30 Years of Bionic Ears

The technology for cochlear implants is evolving toward speech perception and sound vocalization. Image: MED-EL

About the time 1970s sci-fi spy Jaime Sommers put her cybernetic ear to work as a government eavesdropper on TV’s The Bionic Woman, a real-life experimental hearing device was beginning to turn the meaning of deafness on its ear. The cochlear implant, as close as it gets to a true bionic ear, hit the U.S. market following approval by the U.S. Food and Drug Administration in 1984-85. The continually evolving technology doesn’t restore better, stronger, faster hearing, but for people with profound deafness, cochlear implants open a world of sound.

After 30 years, cochlear implants are still making significant noise in the medical device world. Today more than 350,000 people who once lived in silence now use implants to understand conversational speech and hear environmental sounds.

The Ears Have It

Standard hearing aids work by amplifying sound for people with partial hearing loss.  For people who are deaf or have profoundly impaired hearing, that’s not enough; their hearing loss is often linked to damage or other abnormalities in the thousands of tiny sensor hair cells that line the snail-shaped inner ear chamber called the cochlea. These hair cells play a crucial role in hearing, converting acoustic waves from the outside world into electrical signals that stimulate the auditory nerve. The brain understands these signals as sound. When these sensory cells are severely damaged or absent, sound waves literally fall on deaf ears, even if the rest of the ear is anatomically healthy. Cochlear implants work something like a telephone wired directly to the brain to replace the function of the sensory hairs.

A wire connects the implant with a microphone/speech processor behind the ear. Image: MED-EL

In a typical implant, a microphone/speech processor unit is worn semi-discretely behind the outer ear. It is connected by wire to a signal transmitter attached to the side of the head by a strong magnet housed within a subdermal receiver/stimulator device anchored to the skull. A length of wire connects the receiver/stimulator to the cochlea, where the electrodes deliver the converted electrical signals to key regions of the auditory nerve.

The first device to gain approval was the landmark House 3M cochlear implant, a single-channel device developed by the House Ear Institute of Los Angeles and 3M Company. It helped users perceive nearby sounds and read lips with greater ease, but it was a far cry from real hearing. A multichannel alternative approved a year later beginning the current era of research and development. Today the U.S. cochlear implant market is dominated by three highly competitive companies: Advanced Bionics , Valencia, CA; Cochlear Corporation, Sydney, Australia; and MED-EL, Innsbruck, Austria. Each maker has its own formula, but the basic design of a modern system comprises some version of the same components.

Echoes of the Past, Signals of the Future

In 2013, three cochlear implant pioneers received the top U.S. honor in medical science, the Lasker-DeBakey Clinical Medical Research Award, for their respective contributions to the field. Graeme M. Clark, an emeritus professor at the University of Melbourne, Ingeborg Hochmair, co-founder of MED-EL in Innsbruck, and Blake S. Wilson of Duke University shared the award for their independent contributions to the device we know today.  

Their work built on efforts since the 1950s to electronically stimulate the auditory nerve. One of the first significant advances was by California otologist William House, whose simple single-electrode implant helped two test subjects make out sounds from their surroundings. This 1961 prototype evolved into the House/3M implant approved in 1984. Independently in labs in Australia and Austria, Clark and Hochmair – along with her future husband, electrical engineer Erwin Hochmair – developed more sophisticated multichannel devices and experimentally implanted them in the late 1970s. Their common goal was a device that enabled deaf people to comprehend spoken language without reading lips or needing other visual cues. Most hearing experts wrote that off as impossible, but in 1991 Wilson’s continuous interleaved sampling approach to speech processing brought that dream to life, launching today’s commercial market.  

Carmen A. Puliafito, dean of the University of Southern California’s Keck School of Medicine, summed up the impact of their work in his remarks at the award ceremony. “Fifty years ago, there was no effective treatment for patients with severe hearing loss,” he said. “Today patients with these implants can speak clearly.”

Sounds of the Future

Technologies recently introduced commercially or advancing through the development pipeline are focused on issues such as speech perception and sound localization. New rugged and waterproof external housings allow wearers to bathe, swim, or play active sports without harming their bionic ears. Work toward a 50-channel hi-fi implant with more strategically placed electrodes is under way to enrich the sound quality of music and speech. FDA-led tests of hybrid implants that combine electronic stimulation and amplification are promising to make cochlear technology available to people with a wider range of hearing disorders. By using two different devices or sound processors to bring patients a broader spectrum of pitches, this technology could make cochlear implant technology an option for candidates with partial hearing loss. Other groups are working to make the already-discrete implant even less obtrusive, using a wirelessly rechargeable low-power signal processing chip and an internal microphone system to do away with the bulky external components.

The world may be moving toward thought-controlled limbs, total artificial hearts, and 3-D printed skin, but the cochlear implant is still the only practical mechanical device that replaces one of the five human senses. And unlike real ears that can diminish in performance as we age, cochlear implants just keep getting better

Michael MacRae is an independent writer

For Further Discussion

Fifty years ago, there was no effective treatment for patients with severe hearing loss. Today patients with these implants can speak clearly.

Carmen A. Puliafito, Dean, USC Keck School of Medicine