Following a four- to five-week post surgical healing process, it is time to be “hooked up” to the external component of the implant called the “speech processor.” There are body-worn and behind-the-ear (BTE) processors. Most adults and older children are fitted with a BTE processor. Body-worn processors may still be used with very young children as the ear level units may be too large to fit comfortably behind smaller ears and some ear level designs do not lend themselves to being easily monitored to assure sound transmission. Increasing numbers of young children are now beginning to use BTE devices more regularly, however, as newer speech processor designs provide greater ease of monitoring, more streamlined designs, and greater resistance to moisture.  Some individuals may prefer a body-worn device if they do not want the speech processor to sit behind their ear.

Where small children are concerned, smaller devices can become more easily lost. See "What About Insurance?"   for information about extended warranties and insurance.

Parent ingenuity has been helpful in finding ways (toupee tape, body glue, huggies, critter clips, etc.) to keep BTE processors securely behind small ears.

Mapping

Each speech processor must be adjusted or “mapped” specific to each individual. This process requires an initial appointment with an audiologist at the hospital implant center where the surgery occurred. The initial mapping of the device may take about two hours. Several subsequent appointments are then usually required during the following weeks. These ongoing appointments are necessary to adjust the “map” as the brain adapts to incoming sound. What the brain perceives as initially loud may quickly become quiet or inaudible. During these sessions, the electrical stimulation must be adjusted until a good initial map is determined. Once a stable map has been obtained, children may then be seen once a month (at first), then every two to three months for the first year, and every six months for the second and third years, depending on the recommendation of the hospital implant center.

During the initial “hook up,” families anxiously await a child’s response to sound. Listening for the first time, however, may or may not be a positive experience. Some children may smile and demonstrate enjoyment of their early listening experiences through their cochlear implant while others may appear to dislike or be afraid of their new world of sound. If a child does not respond as hoped during early mapping sessions, it does not mean that the child will not ultimately like and benefit from the cochlear implant. It is important that the audiologist adequately prepare the family about what to expect from a child’s first listening experience and the weeks to follow. 

Setting a Map

The basic components of setting a map include determining threshold levels (T levels), comfort levels (C Levels), and “flagging” (turning off) electrodes that may cause problems. A map is determined by setting each of the electrodes to be loud enough for a person to be aware of a sound, but not too loud as to cause discomfort.

Determining a map for a young child is as much of an art as it is a science. It is important that the audiologist doing the mapping has experience working with young children. Responses are typically obtained using pediatric hearing evaluation techniques appropriate to a child’s age (i.e., Behavioral Observation Audiometry, Visual Reinforcement Audiometry, or Play Audiometry).

As young children may not cooperate for the long periods of time needed to set a map, the map may be set by generalizing responses obtained on a few electrodes to the full array of electrodes. The audiologist may also have a child try a map with similar characteristics to those used successfully by other children. 

During the initial mapping session, an audiologist will seek to determine:

• the type of speech strategy to use (see descriptions of speech-processing strategies below),
• the volume setting,
• the sensitivity setting,
• program choices (more than one map may be set in a speech processor), and
• locks and controls (to prohibit children from changing settings inadvertently).

Each of the cochlear implant manufacturers have noninvasive software programs to objectively monitor the integrity of the cochlear implant system and to assist with the mapping process.

The Cochlear Corporation has Neural Response Telemetry (NRT) for Nucleus 24 devices. This computer software objectively measures the response of individual nerve fibers to stimulation and determines a child’s “T” and “C” levels. A map can then be set based on recording the responses of these fibers without expecting a verbal or behavioral response from a child. The process takes less than 10 minutes and can be used either during surgery to determine that the ear is responding appropriately with the implant, or during mapping sessions after implantation. When used during surgery, NRT assures the surgical team that the auditory nerve is responding to the stimulation provided by the implant. Not all hospital implant centers use NRT evaluations during surgery.

The Advanced Bionics software program which confirms that the hearing nerves are responding to electrical stimulation is called Neural Response Imaging (NRI).  Med-El provides Impedance and Field Telemetry to monitor its device function.

Speech-Processing Strategies

A speech-processing strategy is the code used to convert sound to electrical impulses that represent speech. The cochlea is “tonotopic” with the base or bottom of the cochlea responsible for processing the high-frequency sounds, and the apex of the cochlea responsible for processing the low-pitched sounds. The speech processor has the job of transforming sounds into electrical patterns to convey the sounds to the brain by stimulating the various parts of the cochlea.

A variety of sophisticated coding strategies are utilized to best approximate speech.  For example, the processor may be set to stimulate the electrodes:

• simultaneously—all channels stimulated at the same time,
• partially simultaneously—some channels at the same time/some in sequence, or
• non-simultaneously—all channels in sequence.

There may also be different patterns and rates of speed at which the electrodes are stimulated as well. There is no one program suited to all persons with a cochlear implant.

There are varied speech processor names and speech coding strategies used by each implant manufacturer. The names of these coding strategies have changed over the years as new cochlear implant designs have emerged on the market. Below is a description of the cochlear implant  speech processor models and speech-coding strategies available.

Cochlear  Americas Corporation

Cochlear Corporation’s most current device is called the Nucleus Freedom™. This device is available in a lightweight body-worn version and a behind- the-ear (BTE) version.

The Nucleus Freedom™  device offers the option of choosing from a variety of  speech coding strategies including:

• Spectral Peak Strategy (SPEAK)—stimulates electrodes depending on the intensity and frequency characteristics of speech. It dynamically selects the number and location of electrodes to be activated.

• Continuous Interleaved Sampling (CIS)—  a pulsatile (digital) speech coding strategy that stimulates channels at high rates to reproduce the fine temporal changes in the acoustic waveform. Each channel is stimulated sequentially.

• Advanced Combination Encoder (ACE)—stimulates electrodes using a combination of SPEAK, which looks at the spectral components of speech, and the high stimulation rate of CIS.

The Freedom devices also offer other sound technology features including:

Adaptive Dynamic Range Optimization (ADRO): An automatic feature that boosts soft sounds and makes loud sounds quieter and more comfortable in noise.

Beam: A dual microphone system (directional and omni-directional). This feature assists with helping the individual focus on the sounds coming from the front while softening the sounds from other directions. For more information, see: http://www.cochlearamericas.com/Products/383.asp.

Whisper: A compression system that assists in listening to softer sounds. For more information, see: http://www.cochlearamericas.com/Products/382.asp.

Prior to the Freedom, the speech processors had various names. The earlier body-worn devices were called the Spectra and then the Sprint. The earlier BTE devices were the Esprit and 3G .

 Advanced Bionics Corporation

Advanced Bionics Corporation’s  most current devices are the HiRes Auria (BTE device) and the Platinum body-worn device. Each of these external devices are compatible with the HiRes 90K internally implanted device and can be programmed with HiResolution Sound Technology. This system uses a wide sound window to capture as many sounds as possible and provides fast processing power which enables it to read, interpret, and utilize the detailed sound data. The signal processing in HiResolution preserves the original acoustic waveforms before they are delivered to the auditory nerve. For more information, see: http://www.bionicear.com/tour/hi-res_sound.asp.

Prior to the HiRes 90K internal device there were other generations of the body-worn device (Clarion 1.0, Clarion 1.2, S-Series, and Earlier Platinum Sound Processor-PSP) and BTE device (Platinum BTE, CII BTE). Earlier internal devices had the capability of being matched with the following speech coding strategies:

• Simultaneous Analog Stimulation (SAS)—stimulates all electrodes at the same time.

• Continuous Interleaved Sampling (CIS)—uses digital filters and channels are stimulated at high rates to reproduce the fine temporal changes in the acoustic waveform. Each channel is stimulated sequentially.

• MPS—presents pulses partially simultaneously/partially sequentially.

MED-EL
The MED-EL device has an internal device called the Pulsar and a speech processor device called The TEMPO+ . When implanted, the recipient receives a total of five wearing options. It has a modular design and four available battery packs. Users can determine how they want to wear the speech processor.

The TEMPO+ Speech Processor usesCIS and the Hilbert Transform (a precise mathematical algorithm which simulates the shape of sound) to provide a MED-EL speech coding strategy referred to as CIS+. While there may be other manufacturers that use CIS, MED-EL notes that each may implement this strategy in a different way.  It reportedly provides a wide frequency range and highly flexible stimulation parameters. For more information, see: http://www.medel.com/ENG/US/20_Products/20_Speech_Processor/999_tempo_5.asp.

The TEMPO+ continuously self-monitors its programmed maps for data inconsistencies such as those that result from ESD or static electricity. If a problem is detected, the SoundGuard feature ceases stimulation and causes the Status Light to flash. In most cases, all mapping data can be restored by turning the system off and then on again, thus eliminating the need to visit an audiologist to reload the maps.

Revised by:
Debra Nussbaum
January 2006