BERA Test — How It Works, Benefits & Recovery — Procedure Guide, Recovery & Risks | MyMedicPlus

BERA (Brainstem Evoked Response Audiometry), also called Auditory Brainstem Response (ABR), is a non-invasive electrophysiological test that measures the electrical activity generated by the auditory nerve and brainstem nuclei in response to brief auditory stimuli — typically clicks or tone bursts delivered through insert earphones. Surface electrodes placed on the scalp, mastoid, and forehead detect these tiny signals, which are then averaged by a computer to extract five reproducible waveform peaks (Waves I through V) representing successive activation of auditory structures from the cochlea to the inferior colliculus. Wave V latency is the most clinically significant measurement, normally occurring at approximately 5.6 milliseconds at 60 dB above hearing threshold. BERA is frequency-specific when tone bursts are used, enabling audiological threshold estimation across the speech frequency range without requiring a behavioural response from the patient. The test requires the patient to be still and relaxed; it is often performed during natural sleep in infants. No sound is produced by the patient — the test is entirely passive. BERA is considered the gold standard for objective hearing assessment in populations who cannot complete conventional audiometry.

BERA is indicated across a wide range of clinical scenarios. In neonates and infants, it forms the basis of universal newborn hearing screening programmes globally, detecting congenital sensorineural hearing loss that would otherwise remain unrecognised until speech delay became apparent. In older children, it is used when behavioural audiometry is unreliable due to developmental delay, autism spectrum disorder, or non-cooperation. Adults benefit from BERA in the workup of asymmetric sensorineural hearing loss, unilateral tinnitus, sudden sensorineural hearing loss, and suspected retrocochlear pathology such as acoustic neuroma (vestibular schwannoma) or cerebellopontine angle tumour. Neurological indications include multiple sclerosis evaluation — BERA detects demyelinating lesions in the central auditory pathway even when clinically silent — and intraoperative neuromonitoring during posterior fossa surgery to preserve hearing function. Assessment of brainstem integrity in intensive care patients with impaired consciousness or suspected brainstem death is another established indication.

Skin preparation with a mild abrasive gel reduces electrode impedance below 5 kilohms. Disposable self-adhesive or cup electrodes are placed at the vertex (Cz), ipsilateral and contralateral mastoids, and forehead. Insert earphones or headphones deliver broadband clicks (100 microseconds) or frequency-specific tone bursts at rates of 20–80 Hz at intensities from 20 to 90 dB nHL. The recording amplifier captures electrical signals in the 0.1–3,000 Hz bandpass, and approximately 1,000–2,000 sweeps are averaged to improve the signal-to-noise ratio. The computer generates waveforms for each intensity level, and the audiologist or neurophysiologist identifies Wave I (cochlear nerve), III (cochlear nucleus), and V (inferior colliculus). Wave V threshold is determined by reducing intensity until Wave V disappears, providing an objective hearing threshold within 10–15 dB of the behavioural threshold. For infants, the test is performed during natural sleep; if the infant is awake, mild sedation (chloral hydrate orally, 25–50 mg/kg) may be given under medical supervision. The entire test including both ears takes 30–60 minutes for cooperative adults. Skin preparation with a mild abrasive gel reduces electrode impedance below 5 kilohms. Disposable self-adhesive or cup electrodes are placed at the vertex (Cz), ipsilateral and contralateral mastoids, and optionally at the forehead as ground. The patient lies supine in a sound-attenuated room, encouraged to sleep naturally or remain still. Click stimuli (broadband acoustic impulses of 100 microseconds duration) or tone-burst stimuli are delivered through calibrated insert earphones at intensities ranging from 90 dBnHL down to threshold, typically in 10 dB steps. Each intensity level requires 1,000–2,000 sweeps averaged to extract the ABR waveform from background EEG. The audiologist or technician identifies waves I through V — wave V threshold is used for auditory threshold estimation. The complete test takes 60–90 minutes. Sedation (chloral hydrate or midazolam) may be administered to young children unable to cooperate.

The primary benefit of BERA is its objectivity: it provides quantitative hearing threshold data without any active participation from the patient, making it the only reliable hearing test for neonates, infants, and individuals with severe intellectual or communication disabilities. Early identification of congenital hearing loss through newborn BERA screening, when followed by early hearing aid fitting or cochlear implantation before 6 months of age, significantly improves speech, language, and cognitive developmental outcomes compared with late identification. In adult audiology, BERA has a sensitivity exceeding 95% for acoustic neuroma, enabling early detection of small intracanalicular tumours before they cause significant hearing loss or facial nerve compression. For neurological diagnosis, BERA can detect demyelinating lesions in multiple sclerosis that are clinically silent, contributing to the diagnostic criteria. BERA carries no radiation, no contrast injection, and no risk beyond minor skin irritation from electrode gel — its safety profile is unmatched among audiological investigations. Results guide critical management decisions including cochlear implant candidacy assessment and surgical planning.

BERA carries essentially no procedural risk in itself. The test involves only electrodes and sound stimuli with no penetration of the body. Minor skin irritation or redness at electrode sites from the abrasive preparation gel resolves within hours and is the only common adverse effect. If the test is performed under sedation in infants or children, the standard risks of conscious sedation apply — respiratory depression, paradoxical reaction, and the need for monitoring until the child is fully awake. These risks are managed by performing sedated BERA in units with paediatric resuscitation capability and trained staff. In audiological practice, the main limitation is not a safety risk but the possibility of a false-negative result if waveform quality is poor due to muscle artefact — avoidable by ensuring the patient is adequately relaxed. False-positive abnormalities may arise from technical factors such as high electrode impedance, electrical interference, or equipment malfunction. Audiological interpretation requires expertise to distinguish true pathology from technical artefact.

No recovery period is required after a standard BERA examination. The test is entirely non-invasive and patients can drive, work, and resume all activities immediately after the test. If mild sedation was used for a young child, a recovery observation period of 30–60 minutes in the clinic or ward is required until the child is fully awake, alert, and able to swallow safely before discharge with parents. The attending medical professional provides written post-sedation care instructions including activity restrictions for the remainder of the day. Results are typically analysed and reported by an audiologist or neurophysiologist within 24–48 hours of the test. Reports are then reviewed by the referring clinician — often an ENT surgeon, paediatrician, or neurologist — who will discuss the implications with the patient or family and arrange any further investigations such as MRI of the internal auditory canals if retrocochlear pathology is suspected.