Timothy C. Hain, MD
Last updated 9/2012
- What is Vestibular Testing?
- Why Get Vestibular Tests?
- Electronystagmography (ENG) Test
- Rotational Chair Test
- Fistula Test
- Dizziness Questionnaires
- New and Emerging Tests and Research Questions
What is Vestibular Testing?
Vestibular testing consists of a number of tests that help determine if there is something wrong with the vestibular (balance) portion of the inner ear. These tests can help isolate dizziness symptoms to a specific cause that can often be treated.
Why Get Vestibular Tests?
If dizziness is not caused by the inner ear, it might be caused by the brain, by medical disorders such as low blood pressure, or by psychological problems such as anxiety. Recent studies have documented that vestibular tests are more accurate than clinical examination in identifying inner ear disorders (Gordon et al, 1996). Hearing pathway tests (audiometry, auditory brainstem response, electrocorticography) can also be used for the same purpose, and are frequently combined with vestibular tests.
Vestibular tests can help determine if more expensive tests, such as magnetic resonance imaging (MRI), are needed. Studies (Levy and Arts, 1996) have shown that vestibular testing is much more accurate than clinical symptoms in predicting whether neuroimaging tests will be abnormal . [See also Korres et al. (2009) for a comparison of caloric and MRI testing]. Vestibular tests can also document objectively vestibular conditions such as benign paroxysmal positional vertigo (BPPV), and perilymph fistula, which commonly occur after head injury; and bilateral vestibular ototoxicity, which commonly is a side effect of medication.
The following vestibular tests are described:
- electronystagmography (ENG)
- electrocochleography (ECOG)
- rotational chair test
- fistula test
- new and emerging tests
- Gordon CR, Shupak A, Spitzer O, Doweck I, Melamed Y. Nonspecific vertigo with normal otoneurological examination. The role of vestibular laboratory tests. Laryngol Otol 1996 Dec;110(12):1133-1137
- Korres S, Riga M, Papacharalammpous G, Chimona T, Danielidi V Korres G, Xenellis J. J Laryngol Otol. 2009 Aug;123(8):851-6. Epub 2009 Feb 4.
- Levy RA, Arts HA. Predicting neuroradiologic outcome in patients referred for audiovestibular dysfunction. AJNR Am J Neuroradiol 1996 Oct;17(9):1717-1724
- Stewart MG and others. Cost-effectiveness of the diagnostic evaluation of vertigo. Laryngoscope, 109:600-605, 1999
|Figure 1: A typical example of the apparatus used for Electronystagmography (ENG) testing (Image courtesy of ICS Medical, 2001). A computer is used to monitor eye movement induced by visual and vestibular stimulation.|
The ENG test is used to determine whether or not dizziness may be due to inner ear disease. It consists of carefully measuring involuntary eye movement (nystagmus) while the subject’s balance system is stimulated in different ways. There are four main parts to the ENG: the calibration test, the tracking test, the positional test, and the caloric test.
The calibration test evaluates rapid eye movements. The tracking test evaluates movement of the eyes as they follow visual target. The positional test measures dizziness associated with positions of the head. The caloric test measures responses to warm and cold water circulated through a small, soft tube in the ear canal.
The present best method to measure eye movements is an infrared/video system (see Figure 2). Other methods include electrooculography (EOG), and infrared reflectance. Video systems are usually more accurate than the older EOG method because they are less sensitive to lid artifact and are not affected by electrical noise generated by muscle. Infrared reflectance is little used in recent times because of nonlinearity.
The ENG test is the “gold standard” for diagnosis of ear disorders affecting one ear at a time. For example, the ENG is excellent for diagnosis of acoustic neuroma as well as vestibular neuritis. The ENG is also useful in diagnosis of BPPV and bilateral vestibular loss, although the rotational chair test is better at the diagnosis of bilateral vestibular disorders than is the ENG. The calibration and tracking tests are intended to diagnose central nervous system disorders. These tests are generally insensitive compared to an examination by a neurologist or a magnetic resonance imaging (MRI) scan. ENG, however, is much less expensive than an MRI in most institutions.
ECOG is a variant of brainstem audio evoked response (BAER). It is not a vestibular test at all but rather a test of hearing. It is intended to diagnose Meniere’s disease, and, in particular, hydrops. In this test, a recording electrode (gold sponge) is inserted into the subject’s ear canal, a wire or spring is placed on the ear canal, or a needle that transfixes the ear drum is inserted into the ear. The subject receives a series of audible clicks.
The objective is to record wave-1 (there are 5 waves), with greater accuracy and to detect the summating potential, which is a shoulder on wave 1. Needle type ECOGs have fallen out of favor because they are generally judged to be unreasonably invasive.
Noise can be a major problem with ECOG. Because of this, it is not an easy test to perform. Generally, the results are reported as a ratio of the summating potential to the action potential (the SP/AP ratio), for which generally a ratio of 0.5 or greater is considered abnormal. It is important when interpreting ECOG to consider the noise level, which is generally assessed by obtaining multiple trials. If they are all similar, then the standard error is small and the result is likely to be correct. If they vary widely, the reliability of the average SP/AP ratio may be questionable. Subjects with poor high-frequency hearing are likely to have higher noise levels, and therefore the limit of normal for their ECOG should be set higher.
Gamble and others (1999) reported that salt-loaded ECOG may be useful in subjects who have normal ECOGs but a history suggestive of Meniere’s disease. Similarly it has been suggested that ECOG may be useful in detecting allergic Meniere’s disease. ECOG is performed before and after challenge with an allergen (Noell et al, 2001).
References for ECOG testing:
- Gamble BA, and others. Salt-load electrocochleography. Am J. Otol 20:325-330, 1999
- Noell CA, Roland PS, Mabry RL, Shoup AG. Inhalant allergy and meniere’s disease: Use of electrocochleography and intranasal allergen challenge as investigational tools. Otolaryngol Head Neck Surg 2001; 125: 346-50.
|Figure 2: A typical example of the apparatus used for rotatory chair testing (Image courtesy of ICS Medical, 2001). A person is rotated within a darkened room. Eye movements are recorded and used to determine how well the inner ear responds to motion.|
Rotational Chair Test
The purpose of rotational chair testing is to determine whether or not dizziness may be due to a disorder of inner ear or brain. There are three parts to the test: the chair test, the optokinetic test, and the fixation test. The rotational chair tests actually test for dizziness by recording eye movement (nystagmus) while the chair is moved in various ways and the subject looks a different lights.
The chair test measures dizziness while the subject is being turned slowly in a motorized chair (see Figure 2). Subjects with inner ear disease become less dizzy than do normal persons. The optokinetic test measures dizziness caused by viewing of moving stripes. Optokinetic testing is sometimes useful in diagnosis of bilateral vestibular loss and central conditions. The fixation test measures dizziness while the subject is being rotated, and while they are looking at a dot of light that is rotating with them. Fixation suppression is impaired by central nervous system conditions and improved by bilateral vestibular loss.
Rotatory chair tests are the “gold standard” for diagnosis of bilateral vestibular loss. ENG tests by themselves may be falsely positive (they are rarely falsely negative) as, for example, when wax blocks one ear canal. Rotatory chair testing is not affected by mechanical obstructions of the ear. Rotatory chair testing is thus a valuable adjunct to ENG testing by confirming an abnormality.
|Figure 3: VORTEQ (Tm) device used for active head rotation testing (courtesy of Micromedical technology, 2002)|
There are several other alternative procedures involving rotation that provide a subset of rotational chair testing. Two tests use active head movement — brand names for these devices are VAT and VORTEQ. Both of these tests provide a part of the the rotational chair test information (the high-frequencies), and measure something a little different: the contribution of both the inner ear and neck inputs to nystagmus rather than the contribution of the inner ear alone. If you have a rotational chair test, there is no need to get a VAT or VORTEQ test since the information supplied is largely redundant. However, if a rotational chair test is not available, these test may have some value.
|Figure 4: Moving platform posturography device (Micromedical Technology, 2001).|
Moving platform posturography (MVP), or posturography for short, is a method of quantifying balance (although the definition of balance can be tricky). It is most applicable in situations where balance needs to be followed quantitatively, to determine whether a disorder is getting better or worse, or the response to treatment.
Posturography is insensitive to vestibular disorders, and normal posturography should not be considered indicative of normal vestibular function (Jasper et al, 2008). It may add sensitivity to a vestibular battery, when combined with other tests of vestibular function (Zhang, et al., 2009). Stewart et al (1999) suggested that audiometry combined with posturography was a cost-effective method of documenting a vestibular disorder.
Posturography is also very useful in medical legal situations where malingering is a possibility. Click here to see an example of a posturography output screen (courtesy of Neurocom, Inc). The main vendor of posturography equipment used in clinical context is Neurocom incorporated. Other vendors include Micromedical Technology, and several makers of research balance equipment (e.g. AMTI).
References for posturography testing subsection:
- Gordon CR, Shupak A, Spitzer O, Melamed Y. Nonspecific vertigo with normal otoneurological examination. The role of vestibular laboratory tests. J. Laryngology and Otology 110(12):1133-7, 1996
- Stewart MG and others. Cost-effectiveness of the diagnostic evaluation of vertigo. Laryngoscope, 109:600-605, 1999
- Larossa F, Dura MJ, Cordon A, Hernandez A, Garcia-Ibanez L. Prevelence of aphysiologic performance on dynamic posturography in work-related patients. Eur Arch Otorhinolaryngol. 20012 Feb 4.
|Figure 5. A fistula test being performed using a Bruns otoscope and infrared oculography. Image (c) Timothy C. Hain, 2002.|
The purpose of this test is to detect perilymph fistula. Pressure is applied to each ear in turn, and eye movements are recorded with a sensitive infrared recording device. For this reason, fistula testing is about 10 times more sensitive than conventional electrooculography (EOG) based recordings.
Fistula testing can also be done at the bedside. Pressure is applied to the ear through one of the devices seen in Figure 4, while eye movement is either directly observed or measured with an EOG , infrared (IR), examining microscope, or posturography.
Most practices that evaluate substantial numbers of dizzy patients use questionnaires to quantify symptoms. The following table provides a list of some questionnaires:
|Questionnaire used to quantify balance dysfunction||Source|
|Activities specific Balance Confidence Scale (ABC)||Powell and Meyers, 1995; Whitney et al, 1999|
|Modified falls efficacy scale (MFES)||Hill , Schwartz and others, 1996|
|Medical outcomes study short form 36 (SF-36)||Enloe and Sheilds, 1997|
|Dizziness Handicap Inventory||Jacobson and Newman, 1990|
|Vestibular Activities of Daily Living||Cohen et al, 2000|
The Dizziness Handicap Inventory (DHI) is the most commonly used questionaire at this writing (2002).
For a detailed list of questionnaires see Duracinsky et al. (2007).
References for questionnaire section.
- Cohen, H. S., et al. (2000). “Development of the vestibular disorders activities of daily living scale.” Arch Otolaryngol Head Neck Surg 126(7): 881-7.
- Cohen, H. S., et al. (2000). “Application of the vestibular disorders activities of daily living scale.” Laryngoscope 110(7): 1204-9.
- Duracinsky M, Mosnier I, bouccara D, et al. Literature review of questionnaires assessing vertigo and dizziness, and their impact of patients’ quality of life. Value Health (2007) 10(4):273-84.
- Enloe, L. J. and R. K. Shields (1997). “Evaluation of health-related quality of life in individuals with vestibular disease using disease-specific and general outcome measures.” Phys Ther 77(9): 890-903.
- Hill, K. D., J. A. Schwarz, et al. (1996). “Fear of falling revisited.” Arch Phys Med Rehabil 77(10): 1025-9.
- Jacobson, G. P. and J. H. Calder (1998). “A screening version of the Dizziness Handicap Inventory (DHI-S).” Am J Otol 19(6): 804-8.
- Jacobson, G. P. and C. W. Newman (1990). “The development of the Dizziness Handicap Inventory.” Arch Otolaryngol Head Neck Surg 116(4): 424-7.
- Jacobson, G. P., C. W. Newman, et al. (1991). “Balance function test correlates of the Dizziness Handicap Inventory.” J Am Acad Audiol 2(4): 253-60.
- Powell, L. E. and A. M. Myers (1995). “The Activities-specific Balance Confidence (ABC) Scale.” J Gerontol A Biol Sci Med Sci 50A(1): M28-34.
- Whitney, S. L., M. T. Hudak, et al. (1999). “The activities-specific balance confidence scale and the dizziness handicap inventory: a comparison.” J Vestib Res 9(4): 253-9.
New and Emerging Tests
As there are 5 individual motion sensors in each ear, and most of the testing described above is relevant only to one of them (the lateral semicircular canal), there clearly is plenty of room for new tests. In theory, 4/5ths of your inner ear could be destroyed yet conventional vestibular testing might not even detect it. The table below provides an outline of the present status of vestibular testing.
|Part of the labyrinth||Test|
|Lateral (horizontal) semicircular canal||Caloric test, Rotatory chair test|
|Superior semicircular canal||No test exists that isolates one canal. New approaches are needed.|
|Anterior semicircular canal||No test exists that isolates one canal. New approaches are needed.|
|Utricle||Ocular counter roll, Subjective vertical. Neither test isolates a single utricle.|
|Saccule||Vestibular evoked myogenic potential. This test does assess a single saccule.|
Considering first tests of the vertical semicircular canals, very little progress has been made over the last 20 years. In essence, this is because noone has developed a practical way of stimulating individual vertical semicircular canals (the caloric test does this for the lateral semicircular canal). Rotatory chair tests come the closest, but at best they stimulate two vertical canals on opposite sides of the head together.
Considering next the otoliths, the situation is slightly better. With respect to measuring the utricle, there are several methods of detecting ocular-counterroll as well as subjective tilting of the visual world (or absence of it). None of these tests have become popular yet, but at least the technology exists. For example, SMI as well as Synapsys sell devices that can measure ocular counter-roll (twisting of the eye with head tilt vs. gravity). Micromedical Technology supplies a commercial device that will measure subjective tilting of the vertical.
For the saccule, sound evoked vestibulocollic evoked potentials have been described as useful in diagnosing Tullio’s phenomenon from superior canal dehiscence (Brantberg et al, 1999; Watson et al, 2000). This test is called vestibular evoked myogenic potential (VEMP). It is still considered investigational and it may be difficult to locate a laboratory that does it. It requires use of loud sounds to stimulate the inner ear.
Finally, it is possible to test the entire vestibular nerve using galvanic stimulation. This is a old technique in which an electrical current is passed into the ear, and eye movements or postural sway are recorded. This technology is presently not commercial and limited because is is difficult to pass enough current into the ear without causing pain. Nevertheless, it may increase in use once vestibular prosthesis become available to substitute for the vestibular system of persons who have had severe bilateral vestibular loss.
At the American Hearing Research Foundation (AHRF), we have funded basic research on vestibular testing in the past, and are very interested in funding additional research on vestibular testing in the future. Learn more about donating to American Hearing Research Foundation (AHRF).
References for Emerging Tests section
- BrantbergK. Vestibular evoked myogenic potential (VEMPs): usefulness in clinical neurotology. Semin Neurol. 2009 Nov;29(5):541-7. Epub2009 Oct 15. Review.
- Brantberg K, Verrecchia L. Act Otolaryngol. 2012 Oct;132(19(:1077-83. Epub 2012 Jul 10.
We thank ICS medical, Micromedical Technology, and Neurocom inc. for use of illustrations of their devices.