Making Sense of Hearing
It’s hard to imagine experiencing a whole new sense such as smell, taste, touch, sight or hearing for the first time. But at the Department of Communication Sciences and Disorders at the University of Texas at Austin’s College of Communication, researchers and clinicians are helping make that miracle a reality.
With the advent and improvement of cochlear implant technology, those who are profoundly deaf or severely hard of hearing now have the option to realize a whole new sensory sensation.
“It’s the only technology I know of that completely replaces one of the senses,” said Craig Champlin, chair of the Department of Communication Sciences and Disorders (CSD).
There are two faculty members that specialize in cochlear implantation in the College: Su-Hyun Jin, an assistant professor and researcher who studies effective methods of auditory rehabilitation, and Angela Carey, a clinical assistant professor of audiology who applies those best practices of rehabilitation to patients.
“It involves a major surgery and people need to be in good mental and physical health before proceeding,” said Jin. “For most people, though, it can be a positive and life-changing experience.”
A cochlear implant is a surgically implanted electronic device placed under the skin behind the ear that provides a sense of sound to a person’s auditory system. A device consists of one or more microphones, a speech processor, a transmitter, a receiver and stimulator, and an array of up to 22 electrodes that simulate the 16,000 delicate hair cells contained in the average person’s cochlea. The technology was first implemented in the early 1970s but took until December 1984 for the U.S. Food and Drug Administration to approve implantation in adults. The age required for children in the U.S. to receive the device is 1-year-old.
CSD works with two practices in Austin that administer the surgery along with other offices in San Antonio, Dallas and Houston.
“They’re doing the procedure in patients as old as 92,” said Carey. “In Europe, they’ve even performed it on infants as young as 6 months. After the patients have the surgery, they come to a lab like ours for processing and rehabilitation.”
The most successful cases of hearing restoration are in patients that are deaf due to damage of sensory hair cells in their cochlea or those that have lost hearing over time. The quality of sound emanating from the device is different from natural hearing, with less sound information being received and processed by the brain. While cochlear implant devices are recalibrated on a constant basis, the ability of a device to decipher between background noise for example, and that of a person giving a lecture at the front of an auditorium, can be limited.
However, in most cases, patients are able to sufficiently hear and understand speech, listen to music, and process noise.
According to the National Institute of Health, as of December 2010, approximately 219,000 people worldwide received implants with roughly 71,000 in the U.S. Most patients opt for the use of only one implant in one ear’s cochlea but there are a growing segment of recipients choosing bilateral implants of one implant in each ear’s cochlea. Currently, there are only three FDA-approved companies manufacturing devices: Cochlear Limited Australia, Advanced Bionics U.S., and MED-EL.
AUSTIN, Texas -- May 10, 2014 -- Candidates for the operation must meet specific criteria and are judged on an individual basis depending on a person’s hearing history, cause of hearing loss, amount of residual hearing, speech recognition ability, health status, and commitment to auditory rehabilitation and process training. There is also a time window during which children can receive an implant and learn to speak normally. This “critical window” diminishes as time goes on and becomes more difficult if an implant is administered in later childhood.
“We have a cochlear implant facility set up so that people can come in to do mapping--which is the reprogramming of the processor,” said Carey. “Children typically need more mapping sessions so that we can help them get the optimal benefit from their cochlear implant as they grow and develop.”
Most surgeries are performed in two-to-four hours and are usually treated as an outpatient procedure. After one-to-four weeks of healing, implants are activated and auditory training and speech therapy typically continue for a number of years. According to the U.S. National Institute on Deafness and Other Communication Disorders, the estimated total cost of all services involved in a cochlear implant is approximately $60,000. Risks include those that arise with any surgery and the possibility that the procedure may lead to medical complications or disappoint patients in effectiveness of hearing.
“In my research, I’ve been looking at how those with the device understand and differentiate between speech and noise,” said Jin. “We develop experiments on how to improve speech understanding in different environments so they can improve their ability to pick up and decipher sound.”
Interestingly, opposition from the Deaf community has proven adversarial for proponents of cochlear implants. Some in the deaf culture don’t consider deafness a disability and protest the procedure as unnecessary for young people, especially during the critical period of growth when an individual’s brain is learning to interpret sound. Opponents cite that children having the surgery may develop an identity crisis between a hearing and a Deaf culture, and that implantation may make the learning of sign language more difficult.
“A lot of it depends on how much rehab a person designates and is willing to go through,” said Carey. “It really is highly individualized and often hard to fully predict.”
However, staunch opposition is declining as more Deaf community advocates embrace the idea that children could become more enriched by participating in both cultures.
“I met one deaf couple where the husband had done [the surgery] and the wife didn’t even want to talk to him at first,” said Jin. “Gradually, though, there is more support and acceptance, and we are headed towards a more inclusive environment.”