An ENG, or electronystagmography, is a medical test that evaluates your balance system by tracking involuntary eye movements. It works because your inner ear and your eye muscles share a nerve pathway, so when something goes wrong with your balance organs, your eyes respond in telltale ways. Doctors use it to help diagnose conditions like vertigo, Ménière’s disease, and inner ear infections.
How an ENG Works
Your eye has a natural electrical charge: the front of the eye (the cornea) carries a slightly positive charge, while the back (the retina) carries a slightly negative charge. During an ENG, small electrodes are placed on the skin around your eyes to detect changes in that electrical field as your eyes move. Every time your eyes shift, the electrodes pick up the signal and record it as a waveform. This lets clinicians measure the speed, direction, and pattern of eye movements with precision, even movements too small or fast to observe by watching someone’s face.
The connection between your ears and your eyes is the key to the whole test. Your inner ear sends constant signals to your brain about head position and motion, and your brain uses those signals to keep your eyes stable. If the inner ear on one side is damaged or inflamed, the signals become uneven, and your eyes drift or jerk involuntarily. That involuntary eye movement is called nystagmus, and it’s the central measurement of every ENG.
The Three Parts of the Test
An ENG is not a single test but a battery of three, each designed to stress your balance system in a different way.
Gaze Nystagmus Test
You sit or lie down and stare at a fixed light placed directly in front of you or off to one side. The test measures how well you can hold your gaze steady without your eyes drifting or jerking. Healthy eyes stay locked on the target. If your eyes wander involuntarily, it can point to a problem in the brainstem, the cerebellum, or the inner ear.
Positional Test
This portion involves moving your head and body into different positions. You might be asked to turn your head quickly to one side, lie down rapidly from a seated position, or roll onto your back. Each position change can trigger nystagmus if certain balance crystals in your inner ear have shifted out of place, which is the hallmark of benign paroxysmal positional vertigo (BPPV), one of the most common causes of dizziness.
Caloric Test
This is the part most people remember. Warm or cool water is gently flushed into your ear canal using a small syringe, stimulating the balance organ on that side. The standard temperatures are 30°C for the cold irrigation and 44°C for the warm. Each ear is tested separately, and the expected response is for your eyes to move involuntarily in a specific direction. If one ear produces a noticeably weaker response than the other, it suggests that side’s balance nerve or organ is not functioning normally. For people with a damaged eardrum, air is used instead of water.
Conditions It Helps Diagnose
An ENG is most commonly ordered when someone has unexplained dizziness, vertigo, or balance problems. The specific conditions it can help identify include BPPV, Ménière’s disease, vestibular neuritis (inflammation of the balance nerve), labyrinthitis (an inner ear infection), and acoustic neuroma (a benign growth on the nerve connecting the ear to the brain). It can also help evaluate Usher syndrome, a genetic condition that affects both hearing and balance.
The test doesn’t always deliver a single diagnosis on its own. Its real value is in pinpointing whether the problem is in the inner ear, the balance nerve, or deeper in the brain. That distinction shapes what happens next, whether it’s physical therapy, medication, imaging, or further testing.
What the Test Feels Like
The electrode placement is painless. Small adhesive patches go on the skin near your eyes, and no needles are involved. The gaze and positional portions feel straightforward, though the head movements may briefly trigger the dizziness you’re being evaluated for.
The caloric test is the most uncomfortable stage for most people. Flushing water into the ear canal creates a strong but temporary sensation of spinning, and it’s common to feel dizzy or nauseous for a short time during and after. That reaction is actually the point of the test. The sensation fades within a few minutes once the irrigation stops. The full battery typically takes 60 to 90 minutes.
How to Prepare
Preparation matters because several common substances can suppress the eye movements the test is designed to detect. You’ll typically be asked to stop taking antihistamines, anti-nausea medications, sedatives, and some anti-anxiety medications for 24 to 48 hours before the test. Alcohol and caffeine should also be avoided in that window. Your doctor’s office will give you a specific list based on your medications. Eating a light meal a few hours beforehand is usually fine, but a full stomach combined with the caloric test can increase nausea, so heavy meals right before the appointment are best avoided.
Contact lenses should be removed before the test, and eye makeup can interfere with electrode adhesion, so it’s best to arrive without it.
ENG vs. VNG
A newer version of this test, called videonystagmography (VNG), uses infrared cameras mounted inside goggles instead of skin electrodes. The cameras record eye movements directly on video, which many clinicians find easier to analyze. Research from the American Speech-Language-Hearing Association describes VNG as more technologically advanced, and it has largely replaced ENG in many clinics. That said, ENG remains a valid diagnostic tool and is still used when VNG equipment isn’t available or when goggles can’t be worn comfortably. The two tests measure the same things and use the same subtests. The difference is purely in how the eye movements are captured.
Understanding Your Results
Results are typically reported as normal or abnormal for each subtest. The caloric test is especially informative because it compares the two ears directly. A significant difference in response strength between your left and right ears, called unilateral weakness, suggests the weaker side has a damaged or underperforming balance organ. Abnormal nystagmus during the gaze or positional tests can point toward central nervous system involvement rather than a purely inner ear issue.
Your doctor will interpret the full pattern of results alongside your symptoms, medical history, and often a hearing test. A single abnormal finding rarely tells the whole story, but the combination of all three subtests gives a detailed picture of where your balance system is breaking down and why.