Vestibular function tests

Clinical tests of vestibular function assess whether there are problems with the balance structures of the inner ear (vestibular system) and/or their connections with our eyes, central nervous system and the proprioceptive system (sense of self movement and body position). These complex structures sit beside the hearing structure (the cochlea) of the inner ear.

The balance system consists of 5 sensors in each ear - 3 fluid-filled semicircular canals and 2 otolith organs (utricle and saccule). There are tests to assess all 10 of these sensors.

How can I get tested for vestibular function?

Family and emergency doctors, vestibular therapists, and some audiologists routinely do the Dix-Hallpike and/or roll tests for benign paroxysmal positional vertigo (BPPV). These are positional tests that figure out whether your dizziness is triggered or made worse by certain head movements.

Some of these practitioners put specialized goggles on the patient to a get a more precise look at eye movements and better work out which ear canal is affected. Using the goggles, they are able to detect involuntary, rapid movements of the eyes (nystagmus).

More comprehensive vestibular function testing is offered at a number of locations in across Canada. View our guide to Canadian vestibular testing centres.

A full assessment of the vestibular system can take up to 3 or 4 hours and may be done over several appointments.

Will the tests make me dizzy?

The majority of the diagnostic tests cause little or no dizziness. One portion, however, induces temporary dizziness and sometimes nausea.

What if all the tests results are normal?

There is nothing wrong with all of the tests being normal; do not fight normal results. Normal results are helpful and do not mean that the doctor will not believe something is wrong. Although new tests can reveal how your balance system is able to reference gravity, current testing is not sensitive enough to pick up some problems coming from some parts of the balance system. A normal set of tests does not rule out a problem.

Vestibular tests that involve muscles

There are pathways that go from the otolith organs (utricle and saccule) in the inner ear to different muscle sets. These pathways stimulate responses that can be measured on the muscles. Currently, 2 types of muscle tests can be done to assess the utricle and saccule:

• cVEMP (Cervical Vestibular Evoked Myogenic Potential) test
  The cVEMP test uses the muscles in the neck to record a response from one of the balance system structures called the saccule. Sensors are attached to the forehead, collarbone and on either side of the neck. Loud sounds played through earphones activate the saccule as the patient contracts the neck muscle on one side, then the other. A properly functioning saccule will evoke a response. No response on one side or on both sides is abnormal; an asymmetrical response (one side significantly different from the other) also suggests that there is something wrong. One other part of the cVEMP test lowers the sound volume to a level where there should not be a response (it should disappear due to the thickness of the skull protecting the saccule). However, if there is a temporal bone dehiscence (thinning of the bone) these lower volume sounds will evoke a response – this is abnormal. cVEMP testing can take anywhere from 30 to 60 minutes in most diagnostic centres. Occasionally it can cause a slight sensation of brief dizziness.
• oVEMP (Ocular Vestibular Evoked Myogenic Potential) test
  The oVEMP test engages a little eye muscle around and under each eye. Sensors are attached to the collarbone, sides of the nose, and under each eye. At some testing centres a sound is played in the ear. In other centres a device called a “mini-shaker” is used to activate the utricle by strongly tapping the forehead. The response on both sides is again measured. No response on one or both sides, or an asymmetrical response, suggests a problem with the utricle. The oVEMP test can also help detect a temporal bone dehiscence. The test takes about 30 to 60 minutes. Most people do not get dizzy or nauseous with this test.

vHIT (Video Head Impulse Test)
One of the jobs of the balance system is to stabilize the eyes. The vestibular-ocular reflex (VOR) allows us to keep our gaze stable while moving our head. The vHIT assesses how the VOR is functioning. Another name for this diagnostic tool is the HIMP (Head IMPulse) test.

Patients put on special goggles that record eye movements when the head is moved quickly. People with neck problems may not be able to do all or parts of this test. The vHIT test assesses all 6 semicircular canals. Most people do not get dizzy or nauseous with this test.

SHIMP (Suppression Head IMPulse) test
Used along with vHIT, this test helps figure out the extent of vestibular function. It lessens the need for ice water testing when such caloric testing is called for.

VNG (Videonystagmography) tests
VNG tests involve wearing goggles fitted with infrared cameras that record eye movements. VNG tests may reveal nystagmus, an abnormal involuntary repetitive “jumping” movement of the eyes - this may be an indicator of vestibular malfunction. There are 3 main types of tests done with VNG goggles:

• Oculomotor tests
  Oculomotor tests assess the brain’s ability to make and control voluntary eye movements. Abnormal results can indicate problems in the brain stem and/or cerebellum. Most people do not get dizzy or nauseous with these tests.
• Positioning and positional VNG tests
  These tests assess the 6 semicircular canals, as well as look for possible problems in the central nervous system. They are done in a variety of positions, including those that are known to bring on vertigo (spinning sensation) for a patient. Positioning VNG tests can help detect benign paroxysmal positional vertigo (BPPV), a common vestibular disorder. If a patient has BPPV, the test can cause a brief episode of dizziness. This can be very helpful in diagnosing BPPV.
• Caloric test
  Also known as the “water test,” this vestibular function test assesses the lateral (horizontal) semicircular canals and corresponding nerve pathways. The left and the right ear are tested one at a time by putting warm or cool water in the ear for 30 seconds while the patient wears the VNG goggles. Some pressure may be felt in the ear canal. The temperature of the water transfers to one of the semicircular canals and warms it up or cools it down, which briefly changes the fluid density in the vestibular system. This temporarily tricks the vestibular system and often induces brief dizziness. The caloric test is done at least once in each ear with warm water in some centres. Often one warm and one cool irrigation is done in each ear. Very rarely ice water is used to work out if there is any function at all left in that part of the vestibular system. It is helpful both for the patient and also for the assessing clinician to compare the dizziness caused by the water test with the dizziness that the patient is suffering from.

Dynamic visual acuity (DVA) test
A primary function of the vestibular system is to maintain the stability of your eyes while your head is in motion. The DVA (ability to see clearly while moving) test measures gaze stabilization with the head moving versus stationary.

This useful test is done routinely to help measure change in the vestibular ocular reflex (VOR) after vestibular rehabilitation. It shows if you brain has been able to compensate for a vestibular problem. During this test you will be asked to view the letter “E” and decide on its orientation. The test is then repeated with head movement. The DVA test is routinely done during vestibular rehabilitation.

Electrocochleography (ECochG)
ECochG is used by some otologists in some Canadian provinces to help diagnose and monitor elevated inner ear pressure (endolymphatic hydrops) found with Ménière's disease as well as secondary endolymphatic hydrops (SEH), perilymph fistula, and semicircular canal dehiscence (SCCD). Most of the time, however, clinical features, sequential hearing tests, and other vestibular testing are enough to diagnose and manage these inner ear conditions successfully. Additionally, the sensitivity of ECochG is not high, making it even less beneficial. Hearing loss may prevent the test from being carried out and/or interfere in the interpretation of test results.

ECochG is done by placing an electrode either just outside, on, or through the tympanic membrane (eardrum). ECochG outside the eardrum (extratympanic electrocochleography) is done by an otologist or specially trained audiologist. When the electrode is placed through the eardrum, the technique is called transtympanic electrocochleography (T-ECochG). T-ECochG is done by an otologist. The eardrum is pierced with a needle and the electrode is put as close to the cochlea as practical. It is generally considered not worth subjecting patients to the painful, though minimally invasive, surgery needed to do a T-ECochG test.

Other abbreviations used for these electrocochleography tests are ECOG or T-ECOG.