8/24/2015 1 Welcome to Cochlear Dead Regions and Implications for Fittings Presenter: Ted Venema PhD Audiologist, Speaker, Author Fran Vincent Membership and Marketing Manager Ted Annis Senior Marketing Specialist IHS Organizers: Housekeeping This presentation is being recorded CE credit is available! Visit ihsinfo.org for details Note taking handouts are available at ihsinfo.org on the webinar page. Feel free to download now!
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Slideshow - Cochlear dead regions-FINAL - Cochlear dead regions-FINAL.pdf8/24/2015 2 Agenda Describe cochlear dead regions in terms of cochlear hair cells and the cochlear traveling
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8/24/2015
1
Welcome toCochlear Dead Regions and Implications for Fittings
Presenter:
Ted Venema PhDAudiologist, Speaker, Author
Fran VincentMembership and
Marketing Manager
Ted Annis Senior Marketing Specialist
IHS Organizers:
Housekeeping
This presentation is being recorded
CE credit is available! Visit ihsinfo.org for details
Note taking handouts are available at ihsinfo.org on the webinar page. Feel free to download now!
8/24/2015
2
Agenda
Describe cochlear dead regions in terms of cochlear hair cells and the cochlear traveling wave
Outline audiograms associated with cochlear dead regions
Explain the rationale for the Threshold Equalizing (TEN) test
State some examples and implications of cochlear dead regions for hearing aid fittings
Q&A (enter questions in Question Box any time)
COCHLEAR HAIR CELLS, THE TRAVELING WAVE
& COCHLEAR DEAD REGIONS
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Cross Section of the Cochlea
TemporalBone
Helicotrema
SpiralLigament
ScalaVestibuli
ScalaMedia
ScalaTympani
SpiralGanglia
BasilarMembrane
Figure 1.2 Venema, T. Compression for Clinicians 2nd edition, Cengage 2006
Normal Inner & Outer Hair Cells
Figure 1.7 Venema, T. Compression for Clinicians, 2nd edition, Cengage 2006
Inner Hair cells
Afferent
Send soundinformation to the brain
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Damaged Outer Hair Cells
Figure 1.8 Venema, T. Compression for Clinicians, 2nd edition, Cengage 2006
Outer Hair cells
Efferent
Receive soundinformation from the brain
Outer Hair Cells: The Active Cochlear Mechanism
Note how embedded
OHCs actually pull tectorial membrane
down
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Cochlear Dead RegionsAre Not Due to Outer Hair Cell Damage
Total deafness in lows Looks like moderate low‐Hz SNHL
High‐Hz Dead Regions However…Have to Be Severe, Precipitous SNHL
OO OO
O
O
O
O O
Apex Base
OO
High‐Hz Traveling waveIn totally dead IHC region
Will stimulate healthy hair cellsIn mid & low‐Hz regions
Steep wave front must be intenseFor this to happen
Due to asymmetrical TW shapeSevere precipitous SNHL actuallylooks like mirror image of TW front
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For example…
OO OO
O
O
O
OO
Apex Base
OO
For Example…
OO OO
O
O
O
OO
Apex Base
OO
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For Example…
OO OO
O
O
O
OO
Apex Base
OO
“Cookie‐Bite” AudiogramsA Combination of the Above
O
O
O
O
OO
O
O
O
Apex Base
O
O
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TESTING FOR COCHLEAR DEAD REGIONS: THE THRESHOLD EQUALIZING NOISE
(TEN) TEST
TEN Test Noise
It is a broad band noise, delivered ipsilateral to tone
Has unique spectral shape
For normal HL, gives equal masked thresholds
Eg. 50 dB TEN gives 50 dB HL across all Hz’s
So no, you cannot use your speech masking noise
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TEN Noise Spectrum“
Hz
RelativedB
100 10,000
+10
‐20
Eg: 30 dB TEN…
Gives 30 dB HLThresholds
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Main Assumption Behind TEN Test
Soft ipsilateral TEN noise (eg. 30 dB HL) will elevate thresholds for low‐Hz tones.
Low‐Hz cochlear dead region resulting in 50 dB HL thresholds
Apex(lows)
Base(highs)
Why? Because “thresholds” in dead region come from high Hz’sThey do not truly arise from the low‐Hz hair cells
If the HL Is a True Moderate Low‐Hz SNHL (Not a Dead Region)
The soft ipsilateral TEN will have little effect
It will mask the healthy high‐Hz thresholds
And elevate them as a result…
But the low‐Hz thresholds won’t hear the TEN
And the thresholds will be unchanged
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Apex(lows)
Base(highs)
Main Assumption Behind TEN Test
Soft ipsilateral TEN noise (eg. 30 dB HL) will elevate thresholds for high‐Hz tones.
High‐Hz cochlear dead region resulting in 80 dB HL thresholds
Why? Because “thresholds” in dead region come from low Hz’sThey do not truly arise from the high‐Hz hair cells
If the HL Is a True Severe High‐Hz SNHL (Not a Dead Region)
The soft ipsilateral TEN will have little effect
It will mask the healthy low‐Hz thresholds
And elevate them as a result…
But the high‐Hz thresholds won’t hear the TEN
And the thresholds will be unchanged
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SOME EXAMPLES AND IMPLICATIONS FOR FITTINGS
Client with Mild‐Moderate SNHL Cochlear Dead Spots Not Suspected
Masked symbols: thresholds with 30 dB TEN
Figure 2.5 Venema, T. Compression for Clinicians,2nd edition, Cengage 2006
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Client with Profound High‐Hz SNHL Cochlear Dead Spots Suspected
Masked symbols: thresholds with 30 dB TEN
Figure 2.6 Venema, T. Compression for Clinicians,2nd edition, Cengage 2006
Client with Profound High‐Hz SNHL Cochlear Dead Spots Suspected
Masked symbols: thresholds with 50 dB TEN
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Moderate Reverse SNHLFit the transitions
Not the worst thresholds!
OO
O
O
OOO O O
Apex Base
OO OO
O
O
O
O
Apex Base
OO
Severe precipitous high‐Hz SNHLFit the transitions
Not the worst thresholds!
Implications For Fitting
Fitting the “Left Corner” Audiogram??
A “bridge” between
Hearing Aids
&
Cochlear Implants
Frequency Transposition…
125 250 500 1000 2000 4000 8000-10
0
10
20
30
40
50
60
70
80
90
100
110
120
OO
OOOO O O OOO
X XXXXX X X X X X
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Ever Wonder What Sounds Are Like for People with Dead Regions?
Recall testing those with reverse SNHLI suspect dead low‐Hz regions when reliability is poorer for lows,but I’ve never asked them what the pure tones sounded like.
Recall testing those with pronounced, precipitous SNHLThese clients tell me the highs sound like a “scratch,”or that the highs feel like a “tickle.”
Others have reports from their subjects as wellThey report tones in dead regions sound like noise however, this observation is inconsistent.
Ratings of clarity Cannot be used as reliable indicators of dead cochlear regions.
Keep It Simple
“You don’t need a weatherman to tell you where the wind blows” ~Bob Dylan
Wet your finger and stick it in the air!
If you see the suspicious audiograms, then suspect cochlear dead regions
Present tone so client can hear it, then ask as to its quality
If poor, then don’t amplify in those Hz’s!
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• Moore, BCJ (2001). Dead regions in the cochlea: Diagnosis, perceptual consequences, and implications for the fitting of hearing aids. Trends in Amplification 5(1)
• Moore, BCJ (2001). Dead regions in the cochlea: Implications for the choice of high‐frequency amplification. In Seewald, RC & Gravel, JS, eds, A Sound Foundation through Early Amplification, Phonak AG
• Moore, BCJ (2004) New Version of the TEN test with calibrations in dB HL. Ear & Hearing 25(5): 478‐487.
• Moore BCJ. Testing for Cochlear Dead Regions: Audiometer implementation of the TEN(HL) Test.
Hearing Review. 2010;17(1):10‐16,48.
• Venema, TH. Compression for Clinicians (2006); Ch 2Cengage Publishing ISBN 1‐4180‐0959‐8
References
Questions
Enter your question in the Question Box on your webinar dashboard