Cure for paralysis?

In a new way to help people paralysed by spinal cord injury, US scientists have discovered that there are alternative ways for signals to go from the brain to the limbs for movement.

Researchers from the University of California, Los Angeles, have for the first time succeeded in restoring the ability of walking in mice paralysed by spinal cord injuries.

They said their discovery could lead to new therapies for people who suffer from similar conditions.

Spinal cord injury involves damage to the nerves enclosed within the spinal column. Most injuries result from trauma to the backbone.

This affects the brain's ability to send and receive messages below the injury site to the systems that control breathing, movement and digestion.

Patients generally experience greater paralysis when injury strikes higher in the spinal column.

Until now, doctors believed that the only way for injured patients to walk again was to re-grow the long nerve highways that link the brain and base of the spinal cord.

However, the new study, published in this month's Nature, shows that the central nervous system can reorganise itself and follow new pathways to restore the cellular communication required for movement.

"When there is a traffic accident on the highway, 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," said lead researcher Michael Sofroniew.

"We saw something similar in our research," he added. "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."

Using a mouse model, the scientists blocked half of the long nerve fibres in different places and at different times on each side of the spinal cord.

They left untouched the spinal cord's centre, which contains a connected series of shorter nerve pathways. The latter convey 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," said Sofroniew. "They walked more slowly and less confidently than before their injury, but still recovered mobility."

When the researchers blocked the short nerve pathways in the centre of the spinal cord, the regained function disappeared, returning the animals' paralysis.

This step confirmed that the nervous system had rerouted messages from the brain to the spinal cord via the shorter pathways and that these nerve cells were critical to the animal's recovery.

The researchers said they now hope to figure out how to encourage nerve cells in the spinal cord to grow and form new pathways that connect across or around an injury, permitting the brain to direct these cells and avert paralysis.