Auditory brain stem responses to bone-conducted tones in infants

Area of Science:

• Audiology
• Neuroscience
• Pediatrics

Background:

• Infant hearing assessment is crucial for early diagnosis and intervention.
• Bone-conducted auditory brain stem responses (ABRs) offer a non-invasive method to evaluate cochlear function.
• Various external and middle ear conditions can impact hearing assessment in infants.

Purpose of the Study:

• To evaluate the efficacy of bone-conducted (BC) auditory brain stem responses (ABRs) in infants with diverse ear conditions.
• To determine optimal frequencies and hearing levels for BC ABR testing in infants.
• To explore the utility of ABR asymmetries in identifying the cochlear origin of responses.

Main Methods:

• Recorded auditory brain stem responses (ABRs) to 500-Hz and 2,000-Hz bone-conducted (BC) tones.
• Tested 48 infants with normal, otitis media, or auditory meatal atresia ear states.
• Utilized two-channel ABR recordings to assess ipsilateral/contralateral response asymmetries.

Main Results:

• Responses to 500-Hz BC tones showed greater amplitude, longer wave V latencies, and better detectability than 2,000-Hz BC tones.
• 94-100% of infants with normal cochlear sensitivity demonstrated ABRs at 20-dB nHL for 500-Hz and 30-dB nHL for 2,000-Hz BC tones.
• ABR asymmetries aided in determining the cochlear origin of responses, particularly in cases with masking difficulties.

Conclusions:

• Two-channel ABR recordings to BC tones are feasible for assessing normal cochlear sensitivity in infants.
• Specific BC tone frequencies and hearing levels can reliably identify normal hearing in infants.
• This method provides valuable audiological data for infants, even with middle or external ear abnormalities.