A Summary of three articles:  Middle Ear Implantable Hearing Devices by Dr. Haynes, Dr. Young, Dr. Wanna, Dr. Glasscock.  Implantable Hearing Devices by Dr. Shohet.  Implantable Hearing Aids by Ms. Hartl, AuD and Dr. Jenkins.

Let’s start with a big of history:  

The thought of a Middle Ear Implant began with Dr. Wilska in 1935.  He put iron filings onto the eardrum of a patient who was prone on a medical couch.  Dr. Wilska applied a strong magnet field encased in an earphone into the ear.  The patient reported hearing sound despite the absence of an acoustical signal.  Fast forward to the 1970s, when devices were created to be surgically placed into the middle ear.  The technology has greatly evolved over the years.  

There are four main types of hearing implants.  The most common are cochlear implants, and bone conduction hearing implants.  The two less common are: middle ear implants (MEI), and auditory brainstem implants (ABI)

 A Cochlear implant is an electronic medical device that replaces the function of the damaged inner ear. The processor sends hearing sensations to the implant, which then transmits these signals to the auditory nerve of the brain.  These are designed for people with severe to profound hearing loss.

Bone conduction hearing aids versus Bone anchored hearing aids. (BAHA).  These are similar but the BAHA has an abutment that is surgically implanted behind the ear, while the bone conduction hearing aid is not implanted.  This abutment transmits sounds by direct bone conduction to the inner ear, bypassing the external auditory canal and the middle ear.  BAHAs are used primarily in people with a conductive hearing loss or those with single-sided deafness.  

Middle Ear Implants (MEI):  these are essentially surgically implanted hearing aids.  They send a signal to the middle ear which mechanically vibrates the middle ear bones.  This increases the sound vibrations entering the cochlea where the vibrations are converted into electrical signals sent to the brain.  These were developed to treat conductive and sensorineural hearing loss.  MEIs can be either fully or partially implantable.

Auditory brainstem implants (ABIs):  these devices stimulate the auditory brainstem directly, bypassing the ear and auditory nerve to provide a sensation of hearing.  These are often used for adults who have suffered a trauma to their hearing nerve and would therefore not benefit from a conventional hearing aid.  It consists of two parts:  the external part containing a microphone and speech processor.  The internal part is surgically implanted directly onto the brainstem.  It consists of  a receiver and electrodes to directly stimulate the brainstem.

Interestingly, despite the consistent reports of high patient satisfaction and subjective preference over conventional hearing aids, these implantable devices have not been widely adopted.  While some prefer conventional hearing aids to avoid a surgical procedure, other factors may be in play.  Few insurance companies are willing to pay the additional costs.  The codes used to describe any procedure (which are used by insurance companies to determine payments) are lacking, so doctors are concerned they will risk inadequate reimbursement.  Though these implantable hearing devices are less popular, they have the potential to overcome many limitations of conventional hearing aids.  It is to be hoped that these types of devices will continue to be studied and undergo further research.

If you would like to read these articles, or have any questions, please call us at Hears to U.  Happy Hearing!

By Karen M

Kim Fishman, Audiology, Clinic, Minneapolis, Hopkins, Minnesota