Sunday, October 25, 2009

Does anyone have the cochlear implant and is not able to hear with it?


Answer:
While I don't have a CI, I work with a number of people who do have CIs. First of all, "not able to hear with it" can mean two things: Not getting any sound from the CI at all, or not being able to understand speech with it. If it is the latter, there may not have been enough time post activation for the CI patients brain to adapt to having auditory nerve stimulated. The amount of time it takes depends very highly on how long you were deaf before you got the implant, whether or not you wore a hearing aid before implantation, and whether or not you followed the post-implant audiology and therapy regimen (which is EXTREMELY important).

I'm not one of the medical providers at our clinic, but here are some possible reasons why a CI might not work. None of these are *supposed* to happen, but they do happen, albeit rarely. When I say rare, I mean really rare. For example, there are only 3 cases in the US of known rejection of the CI due to silicone allergy. Most of these issues I list below are fixable to the extent that the implant can be replaced or the anatomical issues can be worked around in revision surgery.

1) The electrode might be malfunctioning. One study stated that 5.1 % of CI surgeries every year are to replace malfuctioning or out of date electrodes. The failure rate (after you remove head trauma as the source of the failure) for new implants is about 1 %
2) The patient might not have a cochlear nerve. The CT that you are supposed to have before the surgery is done to eliminate this possibility, but I have heard of people without cochlear nerves being implanted with zero results (not at OUR facility, of course !)
3) The cochlea is ossified (from meningitis) or so malformed (common cavity or Mondini's malformation) that the electrode is incapable of functioning to its fullest extent because of the physical limitations of the patient's anatomy.
4) The electrode has "extruded" that is come out of position from where it is supposed to be in the cochlea.
5) Bad maps. Maps are the software that control the sound processor. Good maps come from good audiologists, we've had CI patients come to our clinic with maps from other facilities that give them hearing in the 35-45 dB range and leave with hearing in the 20-25 dB range just because of a better map being programmed by a more competent audiologist.
6) Bad facial nerve placement. Once again, a limiting factor of the patient's anatomy. If your facial nerve is in a bad location, it is possible that the electrical current from the electrode can stimulate the facial nerve, resulting in eye twitches. If it is annoying or frequent enough, sometimes electrodes have to be deactivated. This doesn't shut down the entire implant, just the electrodes that are causing the twitching (might be as few as 1 out of 24).
7) Allergy to the silicone in the implant, which can cause extrusion (see #4)

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