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Cara Mia

Electrode Impedance

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I would like to know how the specific issues with electrode impedance can affect the quality of sounds. Especially, I am interested in the issues related to the irregularities in low circuits (aka partial short circuits)  that create an atypical ("zigzag") impedance  pattern without being flagged by programming software for electrode exceptions because it don't meet the criteria of short circuits.

Any information related to short or open circuits will be highly appreciated.

@hadron, I am sure you are familiar with this topic very well. I remember you asked some our folks, who reported the problems with electrodes, about if it was short or open circuits. Please.

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@Cara Mia

My left side has unique impedance and by testing each electrode’s threshold individually and setting them manually instead of using Med-El’s default values of 10% of MCL or zero for thresholds it really improved the sound quality on that side.  We chose to test and set each electrode’s threshold individually on the right as well and even though the right has more typical threshold values I still noticed an improvement in sound quality using the tested thresholds.

As you know, I also participated in Vanderbilt’s image guided research study for CI MAPping and greatly prefer the image guided MAPs for quality of sound and clarity of musical pitches.  The left side with the unique impedance levels, received the greatest sound quality benefit from the image guided MAP.

Just sharing in case this helps you in any way.

I have never been told that I have a short circuit nor open circuit and it is my understanding that all of my electrodes can be turned on if desired.  I just perceive better sound quality with the image guided MAPs, which have specifically targeted electrodes turned off.

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Thank you, Mary Beth. Will ask my audi again to check threshold for each electrode. I discussed this idea you share with us somehow. But was unable to move my audi for doing that as she thought that it is sill too early after implantation (activation) to worry about sound quality. But now, when I am post one year mark it should be just the right time especially when I had a great sound until I reached three month mark :)

I wish I can get to Vanderbuilt. Perhaps, I just need to put all aside and get there. I am sure their image guided mapping will be an improvement in any scenario with my issue.

I am sure that currently I have nothing like a short or open circuit. But I see that my left impedance pattern is not flat and smooth and has noticeably lower readings compare to the right side. Just want to digging there to see if there is something there. At least, with some idea and information I can start a new discussion with my audi to address the distorted sound quality I have on that side. 

 

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Hi @Cara Mia sorry to hear you are having issues with one side. I can discuss partial short circuits but I will be telling you things you can read yourself in a much clearer presentation provided by the great book "Objective Measures in Cochlear Implants" by Dr. Michelle Hughes (head of hearing research at Boys Town). Every CI audiologist has read this book or used it in their AuD program. Focus on I believe Chapter 3 Electrode Impedance.  I believe there is a short Preview of the book you can view online. Link is below. 

https://www.pluralpublishing.com/publication_omci.htm

 

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Image of cochlear display of impedance values showing  open and closed circuit.  Open circuits > 30 kOhm, short circuit < 0 kOhm. Offending electrodes in blue. Had to cut of diagram showing short circuit graphic because of file size limit. Can we get this increased? I MP1 and MP2 are the ground electrodes. CG is common ground stimulation.

There are 22 values because Cochlear has 22 electrodes.

Screenshot_2018-01-14-09-41-01-1-1-1.png

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When you first start using the CI the impedance values differ and the curve looks jagged, the more you wear the CI the more flat and smooth the curve becomes. If you stop wearing your CI for a notable time period the curve will become jagged again and your audiologist will know you are not wearing your CI.

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@hadron

@MED-EL Moderator

 

I also agree with Hadron that the limit on size and total space per member for pics is very limiting in trying to help others,  Many times I have reached out to members in other ways in order to show helpful images.

 

The maximum space allotted per member is not helpful for those of us who continue to post here for years.  It never gets increased or renewed.  I have actually gone back to previous posts and removed images in order to post new images.  That makes the previous post seem odd since it now lacks images we had referred to in comments.

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Thank you, Hadron. Will read this book for sure. Mary Beth also mentioned it as a good source to start.

I wear my processors all the time with 6 hours break for a night. I know that some sediments, due to the lack of electric stimulation, can affect the electrode performance. It is definitely no my case. It was only a week between my surgery and activation, so I even didn't have anything like that right after activation. Everything worked just great for several months.

 I am functioning pretty well with that unclear sound from one side. And it is not a big deal when both my processors are on as the second processor masks all imperfections.

But at least I want to find the reason why it happened to my left side. Just like to understand why and how things work.

Hard to explain the sound I get from my left side now. It sounds like a broken glass if compare to the sound of a crystal glass. Like listening to radio between station frequencies. Or. like the coil is not on the right place (I switched coils from the difference sides - this has changed nothing. So, my coils are fine. And I got a new processor in several months after that issue started - all the same with a new processor).

And one more thing that can be related to my case - the battery life. Any rechargeable batteries I use on the "faulty" side last for about 1,5 hour less than the same batteries when used with another processor. I know that EAS takes some additional juice. But I was told that I should make 15-20 minute difference at max.

Thank you guys! I feel inspired on the way to resolving my riddle.

Mary Beth, I completely support you call for more available space for posting visual materials. It will benefit not only us, users, but the forum allowing to make it more informative place with more attention catching means.

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@Cara Mia Study of partial short circuits in a zig zag pattern and impact on performance in pediatric patients.

https://www.researchgate.net/publication/280830522_Atypical_impedance_patterns_in_cochlear_implant_recipients

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There is so much more to our hearing perception than can be objectively measured with the present battery of tests available to our audiologists.  In a way it seems like testing has not kept up with the advanced listening abilities of many present CI users.

 

Speech

Speech in noise

are useful tests but do not measure the sound quality of speech.

I have participated in a few research tests on music but I am not aware of any tests for music being used regularly by our clinical audiologists.  There has been recent chatter about a pitch perception test that can be administered via computer quickly.

Finding a CI audiologist who listens well and understands our reported perceptions and is willing to seek out MAPing solutions makes a huge difference in our journeys.

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Hadron, thank you. The very good articles! 

Mary Beth, I agree with you completely that it would be great to have more tools and solutions to make music a routine part of our CI journey. But so far, it seems our audiologists have not enough time to deal with this complicated topic during our routine visits. And it's not likely that insurance companies are going to cover that our needs despite that everybody is agree that music has a powerful therapeutic effect.  I even not sure that the "classical" hearing tests we undergone each time are used in full force to detect the possible issues with speech comprehension and ways to fix that issues during mapping.

I also wish to all of us to find CI audiologists who listen and understand our perceptions and issues well, willing to resolve any problem reported. I hope as technology is getting more and more advanced it will be easier for our audiologists to fix all problems with our hearing easier and faster,

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