Professor Clark of the University of Melbourne was initially inspired to develop an artificial hearing device through his deaf father. He thus set to work, aided by a dedicated research team, in designing a device that would produce meaningful hearing sensations by electrically stimulating nerves inside the inner ear.
It was Clarks research team in 1978 that enabled Rod Saunders to become the first person in the world to receive a multi-channel cochlear implant. This first operation took place at the Victorian Eye and Ear Hospital in Melbourne. Such an achievement was not previously thought possible as the cochlea (inner ear) is innervated by 10,000 to 20,000 neurons in a complex manner, supposedly making it impossible to provide speech understanding with a small number of electrodes. This kind of attitude within the scientific community made funding difficult, and Professor Clark and his staff had to seek donations from the general public to establish the work.
The multiple-channel cochlear implant resulting from the discoveries of Clark and his co-workers is the first sensori-neural prosthesis to effectively and safely bring electronic technology into a direct physiological relationship with the central nervous system and human consciousness (ref www.bionicear.orf/crc/overview.html). Furthermore, it is the first cochlear implant to give the immeasurable gifts of speech understanding to severely-to-profoundly deaf people and spoken language to children born deaf. In addition, Clark's team was successful in engineering a speech processor small enough for the smallest patient to wear.
Clark demonstrated the safety of the device through a series of studies on experimental animals. His tests confirmed minimal risk of meningitis from middle ear infection if a fibrous tissue sheath was produced around a single-component multiple-electrode array, and this was facilitated with a fascial graft.
After the first successful operation, the Australian Government then awarded a public interest grant to the project that helped develop the Bionic Ear industrially by the Australian firm Cochlear Limited. The implant hit the commercial stage in 1982 when Graham Carrick received the worlds first commercial 22-channel cochlear implant. It was the first device for clinical trial world-wide. The international trial established that it was safe and effective and it was approved by the US Food and Drug Administration in 1985, the first multiple-electrode Bionic Ear to be approved by any world regulatory body.
In 1985, the team implanted the first child with a multiple-electrode Bionic Ear. This Bionic Ear was developed industrially by Cochlear Limited in co-operation with The University of Melbourne and The Bionic Ear Institute. This was the start of a world-wide trial for the Bionic Ear and its use in young children. It was approved as safe and effective for use in children born deaf or developing hearing early in life by the US Food and Drug Administration in 1990 and other world regulatory bodies. It is considered by many to be the first major advance in helping profoundly deaf children to communicate in the last 200 years since sign-language was established at the Paris Deaf School.
Now more than 50,000 hearing-impaired persons in over 120 countries have received such implants, with Cochlear Limited the leader in the field. Indeed, the company has now advanced into early childhood applications, developing an implant designed to suit infants during the very critical early period of psycho-linguistic development.
How does it work?
The Cochlear Implant system is made up of two separate parts:
1) The receiver-stimulator and electrodes are implanted surgically, as shown in Figure 1. These parts are placed under the patient's skin behind the ear. The implant package (or receiver-stimulator) contains the circuits that send electrical pulses into the ear. Attached to the package are tiny wires that join to electrodes. The implant package also contains an antenna that receives radio-frequency signal from the external coil. The 22-electrode array is inserted into the shell-like structure in the inner ear known as the cochlea. The ball electrode is placed under a muscle near the ear. There is also a plate electrode on the outside of the receiver stimulator package. (ref www.bionicear.org)
2) The microphone, speech processor and transmission coil are worn externally and can be removed at any time. The processor can filter out background noise. There are no plugs or wires connecting the internal and external components. The coil is held in position against the skin by a magnet and the microphone is worn behind the ear. The body-worn speech processor (SPrint) can be worn in a pocket, in a belt pouch or in a harness. The ear-level processor (ESPrit) is worn behind the ear. These parts, which are shown in Figures 2a and 2b are normally fitted two weeks after the operation. (ref www.bionicear.org)