Module 4

Objective Tests in Children

Tympanometry and reflexes, otoacoustic emissions, the auditory brainstem response and the auditory steady-state response — the measures that need no deliberate response and carry the diagnosis in the youngest children.

Middle-ear measures: tympanometry and reflexes

Every paediatric assessment begins at the middle ear, because a conductive overlay — usually otitis media with effusion — is the commonest reason a child hears poorly and will distort every other test. A crucial paediatric caveat: in infants under about six months the standard 226 Hz probe tone is unreliable because the immature ear canal is highly compliant, and a 1000 Hz probe tone should be used instead [11]. National guidance reflects this age cut-off [12]. Acoustic reflexes add a cross-check on middle-ear and lower-brainstem integrity.

In the compliant infant ear canal the 226 Hz trace is broad and hard to interpret; a 1000 Hz probe gives a readable peak. Illustrative shapes.

Otoacoustic emissions

Beyond screening, otoacoustic emissions remain useful diagnostically as a quick, frequency-specific probe of outer-hair-cell function and a powerful cross-check. Their defining diagnostic role is in auditory neuropathy: present OAEs with an absent or grossly abnormal ABR is the signature of ANSD, and OAEs may be the only abnormal — or only normal — result that unlocks the diagnosis[13]. Note that OAEs can disappear over time in ANSD, so their early presence must be documented.

The auditory brainstem response

The threshold (or frequency-specific) ABR is the cornerstone objective test of hearing level in infants who cannot give behavioural thresholds. Using tone-burst stimuli at 500, 1000, 2000 and 4000 Hz, and including bone-conduction ABR to separate conductive from sensorineural loss, it estimates ear- and frequency-specific thresholds that correlate closely with behavioural thresholds[15]. Recorded thresholds are reported in estimated hearing level (eHL) after applying age-appropriate correction factors. The neonatal ABR is mature enough to give a valid threshold estimate from birth [16]. Click ABR, by contrast, is a screen-and-neural-timing tool, not a frequency-specific threshold test.

Scrub

As intensity falls, wave V latency lengthens (~0.03 ms/dB) and amplitude shrinks until the response disappears — the basis of threshold ABR. Illustrative model.

The auditory steady-state response

The ASSR complements the ABR: it estimates frequency-specific thresholds from modulated tones using automated statistical detection rather than waveform reading, and can present at very high intensities, which helps probe residual hearing in severe-to-profound loss [17]. Like every objective measure here, an ABR or ASSR estimate is interpreted under the cross-check principle — confirmed against the middle-ear picture, the emissions, and behavioural testing as soon as the child can give it[4].