Using Visual Reinforcement Audiometry to Evaluate Hearing in Infants from 5 to 36 Months
- Once infants reach 5 to 6 months of age, most can be conditioned to make a head turn response to the presence of an auditory stimulus
- Positioning is critical. The infant should be sated to maximize torso control. If the child is having a problem sitting upright and balancing, it will be difficult to make a head turn
- Reinforcement should be provided only when it is certain that the child is responding to the stimulus. Turning on the reinforcing toy when the child has not heard the sound will decrease the reliability of conditioning.
- Visual reinforcement audiometry (VRA) can be used to test children using earphones, the bone conduction transducer, hearing aids, cochlear implants and FM systems.
- Conditioned responses have the advantage of being more repeatable than unconditioned responses, and more responses usually can be obtained during one sitting
Test Protocols: Visual Reinforcement Audiometry
- VRA is the most commonly used reinforcment procedure
- It is used to evaluate hearing in children who are cognitively between 5-6 and 36 months of age
- Operant conditioning is a process by which the frequency of occurrence of a behavior (in this case, a conditioned head turn) is modified by what happens when the behavior occurs
- VRA uses a conditioned head-turning response that is shaped by the examiner's control of a stimulus-reinforcement paradigm
- Positioning is critical
- The infant needs to be seated so that she can easily make a conditioned head turn
- If the child does not sit up easily, she should be positioned in a reclining position, leaning back against someone or in a reclining chair, so she does not need energy to control her torso
- A variety of toys can be useful as distractors
- Accurate VRA depends on the ability of the examiner or test assistant to keep the child attentive
Conditioning Children with Very Profound Hearing Loss
- Children with severe to profound hearing loss, or with auditory attention or auditory processing problems may not have the ability to localize to sound
- For these children in particular, it will be necessary to pair the stimulus with the sound and teach the child to seek the reinforcer
- If the child does not respond to even very loud sounds, it may be useful to train the child to respond to a low-frequency tactile stimulus
- Thresholds do not vary by age
- It is important to take the child into consideration when selecting tests and test order
- soundfield or with insert headphones
- If the concern is for CHL, begin testing at 2000Hz in each ear and then go to 500hz
- SNHL begin at 500Hz then proceed directly to 2000Hz
- If there is a significant difference between the thresholds at 500 and 2000Hz, it will be critical to test 1000Hz before proceeding to other frequencies to obtain a good picture of the audiometric contour
- To entice a child to wear earphones, start by having the test assistant wear the earphones then the parents and then offer them to the child
- Someone needs to keep the child occupied with a toy while someone else puts the earphones on
Protocol for Visual Reinforcement Audiometry
- Seat child in high chair, in a child's chair, or on a parent's lap
- The test assistant or parent keeps child's attention focused to the front using quiet toys
- The auditory stimulus is presented at a comfortably loud level above expected threshold. The conditioning/reinforcing toy is turned on, and if the child does not turn, the test assistant calls attention to the toy. The auditory stimulus and the conditioning toy are dkept on together for 3-4 seconds
- Step 3 is repeated until the child consistently turns to the auditory stimulus
- When the child is conditioned to respond, the auditory stimulus is presented without turning on the conditioning/reinforcing toy. If the child turns toward the sound, the reinforcing toy is turned on and conditioning is complete
- Testing proceeds obtaining thresholds for one low (500Hz) and one high (2000Hz) frequency stimulus. The stimulus intensity is decreased until the child stops responding and is then increased to bracket threshold. Three responses at the same intensity are sufficient.
- Additional frequencies to be tested will be determined by the responses to the initial frequencies tested.
- Testing proceeds using insert earphones, bone vibrator, and technology (hearing aids, cochlear implants, and FM systems)
- The reinforcing toy is turned on only when the child makes a conditioned head turn in response to a sound. When in doubt, do not turn on the reinforcer.
What is Normal Hearing?
- Infant responses should be no more than 15 to 20 dB HL and by 1 year of age, children should be responding at adult levels
- 94% of high-risk infants have essentially normal hearing sensitivity (20dB HL) at 1000, 2000 and 4000 Hz in both ears
Summary of Factors that Affect Test Results
Many factors affect the reliability of test results
- Developmental age is critical
- Neurologic status is also critical
- Behavioral status is also important