Kids do well with two cochlear implants: study
Deaf children who already had one cochlear implant had improvements in speech, hearing and related quality of life measures after a second was implanted in the other ear, researchers from the Netherlands reported this week.
And the degree of improvement didn’t depend on how old kids were when they got their second implant, according to the study, published in the Archives of Otolaryngology - Head & Neck Surgery.
An improved quality of life after a second implant “is not surprising,” said Betty Loy, who studies deafness and cochlear implants at the University of Texas Southwestern Medical Center in Dallas.
“I definitely would expect that to improve over time as the brain adjusts to that second implant. You’re going to get better and better and better at doing all the things that bilateral hearing allows you to do,” added Loy, who was not involved in the new study.
Cochlear implants transmit sound directly to the auditory nerve. Getting an implant requires surgery on the ear, and costs of the procedure and follow-up care can exceed $50,000. There’s also the possibility of complications from infection or damage to the device - but those are relatively rare.
What a cochlear implant is
A cochlear implant is a device that helps some deaf people hear.
A surgeon puts part of the implant under the skin behind the ear and inside the inner ear. The implant has four parts:
The headpiece is worn behind the ear. Magnets hold it in place over the parts that are under the skin. It has a microphone that picks up sounds from the environment. A transmitter sends the sounds to the speech processor.
The speech processor is worn on the body. It takes sounds from the transmitter and changes them into electrical signals. Then it sends the signals to the receiver.
The receiver is placed under the skin behind one ear.
A wire from the receiver goes to the electrodes.
A doctor puts the electrodes in the cochlea. The electrodes take signals from the receiver and send them to the brain.
Because of the costs and risks, Loy said that doctors were initially hesitant to give young kids cochlear implants in both ears. But over time, she added, that trend has changed in the United States, and studies have shown that deaf children with two implants do better on hearing tests than those with a single implant.
Recently, Canadian researchers also provided reassuring news on cochlear implants, reporting that only a small fraction of children they operated on in the last 20 years had technical problems with their cochlear implants and needed new ones (see Reuters Health story of December 21, 2011.)
Who is a candidate for a cochlear implant?
Children and adults who have severe or profound sensorineural hearing loss and derive minimal benefit from hearing aids may be candidates for a cochlear implant. According to the Food and Drug Administration 2002 data,approximately 59,000 people worldwide have received a cochlear implant; in the United States about 13,000 adults and 10,000 children.
The benefit that an adult receives from an implant depends on several factors: their degree of hearing loss, their ability to understand speech before receiving the implant, experience using a hearing aid, and the length of time they have been severely or profoundly deaf. Generally, the more experience a person has had with hearing and the shorter the duration of their deafness, the more benefit they can expect to receive. Benefits vary from excellent, the ability to understand speech without visual cues (as on the telephone), to minimal, the improved ability to lip-read.
Young children are excellent candidates for cochlear implantation because they have robust central nervous system plasticity, which allows them to make use of the sound the implant provides. Children implanted early, who do not have other significant developmental disabilities, and when coupled with intensive post-implantation speech and language therapy, may acquire age appropriate speech, language, developmental, and social skills. They are usually schooled in mainstream educational settings.
The best age for implantation is still being debated but research has clearly indicated that children who receive hearing early have the best results. The FDA, in 2002, lowered the age for inclusion in pediatric clinical trials to 12 months. However, many centers will implant children as early as six months if there is certainty as to the audiologic indications. In addition, the child must weigh about 20-22 lbs., which is important from an anesthesia viewpoint. Another indication for early implantation is bacterial meningitis causing hearing loss because the cochlea (the organ of hearing) will sometimes scar after meningitis, preventing implantation.
The evaluation process is a team approach. Obtaining accurate audiological information is at the core of making appropriate recommendations related to cochlear implant candidacy. It is important that the testing be done by a specially trained pediatric audiologist who is experienced in fitting and facilitating preimplant hearing aid use. The team also includes speech and language specialists, a social worker, an educational consultant and, of course, the operating surgeon. The criteria for implantation become:
audiometric: is the hearing loss of appropriate degree and are hearing aids not sufficient?
speech and language: what is the level of the child’s present speech and language and what postoperative interventions are necessary?
social work: to assure there is a stable family support mechanism and realistic expectations as to outcome
educational: to plan for appropriate school placement to maximize learning
medical: to be sure there is no contraindication to surgery such as chronic ear infections or abnormal inner ear anatomy
For the current study, researchers tracked 30 children who already had one cochlear implant and were getting a second one put in at the Radboud University Nijmegen Medical Centre.
Marloes Sparreboom and colleagues gave parents general and hearing-specific questionnaires related to their kids’ quality of life before the second implant was put in, and one and two years after implantation. On average, kids were five years old when they had their second procedure.
On general health and quality of life questionnaires, there was no change in kids’ scores after the second implant. Those scores were generally within the healthy range for hearing kids anyway, according to the researchers.
But on questionnaires that specifically asked how well the children were able to listen to speech in a noisy environment, and other quality of life measures related to hearing and speaking, kids improved both one and two years after getting their second implant.
For example, on the Speech, Spatial, and Qualities of Hearing Scale, scored here from 0 to 1, children had an average score of 0.48 before getting their second implant, 0.60 a year after getting it and 0.62 after two years.
Children in the study were as old as eight and a half when they got their second implant, and age didn’t seem to factor into their improvement after the procedure.
A comparison group of kids who still had a single cochlear implant didn’t improve on hearing-related quality of life measures over a one-year period.
“The results imply that the second implant causes the effect on the hearing-specific (quality of life) and not simply maturation,” Sparreboom told Reuters Health in an email.
Sparreboom said the findings show that having implants in both ears can be beneficial for listening as measured by doctors and in daily life.
“Classrooms are noisy even for typical-hearing children,” said Loy. “Teachers turn away when they’re writing on the blackboard, you can’t read their lips. The situations that hearing-impaired children find themselves in are difficult even under the best circumstances.”
With multiple implants, Loy added, “You’re going to learn how to localize sound better, you’re going to learn how to focus better on the speech in noise…and you get better at that over time. If you can hear, and you know what’s going on, your quality of life is better.”
SOURCE: Archives of Otolaryngology-Head & Neck Surgery, online January 16, 2012
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Marloes Sparreboom, MA; Ad F. M. Snik, PhD; Emmanuel A. M. Mylanus, MD, PhD
Arch Otolaryngol Head Neck Surg. Published online January 16, 2012. doi:10.1001/archoto.2011.229