The document discusses middle ear implants as a type of hearing aid for patients with mild to severe hearing loss. It describes two main types of transducers used in middle ear implants - electromagnetic and piezoelectric. Several implant devices are discussed, including the Vibrant Soundbridge, Middle Ear Transducer (MET), Carina, and Esteem. Clinical trial results for some devices show significant improvement in functional gain and patient satisfaction compared to conventional hearing aids.

1. Dr.VINOD. M. K
GMC,Amritsar
References
1.Glasscock Shambaugh 6th edi.
2.Scott-Brown 7th edi.

2.  Middle ear implants represent a type of
hearing aid that has a potentially widespread
application to patients with mild to severe
hearing loss.
 The main impetus to develop these devices
has come from patient dissatisfaction with
conventional amplification aids relating to
 performance
 the sound quality, occlusion effects and
 acoustic feedback,comfort
 social stigma and cosmetic implications.
 Wax blocking the receiver
 recurrent otitis externa .

3.  Implantable acoustic/mechanical hearing
devices differ from conventional hearing aids
in that they are partially or totally implanted
and directly couple acoustic energy to the
ossicular chain or cochlea.
 In exchange for the added surgical risks and
costs associated with implantation, they offer
several potential advantages over
conventional hearing aids, including
 increased gain and dynamic range,
 reduced feedback,
 Reduced maintenance,
 improved appearance,
 freedom from ear canal occlusion.

4. Wilska is credited with being the first to
use electromagnetic induction to stimulate
the middle ear.
Implantable middle ear hearing devices
differ from conventional aids in how they
impart sound vibration to the ossicular
chain.
convert the electric signal movement of
an actuator coupled to the ossicular chain.

5. Two basic types of transducers that have
been incorporated into the middle ear
implantable hearing devices:
ELECTROMAGNETIC and
PIEZOELECTRIC.

6.  Electromagnetic transducers generate a
magnetic field using a wire coil carrying a
current that encodes the microphone output.
 This magnetic field induces motion of a
nearby magnet, which can either be separate
from the coil and attached alone to the
ossicles or
 integrated with the coil to become a vibrating
compound mass affixed to the ossicles

7. Piezoelectric devices move ossicles using
a piezoelectric crystal that bends or
lengthens in time with changes in a signal
voltage applied across it.
Piezoelectric ossicular actuators generally
yield greater power and less distortion than
electromagnetic devices.
but they are typically larger and require
precise placement to ensure proper
compressive force between the actuator
and the ossicle it contacts.

8.  Partially implanted devices consist of an
external processor comprising a microphone,
speech processor, battery, and a transmitter
coil that transcutaneously conveys signals
and power to the internal device.
 This approach facilitates replacement of
batteries, service and upgrade of processors,
and minimization of internal device size, but
requires patient acceptance of an external
processor.

9.  fully implantable systems house all of
components within the implanted portion of
the device, including the battery pack and a
microphone.
 This frees the patient from wearing a visible
external processor,
 but it increases the size and complexity of the
implanted components,
-mandates surgical procedures for battery
replacement each ~5 years,
-and complicates design and placement of
the microphone.

10. Vibrant sound bridge- partially implantable
Middle ear transducer(MET)- partially
implantable
Carina- totally implantable
Esteen hearing implant- totally implantable

11. was the first semiimplantable middle ear
hearing device available in Europe (1998)
and the United States (2000).
The device employs a "vibrating ossicular
reconstruction prosthesis" (VORP)
electromagnetic transducer
 It is a magnet/coil combination typically
attached to the long process of the incus
and connected via a thin signal wire to an
implanted receiver/amplifier.

12.  The external processor houses a microphone
and standard zinc battery; it is held in place
behind the ear by a permanent magnet
 The internal device typically is implanted
using a standard transmastoid, facial recess
approach to the middle ear.
 The internal receiver is placed in a bony
trough in the retrosigmoid bone several
centimeters behind the ear, similar to
placement of a cochlear implant processor.
 The VORP is crimped into the long process of
the incus

14.  A prospective, single-subject, repeated-
measures multicenter study of 53 adult
subjects with moderate to severe SNHL
measured
 unaided hearing before and after
implantation,functional gain, speech
recognition, acoustic feedback, occlusion,
patient self-assessment, and device
preference in direct comparison between the
Vibrant Soundbridge™ and appropriately fit
acoustic hearing aids.

15.  Statistically significant improvement was
observed in functional gain at all frequencies
tested from 250 to 8,000 KHz, patient
satisfaction,performance, occlusion,
feedback, and device preference
 Greater than 10 dB improvement in
functional gain was observed in 2,4, and 6
kHz.
 24% of subjects performed significantly better
with the implanted device and 14% performed
significantly worse.

16. As of2008, over 2,500 patients have been
implanted with the device worldwide over
more than a decade.
The proportion of patients who said they
would repeat the procedure (72%) and -
40% said they would consider binaural
implantation.
The most common side effects were
persistent aural fullness (27%) and
persistent taste alteration (8%).

17. A 2005 summary from the device
manufacturer on 1000 Vibrant
Soundbridge™ implant cases described a
0.3% device failure rate since 1999.
a 5% incidence of revision surgery due to
inadequate performance.
1% rate of skin-flap necrosis also noted.

18. The Vibrant Soundbridge™ is suitable for
patients with
hearing loss of up to 70 dB PTA
and is US FDA-approved for patients with
moderate to severe SNHL, adequate aided
speech discrimination, and medical
contraindication or intolerance of a
conventional hearing aid

19. The Otologics Middle ear transducer
(MET™) is an electromagnetic middle ear
hearing aid.
The original, semi-implantable MET has
been replaced by the fully implantable
Carina currently in clinical trials.
MET/Carina mechanism moves the incus
using a linear actuator rigidly connected to
the edges of a limited mastoidectomy
cavity.

21. offers the potential to exert greater force
on the incus than the floating mass
approach;
however, this comes at the expense of
greater complexity in the implantation
procedure!
 must achieve precise positioning to
ensure optimal compressive loading of the
rod/incus junction

22.  Via a postauricular incision, a well is drilled to
house the implant body and then a limited
mastoidectomy is performed to expose the
incus body and malleus head.
 A laser is used to make a small pit in the
posterosuperior incus body,
 then the linear actuator is maneuvered into
the mounting system and its position is finely
adjusted until its rod indents the incus pit with
optimal compression force.
 The receiver capsule and transducer
electronics are placed in the well, and the
microphone is positioned subperiosteal at an
intact region of mastoid cortex.

24. Mean functional gain averaged across
0.5/1/2/4 kHz (for the 160 subjects tested
at 2 to 12 months postoperatively) was 28
dB.
Speech recognition and subjective hearing
scores for the 77-subject cohort were not
significantly different b/W the conventional
aid and MET.
As a fully implanted device reliant on a
rechargeable battery with a ~5-yr life, the
Carina must be exposed via surgery for
replacement of the battery every -5 years

25. is a fully implantable piezoelectric device.
One especially notable design feature of the
Esteem is its use of the tympanic membrane
and malleus as a microphone diaphragm;
a piezoelectric sensor transduces malleus
motion into a signal voltage, which is
amplified and used to drive a second
piezoelectric actuator in contact with the
incus and/or stapes.

26. implantation of the Esteem requires partial
removal of the incus to prevent feedback
from actuator to sensor.
This ensures a maximal CHL in the event
of device failure or removal, unless a
subsequent ossiculoplasty is performed.
• Power is provided by a nonrechargeable lithium-ion
battery designed to last 5 years between
replacements

28. The Esteem is designed for patients with
moderate to severe hearing loss.
Indications include age ^18 years, mild to
severe (35 to 85 dB) SNHL between 0.5
and 4 kHz in the implanted ear, a healthy
ear with normal pneumatization and
adequate space for device implantation on
CT, normal tympanometry, and speech
discrimination ^60%.

29. Overall, the results so far available for
middle ear implantable devices appear
encouraging and without major
complications
and have provided valuable information as
implant design improves.
at present it is only the Vibrant
Soundbridge that is in worldwide use with
viable support and favourable longterm
results.