What are active middle ear implants and how is it different from a traditional hearing aid?
Active middle ear implants is an implantable device that employs a Floating Mass Transducer (FMT) that is coupled to the long process of the incus to generate a magnetic field which in turn induces motion of a nearby magnet and creating vibrations. The sounds are initially picked up the microphone in the audio processor, which converts environmental sounds into electrical signals. These electrical signals are then transmitted through the skin to the implant. The implant relays these signals down the conductor link to the FMT, which in turn converts these electrical signals into mechanical vibrations that set the structures of the middle ear into motion.
Apart from Middle Ear Implants being surgically implanted devices, they can offer better sound quality, less or no occlusion, no acoustic feedback, and more comfort when compared to a traditional hearing aid. While hearing aids convert electrical signals back into acoustic energy, Middle Ear Implants convert electrical signals into mechanical energy.
Types of Middle Ear Impl Partially implantable devices contain an external processor that transcutaneously conveys signals to the inner device, while a fully implantable device houses all of the components within the implanted portion of the device. The external component of a partially implantable device is held in place behind the ear by a permanent magnet. Middle ear implants use two types of transducers. A piezoelectric crystal that is coupled directly to the ossicles and is capable of directly converting the electric signals into mechanical vibrations. An electromagnetic transducer converts electric signals into electromagnetic signals that vibrates a separate unit connected to the ossicles, such that the transducer is not directly in contact with the ossicular chain.
Candidacy and Contraindications
Middle Ear Implants are most suitable for individuals with mild to severe, fairly stable, sensorineural hearing loss. It can also be considered in some conductive or mixed types, provided that the middle ear function is normal, and any middle ear inflammation or infections are controlled prior to the surgery. Middle Ear Implants cannot provide benefit if there is presence of a retro-cochlear or central involvement causing hearing loss.