Deafness: “Not a disease to cure”
We’ve all seen the heartwarming videos on YouTube of people with cochlear implants experiencing the joy of sound for the first time: the eight-month old baby hearing his mother’s voice, pacifier falling out of his mouth in wonder, and the 29 year-old woman hearing her own voice for the first time, immediately dissolving into happy tears. These are just two examples of how life-altering hearing can be.
Recently, a study in Nature reported that researchers were able to restore hearing in gerbils through use of stem cells, a breakthrough that puts us a step or two closer on the path to curing deafness. However, many people in the Deaf community don’t embrace these breakthroughs as enthusiastically. Actress Marlee Matlin, who is deaf, took to her Twitter account to decry this recent breakthrough, stating that deafness “is not a disease to cure.”
So is deafness a disease? Should people pursue every opportunity available to restore one of the basic animal senses? We’ve asked Jeffrey Harris, MD, PhD, chief of Otolaryngology at UC San Diego Health System and Distinguished Professor of Surgery in the UCSD School of Medicine, three questions about deafness.
Question: What are cochlear implants and how do they work? Can anyone with a hearing deficit use them?
Answer: Cochlear implants are devices that pick up sound and convert them into electrical impulses that travel down along a very thin electrode array that is surgically implanted into the inner ear (cochlea). If there are sufficient numbers of remaining nerve endings that can be stimulated, then hearing sound, words, speech and even music can be perceived by the deaf individual. Only people who no longer have benefit from hearing aids and meet the established hearing loss criteria are candidates for this surgery.
Q: Do you often meet resistance from patients with deafness when implants are suggested?
A: Interestingly enough the vast majority of patients that I now implant were originally hearing individuals. These individuals have lost their hearing for a number of different reasons and they greatly desire to have their hearing restored with a cochlear implant. Back in the 1980s, when these devices were first introduced, there were a great number of adults who were born deaf and learned sign language who had great hesitancy to undergoing this surgery for social and cultural reasons. And the results on late implantation were not good because the unstimulated cochlear nerves degenerated well before they could have undergone the operation. Today, most centers implant deaf children early on in order to prevent nerve degeneration from occurring and, as a result, they can be mainstreamed in school and can develop excellent speech and language skills.
Q: Marlee Matlin, who is an advocate for deaf people, stated that deafness is not a handicap and “there are millions of Americans who sign, who are deaf, and are not a ‘disease’ to cure.” Should deafness be approached as just another trait, like being born with blue eyes or having red hair?
A: I firmly believe the options for implantation in a child born deaf need to be presented in a fair and balanced, non-emotional way to the parents and then they can make that decision. Included in this presentation should be educational levels, average income, speech and language acquisition, and quality of life assessments (to name a few) achieved in hearing restored versus deaf children. One striking fact is that a child who is implanted early on, say at the age of two, can achieve the same or nearly close to the level of speech and education as that of a hearing child. If the implant is delayed, say to the age of six, the level of speech and education is significantly reduced. The dilemma, then, is that there is a window of opportunity that exists for the deaf child to be implanted, and, if it is delayed for too long, the child may never achieve the same hearing result because neural degeneration begins to occur in the unstimulated ear. Therefore, this is not a case where one can simply say “let’s leave it up to the child to decide when he or she is an adult and can decide for themselves.”
Hear today, gone tomorrow
The cochlea is the working part of the inner ear, a tiny spiral-shaped cavity filled with a watery liquid called perilymph and lined with a strip of sensory tissue known as the organ of Corti (colored red in this image of a cochlea produced by M’hamed Grati and Bechara Kachar at the National Institute on Deafness and other Communication Disorders).
The organ of Corti itself is lined with rows of auditory hair cells. As sound waves move deep into the ear (outer to middle to inner), they cause vibrations in the perilymph. Thousands of hair cells sense the liquid motion through projecting bundles of hairlike cilia. The hair cells convert the cilia motion into electrical signals that are transmitted to primary auditory neurons, which in turn transform the signals into electrochemical impulses dispatched to the brain for further translation and interpretation.
In other words, we hear something.
It’s a remarkably fast – almost simultaneous – process and understandably delicate.
The three tiniest bones in the human body – the malleus, incus and stapes (Latin for hammer, anvil and stirrup, a reference to their respective shapes) – are all part of the auditory mechanism of the middle ear. The stapes is the smallest of all, just 3.5 millimeters in length – less than the thickness of two nickels.
With age, hearing acuity naturally diminishes, but excessive exposure to noise or overly loud sounds can speed the process by damaging the fragile cilia. The problem has become particularly worrisome among teens, particularly with the advent of devices like the MP3 player and iPod and the widespread use of earbuds, which channel more, louder sound deeper into the ear.
According to a 2010 study published in the Journal of the American Medical Association, adolescents are experiencing significantly greater hearing loss since the early 1990s: 1 in 5 teens may now suffer from impaired hearing.