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Cochlear Implant Story Last modified July 2.
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Cochlear Implant Story Last modified July 2. |
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Jaime Fradera Senior Member
since 2000-11-25
Posts 843Where no tyranny is tolerable |
For background on this story visit the National Federation of the Blind at: www.nfb.org I will begin this piece by claiming to have no pearls of knowledge and no clinical credentials. I don’t even have a job just now, making me one of the 70 percent. Although I have been a student not just once but twice here at the Colorado Center, I am not perfectly adjusted to blindness and deafness. Most of what will be presented here will be familiar to seasoned Federationests. However, as we go through the routine minutia of our daily lives, it may be easy to forget that the greater disability community, and the sighted world in general, still does not know what we know. One remedy for writer’s block I sometimes try is the aphorism: write about what you know or, failing that, write about the person you know best. There is an incredible lack of information about the use of cochlear implants by deaf-blind people on the Internet, at least first-person accounts, perhaps because most deaf people are sighted. It is for this reason that I decide to write and post my experiences using the Nucleus-24 cochlear implant. Although using the implant is now easy and routine for me, I don’t know if my experience is unusual or typical. If you are an implant user, or know someone who is, your comments are invited and welcome. The sense of hearing and the skills of listening are immensely complex. We mostly take them for granted. We learn to listen through socialization, and even after we are grown we get more or less occasional reminders to listen by somebody or another who doesn’t think they’re being heard. The human ear and brain, comprising our auditory system, is a marvel of engineering design, and as long as our auditory system works, we hardly give it any thought. However, to lay the background for what follows, the processes by which we hear will be described in more detail, and the disorder called neural-sensory hearing loss will be discussed. Overview. The human ear consists of three sections: the outer ear, middle ear, and inner ear (referred to as the cochlea. The outer or visible part of the ear is called the ear canal. The middle ear consists of the ear drum and contains bony structures that conduct and filter sound, protecting the inner ear from excessively loud noises. The inner ear is a chamber filled with a fluid. It contains nerve endings (also called hair cells) that carry sound and vestibular information to the brain. In order for us to hear, the following sequence of events takes place. 1: Sound waves transmitted through the air enter the ear canal. The shape of the ear canal focuses and directs the sound waves onto the ear drum. 2: When struck by these sound waves the ear drum begins to vibrate. 3: The vibrations are then conducted to the bony structures of the middle ear. 4: The motion of the structures of the middle ear creates waves that ripple through the fluid in the inner ear. 5: When waves in this fluid strike the hair cells, these nerve endings fire, converting the mechanical energy of the sound waves into electrical impulses. 6: These impulses then travel through the auditory nerve into the brain, where they are recognized and interpreted as “sound.” The most vital structures in our ability to hear are the hair cells in the inner ear. Numbering in the thousands, these delicate structures are highly specialized and work in specific ways. Each hair cell is genetically “wired” to fire when struck by sound waves at a specific frequency, or pitch. In a normal ear, these hair cells allow us to perceive sound at frequencies between 300 Hertz, or cycles per second, and 2,000 Hertz. Sounds at frequencies outside this range will not be heard. To use a musical analogy, consider that each key on a piano is tuned to produce a particular note. Striking middle C will produce middle C; striking F sounds F, etc. The piano, of course, is limited----its keys can only produce the notes of the musical scale. It is the immense number of nerve endings in the human ear that allow us to perceive a world of full and richly textured sound. Sensory-neural Hearing Loss In the condition known as sensory-neural hearing loss, the structures of the outer and middle ear are intact, but the hair cells suspended in the cochlear fluid have been damaged or destroyed. The most common cause of sensory neural deafness is prolonged exposure to high intensities of sound. These sounds can assault the inner ear and literally smash away at the hair cells until they lose there elasticity and function. When this occurs, sound information carried to the brain is degraded and is perceived as garbled or unrecognizable noise, or no sound may be heard. A person with a sensory-neural hearing loss may have trouble understanding speech, music or other sounds depending on the extent of nerve damage. For the same reason, hearing aids, which only amplify sound, may be of little or no use in the damaged ear. Some hearing people think if they just yell at us they will be heard. But shouting into an ear that has been damaged in this way will be about as effective as trying to get music by banging on a badly tuned piano in which most of the strings are missing. The Cochlear Implant. The cochlear implant is an electronic device that simulates the function of hair cells in the cochlea by electrically stimulating the remaining auditory nerve fibers through an electrode array implanted in the inner ear. It converts environmental sounds into electrical impulses. These impulses then travel via the auditory nerve to the brain, where the stimuli are perceived as sound. The concept of applying electrical stimulation to the auditory nerve to restore hearing is not new. In 1956, doctors in Paris operated on a patient with a severe ear infection, which caused substantial tissue damage and exposed the auditory nerve. When a wire was placed on the nerve and an electric current was applied, the patient reported hearing sensations or sounds. Since then, there have been many advances in implant technology which are making implant systems smaller, more sophisticated and easier to use. A cochlear implant system consists of external and internal parts. The external portion consists of a speech processor which is worn either on the body or behind the ear. The speech processor, which is about the size of an audio cassette, has two cables. One cable connects the processor to a microphone which is worn like a hearing-aid. A second cable connects the processor to a transmitting coil. The transmitting coil is worn on the head above the implanted ear and is held in place over the implant body by a magnet. Sounds are first picked up by the microphone and carried via the first cable to the speech processor. The speech processor, a powerful, miniaturized computer, analyzes, codes and digitizes the sounds for radio transmission. The coded signals are then sent via the second cable to the transmitting coil and broadcast across the skin to a receiver on the implant body. The implant body then delivers direct stimulation to the auditory nerve fibers through its attached electrode array. The internal portion of the implant is inserted into the cochlea by the implant surgeon. Its electrodes are seated at selected sites along the inner wall of the cochlea. The incisions are then closed and a dressing is applied which must be worn until the sutures are removed. The surgical procedure generally takes from two to four hours and implant patients may go home the same day surgery is performed. Since as far back as I can remember, listening with my left ear has always sounded rather odd. It wasn’t anything major. I just preferred people and holding the phone on the right side because it sounded a little better. We were given regular hearing tests in school and I always did well on them. My social life was hardly affected. I could hear echoes and had excellent sound localization, played tag and jumped rope. I was a TV Junkie. At age seven I listened to John Glenn and the launching of the first Mercury mission and got upset because I had to go to school that day. I watched the cartoons Saturday mornings and every afternoon after school, and every night “the CBS evening news, with Walter Kronkite. I heard of the assassination of President Kennedy and the shooting of Oswald in the Dallas city jail. I heard the first performance of the Fab Four on television, and the Beatle mania that swept the nation. Like millions of others I heard news coverage of the Vietnam war, The burning of American cities, the rantings of black rage, the destruction of yet another President, and the first human voices from the surface of the Moon. I listened to Black Sabbath and Jimmy Hendricks, Jim Morrison, Frank Zap pa, the Kinks, the Stones, and the Dead. And as a teenager at the school for the blind, it was waking Sunday mornings to the Sounds of: www.oldradioshows.com/at40/020373.html Casey Casem and the American top 40 countdown. It was Stevie Wonder and Stevie Ray, Steely Dan and Steven Stills, the howling, screeching dementia of seventies heavy-metal classic rock. Radio and television, listening to albums and collecting records---the world of sound, had once played an indescribably central role and filled a great void inside me. And as the world of sound began to fade, as it grew harder and harder to do all the things that meant so much to me, it was very, very frightening. For although I could hear, I had yet to come to maturity and grow in philosophy. The worst thing that could have happened happened anyway. A succession of treatments and ever more powerful hearing-aids could not stop the accelerating damage or even identify the illness. In 1980 my dad took me to Los Angeles, perhaps hoping for a cure. The doctors there recommended another treatment, and my life kept falling apart. continued |
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Midnitesun
since 2001-05-18
Posts 28647Gaia |
Jaime, you've spent a lot of time on this. How is the rest of it coming along? When you finish the piece, and bring the reader current to the present time, I really do hope it gets published, along with a couple others you've written. You never cease to amaze me, amigo. |
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Nan
Administrator
Member Seraphic
since 1999-05-20
Posts 21191Cape Cod Massachusetts USA |
Thank you, Jaime - for sharing a very important part of your life with our readers... You're a very special man indeed...  |
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