They used hand-spun electrodes placed at the stump of the hearing nerve to produce sound.
The History and Future of Cochlear Implants
Thursday, March 10, 2022
Hearing is the only sense that can be replicated through a medical device. This is accomplished through electrical stimulation of the auditory (hearing) nerve using a device called a cochlear implant. This life-changing technology has rapidly developed from its humble beginnings of providing basic sound, to helping people live richer and fuller lives through the connections that come with conversation, music, and laughter.
Many of us who have enjoyed a career in the field of cochlear implants have had a unique opportunity to meet our heroes and build upon their work. We have seen these devices bring the joy of hearing to infants and adults, and we have witnessed the life-changing benefits of this technology. Having been inspired by the innovation of the past, we view it as our responsibility and privilege to continue bringing better hearing to even more people in the future.
In the beginning
The ability to use electric stimuli to produce an auditory sensation was first described by Alessandro Volta in the early 1800s. But it wasn’t until 1957 that André Djourno and Charles Eyriès intentionally stimulated the auditory nerve to provide hearing sensation to patients who had undergone major ear surgery in France. They used hand-spun electrodes placed at the stump of the hearing nerve to produce sound. The electric signal from the device was able to reliably produce the sensation of sound, and patients could even differentiate between on/off and soft/loud. However, patients weren’t able to differentiate different pitches or understand speech. Unfortunately, there were complications with the devices, and the researchers abandoned the project.
In 1961, word of the French experiment reached William House, an American surgeon. Together with Jack Urban, an engineer, House developed and tested the first cochlear implant system. It included a single electrode, placed inside the cochlea, and a wearable sound processor. While there were a number of limitations associated with this device, recipients were able to hear sound and demonstrate an improvement in speech understanding with visual cues. These results inspired several surgeons, engineers, and researchers to explore the potential to restore hearing through controlled electrical stimulation within the cochlea.
Implant technology today
In the 60 years since William House and Jack Urban proved out the concept of their single-channel cochlear implant, we have seen rapid and continuous improvement in these devices. Cochlear implants are now designed with more electrodes, which stimulate different places in the cochlea and provide the listener with a wider range of pitch perceptions. Electrical current delivery is far more controlled, so these electrodes can work together to provide “virtual channels” for more detailed pitch. The precise control also helps to improve loudness percepts.
Today, there are cochlear implant recipients ranging in age from under 12 months to over 90 years.
Cochlear implant technology is not only safe, but it has given countless people the opportunity and confidence to participate in social and professional environments, where communication is so important. The field has moved from simply providing auditory perception (hearing sound) to an expectation of understanding speech in complex or noisy listening situations.
The original devices were only prescribed to adults with profound hearing loss in both ears. Today, there are cochlear implant recipients ranging in age from under 12 months to over 90 years. Many of these recipients still have some residual hearing, but they do not receive significant benefit from hearing aids. Thanks to advancements in electrode design and techniques for monitoring the hearing nerve during surgery, surgeons are now better able to preserve hearing. These recipients experience a combination of electric stimulation through their implant and acoustic stimulation through their natural hearing, and are able to achieve very high levels of speech understanding. They report a fuller, richer sound quality.
Modern sound processors
Just like the internal implant, the externally worn devices that detect and process sound have gotten smaller and more powerful over time. CI sound processors have gone from belt-worn devices to a size comparable to hearing aids.
They are controlled by powerful microprocessors that recognize the environment and activate and adjust features to improve the overall listening experience in different situations. With the introduction of Bluetooth®, they can also be paired with your phone, computer, or other tablet to provide a personal and private listening experience.
For patients who have no useable hearing in one ear and some in the other, bimodal solutions, which permit hearing through a hearing aid in one ear and a cochlear implant in the other, have proven to be more beneficial than using a single device. The most advanced cochlear implants have caught up with hearing aid technology, featuring the same sound processing and functionality, allowing them to work seamlessly with compatible hearing aids together as a pair in such bimodal fittings.
More to come
As we look to the future of cochlear implants, millions of dollars are being invested each year to make them an even more powerful and effective treatment option. These efforts include how to better preserve neural structures of the inner ear through electrode design, and how to bring a more natural hearing experience by networking devices worn on both ears. We're also working on ways to improve the hearing experience through artificial intelligence and new signal processing algorithms, and developing app-based remote controls and virtual office visits to improve the user experience
Through these investments, we see an even brighter future for cochlear implant recipients. We see a world where hearing is effortless, and people enjoy a life without limitations.
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