What Is the Video Head Impulse Test (vHIT)?

The video head impulse test, usually called vHIT, is a quick, noninvasive way to measure how well each of your inner-ear balance canals is working. A clinician turns your head in a fast, small movement while a lightweight pair of goggles tracks your eye response with a high-speed camera. The core question it answers is whether your vestibulo-ocular reflex, the automatic system that keeps your vision stable when your head moves, is functioning normally or has broken down on one or both sides. What makes vHIT particularly valuable is that it can test all six semicircular canals individually, something older vestibular tests struggled to do outside a research lab.

How the Test Works in Practice

During vHIT, you sit in a chair and focus on a small target on the wall, usually about a meter away. The examiner stands behind you and delivers quick, unpredictable head rotations of about 10 to 20 degrees. These movements are small but fast, reaching peak velocities around 150 to 250 degrees per second with accelerations that can hit several thousand degrees per second squared. The goggles contain an infrared camera filming your eye and an inertial sensor measuring your head movement. Software compares the two signals in real time: if your balance system is healthy, your eyes should rotate at almost exactly the same speed as your head but in the opposite direction, keeping your gaze locked on the target.

The whole procedure typically takes only a few minutes for the horizontal canals. Testing the vertical canals (the anterior and posterior pairs) takes a bit longer because the head impulses need to be delivered along diagonal planes. The test requires no special preparation, no water in the ear, and no darkened room. That simplicity is a large part of why it has spread so rapidly through dizziness clinics worldwide since its introduction in video form around 2009.

From Research Lab to Clinic

The head impulse concept dates to the late 1980s, when researchers showed that a fast, passive head turn could reveal dysfunction in a single semicircular canal. For two decades, though, the only way to measure it accurately was with scleral search coils, a technique that involved placing a contact-lens-like coil directly on the eye and recording inside a magnetic field. It was expensive, uncomfortable, and essentially confined to specialized labs.¹ The leap to a video-based system changed everything. By using lightweight goggles with a high-speed camera, vHIT brought the same measurement to any clinic that could afford the device. For the vertical canals, the video method proved remarkably close to the coil-based gold standard, with correlations above 0.98 across all canal planes.²

What Gain and Saccades Tell You

The main number vHIT produces is called “gain,” which is simply the ratio of eye speed to head speed. A gain of 1.0 means your eyes are perfectly compensating for the head movement. In healthy people, horizontal canal gains tend to sit in the range of roughly 0.8 to 1.0, with slight asymmetries between sides. A study of 80 healthy subjects across a wide age range found that gains for horizontal impulses toward the right averaged about 0.98 and toward the left about 0.95, while vertical canal gains were somewhat lower, around 0.76 to 0.91 depending on which canal was being tested.³ All canal gains drop slightly as head velocity increases, which is worth keeping in mind when comparing results across different testing speeds.

When gain is reduced, the eyes fall behind during the head turn and have to make a rapid corrective eye movement, called a catch-up saccade, to snap back to the target. These saccades come in two flavors. An “overt” saccade happens after the head has stopped moving and is visible to the naked eye. A “covert” saccade fires while the head is still in motion, making it invisible without instrumentation. Covert saccades are clinically important because a patient producing them may look normal on a bedside exam, yet vHIT will reveal the underlying deficit. One subtlety: catch-up saccades are not exclusively a sign of disease. They appear in roughly half of normal ears, suggesting that the vestibular reflex is naturally a slightly undershooting system.⁴

In vestibular neuritis, one of the most common causes of sudden severe vertigo, covert and overt saccades are prominent on the affected side, especially in the horizontal canal plane. Over months, gain tends to recover in many patients, but covert saccades often persist long after the acute event. One follow-up study found that horizontal canal gain recovered in about 43 percent of cases, yet covert saccades were still detectable in roughly 69 percent of patients in the horizontal plane at follow-up.⁵ Persistent covert saccades can explain why some patients still feel off-balance even when their gain numbers look acceptable.

Why vHIT and Caloric Testing Give Different Answers

If you have had a full vestibular workup, you may have also undergone caloric testing, where warm and cool water or air is flushed into the ear canal to provoke a slow drift of the eyes. Many patients are puzzled when one test comes back normal and the other does not. The reason is that vHIT and caloric testing probe different parts of the same organ at different speeds. The quick head impulses of vHIT activate the high-frequency end of the balance sensor, while the gentle temperature change of caloric irrigation stimulates at an extremely low frequency, thousands of times slower. The two tests are driven by different cell populations within the same structure. Fast-responding cells clustered near the center of the sensor feed into one set of nerve fibers; slow-responding cells along the edges feed into another.⁶

Because they tap into different frequency ranges, the two tests complement each other rather than substitute for one another. A systematic review concluded that vHIT does not replace caloric testing for chronic dizziness, precisely because a disease can knock out one frequency range while sparing the other.⁷ This dissociation pattern, abnormal calorics but normal vHIT, turns out to be diagnostically useful in its own right.

The Ménière’s Disease Clue

Ménière’s disease, characterized by episodes of vertigo, hearing loss, and ear fullness, is notoriously tricky to diagnose because no single test confirms it. But a particular combination of results on vHIT and caloric testing has emerged as a useful marker. In a meta-analysis, about 64 percent of Ménière’s patients had an abnormal caloric response, while only about 28 percent had abnormal vHIT gains. The pattern of abnormal calorics with normal vHIT was found in roughly 47 percent of Ménière’s patients.⁸ A separate study found that among patients who showed this dissociation pattern, the most common final diagnosis was Ménière’s disease, appearing in 27 of 36 such cases.⁹

The likely explanation is that the fluid buildup in Ménière’s disease initially damages the low-frequency response of the balance organ while leaving the high-frequency pathways relatively intact. Patients with this pattern who also show hearing loss on the same side give clinicians a much stronger diagnostic foothold than any single test alone. The dissociation is not exclusive to Ménière’s, however; vestibular schwannomas and other conditions occasionally produce it as well.

Sorting Out Dizziness in the Emergency Room

One of the highest-stakes applications of vHIT is in distinguishing vestibular neuritis from a posterior circulation stroke. Both can present as sudden, severe, continuous vertigo with nausea and difficulty walking, and the early symptoms overlap enough that even experienced clinicians can be fooled. Vestibular neuritis is a benign (if miserable) inflammation of the vestibular nerve that recovers on its own. A posterior circulation stroke is a medical emergency. The critical difference is that vestibular neuritis produces a clear drop in vHIT gain on one side, while most strokes leave vHIT gain normal because the inner ear itself is unaffected.

Clinicians have formalized this into a bedside protocol called HINTS (Head Impulse, Nystagmus, Test of Skew). When vHIT is used instead of the naked-eye version of the head impulse test, the combination has been shown to be about 89 percent sensitive and 96 percent specific for identifying vestibular neuritis, with a false positive rate under 4 percent.¹⁰ Another study found that adding vHIT and videonystagmography to the standard bedside HINTS protocol pushed specificity from about 63 percent up to about 81 percent while keeping sensitivity above 96 percent.¹¹ That improvement matters in an emergency department, where an early CT scan often misses small strokes and clinicians need another way to decide who needs urgent MRI.

Research in this area is still evolving. The cost-benefit of deploying vHIT goggles in busy emergency departments, factoring in device cost, training, and potential reductions in unnecessary imaging and hospital stays, remains an open question that several groups are actively studying.¹²

Bilateral Vestibulopathy and Ototoxicity

When both inner ears lose function, the result is bilateral vestibulopathy, a condition that causes chronic unsteadiness, oscillopsia (bouncing vision during walking), and difficulty navigating in the dark. vHIT is one of the best ways to confirm the diagnosis because it can show symmetrically reduced gain on both sides. In a study of bilateral vestibulopathy patients, the most common identified cause was ototoxicity from aminoglycoside antibiotics, accounting for about 42 percent of cases. Mean vHIT gains in that group were around 0.36 to 0.37, well below normal. The ototoxic subgroup had the lowest gains and reported the worst subjective disability. Across all causes, there was a strong inverse relationship between gain and disability scores: the lower the gain, the worse the patient felt.¹³

This makes vHIT a practical monitoring tool for patients receiving potentially ototoxic medications. Serial testing can detect a decline in gain before the patient notices symptoms, potentially allowing a change in medication before irreversible damage accumulates.

When the Problem Is in the Brain, Not the Ear

vHIT is primarily designed to test the peripheral vestibular system, meaning the inner ear and its nerve. But certain brain lesions can also produce abnormal vHIT patterns, and recognizing these is important to avoid misdiagnosis. Lesions in the brainstem vestibular nuclei or the cerebellum can reduce gain on one or both sides, mimicking a peripheral problem. More unusually, diffuse cerebellar disease can cause the gain to be abnormally high, with corrective saccades firing in the wrong direction. Cross-coupled vertical saccades appearing during horizontal head impulses are another red flag for cerebellar involvement.¹⁴ These patterns are uncommon, but a clinician who interprets vHIT in isolation without considering the broader clinical picture could mistakenly attribute a central problem to the inner ear.

Testing Children

vHIT works in children, but it takes some adaptation. Young children need more time, and the calibration step (staring at small dots) can be challenging for those under about six years old. One clinical study found that using colorful icons instead of laser dots for calibration improved cooperation in three-to-five-year-olds. Reproducible results were obtained in 75 percent of the children tested. Those without balance problems had a median gain of about 1.02, while children with known balance disorders had a significantly lower mean gain of about 0.47.¹⁵ The test took about 20 minutes per child, noticeably longer than in adults.

Normative data for children are still being refined. Gains in the horizontal canals appear slightly lower in the youngest age group (around three to six years) compared with older children and teenagers, but from about age seven onward, the values stabilize and no consistent difference between boys and girls has been found.¹⁶ For pediatric audiologists and neurologists, vHIT fills a gap because many traditional vestibular tests either cannot be performed on young children or require cooperation that toddlers simply cannot provide.

The SHIMP Variant

A newer version of the test, called SHIMP (suppression head impulse paradigm), flips the protocol on its head. Instead of keeping your eyes on a stationary target while the head turns, you try to keep your eyes on a target that moves with your head, essentially a dot on the goggles themselves. In a healthy person, the vestibular reflex will drag the eyes off the moving target, forcing a saccade to catch back up. In someone with a vestibular deficit, the reflex is too weak to pull the eyes away, so no saccade appears. SHIMP and the standard test (sometimes called HIMP) give complementary information.

One advantage of SHIMP is that it is less contaminated by covert saccades. A study of bilateral vestibulopathy patients found covert saccades in about 34 to 35 percent of standard HIMP traces but only 5 to 6 percent of SHIMP traces.¹⁷ The two paradigms agreed on the diagnosis in 93 percent of cases, but all six patients who were classified differently were labeled as having bilateral vestibulopathy by SHIMP but not by HIMP, suggesting SHIMP may be slightly more sensitive for catching bilateral losses.

In acute vestibular weakness, SHIMP has a particular edge. The saccades it detects go in the opposite direction from spontaneous nystagmus, which means the results are less muddied by the background eye drift that is always present in the first few days of vestibular neuritis.¹⁸ SHIMP also appears useful for tracking recovery over time. The reappearance of overt saccades on SHIMP indicates the vestibular reflex is regaining strength, offering a way to monitor rehabilitation progress that may be more informative than gain numbers alone.¹⁹

Artifacts and Practical Pitfalls

vHIT is reliable when performed well, but the recording can be derailed by a variety of artifacts. Goggle slippage is the most common culprit: if the goggles shift even slightly during the head thrust, the sensor reads head movement that never actually reached the skull, inflating or deflating the gain calculation. Patients with prominent brow ridges, oily skin, or heavy eyelids can be more difficult to fit. Eyelid blinks during the impulse produce spikes in the eye trace that the software may misidentify as saccades, and small pupils in bright rooms can make pupil tracking unreliable.²⁰

Examiner technique matters too. Impulses that are too slow, too large, or predictable in timing give the patient a chance to use visual tracking instead of the vestibular reflex, producing a falsely normal gain. The direction of the impulse needs to be clean and aligned with the canal being tested; sloppy or off-axis head turns activate multiple canals at once and blur the result. There are no universally agreed-upon criteria for what counts as an artifact versus a real finding, which means different software platforms and different clinicians can interpret the same raw data differently. Learning to recognize and discard bad traces is one of the biggest practical skills for anyone using the device regularly.

vHIT and Vestibular Rehabilitation

Beyond diagnosis, vHIT gain has a natural role as an outcome measure during vestibular rehabilitation. Gaze stabilization exercises, the core of most vestibular rehab programs, are designed to retrain the vestibular reflex and improve visual stability during head movement.²¹ Tracking gain over weeks or months can show whether the exercises are producing measurable improvement or whether the reflex has plateaued, helping clinicians decide when to adjust the program. For patients with bilateral vestibulopathy, where subjective improvement is slow and frustrating, seeing even a small upward shift in gain can provide motivation to continue therapy. Saccade patterns on vHIT and SHIMP add another layer, revealing whether the brain is developing better compensatory strategies even when the raw reflex gain does not fully recover.

Age-Related Changes in the Normal Vestibular Reflex

Aging does affect vHIT results, but less dramatically than many people assume. In healthy older adults over 60, horizontal canal gains dip only slightly. More interesting are shifts in the vertical canals: in the same study of 80 healthy individuals, posterior canal gains on one side dropped by about 0.09 in the older group, while anterior canal gains on the same side rose by a similar amount, producing a symmetry that was not present in younger subjects.²² All gains across all canals decreased modestly with faster head impulses, a pattern that was consistent regardless of age. What this means in practice is that clinicians need age-appropriate reference values, especially for the vertical canals, rather than applying a single cutoff to everyone. A posterior canal gain of 0.70 in an 80-year-old may be perfectly normal, while the same number in a 30-year-old would raise a flag.