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Our Neurodiagnostic
Test Battery Approach
Human equilibrium is a complex process involving multiple sensory mechanisms and the central nervous system. Audiology Center of Maine utilizes a comprehensive neurodiagnostic equilibrium test protocol.
The protocol comprehensively evaluates the equilibrium system, which is dependent on input from the visual, proprioceptive, and vestibular systems. The central nervous system and brain must integrate information from these sensory modalities for balance to be maintained. Dysfunction or disruption to any of these systems or pathways may result in dizziness or balance problems. A thorough neurodiagnostic examination will evaluate all aspects of equilibrium function with particular focus on the most important component, the vestibular system.
All of the tests are comfortable for patients. Testing can usually be completed in 90-minutes or less and does not require any needle sticks or invasive procedures. Many of these tests were originally developed to test equilibrium function of returning astronauts on the early space shuttle flights.
What Tests Will Be Performed?
Audiologic Testing
Audiology tests can provide information about hearing, middle ear function, and cochlear hair cell function. Some ear-related conditions can cause both hearing loss and symptoms of vertigo. Because of this relationship, the presence of hearing loss may help differentiate certain ear disorders from one another.
Audiology testing often includes:
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Pure tone Audiometry (A behavioral test used to measure hearing sensitivity at different frequencies of sound.)
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Word discrimination tests (A series of behavioral tests that evaluate how loud speech needs to be for best audibility and how clearly spoken words can be understood by the patient)
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Acoustic Immittance Measures (used to determine which part of the ear is affected by hearing loss)
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Otoacoustic Emissions (an objective measure of outer hair cell function within the cochlea.)
Brainstem Auditory Evoked Response (BAER) tests
The Auditory Brainstem Response (ABR) test is a non-invasive, painless procedure neurologic test that provides information about the electrical activity in the auditory pathway between the inner ear and the brain.
What to expect during the test:
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Small, sticky sensors (called electrodes) will be placed on your forehead and your ears.
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You will wear earphones in your ears that will play a variety of clicking sounds.
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The sensors on your skin will pick up your brain and nerve activity in response to the sounds. A computer then records and analyzes these responses.
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The test can be done while you rest quietly or even sleep, since it doesn't require any active response from you.
The Electrocochleography (ECoG) test is a diagnostic test that measures the electrical activity of the inner ear (cochlea) in response to sound stimuli. This test is used to determine whether there is excess fluid in the inner ear by measuring the electrical currents generated by sound stimulation and can help with the diagnosis of conditions that affect the cochlea, such as: Meniere's disease, Endolymphatic hydrops, Sudden sensorineural hearing loss, and Auditory neuropathy spectrum disorder.
What to expect during the test:
-
Small, sticky sensors (called electrodes) will be placed on your forehead and your ears.
-
You will wear earphones in your ears that will play a variety of clicking sounds.
-
The sensors on your skin will pick up your brain and nerve activity in response to the sounds. A computer then records and analyzes these responses.
The BAER tests will check the health of your hearing nerve and the brain pathways related to hearing. These tests can help diagnose certain medical conditions that might affect your hearing system.
Gans Sensory Organization Performance Test
A combination of the Romberg, clinical test of sensory integration of balance (CTSIB) and Fukuda Stepping Tests provide qualitative information on whether an equilibrium dysfunction exists, whether it is CNS or peripheral and also serves as an indicator of impact on balance function. Whether the is patient surface or visually dependent gives insight into the status of the vestibular system. Recovery of function post treatment may also be documented.
Computerized Dynamic Visual Acuity Test (CDVAT)
This tests for a change in vision with controlled head movement. Oscillopsia is a breakdown in gaze stabilization during active head movement caused by peripheral or central vestibular disorders. The vision test is conducted while the patient produces horizontal and then vertical head movement of 2.5 cycles per second. The test indicates the function problem caused by the vestibular dysfunction and can be used as a baseline to latter compare improvement post Vestibular Rehabilitation Therapy (VRT) to document the treatment efficacy.
Vestibular Autorotation Testing
The Vestibular Ocular Reflex (VOR) is a reflex that keeps your vision stable by automatically moving your eyes in the opposite direction of your head movement. It works by using sensors in the inner ear to detect head motion, processing this information, and sending signals to the eye muscles to move the eyes in the opposite direction, ensuring your gaze remains fixed on a target. This rapid, automatic process allows you to see clearly even when walking or turning your head. VOR dysfunction may lead to blurred vision, dizziness, imbalance, and falls.
With Vestibular Autorotation Tests, VOR function gain and phase is quantitatively analyzed using this active rotation techniques for both horizontal and vertical head movements over a frequency range of approximately 2-8 cycles per second. The patient is required only to look straight ahead while moving their head to an auditory cuing signal. This test can be performed using both a passive test like the Rotary Chair, in which the patient simply sits while being harmonically accelerated, or using active tests, in which the person volitionally moves their head to an auditory cue.
Audiology Center of Maine is the only provider in the state to offer Rotary Chair testing. Rotary Chair testing is a state-of-the-art neurodiagnostic tool that can help determine whether dizziness originates from the inner ear or from the brain.
How Does the Rotary Chair Test Work?
The Rotary Chair test measures your eye movements in response to your corresponding head movements. You will wear a goggle-mounted video camera that will record your eye movements. You will be seated in a computerized chair that moves. This test provides more detailed information about the function of the balance system than just the basic Videonystagmography (VNG) test.
When someone turns their head, the vestibular system sends continuous signals to the brain that update it on the head’s position. This causes additional signals to be sent to the muscles of the eyes via the vestibular ocular reflex (VOR). For every head movement in one direction, there is eye movement in the opposite direction. This phenomenon is the basis for the rotational chair testing.
Rotational chair testing can be very helpful in detecting bilateral loss (no function in both ears) of vestibular function or if there are cerebellar ocular motor abnormalities. In recent studies, many people with neurological problems or vestibular ocular reflex (VOR) have been diagnosed with the use of the rotary chair very successfully.
The rotational chair is the gold standard in diagnosing bilateral vestibular loss, and is used to investigate whether dizziness may be due to a disorder of the inner ear or the brain. Audiology Center of Maine is pleased to offer patients of Downeast Maine this unique state-of-the-art diagnostic testing, which is typically found only in major medical facilities like Massachusetts Eye and Ear Infirmary.
Vestibular-Evoked Myogenic Potentials (VEMPs)
Vestibular-evoked myogenic potential testing (VEMPs) is based on the reflex, which occurs between the otolith system (specifically the saccule), and the sternocleidomastoid muscle (SCM). The vestibulo-collic reflex (VCR) has been well studied in animals and humans. The benefit of VEMPs is there is no other vestibular function test, which provides information regarding the saccule or its innervation by the inferior branch of the vestibular nerve. As the VCR is a classic reflex arc with a sensory, CNS, and motor output component, it has been used to provide information regarding both the integrity of the saccule and inferior vestibular nerve, as well as the reflex arc through the brainstem. This has provided information on both otologic and neurologic conditions.
Videonystagmography (VNG) Testing
A VNG is a series of tests that evaluate the health of your vestibular (balance portion of inner ear) and your central motor function. VNG testing can help to uncover the root cause of your vertigo, dizziness or balance issues, and allows your doctor or hearing specialist to treat it appropriately and effectively.
This test measures eye movements to evaluate the inner ear and central motor functions. It can determine whether a vestibular disorder is the cause of a balance problem, and where one or both ears are affected. An infrared video camera attached to a pair of goggles is worn by the patient throughout the test battery.
Most VNG evaluations consist of four main tests:
1) Oculomotility Tests
This test checks for your ability to follow visual targets, such as a moving light on a bar. You will attempt to follow targets with your eyes while an object is jumping, moving slowly, or standing still. Inability to track objects properly could indicate central or neurological problems or possibly an issue with the vestibular system connecting to the brain. Recording and evaluating eye movements is helpful because visual motor neural pathways are connected to the vestibular or balance system of the inner ear.
2) Optokinetic Tests
This test also checks for your ability to follow visual targets. During this test, you will watch an image that is continuously moving and will be asked to follow the movements. Similarly, this test will give clues to possible central or neurological problems or problems with the vestibular system.
3) Positional Tests
This test will help give an idea of the health of your inner ear system. You will be asked to move your head and body into different positions, allowing the hearing care professional to check for inappropriate eye movements in each position.
4) Caloric Testing
This test can help determine if you have vestibular weakness in one or both ears by checking to see if your vestibular system responds properly to stimulus. Your eyes will be monitored while your inner ears are stimulated (one at a time) with warm or cold air.
Preparing for Your Balance Function Assessment
Our staff will provide you with clear instructions on how to prepare for your examination. We may ask you to discontinue certain medications, not to consume any alcoholic beverages or caffeinated drinks at least 48 hours before the tests, to remove contact lenses or eyeglasses or to fast for a few hours prior to testing. The exact instructions may vary from patient to patient. If you have any questions about your instructions or how to prepare for the test, ask your hearing health professional.
The entire evaluation typically takes about 2 hours to complete. Patients may experience some symptoms of dizziness afterward. It is advised that you bring someone with you who can drive you home afterward, if you are unable to drive or do not feel well after the tests.
Call Audiology Center of Maine at (207) 664-2123 for more information or to schedule an appointment.