ABR and BERA Are the Same Test
ABR (Auditory Brainstem Response) and BERA (Brainstem Evoked Response Audiometry) are identical terms referring to the exact same electrophysiological test—there is no clinical difference between them. 1, 2
Terminology Clarification
- Both terms describe an objective neurophysiological method that measures electrical activity in the auditory nerve and brainstem in response to sound stimuli 1, 3
- The terminology varies by region, publication era, and institutional preference, but the underlying test methodology, equipment, and clinical applications are identical 4, 2
- Modern medical literature and guidelines predominantly use "ABR" as the standard nomenclature 5, 6
What This Test Actually Measures
- ABR/BERA assesses auditory pathway structural integrity only up to the brainstem level—it is NOT a true test of hearing because it does not evaluate cortical processing of sound 6
- The test records electrical waveforms (waves I-V) generated by specific anatomical structures: waves I and II originate from the auditory nerve, while waves III-V originate from brainstem structures 1
- Results are independent of consciousness level, sedation, or anesthesia, making it invaluable for testing infants, uncooperative patients, and comatose individuals 1, 4
Clinical Applications
Hearing Assessment
- Provides ear-specific, frequency-specific threshold estimation using air-conducted tone bursts at multiple frequencies to create an audiogram-like map 6
- Can differentiate conductive from sensorineural hearing loss when bone-conduction ABR is performed 6
- Critical limitation: ABR cannot detect auditory neuropathy/dyssynchrony unless click-evoked ABR with both condensation and rarefaction stimuli is used to identify cochlear microphonics 6, 7
Retrocochlear Pathology Detection
- Highly sensitive (>90%) for vestibular schwannomas greater than 1 cm, but sensitivity drops dramatically to 8-42% for small tumors 5
- ABR becomes unreliable or impossible when hearing loss exceeds 80 dB in the 2000-4000 Hz range 5
- MRI with gadolinium is the gold standard for vestibular schwannoma diagnosis and is more cost-effective than ABR followed by MRI 5
Newborn Hearing Screening
- Automated ABR is mandatory for all NICU infants hospitalized >5 days because it detects neural hearing loss that otoacoustic emissions would miss 6
- For well-infant nurseries, either automated ABR or OAEs can serve as initial screening 6
- Infants failing automated ABR in the NICU should bypass rescreening and go directly to comprehensive diagnostic evaluation 6
Common Clinical Pitfalls
- False-negative results occur with mild hearing losses or recovered hearing because ABR sensitivity is proportional to hearing loss severity 5
- High-frequency sensorineural hearing loss may produce abnormal waveforms or absent waves even without retrocochlear pathology 4
- ABR alone is insufficient—comprehensive diagnostic evaluation requires integration with OAEs (to assess cochlear function), tympanometry with 1000-Hz probe tone (to rule out middle ear pathology), and behavioral audiometry when developmentally appropriate 6