North Texas
Cochlear Implant Program
Cochlear Implant Information Index -
General Information -
Internal Components -
External Components
Speech Processing -
Warranty/Loss Information -
Other Resources
Internal Components
A. The Implant
1.
Depth of the Insertion of the Electrode
Array
The nerve fibers that correspond to the
higher-pitched tones are found at the entrance to the cochlea, while
lower-pitched tones are located toward the deeper end of the cochlea. Deeper electrode placement may facilitate
stimulation of the low-pitch nerve fibers and thus contribute to enhanced
speech understanding. However, when the
electrode array is inserted, damage will occur to the hair cells (hearing
cells) within the cochlea. Research is
being conducted to look at the effect of deeper insertion of the electrode
array within the cochlea.
Advanced Bionics Corp. Clarion Hi-Focus
flexible electrode array designed to deliver focused stimulation
to the auditory nerve
the electrode array extends approximately one and a half turns of
the cochlea (~24 mm)
Cochlear Corp. - Nucleus 24 - Contour
flexible perimodiolar electrode array designed to deliver focused
stimulation to the auditory nerve
the electrode array extends approximately one and a half turns into the
cochlea (~25 mm)
MED-EL - Combi 40+
flexible electrode carrier designed for easy bending
the electrode array extends approximately 30 mm into the cochlea
an additional electrode configuration is available for patients
with cochlear ossification
2.
Number of Channels and Electrodes
Multichannel systems provide patients
with access to more than one stimulating method and speech processing strategy.
Advanced Bionics Corp. - Clarion
8
channels and 16 electrodes (1 electrode pair
= channel)
Cochlear Corp. - Nucleus 24
22 channels and 24 electrodes (22 electrodes inside the cochlea and 2
electrodes outside the cochlea)
MED-EL - Combi 40+
Combi 40+: 12 channels and 24 electrodes for the C40+ (1
electrode pair= channel)
B. MRI Compatibility
Magnetic Resonance Imaging (MRI) is
increasingly the diagnostic tool of choice for a variety of medical
conditions. Implants that use
transcutaneous connectors contain an implanted magnet and some ferrous
materials that are incompatible with the high magnetic fields of an MRI
scanner. Implant manufacturers are
redesigning their devices to circumvent this problem. Potential MRI risks should be part of the informed consent
procedure for persons considering an implant.
The external speech processor cannot be made MRI compatible and should
not be taken into the scanner. (NIH, 1995)
Advanced Bionics - Clarion
the electronics and magnet are encased in a metal (alimina) and
ceramic case
because the implant has metal as a component, the patient cannot
undergo an MRI procedure
Cochlear Corp. - Nucleus 24
the receiver is made of titanium, the Nucleus 24 has been
designed so that the internal magnet is removable in a minor surgical procedure
MED-EL - Combi 40+
the antenna and receiver circuitry are sealed in ceramic housing
because the implant contains metal, the patient cannot undergo an
MRI procedure
Research
is being conducted investigating the combination of the use of less powerful
MRI fields and protective devices in patients with cochlear implants.