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Detecting Noise-Induced Hearing Loss

Using Otoacoustic Emissions

Brenda L Lonsbury-Martin PhD

Department of Otolaryngology--Head & Neck SurgeryLoma Linda University Medical Center

[email protected]

Research Service

VA Loma Linda Healthcare SystemLoma Linda CA

[email protected]


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Detecting NIHL Using OAEs

presentation outline

brief review types of OAEs re theirclinical utility for NIHL detection

present a few examples illustratingsome clinical applications re NIHL review current research findings that

hold promise for ability of future clinicalOAE tests to detect early NIHL


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Otoacoustic Emissions

all types discovered by David Kemp by 1978

transient-evoked OAEs distortion-product OAEs

stimulus-frequency OAEs spontaneous OAEs

sounds emitted from the cochlea eithernaturally or in response to acousticstimulation


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sounds emitted by the cochlea

clinical interest in OAEs:their promise in providing an objectivemeasure of behavioral audiogram newborn hearing screening screening toddlers, ill patients forototoxicity, confused elderly, workers inhearing-conservation programs, multiply

handicapped


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Auditory Input

anatomical pathway

OHCCochlear

Amplifier

DescendingEfferent

System


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Types of OAEs

current consensus of field

Primary Generator Sources

TEOAEs, SFOAEs, SOAEs:coherent linear reflection primarily from

irregularities around test-frequency place

DPOAEs:nonlinear distortion primarily from f2 place

with reflection from DP-frequency place


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OAEs Sources

a common view of field

reflection--OHC lateral wallelectromotility

distortion--nonlinearities inopening and closing oftransduction channels at tips ofstereocilia likely introduce basiccochlear nonlinearity


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beneficial clinical features

measure functional status of thehearing receptor type (OHC) that ismost sensitive to cochlear

dysfunction: external agents: noise, ototoxins

internal agents: bacteria, viruses

genetic factors: familial disorders,aging


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beneficial features

measured non-invasively andobjectively thus allowing for:

simple set-up timerapid response acquisitionsystematic assessment restimulus

frequency and level domains


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simple equipment set-up

(Kemp 78)


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beneficial clinical features

operate at low to moderatestimulus levels:

thus have the potential to detect theonset stages of cochlear dysfunction


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beneficial features

measurement instrumentation is:commercially available

relatively inexpensiveeasy to operate


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Transient Evoked Otoacoustic Emissions

ILO88 display


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Transient-Evoked Otoacoustic Emissions

advantages for clinical use

measurement procedure based onfamiliar evoked response methodology:

click-based synchronous (time) averaging

easily measured with most successfuldevice that was commercially available

early on:Otodynamics Ltd ILO88 (1988)


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Transient Evoked Otoacoustic Emissions

normative data

normal

NIHL

(Whitehead et al 96)


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Distortion Product Otoacoustic Emissions

human 2f1-f2


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Distortion Product OAEs

normal vs abnormal ear

Norm NIHL


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Noise-Induced Hearing Loss

symmetrical loss49 y/o M with

25-y Hx ofexposure tofactory noise


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asymmetrical loss

37 y/o M with20-y Hx as latheoperator withR ear (opencircles) nearest

to equipment


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early stages

21 y/o M ex-US

Coast Guard artilleryspecialist with R ear(open circles) nearestto gun barrel of deck-mounted artillery


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DP-Gram

n=20 ears

n=12(Meinke et al 05)

relating hearingthresholds to DP-gram levels hasmostly failed


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Stimulus-Frequency Otoacoustic Emissionsnormal-hearing human

fine structure


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Site of 2f1-f2 DPOAEGeneration


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OAE Generation Mechanisms

clinical implications of basic research

clinical measurement of both typesof emission sources (ie, reflection,

distortion) or only 1 source maybe needed to maximize the powerand specificity of OAEs as probes

of cochlear function andestimators of behavioral hearing


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DP-Gram

eliminating fine structure

Heitmann, Janssen et al (96):developed single-generator DP-

grams (sigDPOAE)suppressing DP-frequency placewith higher-frequencysuppressor


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Distortion Product OAEs

response growth I/O function

22 y/o F


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DPOAE I/O Function

approaches for estimating threshold

fixed signal-to-noise ratio (SNR) criterion:eg, 6 dB measurement-based stopping rule

simple linear regression to extrapolate

DPOAE threshold resulted in modest correlations between

audiometric thresholds and DPOAEthresholds


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OAEs

detecting early NIHL

Marshall, Lapsley Miller: large-scale studies in military personnel:6-mo noise exposure re aircraft carrier duty

significant reductions in average OAElevels without changes in average

audiometric thresholds indicating earlydetection


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Early Detection of NIHL

recreational rifle shooter (R)

43 y/o normal-hearingF complains of:

decreased sensitivitytinnitus

difficulty in hearing inbackground noise


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Temporary Threshold Shift in Humans

DPOAE paradigm: L1-L2

(Sutton et al 94)

Noise Exposure:

test DPOAE=4 kHzexposure=2.8 kHz at

105 dB SPL for 3 min


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Average DPOAE Recovery From TTSeffects of L1-L2

(Sutton et al 94)

lower levels with

L1-L2=25 dB mostsensitive to TTS

relevant to hearing-conservation program

monitoring


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Temporary Threshold Shift

recovery of hearing vs DPOAE levels

(Sutton et al 94)


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DPOAEs in Ear-Canal

total space

TraditionalDP-gram

DPOAE level DPOAE Phase


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Site of 2f1-f2 DPOAEGeneration

distributedgeneratorsources


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Translate HumanDP-gram onto L/P Map


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Rabbit low frequency loss

ADP-gram

Low frequency loss


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Low frequency loss

ADP-gram vs ABR

Notch Loss


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Notch Loss

ADP-gram improvement

Notch Loss


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Notch Loss

ADP-gram vs ABR


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Other Applications of OAEs

noise-induced hearing loss

efferent system evaluation:resistant vs susceptible ears

identifying pseudohypacusis contribute towards decision(s) re

habilitative approach:optimizing digital hearing-aid fitting


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Pseudohypacusis Testingearphone emission in L ear

35 y/o Mtelephoneoperator


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Pseudohypacusis Testing35 y/o M - earphone emission in L ear

C l i


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Conclusions

most promising application of OAEs to NIHL

devising effective protocol for earlydetection of OHC dysfunction:

incorporation into civilian and militaryhearing-conservation programs


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Research on Otoacoustic Emissions

supported by

NIH/NIDCD: DC00613.21

NIH/NIDCD: DC003114.23 VA/RR&D: CL212L.2

VA/RR&D: C4494R.4

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