Cochlear Implant
According to American Speech-Language-Hearing Association (ASHA), nearly 740,000 people in the US have severe to profound hearing loss. 8% of these people are under the age of 18. Until recently, many hearing loss patients for whom hearing aids were not effective were consigned to a silent world. In 1986, AMF made it a mission to help hearing-impaired patients by developing a new version of a device called a cochlear implant that could restore or, in some cases, provide for the first time hearing to the hearing-impaired. The following is the story of that journey.
How do normal ears hear?
In a functional ear, sound travels through three successive portions of the ear on its way from outside the body to the brain, where the sound is processed and interpreted. First, sound travels through the outer ear’s ear canal and past a tympanic membrane commonly known as the eardrum. Beyond the eardrum is the middle ear, an air-filled cavity with three tiny bones: the malleus (or hammer), incus (or anvil), and stapes (or stirrup). Sound energy makes the eardrum and the bones vibrate, and these vibrations are transmitted to the inner ear, which includes a fluid-filled cavity called the cochlea. As the vibrations move through the fluid, thousands of tiny hair cells in the cochlea are set in motion, and the information from their movement is sent into the auditory nerve and from there to the brain.
How does a cochlear implant help a hearing-impaired person?
In hearing-impaired patients, some portion of the hearing process has been disrupted. Hearing aids amplify sounds so that they can be heard through damaged portions of a still somewhat functional ear; cochlear implants, which can be a solution for patients who are too impaired to benefit from hearing aids, bypass the outer and middle ear and are implanted into the cochlea, from which sound data can be sent directly into the auditory nerve. Hearing with a cochlear implant is different than hearing with a normal ear and takes training for a patient to learn or relearn. Although people who’ve experienced hearing loss after birth are often able to regain hearing using a cochlear implant even many years after the damage occurred, infants born with severe hearing loss have a somewhat limited time window to receive a cochlear implant, after which the brain will not be able to process sound information, even if the cochlear implant and auditory nerve are functioning properly together.
What are the parts of a cochlear implant?
A cochlear implant consists of: (1) a microphone, which picks up environmental sounds, and (2) a speech processor, which selects and arranges sounds picked up by the microphone. The microphone and the speech processor are incorporated into a small package that is worn behind the ear. (3) A transmitter, whose antenna sends the processed sound information to (4) a receiver, which sits between the skin and the skull. The receiver’s antenna picks up the transmitted information and converts it into many channels of electrical signals corresponding to higher or lower pitches in the original sound, after which it sends it to (5) an electrode array inside the cochlea consisting of microscopic electrodes which are located in such a way as to stimulate the proper portions of the auditory nerve with higher or lower pitched sounds.
How did the Alfred Mann Foundation get involved with cochlear implants?
In the 1950s and 1960s, researchers began experimenting with placing electrical devices into the inner ear of patients with certain types of hearing loss, and learned that these devices could, in fact, help transmit sound to the brain. Over the years there were many advances in these devices that allowed speech and other noises to become intelligible to these patients, but there was still much work to be done to make these devices maximally useful to hearing-impaired patients.
In 1986, two early Alfred Mann Foundation employees – its then-president, Joe Schulman, and a biomedical engineer, Chuck Byers, were approached by Dr. Robert Schindler, a noted scientist and pioneer in cochlear implant surgeon from UCSF, who had been working on new developments in cochlear implants, and asked if AMF would be willing to take on development of a cochlear implant. Chuck, a former member of the cochlear implant team at UCSF, and Joe invited Dr. Schindler to a meeting with Al Mann during which Dr. Schindler showed Mr. Mann video of formerly deaf patients hearing with their cochlear devices. Mr. Mann concluded that a cochlear implant project should be a priority for AMF, and development on the device began soon after.
The cochlear implant developed at AMF had several key differences from other cochlear devices available at the time:
- The cochlear implant employed 8 bipolar channels in discrete electrode pairs which were positioned very close to the target portions of the auditory nerve. Other existing cochlear implants stimulated larger and less discrete areas of the auditory range.
- The electrode was premolded into a spiral cochlear shape to allow for greater ease in implantation
- Speech processing was improved using new pattern recognition schemes
- The antenna was incorporated into a single unit that was encased in hermetically-sealed ceramic – the first time an electronic implant device was packaged in ceramic. AMF pioneered new brazing and welding techniques to make such a package possible.
In 1991, the first device was ready for a human implant, and more soon followed. Advanced Bionics was incorporated to continue development, and the intellectual property was licensed exclusively to the new company. A few years later, the Clarion® Cochlear Implant was available on the commercial market. Since then, tens of thousands of patients have experienced the pleasures of music and conversation provided to them by the technology developed at the Alfred Mann Foundation.
Clarion® Cochlear Implant is a registered trademark of Advanced Bionics, LLC.