Good articles on identifying cochlear dead spots

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deafdude1

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Identifying Cochlear Dead Spots | March 2005 | The Hearing Industry Resource

common clinical encounters&#59 but do we really know them?

Cochlear Dead Regions

I now suspect I may have cochlear dead regions, someone in another forum says it's possible above 1000Hz. Also read my thread titled "poor aided results above 500Hz" for more details. So much information I never knew before that will solve the mysteries for me and my friends. No audiologist ever mentioned cochlear dead regions to me nor did I know about this.
 
deafduke1

yes my audiologist did mention about cochlear dead regions but not in detail as the articles you have linked. The surprising thing was that with people with a reverse ski slope like I had before you do not need to amplify low frequencies as much with a hearing aid because of the dead region. Another point the article pointed out that even with completely dead regions for the low pitches the mid-range hair cells can take over hearing the lowest notes.
 
deafdude1 said:
I now suspect I may have cochlear dead regions, someone in another forum says it's possible above 1000Hz.
Click to expand...

This is what my former CI audi told me I had when I was evaluated for my first implant. I had no residual hearing aided or unaided at 1000 Hz and above.
 
I've never heard of "dead regions" but I knew that some areas of the cochlea have more hair cells than others, which is why I respond more to low frequencies than high. I guess this is sort of a new term for areas that have a lack or very little hair cells?
 
john57 said:
deafduke1

yes my audiologist did mention about cochlear dead regions but not in detail as the articles you have linked. The surprising thing was that with people with a reverse ski slope like I had before you do not need to amplify low frequencies as much with a hearing aid because of the dead region. Another point the article pointed out that even with completely dead regions for the low pitches the mid-range hair cells can take over hearing the lowest notes.
Click to expand...

Did you hear low frequencies differently, say it sounded the same as the mid frequencies? Did you used to hear low frequencies for real before you lost more hearing? Ive read that with cochlear dead regions, sounds in the dead areas sound the same as sound would be in the adjacant living regions(kinda like what transposition does in some HAs) some people say there's no sound but a feeling of scratching, tickling or wooshing

Hear Again said:
This is what my former CI audi told me I had when I was evaluated for my first implant. I had no residual hearing aided or unaided at 1000 Hz and above.
Click to expand...

In my case, my audiogram does record a response up to 4000Hz but I can't hear much above 2000Hz(2250-2500Hz max) with my hearing aids. Also in another forum, someone suspects I have no cochlear hair cells much above 1000Hz. Would my hair cells at 1000Hz be capable of letting me hear the correct tone/pitch sounds at 1500Hz and even 2000Hz? The other thing ive been wondering is how bad can someone's unaided hearing be before all cochlear hair cells are gone? 120db? 130db? 140db?

Ive read the articles I linked above and it seems that you need at least 50db slope between octive(s) to have a cochlear dead region. Thus if a person hears at 50db at 1000Hz and 100db at 2000Hz, suspect a dead region above 2000Hz even if that person records a response at 100-110db above 2000Hz. Ive also read you can't tell for sure with audiograms, would it become certain if the person reports no sound but a feeling of scratching, tickling or wooshing at a given frequency?

Daredevel7 said:
I've never heard of "dead regions" but I knew that some areas of the cochlea have more hair cells than others, which is why I respond more to low frequencies than high. I guess this is sort of a new term for areas that have a lack or very little hair cells?
Click to expand...

Me either, before that a dead region was a NR on an audiogram but the article explains the phenomenon of dead regions while still having a response. it points out that a reverse slope and a steeply sloping audiogram are the two most likley to harbor dead regions.
 
Ive also read you can't tell for sure with audiograms, would it become certain if the person reports no sound but a feeling of scratching, tickling or wooshing at a given frequency?

This would still be counted as a response. It would be noted as "vibrotactile" or something similar.

I know this because when my residual hearing was tested at 6 months post activation with each ear, my audi told me I had NR across all frequencies even with bone conduction which is designed to test vibratory/tactile response.
 
The other thing ive been wondering is how bad can someone's unaided hearing be before all cochlear hair cells are gone? 120db? 130db? 140db?

I'm guessing when someone has NR across all frequencies at 120 dB. In other words, they are totally deaf.
 
Hear Again said:
This would still be counted as a response. It would be noted as "vibrotactile" or something similar.
Click to expand...

It was measured with air, not bone conduction. Well ill find out, im going to the audiologist in 90 minutes! Ill tell her to test the mids and highs several times and then also let me know what frequency she is testing me at after she completes the tests and retests me. Of particular interest if I respond above 2000Hz, I want to know what it sounds like, ill repeat it and she will let me know if I heard it normally by how I repeat it. If it doesn't sound like a high pitch whistle, then it's suspect.

I know this because when my residual hearing was tested at 6 months post activation with each ear, my audi told me I had NR across all frequencies even with bone conduction which is designed to test vibratory/tactile response.
Click to expand...

How many db can bone conduction go to? I still wonder if I have a bit of a conductive loss, if so surgery can remedy this and ill hear much better with HAs then and may begin to hear sounds unaided!

Hear Again said:
I'm guessing when someone has NR across all frequencies at 120 dB. In other words, they are totally deaf.
Click to expand...

And if they have a response at one frequency and NR at the next frequency above that, all that would be known is the HL is greater than 120db. Is it 125db? 130db? Infinite?(cochlear dead spot equals infinite hearing loss) actually I did see one case study where his unaided hearing was NR at 2000Hz and up, yet he could hear aided up to 2000Hz. Could it be possible the SPL on his hearing aid at 2000Hz was high enough to elict a response? Or could it be cochlear dead spot phenomenon that elicts a false positive?

Page Ten: Dead zones: What are they and what do you do about them? Brian C.J. Moore March 2009 The Hearing Journal

Another good article, download pdf file.
 
And if they have a response at one frequency and NR at the next frequency above that, all that would be known is the HL is greater than 120db. Is it 125db? 130db? Infinite?

Even if an audiometer could go up to 130 dB, that's only an increase of 10 dB. Dangerous listening levels are achieved at 90+ dB, so it wouldn't matter if a person could hear at 120 dB or 130 dB.
 
actually I did see one case study where his unaided hearing was NR at 2000Hz and up, yet he could hear aided up to 2000Hz. Could it be possible the SPL on his hearing aid at 2000Hz was high enough to elict a response? Or could it be cochlear dead spot phenomenon that elicts a false positive?

Being able to hear from 250-1000 Hz does not provide someone with the mid and high frequency hearing they need to understand consonants.

As far as SPL is concerned, it wouldn't matter how high it was set if he doesn't have any residual hearing at 2000 Hz and above.
 
SteveAUD said:
70 dB at 1000, 2000, 4000Hz. Anything above 55dB at 500Hz and 40 dB at 250Hz and you'll begin to feel the oscillator before you hear it.
Click to expand...

That's right. I thought it was 70 dB, but I wasn't sure because when my CI audi told me I had NR at every frequency via bone conduction, I thought she tested me at 120 dB.
 
deafdude1 said:
Did you hear low frequencies differently, say it sounded the same as the mid frequencies? Did you used to hear low frequencies for real before you lost more hearing? Ive read that with cochlear dead regions, sounds in the dead areas sound the same as sound would be in the adjacant living regions(kinda like what transposition does in some HAs) some people say there's no sound but a feeling of scratching, tickling or wooshing



In my case, my audiogram does record a response up to 4000Hz but I can't hear much above 2000Hz(2250-2500Hz max) with my hearing aids. Also in another forum, someone suspects I have no cochlear hair cells much above 1000Hz. Would my hair cells at 1000Hz be capable of letting me hear the correct tone/pitch sounds at 1500Hz and even 2000Hz? The other thing ive been wondering is how bad can someone's unaided hearing be before all cochlear hair cells are gone? 120db? 130db? 140db?

Ive read the articles I linked above and it seems that you need at least 50db slope between octive(s) to have a cochlear dead region. Thus if a person hears at 50db at 1000Hz and 100db at 2000Hz, suspect a dead region above 2000Hz even if that person records a response at 100-110db above 2000Hz. Ive also read you can't tell for sure with audiograms, would it become certain if the person reports no sound but a feeling of scratching, tickling or wooshing at a given frequency?



Me either, before that a dead region was a NR on an audiogram but the article explains the phenomenon of dead regions while still having a response. it points out that a reverse slope and a steeply sloping audiogram are the two most likley to harbor dead regions.
Click to expand...
I never had normal low bass since I was born with small cochlea's with a moderate reverse slope on both ears. The bass sounded normal for me since that was what I was born with.
The articles on dead regions stated that is usually the high frequencies not the low frequencies that may give a feeling of scratching, tickling or wooshing

If you read the articles carefully it is easier for the midrange hairs cells to take over the bass since the "tail" part of the traveling wave extends toward the midrange where you have more hair cells to pick up the sound. For high frequencies only the small "Head" part of the traveling wave can reach the midrange not the tail which extends further. This means to me that even with much loss in the bass I prefer hearing aids with the bass cut out since the deep bass "tail" will be interfering with the midrange hair cells that are trying to pick up the midrange and I will lose clarity of speech with too much bass amplification. The real bass region of my cochlea will not response to the deep bass and there is not much separation of the bass and midrange as far as my hair cells are concerned. I hope that makes some sense.
 
john57 said:
I never had normal low bass since I was born with small cochlea's with a moderate reverse slope on both ears. The bass sounded normal for me since that was what I was born with.
The articles on dead regions stated that is usually the high frequencies not the low frequencies that may give a feeling of scratching, tickling or wooshing

If you read the articles carefully it is easier for the midrange hairs cells to take over the bass since the "tail" part of the traveling wave extends toward the midrange where you have more hair cells to pick up the sound. For high frequencies only the small "Head" part of the traveling wave can reach the midrange not the tail which extends further. This means to me that even with much loss in the bass I prefer hearing aids with the bass cut out since the deep bass "tail" will be interfering with the midrange hair cells that are trying to pick up the midrange and I will lose clarity of speech with too much bass amplification. The real bass region of my cochlea will not response to the deep bass and there is not much separation of the bass and midrange as far as my hair cells are concerned. I hope that makes some sense.
Click to expand...

John,

You seem to know a great deal about how the ear works. How were you able to attain this knowledge? Do you work in the field of CIs or audiology?
 
Hear Again,

I was a student at N.T.I.D. and took some specialize courses that were offered at that time in hearing aid technology. I was a hearing aid research assistant for a private company at one time on micophone technology. From time to time I just read up and keep in touch. I have a engineering degree as well.
 
john57 said:
Hear Again,

I was a student at N.T.I.D. and took some specialize courses that were offered at that time in hearing aid technology. I was a hearing aid research assistant for a private company at one time on micophone technology. From time to time I just read up and keep in touch. I have a engineering degree as well.
Click to expand...

I'm very impressed by your knowledge. :)
 
1250683247018382800.jpg

45db HL 1000Hz drops to 85db HL at 1500Hz. If 50db/octive or 25db/semioctive then suspect dead zones! This person perhaps may have residual hearing up to 1250Hz. Amplify the edge frequencies(750-1500Hz) and transport the highs down to the mids.

1250683305090763700.jpg

Steep drop and rise is indicative of dead zones. Reduce the gains in the dead zones while increasing the gain in the lows and highs.
 
1255556489036285300.jpg


This person has cochlear dead regions at 1000Hz and above. Although the audiogram shows thresholds at profound levels, those thresholds don't truly exist but are due to off-frequency hearing by remote stimulation of hair cells. This person does not experience any improvement with the new HAs. When amplifying into the cochlear dead region, sounds may be sharp and noiselike. The solution for this person would be to try transpositional HAs or simply only max the gains in the nondead zones and roll off the gains(and SPL) past the edge zone.

This person said: Thanks for you response. My audi DID do a speech discrimation test, but this was not shown on the evaluation. I think I did very badly with this...
This audi is quite excited about Starkey's new Destiny range!

I've been wearing these for almost 6 weeks now, with adjustment being made every 10 days or so. I don't know what to tell my audiologist anymore, except that although the power is there, I do not understand much. Some parts of words sound too sharp (like noise) for me making the word get lost.

Another problem i found was that soon after the the last adjustment sounds appeared uncomfortably loud. Now sound is soft, too soft. Understanding speech seem worse now than with my previous programmable analogs - Danovox, despite the Danovox not providing enough power.

Unfortunately my audiologist does not have the equipment for testing HINT or SIN. I had much hope that the Aleva would improve my speech understanding, simply because they are digital, offering so much more options.

What can I do? How can I help my audi help me?

1255557820011851400.jpg


That audiogram is suggestive of a dead zone above 1000Hz. This person does not hear high frequencies nor can he discriminate pitch differences.

This person said: Hi, I'm a hard of hearing person with a ski-slope hearing loss. I
recently attended the SHHH National convention in Orlando, Florida and
attended the all day symposium on hearing aids. I've been trying the
Phonak Audio Zoom but while I like the Audio Zoom feature very much, I
don't think I'm hearing as well in quiet as I could be. The low
frequency sounds seem to mask the higher sounds I hear, although I
feel I'm also not even hearing any of the higher sounds at all in
quiet. For example, I used to be able to hear my microwave oven beep
several times, and I couldn't today even when I was standing right
next to it. I feel I'm also missing some of the temporal information
from high-pitched sounds even if I can't discriminate between high
frequencies.
 
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