What is the role of Brainstem Evoked Response Audiometry (BERA) or Auditory Brainstem Response (ABR) testing in diagnosing hearing loss?

Brainstem Evoked Response Audiometry (BERA/ABR) in Diagnosing Hearing Loss

Brainstem Evoked Response Audiometry (ABR) serves as both a screening tool for newborns and a definitive diagnostic test for infants and children who cannot cooperate with behavioral audiometry, providing ear-specific, frequency-specific hearing thresholds that are accurate enough to guide amplification fitting. 1

Primary Clinical Applications

Newborn Hearing Screening

• Automated ABR is the mandatory screening method for all NICU infants hospitalized >5 days to detect neural hearing loss (auditory neuropathy/dyssynchrony) that otoacoustic emissions (OAEs) would miss 1
• For well-infant nurseries, either automated ABR or OAEs can be used as the initial screening tool 1
• Infants who fail automated ABR screening in the NICU should be referred directly to an audiologist for comprehensive diagnostic evaluation, bypassing rescreening 1

Diagnostic Evaluation (Birth to 6 Months)

When permanent hearing loss is suspected, diagnostic ABR must include: 1

• Frequency-specific ABR using air-conducted tone bursts at multiple frequencies to create an audiogram-like map of hearing thresholds
• Click-evoked ABR with both condensation and rarefaction stimuli to detect cochlear microphonics and rule out auditory neuropathy/dyssynchrony, particularly in infants with risk factors (hyperbilirubinemia, anoxia) 1
• Bone-conduction ABR when indicated to differentiate conductive from sensorineural hearing loss 1

Critical caveat: Any infant showing "no response" on tone-burst ABR must be evaluated with click-evoked ABR, as some infants with neural hearing loss have no identifiable risk factors 1

When ABR is the Definitive Test

Infants and Young Children (Birth to ~3-6 Months)

• Diagnostic ABR is the gold standard when behavioral audiometry cannot be obtained 1, 2
• The test provides sufficiently accurate frequency-specific thresholds to allow hearing aid fitting without behavioral confirmation 1
• Natural sleep is adequate for infants up to 3-6 months of age; sedation is typically required for older infants and children 1, 3

Older Children with Special Circumstances

ABR remains necessary for: 1

• Children with developmental delays, autism, or behavioral problems that preclude accurate behavioral audiometry
• Any child where behavioral audiometry results are unreliable or inconsistent 1, 2
• Confirmation of hearing loss in children younger than 3 years—at least one ABR test is recommended as part of complete diagnostic evaluation 1

Test Characteristics and Limitations

Advantages

• Ear-specific results obtained through insert earphones 1
• Does not require patient cooperation—responses are neurologic, not behavioral 1
• Unaffected by anesthesia or sedation 4
• Can test across multiple frequencies (250 Hz to 8 kHz with appropriate protocols) 1

Critical Limitations

ABR is NOT a true test of hearing because it only assesses auditory pathway structural integrity up to the brainstem—it does not evaluate cortical processing of sound 1

Common pitfalls to avoid: 4, 5

• High-frequency sensorineural hearing loss may produce abnormal waveforms or absent responses even when lower frequencies are normal
• The child must remain quiet during testing; motion artifact invalidates results
• Interpretation is subjective despite objective recording—use evidence-based signal detection criteria and appropriate signal-to-noise ratios 5

Integration with Other Tests

Mandatory Cross-Checks

Never rely on ABR alone. The diagnostic battery must include: 1, 5

• Otoacoustic emissions (OAEs) to assess cochlear function
• Tympanometry with 1000-Hz probe tone (for infants <6 months) to rule out middle ear pathology 1
• Behavioral audiometry as soon as developmentally appropriate—this remains the true standard for hearing evaluation 1

Age-Appropriate Follow-Up Testing

• 6-36 months: Transition to behavioral audiometry (visual reinforcement or conditioned-play audiometry depending on developmental level); use ABR only if behavioral results are unreliable 1
• >2.5 years: Play audiometry becomes the preferred method 1
• >4 years: Conventional audiometry is appropriate 1

Timing and Intervention

Infants with confirmed hearing loss must receive: 1

• Diagnostic evaluation completed by 3 months of age
• Hearing aid fitting within 1 month of diagnosis if family chooses amplification 1, 2
• Early intervention services initiated by 6 months of age 1

For children with risk factors who pass newborn screening: At least one diagnostic audiology assessment (including ABR if behavioral testing is unreliable) should occur by 24-30 months of age, with earlier and more frequent assessment for high-risk conditions like CMV infection or progressive syndromes 1