Lecture 4- Early Identification of Hearing Loss Flashcards
Why is hearing loss an important health problem?
Unrecognized hearing loss in young children compromises the development of speech and language
Hearling loss, along with other factors, can have a strong influence on long-term language outcomes
What is the prevalence of congenital HL in developed countries and high-risk populations?
1-3 per 1000 (0.2-0.3%) in developed countries
1-2% in “high-risk “ populations
How can OAEs and ABR be used as screening tests?
OAEs
- Vulnerable to minor conductive disorders
- Variation in OAE detectability and pure-tone audibility
ABR
- Strong relationship between detectability of ABR and audibility of transient sound
- Can be used to directly estimate thresholds
- Can be time consuming
- Not as susceptible to minor middle ear disorders
- Affected by disorders that reduce temporal synchrony of stimulus-evoked action potentials
What are the limitations of using OAE and ABR as screening tests?
They do not have intrinsic validity
- Responses may be observed consistently in absence of behavioral response to sound (not direct tests of hearing in the perceptual sense) and behavioral responses may be observed in the absence of responses
- E.g., screening click ABR test can miss low frequency losses, notched, or cookie-bite HL, OAE can miss ANSD
Errors due to environmental noise, physiological noise, natural biological variations in response amplitude (inaccuracy)
What are the specificity limitations of OAE/ABR screening (there are 8)?
- Random algorithmic error
- High environmental noise (AOAEs)
- High electromyogenic noise (AABR)
- Partially blocked probe/insert earphone
- Naturally small OAEs/ABRs
- Minor middle ear conditions (AOAE)
- Substantial transient conductive loss (AABR)
- Suboptimal test methods
What are the 1-3-6 benchmarks for timelines?
They are the follow-up procedures after screening
What is the “case definition” in hearing screening programs?
Most current programs target permanent HL of 30-40 dB or greater
What is sensitivity in regards to hearing screening?
Probability of a positive test when disorder is truly present
What is specificity in regards to a hearing screening?
Probability of a negative test when the disorder is truly absent
Describe the protocols and equipment used in hearing screenings?
Most manufacturers target HL of 40 dB or greater
- There is equipment that allows adjustments to be made to the ABR screening level as well as parameters for OAE that can improve detection of milder HL
Automated ABR and OAEs are the primary test methods used in NBHS programs
OAEs may be preferred for hospitals with dedicated personnel who can become proficient at probe placement
- Probe seal not necessary for ABR–often has disposable earphones/cups/muffs
Costs can make ABR prohibitive
What are the follow-up procedures after a screenings?
1-3-6 benchmark
Knowledge of the method used to screen is important so that the outpatient rescreen is the same
- E.g., if the patient failed an ABR screen but passed an OAE screen, neural HL could be missed
Must have a mechanism in place for communicating with parents and primary care providers as well as prompt referral to the EI program
Employ evidence-based practice
What did the study conducted by Yoshinago-Itano find?
Provided evidence that children whose HL was identified early and received early intervention before 6 months of age had better language outcome
What did the study conducted by Norton et al., find?
They found that TEOAEs, DPOAEs, and ABR had similar abilities to identify hearing losses of 30 dB or greater as assessed by subsequent VRA at 8-12 months corrected age
What is classical (pavolvian) conditioning?
A response is elicited by the conditioned stimulus
What is Instrumental (operant) conditioning?
A behavioral response elicited by a stimulus is controlled by the consequences of the behavior
How is classical conditioning related to audiometry?
In early development of behavioral pediatric audiology, psychogalvanic skin response (PSR) was used
Was used as an alternative to play audiometry for measuring hearing in children
It was phased out of use after it was clearly demonstrated that the audiometric results and outcomes were less accurate, more time consuming, and traumatic compared to Instrumental (operant) Conditioning Techniques
How is Instrumental (Operant) conditioning related to audiometry?
The auditory stimulus serves as a discriminative stimulus
- Indicates the time frame during which a response will yield a stimulus
Response–single example of the appropriate behavior
Operant–range of responses that are controlled by their consequences
Consequence–an appropriately selected and appropriately applied reinforcement
When a behavior generates a reinforcing consequence, there is an increased probability that similar behavior will reoccur
What is behavioral observation?
Not considered appropriate for the estimation of hearing in infants under approximately 5-6 months
However, it is appropriate and useful to observe infant responses to sound
- Ensure general compatibility with other physiologic test results
- Confirm parent/caregiver observations
Often helpful to observe babies in a drowsy or light state of sleep
Audiologists should look for gross behavioral responses to broadband noise or speech stimuli
For infants under 2 months of age, expect few if any behavioral levels below those that elicit startle responses (Hicks et al., 2000)
What is visual reinforcement audiometry?
Reliable head-orienting responses are observed in most infants by ~4-5 months
Audiology booths have speakers placed at 45 or 90 degrres
May consider having child sit in a high chair (gentle restraint)
Can be done with earphones or in the sound field
What is the VRA procedure?
Train the Response
Starting Level
- Starting at 30 dB improves probability of starting close to threshold
- If moderate HL is present, increase stimulus by 20 dB
Step Size and Trial Duration
- Larger steps are less precise
- Increase in 20 dB steps if no response is obtained
- Start with 20 dB down and 10 dB up step sizes
- Obtain 2 responses at a specified level to stop at a given frequency
What is Conditioned Play Audiometry?
Use of CPA at developmental age of 3 years and “carefully selected” children at 2 years
- Experience with CPA indicates reliable responses
Response behavior= performance of desired motor behavior within 3 seconds after stimulus onset, no later than 4 seconds
What is reinforcement for CPA?
Social/verbal praise
- Should be natural and meaningful
“Peep show” procedure
- Illuminated pictures following a correct button press
What is the procedure for CPA?
- Get child in a ready state
- If the listener can’t respond to verbal instruction, modeling or hand-over-hand training can be employed
- Generally train with audiologist directly beside the child
