Glossary

Far-field scalp-recorded sum of the neural activity from the cochlea to the auditory thalamus within the first 10 ms after an acoustic stimulus. Five waves anchor interpretation.

Read more: Introduction, Anatomy & Physiology

See also: wave i, wave iii, wave v, ipl

Compound action potential of the distal eighth nerve. Typical adult latency 1.6 ms at 80 dB nHL click. The only ABR wave generated peripheral to the brainstem.

Read more: Anatomy, Normal Waves

See also: wave iii, wave v, ipl, abr

Generated near the cochlear nucleus in the lower pons. Typical adult latency 3.8 ms at 80 dB nHL click.

Read more: Anatomy

See also: wave i, wave v, cochlear nucleus

Generated in the lateral lemniscus near the inferior colliculus. Typical adult latency 5.6 ms at 80 dB nHL click. The most robust ABR wave — used for threshold estimation since it persists longest as intensity drops.

Read more: Anatomy, Normal Waves

See also: wave i, wave iii, lateral lemniscus, latency intensity

Time between two ABR waves on the same trace. The three clinically important IPLs are I–III (~2.2 ms), III–V (~1.8 ms), and I–V (~4.0 ms). Prolongation localises a lesion to the path segment between the two waves.

Read more: Normal Waves, Anatomy

See also: wave i, wave iii, wave v, retrocochlear, brainstem lesion

Absolute difference between right and left wave V latency at the same stimulus intensity. Upper limit of normal 0.4 ms. Historically the single most sensitive ABR finding for retrocochlear pathology.

Read more: Schwannoma

See also: wave v, retrocochlear, schwannoma

100 µs rectangular electrical pulse delivered to a transducer. Produces a broad-band acoustic stimulus that excites a wide cochlear region synchronously — the workhorse stimulus for diagnostic ABR.

Read more: Technique

See also: tone burst, chirp, db nhl

Brief frequency-specific stimulus (typically 2-1-2 or 2-2-2 cycles, Blackman envelope) used in threshold ABR. Smaller and broader waves than click ABR but yields frequency-specific threshold estimates.

Read more: Threshold ABR

See also: click, chirp, threshold abr

Frequency-modulated stimulus where low frequencies precede high frequencies to compensate for the cochlear travelling-wave delay. Yields larger wave V amplitudes than the click — useful in newborn screening and threshold seeking.

Read more: Technique, Neonatal Screening

See also: click, tone burst

Normalised hearing level — the ABR stimulus intensity referenced to the behavioural threshold for the same click in normal-hearing listeners. 0 dB nHL ≈ 30 dB peSPL for a click.

Read more: Technique

See also: db ehl, db pespl, threshold abr

Estimated hearing level — the laboratory's locally-derived correction from ABR-measured threshold (dB nHL) to predicted behavioural threshold (dB HL). Each laboratory establishes its own offsets per stimulus and transducer.

Read more: Threshold ABR

See also: db nhl, threshold abr

Peak-equivalent sound pressure level — the SPL of a continuous tone with the same peak amplitude as the brief click being calibrated. Used because brief clicks have no steady SPL.

See also: db nhl

Plot of wave V latency against stimulus intensity. Slope in normals is ~0.03 ms/dB. The shape of the curve (parallel vs steeper) helps distinguish cochlear from retrocochlear pathology.

Read more: Normal Waves, Threshold ABR

See also: wave v, cochlear loss, retrocochlear

Frequency-specific objective hearing assessment using the lowest intensity at which wave V is reliably detected. Standard for paediatric audiology and any patient whose behavioural responses cannot be trusted.

Read more: Threshold ABR

See also: tone burst, db ehl, neonatal screening

Fixed-intensity (typically 35 dB nHL) ABR with an algorithmic pass/refer decision. Used for newborn hearing screening. Detects ANSD whereas OAE-only screening does not.

Read more: Neonatal Screening

See also: oae, ansd, neonatal screening

Acoustic emissions from the cochlea generated by outer hair cells. Present when outer hair-cell function is intact, regardless of neural transmission. OAE screening misses ANSD.

Read more: ANSD, Neonatal Screening

See also: aabr, ansd, cochlear microphonic

Pre-neural alternating-current response generated by outer hair cells, mirrors the stimulus waveform. Inverts when stimulus polarity reverses — the polarity-reversal test confirms its identity, central to the diagnosis of ANSD.

Read more: ANSD

See also: ansd, oae, polarity reversal

Recording rarefaction and condensation clicks as separate runs. A response that inverts cleanly between the two is the cochlear microphonic. Alternating polarity cancels it and is contraindicated when ANSD is suspected.

Read more: Technique, ANSD

See also: cochlear microphonic, ansd

Disorder of synchronous neural transmission with preserved outer hair-cell function. Defined electrophysiologically by absent or grossly disrupted ABR with preserved OAEs and/or cochlear microphonic.

Read more: ANSD

See also: cochlear microphonic, oae, aabr, eabr, cochlear nerve deficiency

Hearing loss arising from hair-cell or stria vascularis dysfunction. ABR shows parallel rightward shift of the latency–intensity function; IPLs preserved.

Read more: SNHL

See also: latency intensity, audiogram

Hearing loss arising from outer or middle-ear pathology. ABR shows parallel shift of all waves on air-conduction; bone-conducted ABR normalises. The air–bone gap quantifies the conductive component.

Read more: Conductive

See also: audiogram, bone conduction

Pattern of selective prolongation of later waves (III, V) with preserved wave I; IPL I–V exceeds the upper limit of normal; interaural wave V difference > 0.4 ms. Most commonly seen with vestibular schwannoma.

Read more: Schwannoma

See also: schwannoma, interaural v difference, ipl

Benign tumour arising from Schwann cells of the vestibular nerve, typically near the internal auditory canal. MRI with gadolinium is the diagnostic standard; ABR is a useful confirmatory or screening test.

Read more: Schwannoma

See also: retrocochlear, stacked abr, interaural v difference

Derived-band protocol that recovers responses from across the cochlear frequency map, time-aligns wave V across bands, and sums them. Improves sensitivity for small (< 1 cm) intracanalicular schwannomas missed by conventional click ABR.

Read more: Schwannoma

See also: schwannoma, retrocochlear

ABR pattern of selective IPL III–V or I–V prolongation with preserved wave I. Differential includes multiple sclerosis (bilateral, subacute) and pontomesencephalic infarct (typically unilateral, acute).

Read more: Brainstem lesion

See also: ipl, ms

Demyelinating disease of the central nervous system. ABR pattern: bilateral IPL III–V prolongation reflecting lateral-lemniscus demyelination; preserved waves I and III.

Read more: Brainstem lesion

See also: brainstem lesion, ipl

Disorder of auditory processing above the brainstem with normal peripheral and brainstem function. ABR is normal; diagnosis rests on a behavioural test battery including speech-in-noise and dichotic listening.

Read more: Central

See also: mlr

Auditory evoked potential generated between ~10 and 80 ms reflecting thalamocortical and primary cortical activity (Na–Pa complex). Abnormal MLR with intact ABR localises a lesion above the inferior colliculus.

Read more: Central

See also: capd

Plot of behavioural pure-tone threshold against frequency for each ear. The PTA (pure-tone average) of 500, 1000, and 2000 Hz quantifies overall loss; air–bone gap quantifies conductive component.

Read more: SNHL

See also: cochlear loss, conductive loss

Stimulus delivered through a bone oscillator placed on the mastoid, bypassing the outer and middle ear. Bone-conducted ABR is essential for distinguishing conductive from cochlear loss patterns.

Read more: Threshold ABR, Conductive

See also: conductive loss

First central relay of the auditory pathway in the lower pons. Generates wave III. Bushy cells project bilaterally; the lateral lemniscus carries the ascending signal upward.

Read more: Anatomy

See also: wave iii, lateral lemniscus

Ascending auditory tract from the superior olive to the inferior colliculus. Site of wave V generation. Demyelinating lesions of the lateral lemniscus produce the classic MS ABR pattern.

Read more: Anatomy

See also: wave v, ms

Universal screening of newborns for permanent hearing loss within the first month of life. The 1-3-6 rule: screen by 1 month, diagnose by 3, intervene by 6. AABR is the preferred modality, especially in NICU populations.

Read more: Neonatal Screening

See also: aabr, oae, ansd

An ABR evoked by an electrical pulse rather than an acoustic stimulus, delivered through a promontory, round-window, or cochlear-implant electrode. Confirms that stimulable auditory neural tissue exists when the acoustic ABR is absent — used in cochlear nerve deficiency and in ears ossified after meningitis.

Read more: ANSD

See also: cochlear nerve deficiency, ansd, abr

Congenital absence (aplasia) or under-development (hypoplasia) of the cochlear nerve. Can present like ANSD — absent ABR with preserved OAEs — but the lesion is too little nerve to drive, not a synchrony failure. Distinguished from synaptic ANSD by high-resolution IAC MRI and EABR.

Read more: ANSD

See also: ansd, eabr

Irreversible loss of all brain function, established clinically by irreversible coma of known cause, absent brainstem reflexes, and apnoea. ABR can serve as an ancillary (confirmatory) test — bilateral absent waves II–V with cochlear function shown intact — but never replaces the clinical determination.

Read more: Coma & Brain Death

See also: wave i, brainstem lesion