A brain stem implant can help people whose hearing nerves are completely damaged or absent, such as those who have neurofibromatosis, a rare genetic condition that causes tumors to grow on the cranial nerves and spinal column.

"It's bad enough when you have one on one side, when you have one on each side, the compression on the brain stem becomes even more of a problem. Ultimately, it can cause death," otologist Dr. Doug Chen said.

An auditory brain stem implant, when linked to a cochlear device, can return hearing.

Getting the implant right is a tricky procedure in a tiny space, Brooks reports.

"The brain stem controls everything that goes on in our body, including automatic respiration and our heartbeat," neurosurgery chairman Dr. Jack Wilberger said.

Wilberger's biggest challenge is finding a tiny notch in the brain stem for a quarter-of-an-inch electrode.

"We have to slip that up into this crevice and put it directly over a bundle of cells that ultimately generate hearing," he said.

Patients will not be able to understand speech like they did before they lost their hearing, but they can hear things like laughter, birds, phones and barking dogs.

Neurofibromatosis affects one in 40,000 Americans. Perhaps one in 100,000 have tumors on both auditory nerves.