Otological Seminar
Evoked Otoacoustic Emission (EOAE)
2003-5-7
R3 KST
A. Cochlear amplifier:
Electromotility of OHCs (Prestin): ? mechanical source of OAE, Hz-tunning,
enhance vibration of basilar membrane at CF (selectivity), e.g. at low stimulus
levels due to non-linear cochlear characteristics: The peak of traveling wave grow
linearly at low stimulus levels, compressed at moderate to high levels.
B. OAE:
a. Pre-neural byproducts of cochlear amplifier (OHCs): OAE persist despite 8th
nerve is blocked; destruction of OHCs: increases HL~ 60 dB
b. Most efferents: to OHCs: CNS regulation (independent of CN 8 afferent fibers)
c. OAE are low-level signals: Increased SNR by time-synchronized averaging of
signal (amplitude, phase), decreased noise and well-fitted probe
C. SOAE:
a. multiple Hz, (+) in ~ 50 % normal hearing children/adults, (-) > 25-30 dB HL,
b. Higher prevalence in female, right ear, Neonates and infants (2-5 kHz, 8.5 dB) >
children and adults (1-2 kHz, 2.6 dB), and the other ear (+).
c. SOAE: responsible for < 10 % tinnitus cases (apparent: only 2.4%)
D. Characteristics of TEOAEs:
1. Click (COAE, broadband/BB), toneburst (TBOAE)
2. Evaluated in amplitude, amplitude/noise, percentage reproducibility. (Fig 22.4)
3. (+) ~ 100 % in ears with normal sensitivity & ME, (-) in HL > 30 ~50 dB
4. Increased latency with decreased Hz
5. Spectrum (& Hz latency): unique to each individual, depends on:
a. Stimulus: COAE BB & lower level, TBOAE more Hz specific
b. Recording (Time window): Shorter  Loss of low Hz (Longer latency)
c. Filter: more elimination from the start more loss of high Hz (Shorter lactency)
6. Amplitude:
a. Non-linear TEOAE Amplitude Vs stimulus level (Fig. 22.6)
b. varies widely across individual, Hz,
c. COAE: lower & BB spectrum level
TBOAE: narrower and higher spectrum
SOAE: affect spectrum/level of TEOAEs: (+)higher amplitude & more peaks
1
7. Age: No effects on TEOAE level or thresholds.
Higher level in female (? smaller EEC), Right ear
8. Criteria: COAE amplitude> 6 dB SPL, reproducibility >70%, 3dB SNR
E. Characteristics of DPOAEs:
1. Interaction of two closer Hz (f2> f1) “Distortion” of output/product due to
non-linear cochlear systems
2. Exams with constant primary tone levels & differences, Hz & ratio (f2/f1=1.22)
3. Amplitude (Non-linear increase Vs stimulus levels as as TEOAEs):
a. Lower: if SOAE (-), and increased age (Hz -dependent Hz, e.g. high Hz, not
stimulus levels or SOAE status-dependent) & threshold & f2 Hz.
(Sex and Right/left ears: no significant difference)
b. Individualized (Fig 22.9)  clinical exams at lower/moderate primary stimulus
levels. (Higher not as effective due to non-linear, e.g. in identifying HL)
4. 100 % in normal sensitivity & ME, (-) in HL > 50 dB, more stable over time.
5. DP grams: (& 22.10)
suppression of 2f1-f2 DPOAE by f2  2f1-f2 reflects f2 hearing sensitivity.
F. Clinical applications:
A. Identification of HL
1. TEOAEs: best in 2, 4kHz HL by
a. Relative operating characteristic (ROC) curve: (Fig. 22.14)
Criteria of parameters: COAE level >6 dB, COAE/noise>3, reproducibility> 70%
(equal in dDx of (+/-) HL by the 3 parameters in BB-TEOAE & No difference in
COAE or TBOAE), mid-level (65-80 pSPL) stimulus, dDx HL by 20-25 dB.
b. Multivariate/logistic regression analysis of OAE & OAE/noise etc.:
~100 % accuracy, e.g. with two stimulus types (two click & four TBs) at two levels
(e.g. 65/86 dB)
2. DPOAE: better in 4, 6 kHz.
a. DPOAE/noise ratio most sensitive (Vs DPOAE level) (Fig. 22.16): also can
increase accuracy by .
b. logistic regression analysis (9 dB criteria of DPOAE level)
b. Hz (max at 2f1 –f2, e.g. f2/f1=1.22), Stimulus level (unequal primaries at
mid-levels, L1=L2+10~15 dB, e.g. L2 = 55 dB, more sensitive than equal high
levels) (Fig 22.7 & 8)
3. Both TEOAEs and DPOAEs: Hz-specific, similar accuracy at 2kHz,
4. DPOAE: measures higher HL to 50 dB, TEOAE: 25-30 dB HL
2
B. Prediction of hearing threshold:
1. TEAOAE: Low correlation (too complex relationship & high variablity) between
COAE/TBOAE and behavioral threshold for prediction of behavioral thresholds.
2. DPOAEs:
a. High Variability of DPOAEs & I/O (Too large range) across individuals with
similar audiometric threshold unlikely to predict behavioral threshold with
DPOAE amplitudes or thresholds. (Despite correlation between DPOAE
levels/thresholds & DPOAE/noise and audiometric thresholds in high 4, 8 kHz).
b. DPOAE/noise level Vs audiometric threshold to dDx severity of HL (Fig. 22.17)
C. NB hearing screening:
TEOAEs (as effective as DPOAE): decreased fail rates (3-10%) by decreased noise,
more test experience etc.
G. dDx
1. Auditory neuropathy: normal EOAE, but HL in behavioral threshold, abnormal
ABR and acoustic reflexes
2. ? Acoustic neuroma: some EOAE (+) (? Decreased cochlear blood flow), others (-)
3. Monitor HL: ototoxic agents, NIHL, Meniere’s dz etc.
References:
1. Handbook of clinical audiology, 5th eds, Katz J, et al. pp. 440-466
2. Liberman MC, et al. Prestin is required for electromotility of the outer hair cell and for the cochlear
amplifier. Nature 2002;419:300-304
3. Gorga MP, et al. Otoacoustic emissions form normal- hearing and hearing-impaired subjects:
distortion product responses. J Acoust Soc Am 1993;93:2050-2060
4. Gorga MP, et al. From laboratory to clinic: a large scale study if distortion product otoacoustic
emissions in ears with normal hearing and ears with hearing loss Ear Hear 1997;18:440-55
5. Stover L, et al. Toward optimizing the clinical utility of distortion product
otoacoustic emission measurements. J Acoust Soc Am 1996;100:956-967
6. Stover L, et al. The effects of aging on otoacoustic emissions J Acoust Soc Am 1993;94:2670-2681
7. Vinck BM, et al. Multiple analysis of otoacoustic emissions and estimation of hearing threshold:
Transient evoked otoacoustic emissions. Audio 1998;37:315:334
8. Prieve BA, et al. Analysis of transient evoked otoacoustic emissions in normal hearing and
hearing-impaired ears. J Acoust Soc Am 1993;93:3308-3319
3