Get documents about "Cochlear Implant Mapping
Document Sample
By Courtney L. Carver
Those familiar with
the implant process
often hear about the
hook up, activation
day, and getting
mapped. What do all
these terms mean?
An audiologist who
works with cochlear
implant recipients
explains.
Cochlear
Implant
Mapping
What Every CI User and
Candidate Should Know
T he goal of this article is to help
cochlear implant candidates and users
For example, the most common
change after recent activation is a
better understand the mapping proce- change in loudness levels. Since you
dures and why a well developed map have not heard for a while, what seems
is important. By reading this article, loud at first may soon become too
you will know what a cochlear implant quiet. These appointments help you
(CI) map is, the process involved in keep the settings optimally adjusted so
mapping a processor, and how the maximum benefit can be obtained for
map directly affects hearing with a each individual listener.
cochlear implant. Within the first month, there will
Understanding your role in the be several mapping appointments
process of developing an ideal map (see table on page 12). However as
will allow you to use your time produc- the map stabilizes, the appointments
tively time with your audiologist and become farther apart. But remember
ultimately help you attain your goals in that mapping is never finished. It is
staying connected with your implant. an ongoing process. Adjustments will
need to be made periodically, even
What is a “Map“? after many years of use. A cochlear
A map is composed of the individual implant is a lifetime commitment and
Audiologist Courtney Carver works with mapping should be completed on an
parameters that a cochlear implant cochlear implant recipient Joan Kleinrock
user needs in order to have access to during a mapping session at The Listening
annual basis for maximum benefit.
the rich array of daily sounds. (See table Center at Johns Hopkins in Baltimore..
on page 12 for details on the parameters What Else Can I Expect at a
used in developing a map.) How Often Does Programming Appointment?
The “mapping” or “programming” Mapping Occur? Each appointment can include audio-
of a cochlear implant is the process The activation, or “Day One” of hear- logic and speech perception testing
that sets the best parameters for an ing, occurs approximately four to six in addition to mapping. This testing
individual patient. Parameters, or the weeks after implantation surgery. The is often done at the beginning of the
settings that define the map, establish initial activation appointment is the appointment by using the patient’s
the code that will be supplied to your first moment of hearing sounds with a primary map.
implant. This code is a translation of cochlear implant. However, activation The purpose of testing is to obtain
the energies that make up sounds and does not always enable speech under- some objective baseline measures that
include the coding strategy, the rate standing. Many users describe those can be tracked from pre- to post-im-
and duration of electrical pulses, the initial sounds as sounding like beeps plant to monitor your progress. These
number of channels and the indivi- or echoes and are often described as test scores are also useful in determin-
dual T (threshold levels) and M/C tinny, robotic or raspy. ing subtle decreases over time in the
(most comfortable or loud but Each person’s perception of the case of malfunctioning equipment.
comfortable levels). sounds is different. It may take a In some cases, these tests may help
The settings of the map are pro- while to get used to sound and for the us know where changes are needed
grammed by your audiologist, who is sounds to take on meaning. Follow-up in the mapping.
specially trained to judge your respons- programming is important to taking a
es to test signals to set the program. cochlear implant to its fullest poten- The Programming
Each cochlear implant manufacturer tial. Remember, this is a journey and Appointment: What
uses different names to describe various the complexities of the hearing path- Happens Step-by-Step?
parameters, so things can get confusing. way require that the hearing process The first step is for the clinician to run
It is important to understand unfolds slowly. a standard check on the internal device
how the individual parameters relate At each programming appoint- by connecting the speech processor
to one another and that some are ment, the parameters will be reevalu- to the programming computer. This
programmed into the implant soft- ated and adjusted to make sure they will only take a few minutes. You will
ware and, thus, are not changeable. are optimized. As you are learning to not be able to hear this test with your
Since maps are customized to each hear with an implant, the sounds will implant and since you will be connect-
individual, they are unique to each change and the parameters will need ed to the computer, you won’t hear
person. Different techniques are used to be adjusted to make sure you have sounds or voices within the room.
to create maps and are custom fitted continued improved access to sounds Next, the “impedances” of
to an individual patient. and their range of intensities. continued on page 12
1
July/August 2007 1
Mapping continued from page 11 an electrode needs to be turned off or Within the first month, there
kept on for maximum sound quality will be several mapping
the contacts in the cochlea will be benefit. Impedances are often directly appointments…as the map
checked, establishing communication linked to certain parameters, making
between the external and the internal
stabilizes, the appointments
some changes in the software auto-
devices. Impedances measure the ease matic. Changes in electrode impedanc- become farther apart…mapping
of current flow through an electrical es can indicate a change in function is never finished. Adjustments
circuit or, in this case, a cochlear im- and can account for changes in sound will need to be made periodi-
plant electrode. A change in the status perception. Small changes in imped- cally, even after many years of
of an electrode could include an open ances will not affect sound quality or
use. A cochlear implant is a
or short circuit, or just a higher imped- understanding and are quite common.
ance level. An increase in impedance, but lifetime commitment and
In some cases, the audiologist still within normal limits, means that mapping should be completed
may need to turn off those electrodes more stimulation may be necessary to on an annual basis for
to improve sound quality. This does achieve the same level of loudness for maximum benefit.
not mean that the internal device is the listener. Larger changes in imped-
not working; it just means that that ances can be caused by ossification a number of variables which must be
electrode contact may not be providing inside the cochlea or other physio- explored to determine the best combi-
good information at that given time. logic changes. nation for each patient. Some variables,
Don’t panic; the patient and As mentioned before, the soft- such as strategy, rate, and pulse width,
audiologist will determine whether ware used to program each device has are set by default in the map. These
defaults largely go unchanged unless it
is necessary due to certain anatomical
Sample Programming Schedule* influences, high power requirements,
or a lack of sufficient progress.
Appointment Description
Days 1, 2 Activation of the external equipment; Other Adjustments
approximately 4 weeks after surgery Other factors, such as the threshold and
maximal comfort levels, are adjusted at
1 week Audiogram and reprogramming
each appointment. The type of task an
1 month Audiogram and reprogramming audiologist will ask of the cochlear im-
3, 6, 9 plant recipient varies by manufacturer.
months Audiogram, Speech Perception Testing and reprogramming Measurements may be made to deter-
mine the softest sound the patient can
1 year Audiogram, Speech Perception Testing and reprogramming hear (threshold) and the most comfort-
Every 6-12 able or loud but comfortable level.
months Audiogram, Speech Perception Testing and reprogramming The levels set by the patient create
the dynamic range. All sounds picked
* May vary by patient and clinician. up by the microphone will fall some-
where in this dynamic range, with
Select MAP Parameters the softer sounds being closer to the
threshold level and louder sounds
Name Description being closer to the maximal comfort
Strategy Set of rules or defaults that dictate how sound is analyzed level. In some situations, the thresh-
and presented. Varies by company. old is set by the computer, rather than
Advanced Bionics – Fidelity 120, HiRes P, HiRes S, SAS, MPS, CIS judged by the patient.
Cochlear – ACE(RE), ACE, SPEAK
MedEl – CIS+ Electrodes
The audiologist may then go through
Stimulation Describes distance between active and indifferent electrode mode
the electrode array, stimulating every
Rate Frequency at which electrical current (pulse) is delivered, measured electrode, in order for the patient to en-
in pulses per second sure the volume of each is set similarly.
Each electrode stimulates a different fre-
Pulse width Duration of time electrical current (pulse) is delivered, quency range and is balanced to ensure
measured in microseconds that low pitches and high pitches are set
12 Hearing Loss Magazine
at an even loudness. More changes are tion than is appropriate (overstimu- Background noise can never be
made to the map using a live voice. lation), these measurements can be eliminated completely—there
This means that the audiologist convincing evidence to the audiologist is simply too much overlap
will turn on the processor to the sound that levels need to be decreased for between the characteristics of
environment while it is connected to better speech perception performance.
background noise and human
the computer. This enables fine-tuning
speech. However, you can give
of the map. Global adjustments can Going Beyond the Basic Map
be made at this point to change the per- Once the basic map is finalized, differ- your brain some time to learn
ceived volume and the sound quality ent programs can be created for vari- to filter out the desired speech
can be tailored by emphasizing pitches. ous listening situations. For example, from challenging noise and use
programs for listening in background your lip reading skills to help.
Measuring Stimulation noise, listening to music, connecting
of Electrodes to accessories, and talking on the tele- 2) Speak up! If the map is uncomfort-
Objective measures can be used to phone may be helpful. able in any way, tell the audiologist.
determine the approximate level of Keep in mind there are limita- If appropriate, changes can be made
stimulation required for a neural tions to cochlear implant listening in at that point that will save you
response. Such measurement capabili- various situations. The microphone another trip to the cochlear implant
ties are not always available with older will pick up all sounds, not just the center for troubleshooting a week
devices. The most common objective desired sounds. A map created for use or two later.
measures utilize the responses from in background noise may function by 3) Keep in mind that cochlear im-
nerves activated by the device. These reducing the sensitivity of the micro- plants give more high frequency
tests can be used to verify behavioral phone or re-ducing the gain in the low information than hearing aids.
feedback or to determine approximate frequency sounds, thereby reducing Most cochlear implant recipients
levels for the map. the volume of the background noise. notice that voices are more high-
The ability to obtain objective However, background noise can pitched along with most environ-
measures is especially important for never be eliminated completely—there mental sounds, especially early
young children and others who have is simply too much overlap between on. Much of the clarity of speech
difficulty giving feedback on loudness the characteristics of background noise comes from the high-frequency
and sound quality. Objective measures and human speech. However, you can information.
can also be used to confirm subjective give your brain some time to learn to Remember, better speech un-
measurements in adults. In cases where filter out the desired speech from chal- derstanding is the most important
a person is requesting more stimula- lenging noise and use your lip reading thing in programming your cochle-
skills to help. ar implant, so if your understanding
is improved with increased high-
How Can a Person with a frequency information, keep it in
Cochlear Implant Participate your program even though it may
for the Best Map? not be the sound quality you are
used to or would prefer. In most
There are four important things to cases, the quality of sound or
keep in mind: “timbre” will improve with time.
4) Recognize that it can take two
1) Trust in your audiologist is weeks or so to fully adjust to a
crucial. Follow the audiologist’s new map. Your brain needs time
instructions. Don’t try to interpret to learn the new code that has
what he or she is asking for… been programmed into the proces-
ask questions if you are confused sor. Patience and practice will
about what to do. Also, do not try pay off in an improved listening
to guess what the “right answer experience.
is.” There is no right answer.
Each manufacturer has a specific Courtney L. Carver, Au.D., CCC-A, is
recommendation on what instruc- a cochlear implant audiologist at The Listen-
tions to give (most comfortable ing Center at Johns Hopkins in Baltimore.
versus loud but comfortable, etc) She received her Au.D. degree from the
Working with your audiologist during the CI and this will affect how the map University of Florida. She works with adult
mapping process can bring positive results. sounds in the end. and pediatric cochlear implant recipients.
July/August 2007 13
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