Middle ear implants are used to treat people with sensorineural, conductive and mixed hearing losses. These implants are an implantable alternative to hearing aids. Unlike hearing aids that make sounds louder, a middle ear implant takes sound and converts it into mechanical vibrations. A middle ear implant is directly attached to a structure in the middle ear. It causes this structure to vibrate in much the same way that sound (acoustic vibrations) travelling down the ear and through the eardrum causes middle ear structures to vibrate. These acoustic vibrations are amplified and can be adjusted to optimally compensate different kinds of hearing losses. The most successful middle ear implant on the market is the Vibrant Soundbridge. It is a partially implantable hearing system that consists of two parts, an external and an internal component.
The internal, implanted part of the Vibrant Soundbridge is called the Vibrating Ossicular Prosthesis (VORP) and consists of the internal coil, magnet, conductor link and the Floating Mass Transducer (FMT).
a. Audio processor
The external part is called the Audio Processor, which is held onto the head and underneath the hair with a magnet. It contains the microphone, the battery and electronics to convert sound in the environment into a signal that is transferred to the implanted internal part.
The signal from the Audio Processor is transferred across the skin to the internal coil, which relays this signal down the conductor link to the FMT. When activated, the FMT vibrates in a controlled manner, specific to each patient’s hearing needs, causing the structure of the ear to vibrate.
This surgical treatment of hearing loss via vibratory stimulation in the middle ear by using a middle ear implant is defined as Vibroplasty. It is applied in different types of hearing losses for patients who only achieve limited benefit from conventional hearing aids. Vibroplasty is also often performed in patients with insufficient benefit after conventional middle ear surgeries. In Vibroplasty treatments, the FMT may be placed onto different structures in the middle ear, depending on the individual condition and anatomy.
With the Incus Vibroplasty, the FMT is attached to the incus, one of the three small bones of the middle ear. The FMT converts the signal into vibrations that directly drive and move the ossicles, similar to the way normal sound moves them via the ear canal. These vibrations then are interpreted by the brain as sound.