Bera result using headphones
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BERA (Brainstem Evoked Response Audiometry) is a test that measures electrical activity in the auditory nerve and brainstem in response to sound. When performed with headphones (insert or supra-aural), it primarily tests air conduction and helps determine hearing thresholds and site of lesion.
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Good findings. Now let me read the most relevant sections from Cummings (ABR section) and Scott-Brown's (ABRE section) simultaneously.
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Let me get more detail on BERA waves, normal values, and interpretation - particularly what "using headphones" specifically means for test interpretation.
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Now let me get the ABR waveform image and the Scott-Brown section on normal values.
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Excellent - I have a clear Normal ABR waveform image. Let me read a bit more on the Scott-Brown section about normal values and conductive hearing loss effects, and also get the KJ Lee section on BERA normal latencies.
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Now let me fetch the ABR peaks image and also get the Scott-Brown section on conductive hearing loss effects to complete the headphone-specific interpretation.
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I now have comprehensive information. Let me also get the normative values table that was referenced:
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I now have everything needed for a comprehensive answer. Here is the full breakdown of BERA results using headphones:
BERA (ABR) Results Using Headphones - Complete Guide
BERA (Brainstem Evoked Response Audiometry), also called ABR (Auditory Brainstem Response), measures far-field electrical potentials generated by the auditory nerve and brainstem in response to sound. When performed using headphones (supra-aural or, preferably, insert earphones), it delivers sound via air conduction, making it the standard method for most clinical BERA testing.
Why Headphones (Insert Earphones) Are Preferred
- Scott-Brown's recommends insert earphones (e.g., ER-3A) for diagnostic ABR. They reduce stimulus artifact, allow inter-aural attenuation up to 70-80 dB (vs. ~40 dB with supra-aural headphones), and reduce contamination from ambient noise.
- Stimulus is typically a 100 microsecond click delivered at 80 dB nHL (or higher if significant hearing loss is present).
- The click tests predominantly 2000-4000 Hz cochlear region (high frequency).
The Normal ABR Waveform (Waves I-V)
Normal two-channel ABR: IPSI channel strongly emphasizes Wave I; CONTRA channel emphasizes the IV-V separation. Two replicated traces confirm response reliability.
Each wave corresponds to a neural generator - summarized by the mnemonic "EECOL" (KJ Lee's Essential Otolaryngology):
| Wave | Generator | Approximate Latency |
|---|---|---|
| I | Distal 8th nerve (cochlear nerve) | ~1.5 ms |
| II | Proximal 8th nerve | ~2.5 ms |
| III | Cochlear nucleus | ~3.5 ms |
| IV | Superior olivary complex / lateral lemniscus | ~4.5 ms |
| V | Lateral lemniscus (+ inferior colliculus) | ~5.5 ms |
Waves IV and V often appear fused as a IV-V complex. A SN10 negativity may follow wave V (from inferior colliculus).
Normal Values (at 80 dB nHL, click stimulus via air conduction headphones)
From Scott-Brown's Otorhinolaryngology (Table 52.1):
| Measurement | Normal Limit |
|---|---|
| Absolute latency of Wave V | < 6.2 ms |
| Interwave (interpeak) latency I-III | < 2.5 ms |
| Interwave latency III-V | < 2.4 ms |
| Interwave latency I-V | < 4.4 ms |
| Inter-ear latency difference (ILD) for Wave V | < 0.5 ms |
| Fast-rate latency shift | < 1.0 ms |
Cummings Otolaryngology uses slightly tighter values for neurodiagnostic thresholds: I-III ≥ 2.3 ms, III-V ≥ 2.1 ms, I-V ≥ 4.4 ms, and interaural latency difference ≥ 0.4 ms suggest retrocochlear pathology.
How to Interpret the Result (3-Step Hierarchy)
Step 1: Is there a response at all?
- A complete absence of ABR at 85 dB nHL in a patient with near-normal hearing = strongly suggests retrocochlear pathology.
- Absent ABR with severe hearing loss = may simply be due to inadequate cochlear stimulation, not a lesion.
Step 2: Are all major peaks (I, III, V) present?
- Wave V is the most robust - persists even with significant hearing loss.
- Wave I disappears when hearing loss exceeds ~40-45 dB at high frequencies.
- An absent Wave V in the presence of a replicable Wave I or III = definitive indicator of retrocochlear involvement.
Step 3: Measure interpeak latencies
- I-III, III-V, and I-V intervals are the gold standard for neurodiagnostic ABR.
- The I-III interval is the most sensitive for acoustic neuroma (~90% sensitivity).
- Increased I-V or I-III = lesion between cochlear nerve and upper brainstem (e.g., acoustic neuroma, CPA mass, demyelination).
Effect of Headphone Type on Results
| Transducer | Key Feature |
|---|---|
| Insert earphones (ER-3A, preferred) | Greater inter-aural attenuation (~70-80 dB), ~0.9 ms added absolute latency vs. supra-aural (due to tubing), less artefact - normative values must account for this delay |
| Supra-aural headphones (TDH-39/49) | ~40 dB inter-aural attenuation; risk of cross-hearing; historically used for many normative data sets |
When using insert earphones, Wave V latency is approximately 0.9 ms longer than with supra-aural headphones. Laboratories must use transducer-specific normative data.
Conductive vs. Sensorineural Patterns (Headphone ABR)
- Conductive hearing loss: All waves shift to longer latencies uniformly (a parallel shift), with normal interwave intervals (I-III, I-V unchanged). The wave V latency-intensity function is shifted but has normal slope.
- Sensorineural hearing loss: Affects wave morphology variably; slope of the latency-intensity function may increase near threshold.
- Retrocochlear lesion (acoustic neuroma): Prolonged I-III or I-V interwave interval, reduced amplitude of waves, absent wave V, or large inter-ear difference (ILD > 0.5 ms).
ABR Threshold Testing (Hearing Sensitivity)
- Wave V threshold correlates well with behavioral hearing threshold (within 10-20 dB).
- Tone-pip stimuli (500 Hz, 1000 Hz, 2000 Hz, 4000 Hz) can be used for frequency-specific threshold estimation.
- Particularly useful in infants, uncooperative patients, and medico-legal cases where behavioral testing is unreliable.
References:
- Cummings Otolaryngology Head and Neck Surgery, Section on Auditory Brainstem Response (pp. 2577-2580)
- Scott-Brown's Otorhinolaryngology Head & Neck Surgery, Vol. 2, Ch. 52: Acoustic Brainstem Evoked Responses
- K.J. Lee's Essential Otolaryngology, Otology section (Auditory brainstem response, p. 1211)
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