Auditory brainstem response (ABR) Audiometry is a neurologic test of auditory brainstem function in response to auditory (click) stimuli. First described by Jewett and Williston in 1971, ABR Audiometry is the most common application of auditory evoked responses. Test administration and interpretation is typically performed by an audiologist. (Neil Bhattacharyya, MD, Jan 21, 2009, http://emedicine.medscape.com/article/836277-overview)
The primary purpose of Otoacoustic emission (OAE) tests is to determine cochlear status, specifically hair cell function. This information can be used to (1) screen hearing (particularly in neonates, infants, or individuals with developmental disabilities), (2) partially estimate hearing sensitivity within a limited range, (3) differentiate between the sensory and neural components of Sensorineural hearing loss, and (4) test for functional (feigned) hearing loss. The information can be obtained from patients who are sleeping or even comatose because no behavioural response is required. (Kathleen C M Campbell, PhD, Dec 18, 2009, http://emedicine.medscape.com/article/835943-overview)
This test involves the presentation of a continuous tone to determine whether the threshold for the tone has changed (becomes poorer) over time. The test helps differentiate sensory from neural hearing loss, and is used in the diagnosis of cochlear versus retro cochlear lesions and eighth nerve tumours. While this test is still in use, the auditory evoked potential test is largely used in place of the tone decay test.
Behavioural test methods include Visual Reinforcement Audiometry (VRA), Conditioned Play Audiometry (CPA), and Conventional Audiometry. The goal of all testing is to determine the softest levels of tones and speech that a child can hear. The softest sound a child can hear 50 percent of the time, is called a “threshold”. Visual Reinforcement Audiometry (VRA): Generally done in children approximately 5 months to two years old. The child sits on a parent’s lap in the test booth, and is trained to look towards (orient to) a sound presented via a speaker. When the child looks toward the correct speaker, he/she is rewarded by briefly switching on a lighted, moving toy. Using this technique, thresholds can be reliably measured for tones of various frequencies (pitch) and for speech. Many children can be tested with small earphones placed in their ears, using the same technique. Conditioned Play Audiometry (CPA): Generally done in children approximately two to five years old. The child is trained to perform a play activity each time a sound is heard. Activities might include putting a block in a bucket, placing a peg in a hole, etc. Using this technique, thresholds can be reliably measured for tones of various frequencies. Speech thresholds are typically obtained by having the child identify pictures and body parts.
Tympanometry is a test used to detect disorders of the middle air. Air pressure in the ear canal is varied to test the condition and mobility (movement) of the ear drum
This is an assessment of the patient’s ability to understand speech. The patient is played a tape of a series of words at varying intensities. The percentage of words correctly repeated is plotted against the intensity to produce a speech audiogram. Phonetically balanced words are to be used. Outcomes: Normal Hearing – all words are understood if played at a suitable intensity Conductive deafness – all words are again understood but only when played at a much higher intensity Sensorineural deficits – patient may fail to understand all the words despite a higher intensity. Speech discrimination is poor due to loudness recruitment – (a condition associated with cochlear disease in which soft sounds are not heard but loud sounds are heard at their normal or higher intensities).
The testing of hearing is most often carried out by establishing the threshold of hearing, the softest sound which can be perceived in a controlled environment. It is typical to do this testing with pure tones by providing calibrated tones to a person via earphones, allowing that person to increase the level until it can just be heard.
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