Bone Conduction v. Middle Ear Implants
Although both middle ear implants and bone conduction implants are surgical treatments, they treat different types of hearing loss in different ways magnetic stimulation versus direct bone conduction.
Middle ear implants (MEIs) are designed for those with a purely sensorineural hearing loss, which results from nerve damage to the inner ear (cochlea). In order for MEIs to treat effectively, patients must have functioning ossicles middle ear bones.
MEIs involve the surgical implantation of an electromagnet somewhere along the ossicular chain, depending on the method of attachment or technology used. When exposed to sound, an electromagnetic field is generated which stimulates the magnet. The ossicles transmit these vibrations to the cochlea, which turns the sound waves into nerve impulses that are sent to the brain.
Currently, there are two types of middle ear implants available the Vibrant Soundbridge from MED-EL and the Direct System from Soundtec, Inc.
Bone conduction implants are designed for patients with untreatable middle ear conductive or mixed hearing losses and those who have a unilateral sensorineural hearing loss, or Single Sided Deafness. In order the bone conduction implants to treat effectively, patients must have at least one functioning cochlea.
Bone conduction implants are comprised of a tiny titanium fixture, an external abutment, and a detachable sound processor. The fixture is surgically implanted into the mastoid bone and forms a permanent, secure bond during a process called osseointegration. Via the abutment, the sound processor receives natural sound and sends it to the functioning cochlea using the skull bone as a pathway to bypass the middle ear. Candidates for bone conduction implants do not have a functioning ossicular chain.
Currently, there is only one type of bone conduction implant available the Baha System from Cochlear Ltd.