CONTACT: JENNIFER CRONIN
2130 Medical Laboratories
Iowa City IA 52242
(319) 335-9917; fax (319) 335-8034
Release: Oct. 11, 1999
UI analysis shows that eligibility criteria for cochlear
implantation should be expanded
IOWA CITY, Iowa How much hearing an individual
has before receiving a cochlear implant may partially predict how beneficial
the device will be, according to University of Iowa Health Care research findings.
"The more hearing you have before your implant, the
better you do," explained Jay Rubinstein, M.D., Ph.D., UI assistant professor
of otolaryngology, and physiology and biophysics.
A cochlear implant is an electronic device that doctors
surgically place in the cochlea of the ear to restore hearing in individuals
with profound hearing loss or deafness. The device, which receives signals
from a processor worn outside the body, acts as the ear's hair cells, which
have become damaged or are missing and result in hearing problems. The cochlear
implant converts acoustic information into electrical signals that can be
transmitted to the brain and perceived as sound.
Rubinstein decided to investigate the factors affecting
the success of cochlear implants after noticing a difference in two groups
of patients. Patients whom he treated at the Iowa City Veterans Affairs Medical
Center (VAMC) showed marked improvements in average word perception after
implantation as compared to patients treated with the same device at the UI
Hospitals and Clinics five years earlier.
The VAMC patients' average word perception scores
were 40 percent. Five years earlier, the UI Hospitals and Clinics patients'
average word perception scores had been about 30 percent. The VMAC patients'
scores were nearly identical to UI Hospitals and Clinics patients who have
since been treated using a technologically upgraded cochlear implant.
"It didn't seem like the device was responsible for
the improvement," Rubinstein said. "It seemed like there was something different
about the patients."
In fact, something had changed in terms of the patients.
During the five-year period, the Food and Drug Administration (FDA) had modified
the eligibility criteria for receiving cochlear implants. When cochlear implants
first came on the market, the FDA allowed their use only for patients who
were completely deaf. The federal agency then revised the eligibility criteria
to include individuals who had a speech reception limited to less than 40
percent words in sentences in the "best-aided condition."
"This residual hearing is partially responsible for
the better performance," Rubinstein said.
When someone receives a cochlear implant, what, if
any, hearing a person still has is destroyed. Therefore,
finding that all-important cost-benefit equilibrium point is important, Rubinstein
"You have to be careful because the more hearing they
have, the more they have to lose," he said. "At some point, there is going
to be a cutoff in the benefit realized. Where that cutoff is, we currently
don't know. So, we are going to start testing those waters now."
Researchers at the UI Cochlear Implant Clinical Research
Center will begin that testing process armed with data from their analysis
of VAMC and UI Hospitals and Clinics patients.
"We don't know exactly where the cutoff is, but we
can predict, based on our current experience, how people with more hearing
will do," he said.
The UI investigators have developed a predictive index.
The researchers, knowing the duration of individuals' hearing loss and their
level of residual hearing, can plot this data and determine how effective
cochlear implantation will be. For example, if a patient has been deaf for
15 years and has 10 percent residual hearing before surgery, there is 95 percent
certainty that the person will have an after-surgery word perception score
greater than 25 percent.
The index is based on patient information from the
UI Hospitals and Clinics and VAMC.
"If the predictive index holds out to be true in a
bigger population, it is going to be an incredibly valuable tool," Rubinstein
Portions of Rubinstein's research appear in recent
issues of the American Journal of Otology and Current Opinion in Neurobiology.
Rubinstein's collaborators include Mary Lowder, an audiologist in the UI department
of otolaryngology; Richard S. Tyler, Ph.D., UI professor of otolaryngology,
and speech pathology and audiology; and Bruce J. Gantz, M.D., UI professor
and head of otolaryngology.
University of Iowa Health Care describes the partnership
between the UI College of Medicine and the UI Hospitals and Clinics and the
patient care, medical education and research programs and services they provide.