- Oculomotor Testing
- Audiological Assessment
- Positional Testing
- Caloric testing
- Rotational chair testing
- Vestibular evoked myogenic potential (VEMP) testing
The vestibular system is a complex system made up of several different components that work together to control posture, equilibrium, and gaze stabilization. Because your central nervous system is able to compensate for a vestibular problem by using your other senses such as vision, proprioception, and hearing, it can be difficult to find evidence of a vestibular problem in a normal clinical setting. Your physician may refer you to a specialist who has undergone advanced training in vestibular or balance disorders, such as an otolaryngologist or a neurotologist for further medical assessment and vestibular testing.
A comprehensive evaluation performed by your physician will include a detailed medical history and physical examination. Your history can provide many clues related to the onset and cause of your symptoms. One of the most common symptoms of a vestibular disorder is dizziness; therefore, other conditions which may cause dizziness must be ruled out.
If required, an otolaryngologist or a neurotologist may order further medical assessment of the vestibular system. This may incorporate multiple types of testing to study the function of all different components of the vestibular system. These tests are tailored to your personal condition based on your medical history and clinical findings. The most common signs of vestibular dysfunction are nystagmus and abnormal eye movements.
Different testing techniques help to determine if the site of the lesion is in your inner ear (vestibular system), your eyes (oculomotor system), or pathways in your brain (central nervous system). Several of the tests look for typical and atypical eye movements in response to normal and abnormal stimulation. This type of testing may not be available in all regions. Click here to search for a medical center in your region offering this type of testing. A brief description on the different types of vestibular testing is provided.
The following are observed in room light with or without electronystagmography:
- Smooth Pursuit – The ability to track a moving target with your eyes, without moving your head.
- Saccades - The ability to look quickly from one target to another.
- Head Thrust - The ability to keep your eyes on a target while your head is moved rapidly to one side.
- Optokinetic test - The ability to focus on stripes moving across your visual field (like watching a train go by)
The eyes are examined for spontaneous and gaze induced nystagmus in room light and without fixation by using videonystagmography or electronystagmography.
- Spontaneous Nystagmus – Abnormal eye movement which occurs spontaneously.
- Gaze Induced Nystagmus – Abnormal eye movement which occurs as you look in one direction.
- End Gaze Nystagmus - Normal eye movement which occurs as you look hard in one direction.
The following are observed with use of videonystagmography or electronystagmography:
- Head Shake Horizontal and Vertical Tests – Abnormal eye movement which occurs briefly after the head is moved rapidly side to side or up and down ~20 times.
The vestibular system is connected to the cochlear or auditory system; therefore, conditions of the vestibular system may also result in hearing impairments. Several types of vestibular problems result in symptoms of dizziness as well as changes in hearing. Audiological assessment can test for different types of hearing loss and is often ordered when an individual complaints of dizziness. Audiological assessment can assist in the early diagnosis of vestibular disorders. Some of the test used in audiological assessment may include, but are not limited to the following:
An audiogram is performed by having the individual being tested seated in a soundproof room. Different thresholds of sounds are measured by introducing tones either through headphones or a loudspeaker. Hearing thresholds are recorded using a graph called an audiogram.
Speech audiometry tests your speech recognition. This is measured by using different word recognition tests. Words are introduced to the listener at different intensities and frequencies. The listener has to repeat the word introduced. This test assists in the diagnosis of different conditions, and helps to assess the listener's ability to communicate.
Acoustic immittance measurements look at the function of your tympanic membrane (eardrum). The tympanometry test is performed by introducing ear pressure in the external ear canal in order to match the pressure in the middle ear. This test helps in the diagnosis of middle ear disorders as well as sensorineural hearing losses. Middle ear disorders include; polyps, granuloma, otitis media, tympanic membrane perforation, serous otitis media, blocked eustachian
Electrocochleography (ECoG) is performed by introducing loud clicks or tone bursts to mimic an acoustic stimulation. This results in an electrical potential arising from your cochlear nerve which is recorded. This can help to identify the site of the lesion and helps to monitor conditions such as Meniere's disease.
Positional testing is used for the evaluation of benign paroxysmal positional vertigo (BPPV). The Dix-Hallpike maneuver is the standard test performed to diagnosis posterior canal BPPV. When performing the Dix Hallpike maneuver, you are seated lengthwise on the exam table, you are head is then turned approximately 45° to the side being tested, and you are laid back quickly with your head slightly extended over the edge of the table. You will be held in this position and your eyes will be observed for nystagmus (it is important to keep your eyes open and not close during this procedure). You are then returned to a sitting position, during which time your eyes will continue to be observed for nystagmus. This test is performed with your head turned in each direction. Click here to see a video of the Dix Hallpike test.
Nystagmus is observed with the use of Frenzel lenses or videonystagmography. Nystagmus may also be measured with use of electronystagmography. The direction, duration, and degree of nystagmus is observed and helps to identify which type of BPPV an individual may have (cupulolithiasis versus canalithiasis) as well as the semicircular canal affected (posterior, anterior, or horizontal canal.
The typical nystagmus seen in posterior canal BPPV can occur anywhere from 1 to 30 seconds after your head is lowered, and will last anywhere from a few seconds to a minute with an average of approximately 15 to 20 seconds. The direction of nystagmus will typically be up-beating and torsional. When you return to a sitting position nystagmus may reverse in direction. If the Dix Hallpike maneuver reproduces your symptoms and elicits nystagmus, this may be a positive test for BPPV. If the Dix Hallpike test fails to reproduce your symptoms, it may need to be repeated. Click here to see a video of typical posterior canal BPPV nystagmus, recorded with the use of videonystagmography.
Atypical types of nystagmus may be observed during the Dix Hallpike maneuver. Atypical types of nystagmus may be a result of more complicated cases of BPPV (such as multi-canal involvement); however, may not be related to BPPV. Atypical nystagmus may occur in many different conditions, and may or may not be related to vestibular function. If atypical nystagmus is observed, further diagnostic testing may be warranted.
On the other hand, for Dix Hallpike test may not reproduce your symptoms if you have an atypical type of BPPV. In this case your lateral canals will need to be tested. To test your lateral canals you will be laying back in a supine position. Your head will then be quickly turned toward the side being tested. If you have limited neck mobility, or have a neck condition, you will roll your body onto your side. This may reproduce your symptoms and elicit nystagmus. Lateral canal BPPV will often produce stronger more intense symptoms of dizziness associated with nausea and sometimes vomiting.
If the Dix Hallpike test is positive for BPPV your healthcare provider may perform a particle repositioning maneuver to treat BPPV, or may send you to a specialist such as; an otolaryngologist, neurotologist, or certified vestibular physical therapist. Click here to read more about BPPV.
Videonystagmography (VNG) is an important and standard tool used in the assessment of vestibular disorders. VNG allows the user to observe, record, and playback eye movements as well as subjective observations during vestibular testing. VNG allows the tester to observe the eyes for nystagmus without an individual being able to fixate on a target. VNG is performed by having the individual wear special goggles, similar to those used in scuba diving or snorkeling. The goggles are hooked up to an infrared camera inside. An image of the individual’s eye will be displayed on a screen. The image, as well as sound, can be recorded while testing is performed. Click here to see a demonstration of the Dix Hallpike maneuver performed with video nystagmography.
Videonystagmography can be used to observe:
· Spontaneous or gaze induced nystagmus associated with an acute vestibular disorder Click here to see spontaneous and gaze induced nystagmus associated with acute vestibular neuritis.
· Nystagmus elicited during caloric testing
· Nystagmus during positional testing Click here to see a video of nystagmus associated with BPPV.
Specialist such as otolaryngologist, neuro-otologist, skilled vestibular therapists, and audiologist specializing in vestibular disorders may perform videonystagmography testing. Videonystagmography testing is not currently available in all regions. Click here to search our database for a professional in your region with videonystagmography technology.
Electronystagmography (ENG) is used to provide an objective assessment of the oculomotor and vestibular system. ENG uses electrodes to record eye movements during oculomotor evaluation, positional testing, and caloric testing. ENG compares the results of each eye and can assist in determining whether there is a peripheral vestibular nerve lesion or a central lesion. ENG is performed by placing small electrodes above, below, and on the side of each eye. The electrodes are attached by an adhesive after your skin has been cleaned with an alcohol swab. An electrode is also attached to the fore head. The electrodes sense the length and speed of the eye movement, sending a signal to a computer which records the results. ENG provides exact measurements of eye movements and can detect nystagmus whether the eyes open or closed.
Electronystagmography may be used to gather objective data during the following tests:
· Oculomotor Testing - a battery of tests including: smooth pursuit, saccades, post headshaking, optokinetic nystagmus, spontaneous or gaze induced nystagmus (described earlier in this text).
· Caloric Testing
· Positional Testing
Caloric testing is used to provide objective data on the function of the vestibular nerve. Caloric testing is only able to evaluate one branch of the vestibular nerve by stimulating the horizontal semicircular canal. Caloric testing is performed by introducing warm or cold water into the ear canal using a noninvasive syringe. The water comes in contact with the tympanic membrane (eardrum) and stimulates the vestibular nerve by changing the temperature in the inner ear. Each ear is tested separately. In some settings, air is used in replace of water. Air may also be used in individuals with damage to the eardrum.
This test is performed with the aid of electronystagmography and videonystagmography in order to measure the degree of eye movement elicited. After the test, the response of each ear is compared. If you have no problem with your vestibular system, this test will elicit nystagmus or involuntary eye movement and may result in a sensation of dizziness or vertigo. If you do not experience nystagmus or a sensation of dizziness, this may indicate a problem with your vestibular nerve or inner ear. In the presence of the vestibular problem, you will typically experience a different response in each ear.
During the caloric test, nystagmus is being observed with use of videonystagmography. When cold water is introduced into the ear, this should result in a rapid horizontal (side-to-side) nystagmus or eye movement. With cold water, the eyes should move in a direction away from the cold water then slowly back. When warm water is introduced into the ear, this should result in a somewhat more mild horizontal (side to side) nystagmus or I'd movement. With warm water, the eyes should move in a direction towards the warm water then slowly away
Rotational chair testing
Rotational chair testing is used to provide objective measurements on the function of the semicircular canals. Unlike caloric testing, which measures the response of each ear separately, rotational chair testing is able to measure the response of the ears working together. Rotational chair testing can help to identify; a unilateral peripheral vestibular nerve lesion, bilateral peripheral vestibular nerve lesions, as well as the level of compensation for vestibular nerve lesions. This testing can also identify certain central nervous system problems. Rotary chair testing can be useful for monitoring changes in vestibular nerve function overtime.
During the rotational chair testing several conditions are simulated. A few of the tests may include but are not limited to the following;
- a person is rotated in the chair while nothing is provided to focus on while the chair accelerates and decelerates
- a person is rotated in the chair while looking at a dot of light that is stationary
- a person is being rotated in the cylinder while looking at a dot of light that is rotating with them
- a person is stationary while different stripes of lights appear on the wall causing the eyes to follow a stripe and then make a quick jump to the next stripe
In each situation the patient's level of dizziness is measured as well as the nystagmus or eye movements. This testing may reveal asymmetries or weakness in one or both vestibular nerves. This testing may also reveal central vestibular disorders.
Vestibular Evoked Myogenic Potential
(Information coming soon)
Computerized Dynamic Posturography
Computerized dynamic posturography is used to test an individual’s motor control and postural stability. This test calculates an individual’s ability to maintain their balance under 6 various conditions. Each condition analyzes the interaction between the different systems used to maintain balance. The systems used to maintain our balance include the visual system, the vestibular system (inner ear), and the somatosensory system (information from our joint, skin, and muscles).
An individuals balance reactions are observed while they are standing on a pressure platform and responding to the stimulation induced by challenging conditions. These conditions include stimulation such as watching a visual target that moves, standing on a platform that moves, standing on a platform that moves while the visual target is moving. The individual being tested is strapped into a safety harness to prevent falling during the test. The result of the posturography test provides information on how well an individual can maintain their balance and aids a physician in developing a plan of care for the individual.