weaker than the other. A significant difference, called a unilateral weakness, is a hallmark of conditions like vestibular neuritis or damage to one inner ear.
Distinguishing Inner Ear Problems From Brain Problems
One of the most valuable things a VNG does is help separate peripheral vertigo (originating in the ear) from central vertigo (originating in the brain). This distinction matters because central causes, such as brainstem strokes or cerebellar disorders, can be medically urgent.
Several patterns help make this distinction. In peripheral vertigo, nystagmus typically beats in one consistent direction. In central vertigo, the direction of the fast-phase eye jerking may change when you look in different directions. Skew deviation, where your eyes become vertically misaligned, is frequently seen with brainstem problems but is absent in peripheral conditions. A normal response on the head impulse portion of the exam, paradoxically, can actually suggest a central cause like a cerebellar stroke rather than a peripheral one like vestibular neuritis. Your provider looks at the full combination of findings across all subtests to make this call.
What the VNG Cannot Do Alone
A VNG test doesn’t always produce a single, definitive diagnosis by itself. It narrows the field significantly and can confirm conditions like BPPV quite clearly, but your provider may need additional tests to reach a final answer. Imaging like an MRI might follow if an acoustic neuroma or brain lesion is suspected. Hearing tests often accompany VNG evaluation, particularly when Meniere’s disease or labyrinthitis is on the table. Think of the VNG as the most detailed map of your balance system’s function, which your provider then combines with your symptoms and other test results to land on a diagnosis.
How to Prepare for the Test
Preparation matters because many common substances can alter your eye movements and produce misleading results. You’ll typically be asked to stop certain medications two days before the test. Drugs with known effects on vestibular testing include antihistamines (the older, drowsy kind), anti-nausea medications, sleeping pills, sedatives like benzodiazepines, opioids, antidepressants, and marijuana. Alcohol should be avoided for at least 48 hours beforehand.
Some medications should not be stopped, even for testing. Life-sustaining drugs for heart conditions, diabetes, blood pressure, and epilepsy should always be continued. Medications with serious withdrawal effects, such as anticonvulsants, certain antidepressants, and blood pressure drugs, should also generally be continued. Your provider will help you sort out which of your specific medications to pause and which to keep taking.
A few substances you might worry about are actually fine. Caffeine, newer antihistamines like fexofenadine, and certain anti-nausea medications (like ondansetron) do not appear to affect vestibular test results based on current evidence. If you smoke, avoid tobacco for at least 20 minutes before the test, as it can temporarily cause abnormal nystagmus and disrupt smooth pursuit tracking for several minutes after your last cigarette.
What the Test Feels Like
The test is noninvasive. You sit in a darkened room wearing the infrared goggles while a technician guides you through each portion. The oculomotor and positional parts are generally comfortable, though position changes may trigger vertigo if you do have BPPV. The caloric test is the part most people find unpleasant: the temperature changes in your ear deliberately provoke a brief sensation of spinning. This dizziness is temporary and typically fades within a minute or two after each stimulation. Some people feel mildly nauseated during or after the caloric portion. The entire test generally takes 60 to 90 minutes, and any lingering dizziness usually resolves shortly after it’s finished.