Timothy C. Hain, MD. Page last modified: December 30, 2011
An exciting recent development is an ability to provide hearing to some bilaterally deafened individuals through implantation of a device which directly stimulates the hearing nerve (actually the spiral ganglion). Although this device is not generally considered as a "hearing aid", it performs the same purpose for individuals with severe hearing impairment involving both ears. At the time of writing of this section, there are three companies that make implants -- Advanced Bionics, Med-El, and Cochlear Ltd. Generally an electrode is threaded into the cochlea.
|Cochlear implant from a patient of Dr. Hain's practice in Chicago.|
Cochlear implants do not completely substitute for a normally hearing ear,and at very best, may allow someone who was previously totally deaf to understand conversation on a telephone. Cochlear implant packages, including the device, surgery, and rehabilitation are much more expensive than hearing aids (roughly $45,000), but when one is indicated they are sometimes covered by insurance, unlike the usual situation with hearing aids.
With respect to cost-effectiveness of cochlear implants, Lammers et al (2011) reported that it varies widely, and more data is needed to come to a firm conclusion. This doesn't speak very well for the cost effectiveness of implants -- if they were very effective, there would be no quibbling. Our observations is that cochlear implants in the US are generally found in persons with special financial resources -- they may be very wealthy, they may very well insured, or they are indigent and the cost is paid by government programs. Obviously, the great majority of people in the middle are left out.
A patient-contributed history is found here. Remarkable improvements in performance have been accomplished since 1980.
Unless one is independently wealthy, one wants one's cochlear implant to be "indicated" so that insurance will cover the extremely high cost. At the present writing (2011), this means that one should be "unaidable" -- meaning that hearing aids do not provide reasonable hearing. Roughly speaking, "unaidable" is assessed by the 50-50 rule -- more than 50db down, and less than 50% word recognition.
There has been a trend towards implants being used in people who are not "unaidable". For example, persons who have one implant already seeking a second implant. In Germany, implants have been used for single-sided deafness -- i.e. people with good hearing on one ear (Jacob et al, 2011). Our take on this is that in general, the costs of bilateral implants are very high, and the benefits are low, and thus medical/social resources would be better spent elsewhere. In other words, we don't think that government funding should be paying for these devices. Of course, the independently wealthy are in another category. We also think that the BAHA device for unilateral deafness is a far better choice than a cochlear implant as it is not nearly as invasive.
Further information about cochlear implants can be found at the following sites:
Cochlear implants sometimes have complications. Dodson reported a 9.3% overall complication rate, with 59% being due to device failure (Dodson et al, 2007).
Vertigo or imbalance occurs in 40-74% of patients who have cochlear implants (Steenerson et al, 2001). Caloric responses are not necessarily eliminated by cochlear implants (we have seen this), and thus the underlying process that affected hearing can continue to cause dizziness and balance. About 50 % of these patients develop positional vertigo and can be treated with vestibular rehabilitation. Although one might think that dizziness could be related to inadvertent electrical stimulation of the vestibular nerve, dizziness is not usually related to implant activation, (Fina et al, 2003). We have found a few patients however who are affected by activation.
Todt et al(2008) suggested that dizziness was common post implant, and that insertion through the round window decreased the risk of dizziness associated with insertion.
Impaired fixation suppression is a risk factor for vertigo after cochlear implantation (Krause et al, 2009)
The BAHA (bone attached hearing aid) is an excellent implantable device for persons who have either primarily a conductive hearing loss or good hearing on the opposite ear.
There is also a device that is implanted into the middle
ear, in essence, implanting the speaker part of the hearing aid. This device, the Symphonix Vibrant Soundbridge,
is mainly used for individuals who are unable to tolerate conventional hearing
aids. It avoids the "occlusion" effect and feedback. These devices often have mechanical problems. The Vibrant Soundbridge is now available in the US through MED-EL Corporation.
The auditory brainstem implant (ABI) is mainly used for people with "nerve" deafness, such as persons with neurofibromatosis. It provides sound quality similar to a single-channel cochlear implant (i.e. sound awareness, but not speech comprehension).
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