First Person Report: Cochlear Implant Channel Crossover

Melbourne piano teacher Daniela Andrews (Blog | Facebook)  accidentally leveled a Very Damning Indictment of her simultaneously implanted Nucleus 5 CI’s, where she points out a major flaw in Cochlears’ design, with its’ 22 electrodes spaced too close together for its’ 22 hardware channels: This causes Channel Crossover, which Daniela unintentionally — Yet so eloquently — described. If you remember back in February, there was the special Interior Design Concert by the Bionic Ear Institute for people with CI’s. Daniela, as a music professional, was one person involved with it; so you know she has the “street creds.”

At some point after she was implanted, she wrote the following that was picked up in the Australia Hears blog under Listening to music with a hearing loss. I copied & pasted it below; with my notes [blue, in brackets]:

3. Playing music

There is not a large amount of research investigating whether playing music can help with re-training the brain after a hearing loss. However there are some personal stories we can share. Daniela Andrews lost her hearing around 4 years ago, and for the last 10 months [implanted April 2010] has bilateral cochlear implants:

“At first, the piano sounded terrible. Like somebody had broken into it while I was in surgery and mixed up all the notes for fun. Playing scales barely resembled an up and down pattern at all. [This is channel crossover, caused by the electrodes being spaced too close together, stimulating the wrong nerve endings in the spiral ganglion] There were random low tones in between higher ones, and vice versa. Being simultaneously implanted brought another challenge – each processor rendered two different tones for the same note. [This is diplacusis — the same tone sounding different in each ear — which is exacerbated by the randomness caused by the channel crossover.] Familiar songs sounded alien-like with all these extra wrong notes thrown in. How was my brain ever going to make sense of that mess?”

Technically, each channel could have been remapped to produce a chromatic scale; but that would be painstaking and time consuming… And according to feedback from several CI manufacturer insiders, is above the skill level of many CI audies.

There are two parts to the solution for better music enjoyment: 

  • Wider electrode spacing, to stop the crossover;
  • Current steering (think of a spotlight, instead of a floodlight), to shape the charge distribution, which will fill in the gaps between the electrodes.

Of the four CI manufacturers, Advanced Bionics uses 16 electrode contacts spaced out over 21mm; Neurelec (not available in the USA) uses 12 electrodes spaced out over 23mm; while MedEl uses 12 electrodes spaced over 31.6mm. In addition, both AB (Fidelity 120) and MedEl (FineHearing) have current steering, for much better music performance (though AB has severe implant reliability problems, with five recalls in the last decade).

There are many factors that go into choosing a CI, as indeed there are differences in performance, as well as ergonomics and reliability. We recommend treating the issue of channel crossover as one data point in your decision matrix.

 

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About the author

Dan Schwartz

Electrical Engineer, via Georgia Tech

6 Comments

  1. Symgardiner
    June 3, 2011 at 6:25 am

    It would be really useful to take the CI comparison from the CIO website which has a really good base of info and add some of this more technical info. A collaborative effort between this site and CIO could produce something really useful.


    • Dan Schwartz, Editor
      June 3, 2011 at 3:45 pm

      Unfortunately, Miss Chaikoff is of the mistaken belief that all CI brands are alike; and her willingness to be educated is lacking. However, the Funny Old Life website is much better; and indeed we collaborate with Tina.


    • James
      May 19, 2014 at 8:52 am

      Great quality, long ltanisg Good brand, I believe these are original batteries for my Nucleus Freedom as received from Cochlear. Generally lasts 2-3 days with regular (8-12 hours per day) usage. I was suprised by the packaging, as the batteries came as ten bubble wrapped packages in a plastic bag, but no harm no foul, and shipping was free. And fast, I received the batteries within 2 days of placing my order. Definitely my provider of choice from now on.


  2. Sym Gardiner
    June 4, 2011 at 12:08 am

    I’ve seen this website. I think Rachel thinks, as I do, that each CI has its pluses and minuses. (For instances, Med El looks like it is currently leading the available technology. AB could do this if they could get their manufacturing right. Cochlear leads in robustness, reliability and user friendliness. So you end up weighing these issues out). But regardless of that, it would be useful to have a more in depth comparison because it is a nightmare finding even very basic stuff on the respective company websites.


    • Dan Schwartz
      June 4, 2011 at 6:02 pm

      Sym, the reliability is about the same between MedEl and Cochlear.

      Also, the Nucleus 5 is the least user-friendly, as the input dynamic range is only 45dB, and needs to be shifted as noise conditions vary; however both AB and MedEl have much better AGC action. Also, surgeons love the MedEl electrode, because it has the lowest insertion trauma.

      Lastly, with Danielas’ unsolicited first person report, I would shy away from recommending the N5 for post-lingually deafened people.


  3. Sym Gardiner
    June 5, 2011 at 12:24 am

    Dan… my daughter has Freedom processors and a friend’s daughter has Opus 2 processors. The Freedom is much more user friendly (user friendliness is quite different to technical performance). What I have seen of the N5 is it is a step up on the Freedom. I would think again about your assessment regarding user friendliness.
    From what I have read, the Cochlear implant is right up there in terms of residual hearing retention. But you rightly point out that the Med El and AB seem to have got their design technically better. Its a real pity AB have manufacturing issues.
    If we were making the choice now, we would probably go for an Opus 2, despite it being a pain to know if its working correctly on a child who can’t tell you.


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