Hearing disorders (audiology)
Our department audiology is a complete state of the art suit with modern technology in audiological hearing evaluation and revalidation.
Mrs. Cabenda is a trained audiologist and is working 15 years for our clinic. She was trained in the Netherlands and she returns yearly back to the Netherlands for post-graduate training and updating.
She performs both pediatric and adult hearing evaluations.
Pediatric hearing evaluation
Left undetected, hearing impairments in infants can negatively impact speech and language acquisition, academic achievement, and social and emotional development. If detected, however, these negative impacts can be diminished and even eliminated through early intervention. Because of this, all infants should be screened for hearing impairment, preferably prior to hospital discharge.
Infants referred from their newborn hearing screen should receive a follow-up diagnostic audiological evaluation before 3 months of age. This evaluation serves to verify the existence of a hearing impairment, and when present, the etiology and severity.
Data show that an infant with a significant hearing impairment who receives intervention by 6 months of age will perform significantly better in language development than the infant who is identified after 6 months of age (Yoshinago-Itano et al, 1998)1.
When should a Diagnostic Audiological be performed?
Diagnostic Audiology occurs after a baby fails to pass a follow-up rescreen, between 1 and 3 weeks of age. The diagnostic evaluation should occur between the ages of 1-3 months of age.
Some key Components in Diagnostic Audiology of Infants and Children:
This refers to the Audiologist who is trained, has the technical expertise and desire to work with the infant population. The Audiologist performs an audiological test battery to include physiologic measures and developmentally appropriate behavioral techniques.
Case History Documentation
A completed child and family case history to include congenital family history of hearing loss, medical factors, and risk indicators for hearing loss that may be present.
Auditory Brainstem Response (ABR)
This should include: Clicks, Tone bursts, and Bone Conduction testing. (This technology reflects the activity of the cochlea, auditory nerve, and auditory brainstem pathways.)
Otoacoustic Emissions (OAE)
(This technology is sensitive to outer hair cell dysfunction.)
Acoustic Immittance Audiometry
Tympanometric capabilities that use probe tones greater than 220/226 Hz. This should also include acoustic reflexes using a higher frequency probe tone, such as 660 Hz or 800 Hz. (This technology assesses middle ear status.)
Visual reinforcement audiometry can be effectively used with infants as young as 5 months. A confirmatory audiologic test battery for infants and toddlers age 6 through 36 months should include this procedure in addition to the components previously mentioned. (This procedure assesses the infant/child?s behavioral response to auditory stimuli in a sound proof booth.)
If a child has unilateral, mild, or chronic conductive hear loss or is "at risk" for progressive or delayed onset hearing loss, ongoing audiological services should include audiologic monitoring every 6 months until at least 3 years of age.
Parents of children with hearing loss have many different options about how they will communicate with their child and the types of educational services in which they would like the child to participate. Understanding the information about these choices can be confusing and overwhelming. Clearly, there is no best answer for everyone.
We would like to be a help for you and assisting you to make the right choice. Themes as cocheair implants and training and education will be discussed.
Accurate assessment of hearing (audiometry) is vital to the diagnostic evaluation of patients with suspected otologic disorders for the determination of the underlying process, as well as in the planning of rehabilitation of hearing loss. Originally, audiometry was limited to the psychophysical measurement of the sensation of hearing; thus, patient cooperation was essential. However, other tests have been developed over the years which permit more objective assessment of hearing even in infants, small children, malingerers, and hysterics.
Most humans hear sounds in the range of 20 to 20,000 Hz. Sensitivity varies as a function of frequency, with sounds in the middle frequencies being heard best. The ability to hear higher frequencies declines with age.
Adequate testing requires an audiometer (device for presenting sounds to the patient at precisely controlled intensity), a sound-proof environment, a competent audiologist, and a cooperative patient. The standard testing battery includes Pure Tone Audiometry, Speech Audiometry, and Immittance Audiometry.
- A. Pure Tone Audiogram:
This is a graphic plot of the patient's thresholds of auditory sensitivity for pure tone (sine wave) stimuli. Threshold hearing levels are indicated for each frequency tested. By convention, normal hearing levels are shown at top of the graph; a decrease in hearing sensitivity is indicated by larger values of hearing level. Hearing level is plotted on a logarithmic decibel scale. Sounds are tested with presentation by air conduction (earphones) as well as bone conduction (skull vibrator). An air bone gap indicates a conductive component of hearing loss. A decrease in threshold sensitivity by bone conduction reflects a sensory or neural loss.
- B. Speech Audiometry:
These tests utilize spoken words and sentences rather than pure tones. Tests are designed to assess sensitivity (threshold) or understanding (intelligibility).
- Threshold - the level at which the patient can correctly repeat 50% of test materials-- phoneme-balanced words (PB), synthetic sentences, etc.
- Intelligibility - by convention, the percentage of words or sentences a patient can correctly repeat when presented at supra-threshold levels.
- Provides information about hearing handicap. Problem maybe worse than indicated by pure tone average (PTA) for the speech frequencies.
- Useful to determine candidacy for hearing aid.
- Very poor results, out of proportion to PTA, suggests probable retrocochlear cause of hearing loss.
- C. Immittance Audiometry:
These hearing tests utilize the electroacoustic immittance bridge. This device is designed to quantify the impedance (resistance to movement) of the conductive mechanism of the ear by bouncing a probe tone off the tympanic membrane and measuring the proportion of reflected sound.
Maximal reflection of sound occurs when the mechanism is very stiff, while a compliant system transmits more sound and reflects less. There are two principal applications of this device.
- Tympanometry: A tympanogram is a graphic representation of the relationship of external auditory canal air pressure to impedance; the latter is usually reported in terms of tone of its derivatives, compliance in arbitrary units. Pressure in the external auditory canal is varied from -200 daPa* through +200daPa while monitoring impedance. Impedance is lowest (maximal compliance) when pressure in the canal equals pressure in the middle ear. Ears can be classified into three basic groups on the basis of the configuration of the tympanogram.
- Acoustic Reflex measures (AR): Contraction of the stapedius muscle occurs with loud sounds, producing a measurable change in compliance. Abnormalities of hearing may be suspected by the following results:
- Elevated threshold - indicates cochlear sensitivity loss or VIII nerve disorder
- Absent reflex
- Abnormal middle ear system
- Severe sensitivity loss
- VIII nerve lesion
- Ipsilateral VII nerve lesion
- Some otherwise "normal" ears
- Threshold low in proportion to sensitivity level ("recruitment")- seen in cochlear loss
- Abnormal "shape" of reflex.
A battery of tests intended to determine the site of lesion inpatients with otologic or neurotologic disorders. The constellation of tests varies according to the available test battery and provisional diagnosis.
A. Immittance audiometry
B. PI-PB functions
Speech discrimination is plotted as a function of sound intensity. Normally, discrimination improves with intensity up to a maximal level, then plateaus. In VIII nerve disorders, discrimination often declines dramatically as intensity increases above the level yielding maximum performances.
C. Bekesy Audiometry
This test has significant historical interest in development of assessment of hearing. However, today it is used predominately only in industrial and military hearing screening situations. Patient traces his own auditory threshold by means of a self-recording audiometer. Tracings are obtained for pulsed as well as continuous tones. The relationship between the two categories can be categorized into diagnostic patterns.
D. Tone decay tests
Abnormal adaptation to a continuous tone is seen in retro-cochlear lesions.
E. Stenger Test
Performed to detect malingering of unilateral loss. If sound is presented to both ears, patient will deny hearing in the ear with the feigned loss. If sound is presented to the good ear at a suprathreshold level, simultaneous to a louder sound in the questionable ear, a malingerer will localize the sound to his "bad" ear, and therefore deny hearing anything at all.
F. ABR - evoked auditory brainstem responses
Scalp electrodes measure electrical activity in response to sound clicks. The response is quite small in relation to other ongoing brain activity, but by presenting a large number of clicks and averaging the responses by computer, unrelated events can be canceled out.
G. ECOG (electrocochleography)
Electrical activity is measured from the promontory, and responses to a large number of clicks are averaged. These will be abnormal in eighth cranial nerve lesions and certain cochlear disorders.