Electrophysiological Measures of the Auditory System
description
Transcript of Electrophysiological Measures of the Auditory System
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