Wired For Sound: Implant Sends Signals Direct To Brain

A delicate surgery that involves placement of tiny electrodes onto the brainstem is helping some people avoid total hearing loss.

The electrodes, connected to a device known as an auditory brain implant, are being placed in patients who require surgery to remove noncancerous tumors associated with a disorder called neurofibromastosis type II. The tumors are often entwined around the nerves that facilitate hearing. Over time the tumors - or the surgical intervention to remove them, can result in fractional or total hearing loss.

Only about 500 people have received the implants around the world, but the benefit is substantial, according to Dr. Bradley Welling, chair of otolaryngology at Ohio State University Medical Center and one of the handful of surgeons in the United States trained to implant the devices.

"The primary advantage of the auditory brain implant is that it helps patients lip read and receive environmental sounds, whether it is traffic, warning signals or other alerts," said Welling. "It also helps them to modulate their speaking and improve their own voice since it's very difficult to modulate speech when you are without hearing."

The implants bypass the damaged nerves and form a direct pathway to the brainstem. The electrodes are positioned against the brainstem and receive signals from a pager-sized processor carried on the belt. A tiny microphone on the ear sends the sounds to the processor, which converts them to frequencies that are picked up by the brainstem.

Sounds from the implant may not replicate exactly the actual sounds and voices the patient was once accustomed to hearing, but they're close enough, says Phyllis Lee, who lost her hearing in 1986 due to neurofibromastosis.

"It has helped me step back into life," says Lee, who had the device implanted last year. "I can hear my cat and many things that others take for granted, like running water. It's funny, just the little things you get so excited over, these little sounds," she added.

Because the tumors often envelope the auditory nerves or push against other vital nerves around the face, surgeons require a microscope to make the tedious manipulations necessary to remove the tumors and implant the device.