A new implant that stimulates neurons directly at the brain stem may help children born without a cochlear nerve hear.
A three-year study, launched in March 2014, has successfully implanted an auditory brain stem implant (ABI) device in four children who couldn’t be helped by hearing aids or cochlear implants.
“Initial activation of the ABI is like a newborn entering the world and hearing for the first time, which means these children will need time to learn to interpret what they are sensing through the device as ‘sound,'” says audiologist Laurie Eisenberg, professor of otolaryngology at the Keck School of Medicine at University of Southern California.
No sound, no matter how loud
“All of our study participants whose ABIs have been activated are progressing at expected or better rates. We are optimistic that, with intensive training and family support, these children will eventually be able to talk on the phone,” says Eisenberg.
Hearing loss manifests in various forms, most of which can be partially restored through hearing aids and cochlear implants. But those devices can’t help a small population of people who do not have a cochlear, or hearing, nerve. These people are unable to perceive sound, no matter how loud, outside of feeling vibration.
The new device gets around this by bypassing the inner ear entirely and stimulating neurons directly at the human brain stem.
Surgeons outside the United States have been doing ABI surgeries in children for more than 10 years, but there was never a formal safety or feasibility study under regulatory oversight.
In the United States, the ABI is approved for use only in patients 12 years or older with neurofibromatosis type II, an inherited disease that causes a non-malignant brain tumor on the hearing nerve. But it has shown limited effectiveness in adults.
The ABI would be more effective in younger children, when their brains are more adaptable, researchers say.
The clinical trial will attempt to prove that the surgery is safe in young children and allow researchers to study how the brain develops over time and how it learns to hear sound and develop speech.
“Hearing loss can be devastating to a child’s social development, and for some children, the ABI is their last viable chance to hear,” says professor Robert Shannon, an investigator for the trial.
“Several of the young children who had ABIs implanted outside the United States have sought help at the USC-CHLA Center for Childhood Communication, and we know that they now have the potential to understand speech. This really shows how powerful and flexible the brain is.”
Researchers presented their preliminary findings at the annual meeting of the American Association for the Advancement of Science on February 14.
The NIH clinical trial covers the costs of the device, procedure, and subsequent testing. To qualify for participation, patients two to five years old must show that standard treatment such as hearing aids and cochlear implants have been ineffective.