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Loss / Disorders
Dizziness / Balance Testing - (see also ENT Dizziness Balance Disorders)
Auditory Brainstem Response (ABR)
What is an ABR?
An ABR (Auditory Brainstem Response test) is not a hearing test, but rather a test of auditory function above the level of the ear (from the auditory nerve through the brain stem to higher brain regions). When sound enters the ear and stimulates the cochlea in the inner ear, the cochlea produces an electrical response to the sound along the nerve pathways. This electrical response is the same type of response that is measured in an Electroencephalogram (EEG), a study of brain waves that may be more familiar to you. ABR waveforms (the electrical "waves" of nerve/brain activity in response to sound) can be measured on your skin using measurement electrodes. The responses can be interpreted to yield valuable information about the function of the auditory pathways. In analyzing the ABR, the audiologist and physician look at the presence of the various waveforms, at how long it takes each wave to occur, the distance between certain waves and the shape and height of the waves. The waves or responses of the two ears are compared to each other to further aid diagnosis.
Most commonly, the test is used to verify normal function of auditory pathways. ABRs are often ordered by your physician when there is greater loss of hearing in one ear or if you have complaints of dizziness or tinnitus (ringing). It can also be used to help determine the degree of hearing loss in infants, young children and other patients who are otherwise unable to provide reliable responses through traditional behavioral hearing tests or when additional confirmation of behavioral test results is needed. The ABR requires no active participation on the part of the patient and can provide reliable information whether the patient is awake or asleep.
What Adults Can Expect During the Test
We sometimes refer to the ABR as the "La-Z-Boy Test" because during the test the patient sits in a comfortable recliner and is instructed to just sit back, relax, and go to sleep if desired while the lights are turned down low. Prior to starting the test, one of our ACENTA audiologists will clean your skin on the forehead area and in the outermost part of your ear canals with gauze or a cotton swab. Electrodes are then applied to your forehead and earphone-electrodes (like little earplugs) are inserted in each ear. The ear canal electrode doubles as an earphone, producing a clicking sound once the test begins. A fairly loud clicking sound is presented to each ear. Muscle tension and muscle movement can interfere with measurement and cause the test to be prolonged or even decrease its accuracy. Patients are therefore encouraged to relax, especially in the jaw, face and neck. Sleeping is fine as long as the patient does not begin to snore. This test is quick and painless and for many people it is a fairly relaxing experience. The test lasts approximately 30 minutes when patients are fully relaxed and still.
ABR Testing For Infants
ABR testing for infants often takes more time than when testing adults. Infants are required be asleep during testing since they are not capable of relaxing and lying motionless. Sometimes young infants are able to sleep naturally during the test, but other infants require a mild oral sedative such as chloral hydrate. This prescription is ordered by your physician and is based upon the weight of your child. Chloral hydrate is typically administered by ACENTA's nurse and your child's breathing and pulse are monitored throughout the test. Parents should ensure that their child is somewhat sleep deprived and should prevent the child from napping prior to the test to increase the likelihood that the child will sleep throughout the test. Testing time depends upon how quickly your child goes to sleep, but most tests are scheduled for an hour-and-a-half. Parents are also encouraged to bring a bottle or sippy cup to the appointment as well as a pacifier when appropriate. Feel free to let your child wear pajamas or other warm, cozy clothes and do not hesitate to bring a blanket and favorite stuffed animal or quiet toy that relaxes the child.
An Electronystagmogram (ENG) is the most common audiological test ordered for individuals complaining of dizziness or vertigo. This test records and measures voluntary and involuntary eye movements (the vestibular ocular reflex), specifically nystagmus. Nystagmus is an involuntary back and forth jerking movement of the eyes that occurs when the entire balance system is stimulated. When the vestibular and ocular systems are functioning normally, nystagmus is only rarely seen. For the purpose of testing, nystagmus can be elicited through certain movements or stimulation of the vestibular system (the balance organs of the inner ear). This helps to determine the cause or origin of your dizziness. An ENG evaluates the oculomotor system and the vestibular system. The test takes approximately an hour and a half to complete.
The ENG is Comprised of a Series of Subtests or Tasks. There are Three Main Parts:
• Oculomotor Analysis -- patients perform various visual tasks that require eye movement
• Positional Testing -- patients are placed in various body positions to determine if dizziness develops and to see if nystagmus occurs
• Caloric Stimulation -- small amounts of both warm and cool water are introduced into each ear canal to independently stimulate the inner ear vestibular system
Throughout each part of the test, patterns of normal and abnormal eye movements are analyzed. The main purpose is to look for the presence of nystagmus in both the absence and presence of vestibular stimulation, as well as look for symmetry of responses. Analysis allows for determining if the disorder is central, peripheral or systemic.
• Central problems are caused by disturbances in the brain or central nervous system
• Peripheral problems arise from disturbances in the labyrinth (inner ear balance organ)
• Systemic problems are the result of disturbances in the organs and peripheral nerves (nerves outside of the brain or spinal column)
Diagnosis allows your physician to prescribe appropriate treatment options.
Preparing for The Test
In order to achieve the best test results, it is important that you carefully follow the instructions below:
1. Wear comfortable clothing and shoes (low-heeled shoes). Female patients may prefer to wear pants. You may want to have a light jacket or sweater with you.
2. The face should be washed thoroughly and be clear of any foundation, mascara, eyeliner and eye shadow. Makeup can be applied after the test.
3. NO coffee, tea or cola after midnight on the day of the test.
4. NO solid foods or milk for four (4) hours before the test. Use only SMALL amounts of water when brushing your teeth.
5. NO aspirin or medications containing aspirin for two (2) days before the test.
6. NO alcoholic beverages or liquid medications containing alcohol for two (2) days before the test.
7. DISCONTINUE medications such as allergy pills, decongestants, antihistamines, tranquilizers, sleeping pills, barbiturates, sedatives, pain pills, diet pills, nerve pills and pills or patches for dizziness one (1) week prior to your test.
8. CONTINUE to take medications for your heart, blood pressure and diabetes as directed by your physician. If you have any questions about other medications that you are taking please consult your physician or our office prior to your test date.
9. If you are having severe dizziness you may want to arrange to have a driver.
Medication can be resumed immediately following the ENG. Your cooperation in following these instructions will greatly improve the quality of your examination.
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