What are the different type of special audiometry test and what are their indications
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special audiometry tests indications SISI ABLB Bekesy impedance audiometry
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Special audiometry tests are supplementary tests used after routine pure-tone audiometry when there is a need to localize a sensorineural lesion, assess middle-ear function, evaluate speech understanding, detect non-organic hearing loss, or test infants/uncooperative patients.
1. Suprathreshold tests
These assess hearing at levels above threshold, mainly to differentiate cochlear from retrocochlear hearing loss.
| Test | Principle / typical result | Main indication |
|---|---|---|
| SISI test (Short Increment Sensitivity Index) | Ability to detect repeated 1 dB increments in a continuous tone, usually 20 dB above threshold. A high score suggests cochlear recruitment. | Suspected cochlear lesion, especially to demonstrate recruitment in Ménière disease or cochlear SNHL. |
| ABLB test (Alternate Binaural Loudness Balance, Fowler test) | Compares loudness growth between ears. Rapid loudness growth in the affected ear indicates recruitment. | Unilateral/asymmetrical SNHL with a normal or near-normal opposite ear; helps distinguish cochlear from eighth-nerve pathology. |
| Tone-decay test (Carhart test) | Measures inability to sustain perception of a continuous tone just above threshold. Marked decay is classically associated with auditory-nerve involvement. | Suspected retrocochlear lesion, such as vestibular schwannoma. |
| Békésy audiometry | Patient traces thresholds for continuous and interrupted tones. Type II pattern favors cochlear pathology; Types III/IV may suggest retrocochlear disease. | Site-of-lesion assessment in SNHL and assessment of test reliability. |
| Loudness discomfort level / UCL | Determines the intensity at which sound becomes uncomfortably loud. | Demonstration of recruitment, hyperacusis assessment, and setting safe hearing-aid output. |
| Speech discrimination and rollover test | Measures word recognition at increasing intensities. Disproportionately poor discrimination or rollover raises concern for retrocochlear involvement. | Speech-understanding complaints, hearing-aid evaluation, and suspected retrocochlear pathology. Poor speech discrimination despite relatively preserved pure-tone thresholds warrants further work-up. |
Historically, SISI and tone-decay were central for differentiating cochlear from retrocochlear disease. Their results are not fully specific, so modern evaluation of asymmetric SNHL or suspected vestibular schwannoma usually relies on audiometry plus ABR and/or MRI rather than any single special test. This limitation is described in Scott-Brown's Otorhinolaryngology Head & Neck Surgery, which notes that imaging and objective tests have largely replaced these tests for localization. A recent systematic review also addresses audiological criteria used to select patients for MRI in suspected vestibular schwannoma (PubMed PMID 42531485).
2. Impedance or immittance audiometry
Includes tympanometry, acoustic reflex testing, and reflex-decay testing.
| Component | Main indication |
|---|---|
| Tympanometry | Assesses tympanic-membrane mobility and middle-ear pressure. Used for otitis media with effusion, Eustachian-tube dysfunction, tympanic-membrane perforation, ossicular problems, and otosclerosis. A flat trace supports middle-ear effusion. |
| Acoustic stapedius reflex | Helps assess the middle ear, cochlea, auditory nerve, and facial nerve reflex arc. Useful in suspected otosclerosis, facial palsy, and retrocochlear pathology. |
| Reflex decay | Decay of an acoustic reflex during sustained stimulation may suggest retrocochlear involvement. |
Immittance testing assesses middle-ear sound transmission, while ABR assesses neural transmission from cochlea through brainstem, as summarized in Clinical Methods.
3. Objective audiometry
These do not require a reliable behavioural response.
| Test | Main indication |
|---|---|
| BERA / ABR (Brainstem Evoked Response Audiometry) | Estimation of hearing threshold in infants, young children, sedated/uncooperative patients, suspected auditory neuropathy, and suspected retrocochlear lesion. Also used in newborn hearing screening pathways. |
| ASSR (Auditory Steady-State Response) | Frequency-specific objective threshold estimation, particularly in infants and patients with severe or profound hearing loss; useful when fitting hearing aids or considering cochlear implantation. |
| OAE (Otoacoustic emissions) | Tests outer hair-cell function. Used for newborn hearing screening, monitoring ototoxicity/noise-related cochlear injury, and distinguishing normal cochlear outer-hair-cell function from many cochlear losses. OAEs can be present in auditory neuropathy. |
| Electrocochleography (EcochG) | Records cochlear/auditory-nerve potentials. Used as an adjunct in suspected Ménière disease/endolymphatic hydrops, auditory neuropathy, and selected intraoperative assessments. |
4. Tests for non-organic or functional hearing loss
| Test | Indication |
|---|---|
| Stenger test | Best test for suspected unilateral or asymmetrical non-organic hearing loss. A positive Stenger result supports functional exaggeration of unilateral loss. |
| Lombard test | Detects non-organic hearing loss by observing involuntary increase in voice intensity when masking noise is introduced. |
| Doerfler-Stewart test | Speech-based test for suspected functional unilateral hearing loss. |
| Objective tests: OAE and ABR | Used to confirm cochlear/neural function when behavioural audiometry is unreliable or inconsistent. |
Short exam-oriented summary
- Cochlear lesion/recruitment: SISI, ABLB, UCL, Békésy Type II.
- Retrocochlear lesion: Tone decay, Békésy Type III/IV, speech rollover, reflex decay, ABR, MRI.
- Middle-ear disease: Tympanometry and acoustic reflexes.
- Infants or uncooperative patients: OAE, ABR/BERA, ASSR.
- Functional hearing loss: Stenger, Lombard, objective electrophysiological tests.
- Hearing-aid planning: Speech audiometry, UCL/MCL, speech-in-noise testing, real-ear measures.
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