Electrophysiological Measures of the Auditory System

Perry C. Hanavan, Au.D.Audiologist

Electrophysiological Tests

• Immittance• Evoked Potential• Otoacoustic Emissions

First

• Observations– Appearance of person, age, gender, unusual

characteristics– Patient information, case history, self-

assessment, other clinical data– Otoscopic exam

Electrophysiologic Triage Trio

• Tympanogram• Acoustic Reflex• Otoacoustic Emissions

Triage TrioTympanogram

Type A

Acoustic ReflexesAbsent or Elevated

OAEAbsent or Depressed

TympanogramType A

TympanogramType A

Acoustic ReflexesNormal RangeNormative Data

OAENormal

Acoustic ReflexesNormal

OAEPresent

Normal peripheral and lower brainstem function (possible APD) normal hearing

Auditory Neuropathy/

Auditory Dys-synchrony

OAEAbsent

TympanogramType A

Cochlear loss, outer hair cell loss, ABR

normal, hearing aids beneficial

TympanogramNot Type A

Severe or profound inner ear loss (occasionally otosclerosis)

Conductive or mixed loss (possible severe/profound loss)

Acoustic ReflexesAbsent

Acoustic ReflexesAbsent

OAEAbsent

Immittance

• Ear Canal Volume (ECV or PVT)• Tympanometry• Static Compliance• Acoustic Reflex, Decay, & Latency

Ear Canal Volume

• Measure at +200 mmH20• Provides measure of volume of external

ear canal• Volumes based on age• Volumes greater than 2.5 mmH2O (adult)

or 2.0 (child) suggest:– Perforation or– Patent PE tube

Tympanometry

• Objective measure of the function of the TM and middle ear

• 5 or 6 basic shapes

Which type tympanogram indicates normal middle ear function?

A.AB.B loC.CD.AdE.AsF.Ap

Tympanogram Types

Type A TympanogramOE ME IE AN CNS

Type AD TympanogramOE ME IE AN CNS

Type AS TympanogramOE ME IE AN CNS

Type BLow TympanogramOE ME IE AN CNS

Type BHi TympanogramOE ME IE AN CNS

Type C TympanogramOE ME IE AN CNS

Type AP TympanogramOE ME IE AN CNS

Static Compliance (Peak Compliance)

Static Compliance – SCEar Canal Volume – ECVMiddle Ear Volume – MEVPeak Volume – PV

SC = PV – ECV

The ECV reflects the volume in the ear canal as the ECV measure is often made at +200 in which the TM is very stiff reflecting most of the acoustic energy (acoustic energy is not absorbed by middle ear)

The PV reflects the ear canal volume AND the middle ear volume as the measure is made where the tympanogram peaks or in other words, the measure is made where the TM is most compliant or mobile; thus it is assumed that the PV represents the volume of the OE and the ME.

Thus, the SC, or PV minus the ECV, represents the ME volume

The normal range for our equipment ranges from .25 to 2.5

OEEar Canal Volume

(ECV)

MEVolume

(Static Compliance)

OE and MEVolume

(Peak Volume)

Static Immitance• The terms peak compliance (ml, cc or cm3) and peak

static acoustic admittance (mmho) can be used interchangeably when using a 226Hz probe tone.

• Most references use the term static admittance (SA) when reporting results.

• In the most recent edition of Katz et al 2009, there is a comprehensive list of large scale studies that reported normative ranges for peak SA.

• Summarizing across these studies, the 90% range for a normal tympanogram is .2 to 1.8. 

Shanks, J., & Shohet, J (2009). Tympanometry in clinical practice. In J. Katz, L. Medwetsky, R. Burkard, & L. Hood (Eds.), Handbook of clinical audiology (6th ed.) (pp. 157-188). Baltimore: Lippincott, Williams & Wilkins.

Static Compliance(Peak Compliance)

Acceptable Range by Age

0.2

0.9

Flaccid: disarticulation, flaccid TM, etc.

Normal mobility

Stiff: otosclerosis, fluid, tympanosclerosis, etc.

1.8

0.3

Child Adult

Tympanometric Width

Normative Cutoff Values (if larger, abnormal)Infant: 235 daPa1 – 10 yr olds: 200 daPaAdults: 235 daPa

ART

Abnormal ART

Recruitment

• ART – AC PT =< 60 indicates recruitment– (cochlear

pathology)

Reflex Decay

Bekesy vs. Gold

• Bekesy– Passive– Broadly tuned– Studied dead cochlea– Awarded Nobel Prize

• Gold– Active– Fine tuned– Studied live responses– Went on as an

astronomer

Otoacoustic Emissions• David Kemp disovered

OAEs• Acoustic energy produced

by the cochlea and recorded in the external auditory canal

• Most likely energy produced by outer hair motility and possibly outer hair cell cilia

• Objective test– DPOAE– TEOAE

DPOAE

DPOAE

Tympanogram type?

Acoustic thresholds?

OAE results?

Expected type of hearing loss?

ECV? Normal?

Static Compliance? Normal?

Tympanogram type?

Acoustic thresholds?

OAE results?

Expected type of hearing loss?

ECV? Normal?

Static Compliance? Normal?

Tympanogram type?

Acoustic thresholds?

OAE results?

Expected type of hearing loss?

ECV? Normal?

Static Compliance? Normal?

Tympanogram type?

Acoustic thresholds?

OAE results?

Expected type of hearing loss?

ECV? Normal?

Static Compliance? Normal?

Tympanogram type?

Acoustic thresholds?

OAE results?

Expected type of hearing loss?

ECV? Normal?

Static Compliance? Normal?

Tympanogram type?

Acoustic thresholds?

OAE results?

Expected type of hearing loss?

ECV? Normal?

Static Compliance? Normal?

Why was the AB-Gap in the left ear not expected?

Evoked Potentials

• EcochG• ABR• Middle Latency• Late Response

OAE & ABR Screen

ABR Wave

I Auditory Nerve

II Auditory Nerve

III Cochlear Nuclei

IV SOC

V ???

Absolute Latencies

Interwave Latencies

ABR Supra-aural Phone Data

Add .9 to Absolute values when using insert phones

Newborn ABR Latency Data

Auditory Processing• Dichotic Sentence

Identification– Dichotic sentence testing is a

binaural separation test procedure used to determine levels of auditory maturation, hemispheric dominance for language, and to identify disordered or damaged central auditory pathways.

– The advantage of testing binaural separation with both word and sentence stimuli is to compare findings obtained with both simple and more complex linguistic levels of auditory stimuli.

Dichotic Sentence Identification• The DSI test uses 6 of the same sentences as the

SSI-ICM test but presents 1 sentence to each ear simultaneously at 50-dB SL, and the participant is asked to select from a printed list which 2 sentences were heard.

• Fifer et al showed that the test is resistant to the effects of SNHL below 50 dB HL.

• The DSI test is administered in both a free and a directed mode.

• In the directed mode, only the sentence heard in test ear is noted, whereas in the free mode, the sentences heard in both ears are reported.

• Five presentations are used if the score is 100%; otherwise, another 5 sentences per ear are administered.

• Scores are better in the directed mode than in the free mode, and the right ear scores are normally higher in adults than the left ear scores, presumably due to age related corpus callosum dysfunction.

• Normal scores are 80% correct and above.

Pediatric Speech Intelligibility(Closed Set)(Recorded)

• PSI– Both monosyllabic words

and sentences recorded in quiet and with competition.

– Employs color plates with pictures of animals (animals used to avoid ethnic biases) which represent either the sentences or the words.

– Investigates peripheral and auditory processing disorders.

BKB-SIN (Adults)

BKB-SIN (Children)

Fig 8-1

ECV= .5

ECV= .6

Fig 8-2

ECV= .9

ECV= 1.3

Fig 8-3

Fig 8-4

Fig 8-5

Fig 8-6

Fig 8-7

Fig 8-8

Fig 8-12

Fig 8-14

Fig 8-15