Middle ear implants

Prepared by :Dr . Sayf M. Dehaies

M.B.Ch.B SHO ORL-HNS

Scott-Brown's Otorhinolaryngology, Head and Neck Surgery7th editionRichard M irving MD FRCS (ORl-HNS) Consultant in Neurotology University Hospital Birmingham NHS Trust and Diana Princess of Wales (Birmingham Children's) Hospital; and Honorary Senior Lecturer University of Birmingham Birmingham, UK

Andrew Scott FRCS (ORL-HNS) The Royal Shrewsbury Hospital Shrewsbury, UK

Middle ear implants

These are a type of hearing aid with potential benefit over the conventional one .

Its superior to the conventional hearing aid in the following point :

• Better sound quality , no occlusion effects ,no acoustic feedback.• More comfortable• Better cosmoses• No wax blocking or recurrent OE.

they are not beyond the reach of the conventional hearing aid. i.e. the patient should be able to hear by the conventional hearing aid but complaining about the sound quality or comfort or cosmoses ….

The current device are most suitable for mild to sever SNHL , recently the sound bridge device approved for use in conductive or mixed losses in combination with passive middle ear prostheses.

ME function should be normal , any ME inflammation should controlled prior to surgery.

There should be absence of retro-chochlear or central involvement.

The patient should not have any skin condition that prevent the attachment of any external part.

structure

The conventional hearing aid consist from:

• Microphone : receive the sound energy.• Amplifier or processor unit ( digital or analouge )• Transmitter or speaker : transmit the sound energy through the normal

auditory pathway of TM & ossicles to the ME.

Middle ear implants differ only in the 3rd part i.e it not convert the electrical energy from the amplifier to acoustic energy but to mechanical energy through the TRANSDUCER _ then the mechanical energy is coupled directly or indirectly to the ossicular chain

• Piezoelectric transducer : the piezoelectric crystal is capable of converting the alternating voltage from the electrical sound signal from the amplifier to mechanical vibrating force that is coupled directly to the ossicular chain.

• Electromagnetic transducer : contain a coil which convert the electrical signal from amplifier to electromagnetic signal which will vibrate ferromagnetic unit coupled directly to the ossicular chain – so the transducer is not in direct contact with the ossicular chain.

There are 2 type of transduce

r :

Current device :

Vibrant sound bridge :

• developed by Symphonix and currently by Med-El • is an active semi-implantable electromagnetic hearing device. • It consists of an internal, surgically implanted part - the vibrating

ossicular prosthesis (VORP) - and an external audio processor. • The VORP is made up of a receiving coil, conductor link and

transducer. • The transducer have small electromagnetic coil and enclosed

magnet to produce vibrations in this floating mass transducer, which is coupled to the long process of the incus.

• The approach for implanting the Vibrant Soundbridge is similar to that for a cochlear implant and the siting of the transducer shares similar demands to stapes surgery

• Different incisions are used1. extended endaural, 2. postaural or 3. extended postaural

• cortical mastoidectomy is done and then a posterior tympanotomy Which should be large enough to take a 3-mm diamond burr to ensure sufficient space to site the transducer.

• An implant bed is drilled in the squamous temporal bone to accommodate the internal receiver and conductor link.

• The floating mass transducer is placed in the middle ear via the posterior tympanotomy with its attachment clip around the long process of the incus using the special forming forceps provided with the implant.

• there is concern about crimping the clip to the long process of the incus. If the clip is crimped too tightly there is a potential for necrosis of the long process of the incus, and if it is too loose the implant may fail.

Otologics™ middle ear transducer

fully implantable device,

The device consists of a subcutaneous microphone and an electronic receiver connected to a transducer.

The transducer drives a probe coupled to the body of the incus. The tip of the probe is made of aluminium oxide and this forms a fibrous connection with the laser-made hole in the incus body.

The ossicular chain is left intact.

The Otologics MET ossicular stimulator is currently under FDA-approved clinical trial in the United States.

Esteem®-Hearing Implant™fully implantable piezoelectric device currently under FDA trial .

The device comprises a piezoelectric sensor on the incus body and driver cemented to the stapes head.

Implantation of the device require disarticulation of the ossicular chain with removal of the lenticular process of the incus.

DEVICES NOT CURRENTLY AVAILABLE

• Soundtec® Direct Drive Hearing System • Rion partially implantable hearing aid • Totally implantable cochlear amplifier

The initial trail have establish the safety & efficacy of these device.

Medium term date ( 10 years ) are now available & suggest that the benefit is well maintained over time & the patient satisfaction is high.

Thank You