Mediaplanet: What percentage of people with hearing loss can benefit from cochlear implants (CIs)? What about other types of implants?

David Haynes: In the U.S., approximately one million patients with severe inner ear hearing loss may benefit from cochlear implantation. Another half million patients with less severe hearing loss may benefit from a "hybrid" cochlear implant, a device with a shorter electrode that fits in the cochlea potentially preserving existing hearing. One million patients may also benefit from bone conducting hearing aids indicated for single sided inner ear deafness or significant conductive (non-inner ear) hearing loss.

MP: What makes someone a good candidate for CIs?

DH: Anyone with severe inner ear hearing loss who is not receiving benefit from standard hearing aids. In the early years of cochlear implantation only patients with profound losses were implanted. Currently the criteria for implantation have expanded to patients with more hearing. This expansion is due in part to advanced technology, improved surgical techniques, and improved post-surgical implant programming.

"In the U.S., approximately one million patients with severe inner ear hearing loss may benefit from cochlear implantation."

MP: How does a CI work?

DH: A cochlear implant is a small complex electronic device that consists of two parts: an external component and a surgically implanted internal component.

The external component sits behind the ear and resembles a hearing aid.  It consists of three parts: the microphone, speech processor and the transmitting coil. The microphone picks up sound that then sends the signal to the speech processor. The speech processor analyzes and digitizes the sound picked up by the microphone. The signal is then sent via the transmitting coil to the internal receiving coil housed in the receiver stimulator. The internal receiver stimulator converts the signal to electrical impulses that are distributed to an electrode array which is placed in the cochlea (inner ear). The electrode array is designed to stimulate specific areas of the inner ear and subsequently the auditory nerve.

While standard hearing aids amplify sound, the cochlear implant has the capacity to break down sound and deliver this signal to specific areas of the cochlea improving understanding.

MP: How do you prepare before and what steps do you take after CI surgery?

DH: Cochlear implant centers function as teams. A patient will be evaluated by a surgeon who will evaluate the patient by history and physical examination. An imaging study (MRI or CT) is usually done to determine the suitability of the cochlea to be implanted. An audiologist will perform pre-operative hearing tests to determine the candidacy of the patient for the appropriate technology - hearing aids, cochlear implants or other implantable devices.

After surgery, extensive programming of the device is performed by the audiology team. They work closely with the patient to maximize the performance by determining which parts of the cochlea respond best to sound and constantly adjust the volume and complexity of the signal to achieve the best results.