what-when-how
In Depth Tutorials and Information
The screw osseointegrates with the bone to form a direct
union. This allows vibrations to pass through to the bone
to the inner ear cochlea without loss of volume (as hap-
pens when soft tissue is between the bone and the hear-
ing aid). This is the same type of procedure that is used
to hold implantable teeth. The bond is very strong when
the bone is normal. The problem with OI is that the
bone may not tolerate the forces transmitted and may
fail to hold the screw tightly.
49-51
Although some dental
implants have been successful, the failure rate is high
enough that most dentists will not use the implant in OI
patients. Whether or not the hearing aid forces are toler-
ated is not known to date; no data on their use are avail-
able in OI patients. A newer bone conduction hearing aid
known as the Sound Bite does not rely on osseointegra-
tion and may be a more favorable option.
auditory function to normal. However, there are some
individuals with markedly impaired speech processing
abilities who cannot benefit from hearing aids for whom
other intervention will be necessary.
COCHLEAR IMPLANTS
Some people have such poor hearing that hearing aids
do not help: 2-11% of patients with OI will have such dete-
rioration. Cochlear implants provide an option for restor-
ing hearing.
54-56
Cochlear implants are electronic devices
that are implanted directly into the inner ear. They have
an internal device that has multiple electrodes spaced
along an implanted coil. The electrodes can be activated
separately to stimulate the cochlear nerve directly at dif-
ferent sites in the cochlea. Since the cochlear nerve is ori-
ented in the cochlea based on sound frequency, the device
can stimulate the appropriate nerve endings equivalent to
the sound it receives. Stimulus intensity and timing can
also be transmitted to replicate the normal function of the
inner ear. An external speech processor that is similar to
a behind-the-ear hearing aid is attached via a magnet to
the inner ear device. Sound is processed in the external
device and relayed to the appropriate inner ear electrodes.
Coding strategies continue to improve. Cochlear implants
have proven to be effective and cost-effective for all ages
with the average implant user not only hearing sounds but
understanding 30-40% of the words received.
57
The surgery for cochlear implantation in OI patients is
a little more difficult because of hypervascularity of the
bone and possible narrowing of the inner ear dimensions
of the cochlea. Also once the device is placed, the bone
does not shield the electrical stimulations from spread-
ing because of the lower bone density. This requires some
adjustments in the current settings to control the spread
and prevent stimulation of the facial nerve. Programming
of the cochlear implant can be impacted by stimulation of
the facial nerve which may lead to rejection of the device
should problems persist.
54
In addition, indications of
special spread of neural excitation have been reported.
54
Surgeons must also be aware of potential cavitary lesions,
often noted on preoperative CT, which could lead to
electrode migration. Despite these limitations, cochlear
implants in OI patients are highly successful with up
to 81% open-set phoneme scores reported
54
for some
patients. However, it should be noted that the numbers of
patients reported upon is very low.
IM
PLANTABLE HEARING AI
DS
Implantable hearing aids are starting to become an
acceptable option for treatment of hearing loss. These
devices are surgically implanted and drive the ossicu-
lar chain directly rather than amplify sound transmitted
through the air. Some are partially implanted devices
and some are fully implanted devices. The major poten-
tial problem with these devices is that they attach to ossi-
cles that are not of normal strength. Given the fragility of
the ossicles in OI, they may not be a good option. One
recent ongoing study attached the Vibrant SoundBridge
implant to the incus in combination with a stapedec-
tomy.
52
Initial reports are favorable in three patients with
OI.
52
No long-term results are yet available.
SENSORINEURAL HEARING LOSS AND
HEARING AIDS
Sensorineural hearing loss is common in OI patients.
Treatment is the same as for those without OI - i.e., hear-
ing aids. Whether the loss is sensorineural, conductive
or mixed, hearing aids help by increasing the volume of
sound presented to the ear. This can overcome the loss
due to middle and inner ear problems. Hearing aids can
modify the sound that is being presented by boosting the
weaker heard sounds more than the better heard sounds.
This can even out the speech so that the missing pieces
are heard clearly. Hearing aids with special processing
or used in conjunction with FM systems can also help
filter out background noise so that voices become more
distinct. In many people understanding the words is just
as much a problem as hearing the sounds; especially in
the background of competing speech or background
noise.
53
Hearing aids may be of some help in these indi-
viduals but should not be viewed as capable of restoring
CONCLUSIONS
Hearing loss is commonly found in OI. The initial
presentation of hearing loss is typically conductive with
sensorineural involvement appearing with increasing
