Cochlear Implant

The Cochlear Implant Promises Hope for the Profoundly Deaf

Although millions of people around the world have benefitted from the use of conventional hearing aids, and have been able to live full lives despite varying degrees of deafness, a significant proportion of those whose hearing loss is more severe are unable to derive any significant benefit from these devices. If it wasn’t for an experiment conducted in 1800 by the inventor of the battery, the Italian physicist, Count Volta, the revolutionary device now known as a cochlear implant might never have been developed.

At the time, he connected his battery to a pair of metal rods and inserted them in his ears, whereupon, after an initial jolt, he experienced a crackling sound. Some 50 years later a Frenchman named Duchenne repeated his experiment using an alternating current source and experienced a clicking sound. Both of these researchers had confirmed, albeit inadvertently, that the auditory nerve could be electrically stimulated.

Whether either of these men appreciated the potential of their observations or not, is not recorded. However, the first attempt to stimulate the auditory nerve directly was made only a century later, in 1950, during an operation conducted by one Doctor Lundberg. Just seven years later, another pair of surgeons implanted electrodes in the inner ear and transmitted signals to them via an external antenna. The profoundly deaf patient not only heard a series of noises, but was also able to distinguish a couple of simple words, and so the first, if somewhat crude, cochlear implant was declared a success.

More experiments followed, and it was eventually determined that these devices were most effective when an array of several electrodes was implanted. Today, Professor Graeme Clarke of the University of Melbourne is generally regarded as the inventor of the first practical device. Developed in 1979, it was also the first to receive FDA approval for its purpose.

While there are variations between the products of different manufacturers, all of them consist of the same basic components. A tiny, but highly sensitive microphone gathers sounds and relays them to a speech processor, which then relays the digitised signal to a miniature transmitter. Thus, assembly is worn externally and the transmitter, behind the ear, secured magnetically to a receiver embedded below the skin. Signals from the receiver are passed via an electrode array to the inner ear, where they stimulate the auditory nerve.

Similarities between these, the cochlear implant and the super hearing displayed by Steve Austin, the surgically-reconstructed cyber-hero of the ‘70s TV series, “The Six Million Dollar Man”, led to it being christened the bionic ear. In practice, however, the effect of its signals are not to amplify speech, but to create a series of sound sensations in the brain that, with practice, subjects soon learn to interpret as speech, music etc.

Often, those who lose their hearing later in life, when they are already familiar with the sounds of normal speech, tend to take a little longer to adjust and to interpret these new sound sensations accurately. By contrast, infants who may be deaf from birth, and have therefore not yet learnt to talk or to interpret sounds, when fitted with a cochlear implant, will invariably proceed to develop at much the same pace as children who have no hearing impediment. This, of course, also means that, when the time comes, they will be able to receive their education in the same schools as their hearing companions.

While these implanted hearing devices may seem like the perfect solution, it needs to be understood that they are not suitable for everyone. While most of those who are profoundly deaf and unable to gain any significant benefit from the use of a conventional sound amplification device, are likely to benefit from surgical implantation, some are not suitable candidates for this procedure. Before they can be accepted, all candidates are required to undergo a thorough evaluation, consisting of both audiological testing and surgical assessment. Only those candidates whose results conform to the defined criteria will be considered suitable for surgical implantation.

In South Africa, Ear Institute is widely acknowledged as the authority on the assessment of hearing loss and its remediation. A supplier of world-class, state-of-the-art hearing aids and cochlear implants, our well-equipped audiology facilities are staffed by experienced and qualified healthcare professionals, and are open to the public without the need for a referral from a GP or an ENT specialist.
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