About 1-2 weeks following a child’s surgery and 1-4 weeks following an adult surgery (depending on what type of incision is used), the recipient will return to the hospital for initial stimulation (or device activation) and orientation of all of the external equipment. The delay between surgery and initial stimulation is necessary to allow the incision to heal and any swelling to subside. It is important to note that the child will not be able to hear with the implant or with a hearing aid in the implanted ear during this time.
The initial stimulation session, also called the initial “hook-up” or “activation”, involves fitting the individual with the external equipment (external transmitter coil/headpiece and speech processor) and programming of the device. After the ear surgeon has ensured that the surgery site has healed appropriately, the audiologist will select a magnet of appropriate strength to align the external transmitter coil with the implanted internal receiver. The audiologist will then connect the speech processor to the programming computer and will conduct a test that will verify appropriate internal device function. This brief test does not require participation from the recipient.
Next, the audiologist will create the initial program or “MAP” that will allow the individual to hear sound for the first time through his/her implant. The MAP contains information about how incoming sounds are converted to electrical stimulation levels. Each MAP is created specifically for the individual to ensure that soft sounds are audible, and that loud sounds are loud but never uncomfortable. To create a MAP, the audiologist activates the electrodes or electrode pairs and the recipient indicates the softest sounds he/she hears (threshold, or “T” levels) as well as the level at which sounds are louder, yet comfortable (most comfortable “M” levels, or comfortable loudness “C” levels). Once the speech processor program/s have been created, the processor microphone is activated so that the recipient will hear speech through the implant for the first time. It may be necessary to adjust additional parameters on an individual basis to enhance the quality of the sound derived from the cochlear implant.
After the final programs have been downloaded to the speech processor, the individual and his/her family are instructed on the operation, care, and maintenance of the device and accessories. Information regarding precautions, warranties, repairs, and insurance is also shared with those present. In addition, suggestions for incorporating listening practice at home may be given.
Children Hearing Sound for the First Time
Many children who receive cochlear implants have never heard spoken language which makes “MAP”ing their cochlear implant more detailed than an adult who remembers sound. For older children, threshold levels are obtained using a procedure similar to a hearing test wherein the child raises his/her hand or verbally indicates when a sound is heard. For younger children, play audiometry techniques (such as putting a block in a bucket when a sound is heard) or procedures similar to visual reinforcement audiometry (a reinforcement toy is activated when the child responds to sound) can be used. In order to obtain comfortable loudness levels, a loudness-scaling task (having the child indicate whether the sound is “soft”, “comfortable”, or “loud”) can be used for older children. For younger children, the audiologist observes the behavioral reactions to the stimuli and looks for signs of loudness intolerance.
Objective measures also are used in programming the speech processor, particularly with infants and very young children who have no knowledge of sound and are unable to provide information regarding threshold and comfort levels. These procedures do not require active participation from the child, and therefore can be performed while the child is playing or sleeping. An example is Neural Response Telemetry or Neural Response Imaging (NTR/ NRI). NRT/NRI is a method by which responses from the auditory nerve can be measured using the cochlear implant system. With this telemetry system, the audiologist uses a computer program to stimulate the auditory nerve with the implant. The resulting electrical activity from the nerve is recorded using the electrodes inside the implant and is displayed on the computer. NRT/NRI can provide a general indication of program levels, confirm neural function, provide baseline information, and assess device functionality.
Once the program(s) or MAPs have been created, the processor microphone is activated so that the child will hear speech through the implant for the first time. Further adjustments to the program(s) may be necessary prior to downloading the final program(s) to the child’s speech processor. The initial stimulation is an exciting and much anticipated time for the child and the family. The child’s reaction to the initial activation of the device can range from happiness and excitement to fear or alarm to little or no reaction at all. It is important to realize that each child will react differently to the new sound through the implant.
Visit Parents’ Perspectives for a list of helpful websites and comments from parents who have children with cochlear implants.