Cochlear implants may be losing their awkward external hardware
By Ben Coxworth
February 10, 2014
Thanks to the development of cochlear implants, many people who would otherwise be quite deaf are able to regain a limited sense of hearing. Unfortunately, the implants also incorporate external components that can get in the user's way, and that look ... well, that look like the user has something hooked up to their ear. Now, however, researchers at MIT, Harvard Medical School and the Massachusetts Eye and Ear Infirmary have developed a chip that could lead to cochlear implants that are entirely implanted.
With a regular cochlear implant, the external bits consist of a microphone, a speech processor/power source that enhances voices in the audio picked up by that microphone, and a transmitting coil that rests against the skin. The implanted components include a receiver that picks up the audio signal from the transmitter, a stimulator that converts that signal into electrical impulses, and electrodes that use those impulses to stimulate the auditory nerves.
Instead of a cochlear implant, some other patients (with a different type of hearing loss) have a middle ear implant. It fills in for a defective bone inside the ear, which relays vibrations from the eardrum to the cochlea. Drawing upon the principles used by these middle ear implants, a system utilizing the MIT chip should hopefully make all of the external parts of a cochlear implant unnecessary.
As opposed to a man-made microphone, it would utilize the natural microphone of the middle ear – this part of the ear is usually still intact in cochlear implant recipients. Like a middle ear implant, it would use a sensor to detect movement of the ossicle bones. The resulting signal from that sensor would be sent to the chip, which would also be implanted in the ear. It, in turn, would convert that signal into electrical impulses, which would travel to an electrode in the cochlea. The cochlea would then be stimulated, allowing the patient to hear.
The chip-based system could be completely implanted not just because it would be much smaller than all the parts of a conventional cochlear implant, but also because it would have considerably lower power requirements. This means it could be charged wirelessly in about two minutes, using a charger attached to a smartphone – a prototype already exists.
Installation of the system would require longer, more complex surgery than traditional implants, although the scientists believe that the procedure would get quicker as specialists got more familiar with it.
Another fully-internal alternative to regular cochlear implants is being developed at the University of Utah.