What cats tell us about hearing

Research by Hopkins otolaryngologist David Ryugo may explain why cochlear implants are 80 percent effective in restoring hearing to young children born deaf, but are rarely successful in congenitally deaf adults.

In his study, published in Science online December 2, Ryugo used cochlear implants to electrically stimulate the nerves responsible for hearing in young, deaf cats. His results point to a link between introduced nerve activity and the structure of the auditory nerve ending. According to Ryugo's study, the success of implants depends on how far abnormalities at nerve endings have advanced, a process he observed in the cats. If children born deaf are left untreated for too long, their nerve endings may start to wither. Eventually, the abnormality becomes irreversible, and the nerve activity introduced with implants can't restore the nerve ending. "It is always difficult to know the age at which a child is strong enough to endure the surgical process," Ryugo says. "What we think this study tells parents of deaf children is that if cochlear implants are being considered, the earlier they're done, the better."
—Meagan White, A&S '06 (MA) February 1, 2006