Early Cochlear Implants Aid Deaf
Children
Source: Press Release
January 3, 2001
Deaf and hearing-impaired children get more benefit from
a cochlear implant the younger they are when they receive it, and will
do better on speech recognition tests later on in life, according to a
new study from the University of Michigan Health System.
Cochlear implants transform speech and other sounds into
electrical impulses that stimulate auditory nerve terminals within the
inner ear. Children and adults with severe to profound sensorineural
hearing loss in both ears are able to have their hearing restored and
improve their communication with the implants. Cochlear implants are
for people who cannot benefit from hearing aids.
The report states that the positive effect of early
implantation is noticeable even when comparing older and younger
children who have had their implants for the same period of time,
despite the older children's maturity advantage.
The report's findings, published in the January issue of
the journal Otology and Neurotology (formerly the American Journal of
Otology), add more evidence to the belief that hearing-impaired
children should get cochlear implants as soon as possible if they are
unable to gain any benefit from hearing aids.
"We found a significant difference in speech recognition
between those who got their implants between the ages of two and four
years, during the critical language development period, and those who
received them later," Paul Kileny, Ph.D., lead author of the study and
professor and head of audiology at UMHS explained. "We also found that
the longer
children had had their implants, the better they did, though the
effect was still largest in those who were implanted earliest."
Test results were examined from 101 children between the
ages of 2 and 14 years who received the same model of cochlear implant
at UMHS. The study is more relevant than similar studies done in the
past because of the size of the group and the identical management of
the patients. The group of children represents a third of all
pediatric patients treated in the history of the UMHS program, which
is one of the oldest and largest in America.
The group was divided almost equally allowing for two
analyses to isolate the effect age at implantation has on speech
perception. A group of 48 children were tested on their
speech-recognition skills once they turned 7, regardless of when they
received their implants.
The other group of 53 children of various ages was
tested three years after implantation. Each child was given six
standard tests measuring their ability to recognize sounds, words, and
sentences. The results showed a combined effect of age at implantation
and the length of time children had their implants. The authors,
Kileny, audiologists Teresa Zwolan, Ph.D., and Carissa Ashbaugh, M.A.,
collected the data used in the study over a period of several years
from routine tests given to UMHS cochlear implant recipients. The
children evaluated were between the ages of 5 and 17. The children in
each part of the study were divided into four subgroups. Those tested
at 3 years post-implant were divided according to their age at
implantation and those at age 7 according to time since implantation.
The differences between the groups were most noticeable
in the 7-year-olds who had their implants for four or more years, and
the children whose implantation had occurred between the ages of 2 and
4. However, even the 7 year olds who had only had their implants for
three years scored significantly better than those who had them one or
two years. Children who were able to hear for the first time between
the ages of 5 and 7 did better than children who did between the ages
of 10 and 13.
While some speech perception test results didn't show
clear differences among the groups, Kileny pointed out that some tests
required sophisticated linguistic and vocabulary skills which the
youngest patients might not have developed regardless of their age at
implantation.
The reason for the better speech perception performance
because of longer and earlier use of an implant is probably due to the
effects cochlear implants have on developing auditory nerves,
according to Kileny. Nerve cells used in the auditory system need
early and constant stimulation to develop important connections and
patterns of activation used in speech perception. Clinical studies
have shown that both children and adults continue to improve their
speech perception over time, although adults plateau eventually.
Because of this, Kileny says, the "wait and see"
approach to newly diagnosed young children may do them more harm over
time. "I have seen several youngsters whose parents have opted to wait
for new technological developments, in some cases for two to four
years. These patients, though they began with great potential, ended
up deriving minimal benefit from their cochlear implant, having missed
crucial speech and language development milestones."
Childhood development researchers consistently find that
toddlers and young children reach important milestones in speech and
language development early in life. The results of this study may
indicate the risk of missing or delaying those milestones because of
hearing impairment.
Long-term effects of cochlear implantation before the
age of two are still being examined. The U.S. Food and Drug
Administration has improved implants for children in as young as 12
months. Clinical trials involving 12 to 24 month old children are
underway at UMHC among other places.
http://www.cosmiverse.com/science01030102.html