Assessment of Assessment of Peripheral and Peripheral and

Central Auditory Central Auditory FunctionFunctionFebruary 11, 2004February 11, 2004

Steven T. Wright, M.D.Steven T. Wright, M.D.

Arun K. Gadre, M.D.Arun K. Gadre, M.D.

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Auditory FunctionAuditory Function Complex auditory pathwayComplex auditory pathway Peripheral Auditory AssessmentPeripheral Auditory Assessment

Basic armament of the otolaryngologistBasic armament of the otolaryngologist

Central Auditory AssessmentCentral Auditory Assessment Relatively new interestRelatively new interest MultidisciplinaryMultidisciplinary

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Ossicular AmplificationOssicular Amplification

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AnatomyAnatomy

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Tonotopic organizationTonotopic organization

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AnatomyAnatomy

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Peripheral Auditory Peripheral Auditory AssessmentAssessment

Pure Tone AudiometryPure Tone Audiometry Speech AudiometrySpeech Audiometry Acoustic ImmittanceAcoustic Immittance Auditory Brainstem ResponsesAuditory Brainstem Responses ElectrocochleographyElectrocochleography Otoacoustic EmissionsOtoacoustic Emissions

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Pure Tone AudiometryPure Tone Audiometry Most common Most common Pure tones (sinusoids) are Pure tones (sinusoids) are

tonotopically maintained by the tonotopically maintained by the cochlea.cochlea.

Air conduction testingAir conduction testing Octave frequenciesOctave frequencies Interoctave frequenciesInteroctave frequencies

Bone conduction testingBone conduction testing

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Pure tone audiometryPure tone audiometry

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Decibel ScaleDecibel Scale Audiologic unitsAudiologic units

dB SPL: sound pressure leveldB SPL: sound pressure level dB HL: hearing leveldB HL: hearing level dB SL: sensation leveldB SL: sensation level

Audiometric 0Audiometric 0 dB= 10 log 10dB= 10 log 10

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Frequency SensitivityFrequency Sensitivity Human hearing spectrum from 20- 20,000Hz.Human hearing spectrum from 20- 20,000Hz. Differentially sensitiveDifferentially sensitive

125Hz : 45dB125Hz : 45dB 1000Hz: 6.5dB1000Hz: 6.5dB 10,000Hz: 20dB10,000Hz: 20dB

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Audiogram LevelsAudiogram Levels NormalNormal

0 - 20dB 0 - 20dB MildMild

20 - 40dB20 - 40dB ModerateModerate

40 – 60dB40 – 60dB SevereSevere

> 60 dB> 60 dB

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Audiogram- Speech Audiogram- Speech BananaBanana

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CrossoverCrossover Audiometric results are only valid Audiometric results are only valid

when the results are actually of the when the results are actually of the test ear.test ear.

Interaural attenuation reflects Interaural attenuation reflects crossover.crossover.

Air conduction from 40-80dBAir conduction from 40-80dB Bone conduction even at 0dBBone conduction even at 0dB

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MaskingMasking The audiometric technique used to The audiometric technique used to

eliminate responses by the non-test eliminate responses by the non-test ear.ear.

An appropriate noise is presented to An appropriate noise is presented to the non-test ear while the test ear is the non-test ear while the test ear is being tested.being tested.

Masking level must exceed the non-Masking level must exceed the non-test ear threshold, but not create test ear threshold, but not create crossover.crossover.

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Speech AudiometrySpeech Audiometry Determines how well a person hears Determines how well a person hears

and understands speech.and understands speech. Spondee wordsSpondee words SRTSRT SRT should be in close correlation SRT should be in close correlation

with PTA.with PTA.

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Speech AudiometrySpeech Audiometry Word recognition scoring %Word recognition scoring % 20-50 Phonetically balanced words20-50 Phonetically balanced words Conductive hearing lossConductive hearing loss

Excellent WRSExcellent WRS Sensorineural hearing lossSensorineural hearing loss

Poor WRSPoor WRS RolloverRollover

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RolloverRollover Code intensity of neural discharges Code intensity of neural discharges

usually occurs by 3 mechanisms:usually occurs by 3 mechanisms: Pure monotonicPure monotonic

- - - - - - - - - --------------- - - - - - - - - -------------- Monotonic at low intensityMonotonic at low intensity

- - - - - - - - - - - - - - -- - - - - - - - - - - - - - - Monotonic with reversal at increasing Monotonic with reversal at increasing

frequencyfrequency

- - - - - - - - - - -- - - - - - - - - - -

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Auditory behavior index for Auditory behavior index for infantsinfants

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Acoustic ImmittanceAcoustic Immittance Impedance: resistance to acoustic Impedance: resistance to acoustic

flowflow Admittance: ease of acoustic flowAdmittance: ease of acoustic flow Tested by:Tested by:

TympanometryTympanometry Acoustic Stapedial ReflexAcoustic Stapedial Reflex

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TympanometryTympanometryby Jergerby Jerger

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Stiffness vs. MassStiffness vs. Mass

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Acoustic Stapedial ReflexAcoustic Stapedial Reflex Lowest intensity required to elicit a Lowest intensity required to elicit a

stapedial muscle contraction.stapedial muscle contraction. 3 primary acoustic reflex 3 primary acoustic reflex

characteristicscharacteristics Presence or absence of the reflexPresence or absence of the reflex Reflex thresholdReflex threshold Reflex DecayReflex Decay

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Acoustic Reflex DecayAcoustic Reflex Decay Measures the ability of the stapedius Measures the ability of the stapedius

muscle to maintain sustained muscle to maintain sustained contraction.contraction.

Lower frequency tone/noise for 10 Lower frequency tone/noise for 10 secondsseconds

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Acoustic Reflex in Cochlear Acoustic Reflex in Cochlear DisordersDisorders

Primarily determined by the degree Primarily determined by the degree of hearing loss.of hearing loss.

Less than 50dB: normalLess than 50dB: normal Between 50-80dB: proportionally Between 50-80dB: proportionally

elevatedelevated Greater than 50dB: absentGreater than 50dB: absent

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Acoustic ReflexAcoustic ReflexTone vs. NoiseTone vs. Noise

Broadband Noise usually has 20-Broadband Noise usually has 20-25dB lower thresholds than the 25dB lower thresholds than the reflex thresholds for tones.reflex thresholds for tones.

Physiologically not possible to have Physiologically not possible to have behavioral thresholds higher than behavioral thresholds higher than acoustic reflex thresholds for tones. acoustic reflex thresholds for tones. (malingerers)(malingerers)

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Facial ParalysisFacial Paralysis Absent or abnormal stapedial reflex Absent or abnormal stapedial reflex

when the recording probe is when the recording probe is ipsilateral to the side of the lesion.ipsilateral to the side of the lesion.

Can also be helpful in locating Can also be helpful in locating lesions proximal or distal to the lesions proximal or distal to the stapedial muscle.stapedial muscle.

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Eighth nerve lesionsEighth nerve lesions Absent reflexes when stimuli is Absent reflexes when stimuli is

presented to the affected ear.presented to the affected ear. Reflexes in eighth nerve lesions are Reflexes in eighth nerve lesions are

not dependent on the degree of not dependent on the degree of hearing loss.hearing loss.

Rapid reflex decayRapid reflex decay

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Auditory Brainstem Auditory Brainstem ResponsesResponses

Impulses that are generated by the Impulses that are generated by the auditory neural pathway that can be auditory neural pathway that can be recorded on the scalp.recorded on the scalp.

Not a direct measure of hearing.Not a direct measure of hearing. Detected as early as 25wks Detected as early as 25wks

gestation.gestation. Not affected by sleep, sedation, or Not affected by sleep, sedation, or

attention.attention.

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Click or Transient EvokedClick or Transient EvokedABRABR

Most widely usedMost widely used Moderate intensity levels with Moderate intensity levels with

resultant firing of a wide range of resultant firing of a wide range of neural frequency units.neural frequency units.

Repeatable Wave V to within 10dB Repeatable Wave V to within 10dB of behavioral responses.of behavioral responses.

Limited by frequency specificityLimited by frequency specificity

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Tone Burst ABRTone Burst ABR More accurate results than click-More accurate results than click-

evoked ABRevoked ABR Increased latency periods than click-Increased latency periods than click-

evoked.evoked.

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Bone Conduction ABRBone Conduction ABR As reliable and repeatable as air As reliable and repeatable as air

conduction ABR.conduction ABR. Particularly useful in structural Particularly useful in structural

abnormalitiesabnormalities Canal Atresia or stenosisCanal Atresia or stenosis

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ABRABR Primary goal is a clear and reliable Primary goal is a clear and reliable

Wave IWave I Wave I : distal 8Wave I : distal 8thth nerve nerve Wave II : proximal 8Wave II : proximal 8thth nerve nerve Wave III : cochlear nucleiWave III : cochlear nuclei Wave IV : SOCWave IV : SOC Wave V : Lateral LemniscusWave V : Lateral Lemniscus

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ABRABR

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ABRABRInfant vs AdultInfant vs Adult

Less waveform morphologyLess waveform morphology Increased absolute and interwave Increased absolute and interwave

latencieslatencies Should correct by 18-24 months of Should correct by 18-24 months of

age.age.

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ElectrocochleographyElectrocochleographyEcoGEcoG

Measures stimulus related potentials Measures stimulus related potentials of the most peripheral portions of of the most peripheral portions of the auditory system.the auditory system.

3 major components:3 major components: Cochlear microphonicCochlear microphonic Summating potentialSummating potential Action potentialAction potential

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EcoGEcoGElectrode placementElectrode placement

NoninvasiveNoninvasive Ear canalEar canal

>50%>50% Tympanic membraneTympanic membrane

>40%>40%

InvasiveInvasive TranstympanicTranstympanic

>30%>30%

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EcoGEcoGMeniere’s diseaseMeniere’s disease

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Otoacoustic EmissionsOtoacoustic Emissions Low energy sounds produced by the Low energy sounds produced by the

cochlear outer hair cells.cochlear outer hair cells. Cochlear amplification.Cochlear amplification. Spontaneous emissionsSpontaneous emissions

Not present in greater than 25dB hearing Not present in greater than 25dB hearing loss.loss.

Evoked EmissionsEvoked Emissions Transient evokedTransient evoked Distorted ProductDistorted Product

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TEOAETEOAE Transient stimuli, clicks, evoke emissions Transient stimuli, clicks, evoke emissions

from a large portion of the cochlea.from a large portion of the cochlea. Generally present when hearing Generally present when hearing

thresholds are below 35dB.thresholds are below 35dB. AdvantagesAdvantages

Reliable separate normal from abnormal at Reliable separate normal from abnormal at 20-30dB20-30dB

FastFast DisadvantagesDisadvantages

Poor at higher frequenciesPoor at higher frequencies

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DPOAEDPOAE DP are additional tones that are DP are additional tones that are

created when two tones are created when two tones are presented. f1 and f2presented. f1 and f2

DP occurs at 2(f1-f2) by a nonlinear DP occurs at 2(f1-f2) by a nonlinear process.process.

Generally present when hearing Generally present when hearing thresholds are below 50dB.thresholds are below 50dB.

Advantage is higher frequency Advantage is higher frequency (6000Hz)(6000Hz)

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OAEOAE

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OAE and middle ear OAE and middle ear pathologypathology

Transmission properties of the Transmission properties of the middle ear directly influence the middle ear directly influence the OAE characteristics.OAE characteristics. Otitis mediaOtitis media NewbornsNewborns Tympanic membrane perforationsTympanic membrane perforations

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Central Auditory Central Auditory ProcessingProcessing

No accepted definition of CAP.No accepted definition of CAP. Task Force on CAP consensus and Task Force on CAP consensus and

developmentdevelopment Sound localizationSound localization Auditory discriminationAuditory discrimination Auditory pattern recognitionAuditory pattern recognition Temporal aspects of auditionTemporal aspects of audition Auditory performance decrements with Auditory performance decrements with

competing and degraded acoustic signals.competing and degraded acoustic signals.

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CAPD CategoriesCAPD Categories DecodingDecoding Tolerance Fading MemoryTolerance Fading Memory IntegrationIntegration OrganizationOrganization

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Buffalo ModelBuffalo Model Takes into account the classification Takes into account the classification

of CAPD as well as speech and of CAPD as well as speech and language evaluation and academic language evaluation and academic characteristics.characteristics.

CAP batteryCAP battery Staggered Spondaic Word (SSW) testStaggered Spondaic Word (SSW) test Phonemic Synthesis (PS) testPhonemic Synthesis (PS) test Speech-in-Noise (SN) testSpeech-in-Noise (SN) test Masking Level Difference (MLD) testMasking Level Difference (MLD) test

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Decoding CategoryDecoding Category Most common (50%)Most common (50%) Breakdown of auditory processing at Breakdown of auditory processing at

the phonemic level.the phonemic level. Difficulty reading and speaking & Difficulty reading and speaking &

Articulation Errors “r” & “l”Articulation Errors “r” & “l” Posterior temporal lobePosterior temporal lobe

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Decoding categoryDecoding category Management strategies center on Management strategies center on

improving phonemic and improving phonemic and metaphonemical skills.metaphonemical skills. Hooked on Phonics and Phonemic Hooked on Phonics and Phonemic

Synthesis Skills programSynthesis Skills program Clear and concise instructionsClear and concise instructions Outlining objectivesOutlining objectives Written instructionsWritten instructions

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Tolerance-fading memory Tolerance-fading memory categorycategory

Second most common (20%)Second most common (20%) Poor auditory memory and difficulty Poor auditory memory and difficulty

understanding speech in adverse conditions.understanding speech in adverse conditions. Deficits in expressive language and writing.Deficits in expressive language and writing. Impulsive responders, short attention spans.Impulsive responders, short attention spans. Auditory continuous performance test can Auditory continuous performance test can

screen for ADHD.screen for ADHD. Linked to Broca’s area of the inferior frontal Linked to Broca’s area of the inferior frontal

lobe.lobe.

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Tolerance-fading Tolerance-fading memorymemory

Management focuses on improving Management focuses on improving the signal to noise ratio and the signal to noise ratio and strengthening short term memory strengthening short term memory skills.skills.

FM system is beneficial.FM system is beneficial. Noise desensitization.Noise desensitization. Earplugs and quiet study areas.Earplugs and quiet study areas.

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Integration categoryIntegration category Difficulty integrating auditory information Difficulty integrating auditory information

with visual and nonverbal aspects of with visual and nonverbal aspects of speech.speech.

Deficits of the corpus callosum and angular Deficits of the corpus callosum and angular gyrus.gyrus.

Dyslexics and poor readerDyslexics and poor reader ManagementManagement

Improving signal to noise ratioImproving signal to noise ratio Structured phonetically based reading Structured phonetically based reading

exercisesexercises

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Organizational categoryOrganizational category Least common category.Least common category. Characterized by reversals and Characterized by reversals and

sequencing errors.sequencing errors. Individuals are often disorganized at Individuals are often disorganized at

school and at home.school and at home. ManagementManagement

Improving sequencing skills and Improving sequencing skills and organizational habits.organizational habits.

Consistent routines, checklists, Consistent routines, checklists, calendars.calendars.

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CAPDCAPD Multidisciplinary approachMultidisciplinary approach

OtologistOtologist Speech PathologistSpeech Pathologist AudiologistAudiologist SchoolsSchools

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ConclusionConclusion Peripheral AssessmentPeripheral Assessment

Measures of objective hearingMeasures of objective hearing Measures of physiologic hearingMeasures of physiologic hearing

Central AssessmentCentral Assessment

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