AUDIOLOGICAL EVALUATION OF CHILDREN 0-6 MONTHS
Audiological Diagnostic Assessment Protocol
To be considered a diagnostic procedure, ear specific estimates of type, degree, and configuration of the hearing loss must be obtained. This differs from a simple screening.
Adequate confirmation of an infant's hearing status cannot be obtained from a single test measure; rather the initial test battery must include physiologic measures and, if possible, developmentally appropriate behavioral techniques.
1. Detailed history should include but is not limited to:
- Parental report of auditory and visual behaviors
- Motor development
- Family history of hearing loss
- History of middle ear pathologies
- Parental concerns
- Prenatal, birth, and neonatal history
- Medical history including: Syndromes or other inheritable conditions, craniofacial anomalies, kidney issues, conditions of limbs/digits, pigmentation issues, exposure to ototoxic medications
Visual inspection for obvious structural abnormalities of the pinna and ear canal should be included.
3. Evoked Otoacoustic Emissions
- Either Transient or Distortion Products Emissions are acceptable.
- TEOAE click stimuli: One level (e.g., 80-85 dB SPL) should be completed.
- DPOAE stimuli: Use L1/L2 of 65/55 dB SPL.
- Pass criterion: An emission of 6 dB signal to noise ratio for at least three frequencies in each ear.
- At least one frequency should be located between 2000 and 3000 Hz A second frequency should be located between 3000 and 4000 Hz The third point could be at any other frequency between 1000 Hz and 6000 Hz
4. Acoustic Immitance Testing
- Tympanometry - 660 Hz or higher probe tone
- Acoustic Reflex- Ipsilateral middle ear muscle reflex thresholds for 500, 1000, 2000, and 4000 Hz if possible. Currently there is insufficient data for routine use of acoustic middle ear muscle reflex in infants younger than 4 months.
- Pass criterion: Type A tympanogram
5. Diagnostic Auditory Evoked Potential Testing (Non-sedated)
ABR to air-conducted clicks:
- Diagnostic testing should include Wave V latency-intensity function responses to at least three diiffering iintensity levels ending with at least one tracing at or below threshold.
- Pass Criterion: Normal results consist of Wave V responses for clicks at 25dBnHL within a normal absolute latency range adjusted for the child's correct gestational age.
Change polarity of clicks
- Supra-threshold click testing should also include one average with condensation clicks and anotheraverage at the same intensity with rarefaction clicks to rule-out auditory neuropathy/dys-synchrony.
- In a normal ABR the waveforms will be essentially the same morphology and latency with both polarities. If all waveforms in the tracings at one polarity invert when compared to the other polarity, that represents the presence only of the cochlear microphonic (CM) with no neural response. If only the CM is observed, that is consistent with auditory neuropathy/dys-synchrony.
- Even though the ABR is abnormal, in this case toneburst testing is not necessary, as it will not yield any additional information.
ABR to tonebursts:
- In order to obtain more frequency-specific information, ABR stimuli should include at least one lowfrequency toneburst (such as 500Hz) in combination with clicks.
- For even greater specificity both low and high frequency tonebursts could be used in place of clicks (such as 500Hz, 2000Hz and 4000Hz).
If conductive hearing loss is suspected, testing must also include:
Bone conduction ABR:
- Stimuli should be bone-conducted clicks; masking of the non-test ear should be applied, as appropriate.
- Diagnostic testing should include Wave V latency-intensity function responses to at least three differing intensity levels ending with one tracing below threshold.
- Diagnostic testing at minimum should include Wave V latency-intensity function responses to at leastthree differing intensity levels ending with at least one tracing at or below threshold.
- Pass Criterion Normal results would consist of Wave V responses at 25dBnHL for higher frequencies and 35dBnHL at lower frequencies.