Bone-Assisted Aids Can Double Hearing

May 6, 2008 -- A device screwed into the skull that transmits sound via bone can improve hearing in patients with certain kinds of hearing loss by as much as 50 percent, according to the largest study of devices, known as bone-assisted (or bone-anchored) hearing aids, or BAHAs.

"This is a very important technology for a number of patients who have difficulty hearing," said Daniel Lee, a doctor at the Massachusetts Ear and Eye Infirmary in Boston, Mass., who was not involved in the study.

"Patients are getting better choices for improving their hearing," said V. Suzanne Jeter, a researcher at Loyola University who presented the study at the 10th International Conference on Cochlear Implants and Other Implantable Auditory Technologies in San Diego.

BAHAs have been used for years to restore hearing to patients who suffer from outer and middle ear problems like tumors, chronic infection, congenital disorders and other problems that stop sound from entering the inner ear.

Unlike cochlear implants, the device cannot help deaf patients whose inner ear, which contains three tiny bones that contribute to hearing, has been damaged or destroyed.

Deaf patients sometimes use cochlear implants, which electrically stimulate the nerve leading from the ear to the brain, to regain hearing. Instead, BAHAs mechanically vibrate the bone that then stimulates the intact inner ear, triggering a nerve impulse that then travels from the ear and into the brain.

Simple surgery is required to implant the device.

After a patient is anesthetized, a small U-shaped incision is made, and a 2- to 3-mm hole is drilled into the mastoid bone behind the ear. A small titanium screw is then inserted into the hole, and the incision is sealed.

Over the next three to six months the bone grows into the screw, locking it into place.

Then all the patient has to do is clip a microphone and sound processor the size of a thumb knuckle to the screw.