Research Focuses on the Role of Genetics in Deafness

A new pediatric otolaryngolgist (ears, nose and throat specialist), whose research helped to pinpoint the genetic cause of deafness, is now working to further understand the role of genetics in deafness.

"We now know that mutations in the gene encoding connexin 26 are the predominant cause of newborn deafness. About half of deaf children have this genetic mutation," said Dr. Glenn Green, who recently joined the UA faculty as assistant professor in pediatrics, surgery, and speech and hearing sciences at the University of Arizona College of Medicine.

"However, one in five children with connexin 26 deafness will have only moderate hearing loss. And one in 30 children with connexin 26 deafness don't even need hearing aids. It appears that some children are born with a resistance to this genetic deafness."

Along with researchers at the University of Iowa, Boys Town National Research Hospital, the Pasteur Institute in France, the Murdoch Institute in Australia, the MRC Institute of Hearing Research in England, and Tel Aviv University in Israel, Green has evaluated the hearing of 700 deaf newborns. Some of the babies passed the newborn hearing screen, even though it was later learned that they had connexin 26 deafness and had become completely deaf.

"This could mean that there's a brief opportunity for medical intervention to prevent the complete loss of hearing, but we don't know it yet," said Green.

The only fellowship-trained pediatric ENT in Arizona, Green is also studying how genetics influence how well kids do with cochlear implants. Sensory cells within the cochlea, the snail-shaped cavity of the inner ear, hold thousands of tiny hair cells that convert the vibrations of sound into electrical impulses that are transmitted to the brain. The brain interprets these impulses enabling us to hear. No electrical impulses are produced if the hair cells are missing or damaged.

A cochlear implant involves surgically implanting a sound-activated electronic devise that directly stimulates the cochleas of deaf individuals. Hearing aids, which make the most of residual hearing, don't work for those whose hair cells are absent or significantly damaged. According to Green, cochlear implants have been available to children since the 1980s, though most of the advancements have only been made recently.

From tracking the academic achievement of deaf children, Green has learned that children with the gene for deafness who have cochlear implants perform as well academically as their hearing peers. Children who are deaf for other reasons and have cochlear implants outperform their deaf counterparts, but are not equal to their hearing peers.

"This research leads to improved diagnostic and intervention strategies for deaf children," he said.