OtolaryngologyWords
From Impulse to Instrument: Cochlear Implants Come to Be
[beginning only!]
Modern cochlear implants were born in the 1950’s, but the first electrical experiments to improve hearing actually began over 200 years before that, in picturesque Como, Italy, when Count Alessandro Volta put 2 metal rods in his head and used his own invention, the electric battery, to pass a current between his ears. As electricity surged into his skull,Volta heard a noise like a “thick, boiling soup.” He was trying to understand the relationship between tissue and metals, and the electric current that was produced when they touched, and in doing so,Volta had shown that stimulating the auditory system with an electrical impulse could create perception of sound. Volta had done so, however, by stimulating the wrong part of the auditory system, the cochlea. Prior to 1950 in fact, all attempts to create hearing with current made this mistake; instead of bypassing the nonfunctional organ, they electrically stimulated the cochlea, or whatever was left of it, by acting on a few, remaining, intact cochlear hair cells.
In 1950, however, the French hit a nerve. While attempting to help a deaf man whose inner ear was riddled with tumors, French otolaryngologist Charles Eyriès teamed up with a biophysicist named André Djourno. Djourno had had extensive experience in stimulating nerves with metal wires, and Eyries was eager to try this kind of neural stimulation in the ear of his patient. During the operation, the two decided to implant a wire-wrapped iron rod under the skin and close to the remaining end of the deaf man’s acoustic nerve. They connected the rod to a circuit and the patient reported hearing sounds like "roulette wheels and crickets.” Together, the otolaryngologist and the biophysicist had proved a connection between neural, not cochlear, stimulation and perception of sound that would lay the framework for formation of modern implants. But Eyries and Djourno did not pursue implant research further. Instead, an otologist a continent away in California picked up where the French team left off.
In 1957, a patient rushed to the Los Angeles office of Dr. William House bearing a newspaper article that claimed a once totally deaf patient in France could now hear due to an electrical device— the device implanted by Dijourno and Eyries. House became interested in restoring hearing with electricty and after translating their paper from French to English, attempted to make similar mechanisms himself. He implanted them into three patients in 1961, but the devices worked only briefly before being hampered by technical barriers. The electronics of the process had eluded House. Also, the insulating material he had used to cover the metal in these makeshift implants was being rejected by the patient’s body. Neurophysiologists rejected House’s ideas, too; he was treading on their cochlear turf, which bread hostility, and they were also skeptical of his method since they thought electrical currents near the deafened cochlea would destroy remaining nerve tissue.
In 1969, however, the outlook for House’s work into hearing restoration improved. That year, an innovative engineer named Jack Urban became interested in the idea of cochlear implants, and he offered House help. As House explained in his memoir, My Perspective, each of these men brought important skills to the table: “My orientation was the selection of the patients and the surgical approach for implants,” House said, “and Jack applied his genius for electronics to the problems we faced.” They tried many different systems of stimulating the cochlea. Over time, though, House and Urban actually had most success with a method in which they put precisely the same signal into the electrode, rather than trying to sort sound by frequency before it reached that point. The electrode would do resolving and sifting of frequencies in sound, before presenting them to the acoustic nerve. In 1969, while fitting their deaf patients with models using this technique, House and Urban were excited to see that they responded, that they perceived the sensation of sound. They would walk out of House’s laboratory moments after surgery and point to objects—like birds—whose sounds they could actually hear. The otologist-engineer team had created the first successful, wearable cochlear implant. It used a single electrode and was designed mostly to aid lip-reading and House was adamant about Urban’s contribution to this milestone: “I firmly believe that without Jack, cochlear implants would have taken many more years to develop. Many of us owe him an unpayable debt of gratitude.”
But even though House’s patients were hearing, skepticism lingered. For those who had not actually seen the patients, the belief that cochlear implants had limited potential was common. Neurophysiologists, like Harvard’s prominent Nelson Kiang, felt that a single-electrode device could not really produce hearing, but only a kind of buzzing. “Dr. Kiang felt strongly,” House explained in his memoir, “that if an electric field was generated around the neural tissue in the inner ear, the nerve fibers would all fire, go into a refractory state, and then fire again repeatedly for as long as the stimulation lasted.” But those House had implanted proved otherwise; they had heard more than a buzzing caused by wires in the head. They’d heard something caused by the outside, like the sound made by the chirping birds, which only a functional implant could have permitted. With his patients’ stories to buoy him, House requested to present his preliminary anecdotal findings at a national meeting. “I was turned down on the basis that reporters would be [there],” House wrote, “and that their reports of the implant would cause otologists to have to contend with a flood of patients with unrealistic expectations.” Finally, however, in 1973, The American Otological Society’s Saint Louis meeting held a session on cochlear implants.
After that, the pace of progress quickened, mostly due to Australian researcher Graeme Clark. He sought to take implants, then single-electrode devices, to the next level and toyed with the idea of putting multiple electrodes inside. This move to more electrodes would provide more “notes” for deaf ears, and make their perception of sound closer to that of a normal person’s. Clark’s experiments were successful, and in 1978, a resident of Melbourne named Rod Saunders become the first person in the world to receive a multi-electrode cochlear implant...
.MGW.
[beginning only!]
Modern cochlear implants were born in the 1950’s, but the first electrical experiments to improve hearing actually began over 200 years before that, in picturesque Como, Italy, when Count Alessandro Volta put 2 metal rods in his head and used his own invention, the electric battery, to pass a current between his ears. As electricity surged into his skull,Volta heard a noise like a “thick, boiling soup.” He was trying to understand the relationship between tissue and metals, and the electric current that was produced when they touched, and in doing so,Volta had shown that stimulating the auditory system with an electrical impulse could create perception of sound. Volta had done so, however, by stimulating the wrong part of the auditory system, the cochlea. Prior to 1950 in fact, all attempts to create hearing with current made this mistake; instead of bypassing the nonfunctional organ, they electrically stimulated the cochlea, or whatever was left of it, by acting on a few, remaining, intact cochlear hair cells.
In 1950, however, the French hit a nerve. While attempting to help a deaf man whose inner ear was riddled with tumors, French otolaryngologist Charles Eyriès teamed up with a biophysicist named André Djourno. Djourno had had extensive experience in stimulating nerves with metal wires, and Eyries was eager to try this kind of neural stimulation in the ear of his patient. During the operation, the two decided to implant a wire-wrapped iron rod under the skin and close to the remaining end of the deaf man’s acoustic nerve. They connected the rod to a circuit and the patient reported hearing sounds like "roulette wheels and crickets.” Together, the otolaryngologist and the biophysicist had proved a connection between neural, not cochlear, stimulation and perception of sound that would lay the framework for formation of modern implants. But Eyries and Djourno did not pursue implant research further. Instead, an otologist a continent away in California picked up where the French team left off.
In 1957, a patient rushed to the Los Angeles office of Dr. William House bearing a newspaper article that claimed a once totally deaf patient in France could now hear due to an electrical device— the device implanted by Dijourno and Eyries. House became interested in restoring hearing with electricty and after translating their paper from French to English, attempted to make similar mechanisms himself. He implanted them into three patients in 1961, but the devices worked only briefly before being hampered by technical barriers. The electronics of the process had eluded House. Also, the insulating material he had used to cover the metal in these makeshift implants was being rejected by the patient’s body. Neurophysiologists rejected House’s ideas, too; he was treading on their cochlear turf, which bread hostility, and they were also skeptical of his method since they thought electrical currents near the deafened cochlea would destroy remaining nerve tissue.
In 1969, however, the outlook for House’s work into hearing restoration improved. That year, an innovative engineer named Jack Urban became interested in the idea of cochlear implants, and he offered House help. As House explained in his memoir, My Perspective, each of these men brought important skills to the table: “My orientation was the selection of the patients and the surgical approach for implants,” House said, “and Jack applied his genius for electronics to the problems we faced.” They tried many different systems of stimulating the cochlea. Over time, though, House and Urban actually had most success with a method in which they put precisely the same signal into the electrode, rather than trying to sort sound by frequency before it reached that point. The electrode would do resolving and sifting of frequencies in sound, before presenting them to the acoustic nerve. In 1969, while fitting their deaf patients with models using this technique, House and Urban were excited to see that they responded, that they perceived the sensation of sound. They would walk out of House’s laboratory moments after surgery and point to objects—like birds—whose sounds they could actually hear. The otologist-engineer team had created the first successful, wearable cochlear implant. It used a single electrode and was designed mostly to aid lip-reading and House was adamant about Urban’s contribution to this milestone: “I firmly believe that without Jack, cochlear implants would have taken many more years to develop. Many of us owe him an unpayable debt of gratitude.”
But even though House’s patients were hearing, skepticism lingered. For those who had not actually seen the patients, the belief that cochlear implants had limited potential was common. Neurophysiologists, like Harvard’s prominent Nelson Kiang, felt that a single-electrode device could not really produce hearing, but only a kind of buzzing. “Dr. Kiang felt strongly,” House explained in his memoir, “that if an electric field was generated around the neural tissue in the inner ear, the nerve fibers would all fire, go into a refractory state, and then fire again repeatedly for as long as the stimulation lasted.” But those House had implanted proved otherwise; they had heard more than a buzzing caused by wires in the head. They’d heard something caused by the outside, like the sound made by the chirping birds, which only a functional implant could have permitted. With his patients’ stories to buoy him, House requested to present his preliminary anecdotal findings at a national meeting. “I was turned down on the basis that reporters would be [there],” House wrote, “and that their reports of the implant would cause otologists to have to contend with a flood of patients with unrealistic expectations.” Finally, however, in 1973, The American Otological Society’s Saint Louis meeting held a session on cochlear implants.
After that, the pace of progress quickened, mostly due to Australian researcher Graeme Clark. He sought to take implants, then single-electrode devices, to the next level and toyed with the idea of putting multiple electrodes inside. This move to more electrodes would provide more “notes” for deaf ears, and make their perception of sound closer to that of a normal person’s. Clark’s experiments were successful, and in 1978, a resident of Melbourne named Rod Saunders become the first person in the world to receive a multi-electrode cochlear implant...
.MGW.
posted by Meagan G at
8:52 AM
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