Lecture 4- Early Identification of Hearing Loss

Question 1

Why is hearing loss an important health problem?

Answer 1

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

Question 2

What is the prevalence of congenital HL in developed countries and high-risk populations?

Answer 2

1-3 per 1000 (0.2-0.3%) in developed countries

1-2% in “high-risk “ populations

Question 3

How can OAEs and ABR be used as screening tests?

Answer 3

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

Question 4

What are the limitations of using OAE and ABR as screening tests?

Answer 4

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)

Question 5

What are the specificity limitations of OAE/ABR screening (there are 8)?

Answer 5

1. Random algorithmic error
2. High environmental noise (AOAEs)
3. High electromyogenic noise (AABR)
4. Partially blocked probe/insert earphone
5. Naturally small OAEs/ABRs
6. Minor middle ear conditions (AOAE)
7. Substantial transient conductive loss (AABR)
8. Suboptimal test methods

Question 6

What are the 1-3-6 benchmarks for timelines?

Answer 6

They are the follow-up procedures after screening

Question 7

What is the “case definition” in hearing screening programs?

Answer 7

Most current programs target permanent HL of 30-40 dB or greater

Question 8

What is sensitivity in regards to hearing screening?

Answer 8

Probability of a positive test when disorder is truly present

Question 9

What is specificity in regards to a hearing screening?

Answer 9

Probability of a negative test when the disorder is truly absent

Question 10

Describe the protocols and equipment used in hearing screenings?

Answer 10

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

Question 11

What are the follow-up procedures after a screenings?

Answer 11

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

Question 12

What did the study conducted by Yoshinago-Itano find?

Answer 12

Provided evidence that children whose HL was identified early and received early intervention before 6 months of age had better language outcome

Question 13

What did the study conducted by Norton et al., find?

Answer 13

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

Question 14

What is classical (pavolvian) conditioning?

Answer 14

A response is elicited by the conditioned stimulus

Question 15

What is Instrumental (operant) conditioning?

Answer 15

A behavioral response elicited by a stimulus is controlled by the consequences of the behavior

Question 16

How is classical conditioning related to audiometry?

Answer 16

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

Question 17

How is Instrumental (Operant) conditioning related to audiometry?

Answer 17

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

Question 18

What is behavioral observation?

Answer 18

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)

Question 19

What is visual reinforcement audiometry?

Answer 19

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

Question 20

What is the VRA procedure?

Answer 20

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

Question 21

What is Conditioned Play Audiometry?

Answer 21

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

Question 22

What is reinforcement for CPA?

Answer 22

Social/verbal praise
- Should be natural and meaningful

“Peep show” procedure
- Illuminated pictures following a correct button press

Question 23

What is the procedure for CPA?

Answer 23

• 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