By Jennifer Warner
WebMD Medical News

Rewiring healthy nerves may offer a new way to increase the odds of walking again after spinal cord injuries.

A new study shows rewiring nerve fibers near the injury site allowed mice to walk again after a spinal cord injury.

Although these results are only preliminary, researchers say the findings suggest that rewiring may be an easier way to restore walking after a spinal cord injury. People with spinal cord injuries lose the ability to walk because nerves in the spinal cord that send and receive signals to and from Motor neurons in the brain are severed and crushed.

Until now, efforts to restore movement have mainly focused on the difficult task of finding ways to regrow these damaged nerve fibers.

But researchers say neurons within healthy portions of the spinal cord near the injured portion rewire themselves after injury; harnessing this natural healing power may provide a simpler and better way to regain walking after spinal cord injury.

"Imagine the long nerve fibers that run between the cells in the brain and lower spinal cord as major freeways," says researcher Michael Sofroniew, MD, PhD, professor of neurobiology at the David Geffen School of Medicine at UCLA, in a news release. "When there's a traffic accident on the freeway, what do drivers do? They take shorter surface streets. These detours aren't as fast or direct, but still allow drivers to reach their destination."

"We saw something similar in our research," says Sofroniew. "When spinal cord damage blocked direct signals from the brain, under certain conditions the messages were able to make detours around the injury. The message would follow a series of shorter connections to deliver the brain's command to move the legs."

Rewiring After Spinal Cord Injury

In the study, researchers blocked half of the long nerve fibers in the spinal cords of laboratory mice at different places along each side of the spinal cord, leaving the center untouched. The center contains a series of shorter nerve pathways, which send information over short distances up and down the spinal cord.

"We were excited to see that most of the mice regained the ability to control their legs within eight weeks," says Sofroniew. "They walked more slowly and less confidently than before their injury, but still recovered mobility."

When they blocked the short nerve pathways in the center of the spinal cord, this regained movement was lost, which confirmed that the nervous system had rerouted the messages from the brain to the spinal cord.

Researchers say the results demonstrate that the spinal cord has the ability to reorganize and rewire itself after injury.

"Our study has identified cells that we can target to try to restore communication between the brain and spinal cord," says Sofroniew. "If we can use existing nerve connections instead of attempting to rebuild the nervous system the way it existed before injury, our job of repairing spinal cord damage will become much easier."

The researchers say the next step is to learn how to entice nerve cells in the spinal cord to grow and form new pathways that connect across or around the damaged area.

SOURCES: Courtine, G. Nature Medicine, Jan. 7, 2007, advance online publication. News release, University of California Los Angeles.