The Parents' Guide to Cochlear Implants

3. Options in Implant Devices

25 OPTIONS IN IMPLANT DEVICES Options in Implant Devices Chapter 3 hether occurring simultaneously with the candidacy evaluation or after candidacy has been determined,a discussion W of the types of implant devices available at the center is an important part of the pre-implant period. One of the choices to be considered during this time concerns the actual device that will be implanted. In some cases, the parent does not make the device selection because the cochlear implant center offers only one type of implant system. As noted in chapter 1,parents may wish to investigate the access a particular center has to the numerous types of technology before making a commitment to that center. The number of cochlear implants on the market is far fewer than the number of hearing aids. Changes in hearing aid technology can be made more easily since there are no surgically implantable components. The fact that implantation involves surgery makes the choice a more critical one. Decisions regarding cochlear implant technology have more long-term ramifications since portions of the device are internally implanted. While there are more than forty manufacturers of hearing aids with hundreds of models to choose from,there are only three manufacturers of multichannel cochlear implant systems in the United States. Although each of these manufacturers would have you believe that its product is the best,the fact remains that no implant (or hearing aid) can guarantee a particular result. Fortunately, each cochlear implant system, regardless of manufacturer, provides children with adequate auditory information that can be processed meaningfully if properly fitted and supported. 26 CHAPTER 3 Before describing each of the presently available cochlear implant systems, it is first important to review the basic components of cochlear implants. Every cochlear implant device is composed of internal and external parts. (See figure 3.1.) The internal components are those that are surgically placed inside the head behind the ear. Electrodes, a receiver-stimulator (electronics that receive and deliver the signal),an antenna,and a magnet are all considered part of the internal workings of the device. These components can only be changed with additional surgery. The external portion of the implant consists of a microphone , speech processor, external transmitter and cord(s). Because these components are external,they can be easily replaced and upgraded as technology evolves. Parents should keep in mind several issues when selecting a system for their child. Some of these may be more important for one family and their child than another. The internal components of the implant contain the electronics that interact with the external system. Therefore, selecting sophisticated internal technology is critically important since it cannot be readily changed. Consideration of the type of material that houses the receiver, MRI (Magnetic Resonance Imaging) compatibility,number of electrodes offered by the system,and overall reliability of the devices is also required. When considering external features, parents should investigate the size and outward appearance of the speech processor and headset, the software programs that are available to deliver speech to the internal receiver,the cost of maintaining the device over time,and the presence of accessories. The terms of the warranty and the level of company and/or center support for any given device require some assessment to assist parents in making the choice. Regardless,under no circumstances should a parent select a device for their child simply because the parent knows another child who has had success with the same type of implant. Nor should parents be swayed by either wellmeaning professionals or other parents who have allegiance to 27 OPTIONS IN IMPLANT DEVICES 5 6 7 Figure 3.1. Internal and external components of a cochlear implant system and how it works. The Nucleus cochlear implant system works in the following manner: 1. Sounds are picked up by the small, directional microphone located in the ear level processor. 2. The speech processor filters, analyzes and digitizes the sound into coded signals. 3. The coded signals are sent from the speech processor to the transmitting coil. 4. The transmitting coil sends the coded signals as FM radio signals to the cochlear implant under the skin. 5. The cochlear implant delivers the appropriate electrical energy to the array of electrodes, which has been inserted into the cochlea. 6. The electrodes along the array stimulate the remaining auditory nerve fibers in the cochlea. 7. The resulting electrical sound information is sent through the auditory...