Author: Neil Majithia
Institution: Virginia Commonwealth University
Date: January 2008
Defying current beliefs about the spinal cord, a UCLA study has shown that the central nervous system is capable of reorganizing signaling pathways in response to spinal cord damage. The discovery, published in the January 2008 issue of Nature Medicine, could lead to new approaches in the way researchers and clinicians seek to restore mobility following spinal cord injury.
Spinal cord damage results in paralysis because it blocks pathways used by the brain to control walking. For many years the prevailing belief was that these long nerve pathways, stretching from the brain all the way to the lower regions of the spinal cord, must be restored before a patient could regain mobility. Dr. Michael Sofroniew, lead investigator and professor of neurobiology at the UCLA David Geffen School of Medicine, suggested that this paradigm of a static central nervous system undermines the body's true capabilities. Dr. Sofroniew likes to think of the central nervous system as an extension of major freeways.
"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."
According to Dr. Sofroniew, a similar result was witnessed in this study. Using a mouse model, the investigative team blocked off half of the long nerve fibers on each side of the spinal cord at different places and times. In each scenario, the center of the spinal cord, a region that contains shorter nerve pathways, was left untouched.
"When spinal cord damage blocked direct signals from the brain, under certain conditions the messages were able to make detours around the injury," Dr. Sofroniew explained. "The message would follow a series of shorter connections to deliver the brain's command to move the legs."
Researchers were excited to find that the mice regained control of their legs within eight weeks. And though the mice walked more gingerly and with less confidence than before, they still recovered mobility.
The next step for the team is to develop a strategy that encourages such signal re-routing to occur. This marks a major change in the way researchers have been approaching therapy after spinal cord injury. Up until now, much effort has been focused on finding a way to repair damaged spinal cord nerves. The team's discovery suggests that such extensive repair may not be necessary, and restoration of mobility is possible even by manipulating the existing connections in the central nervous system. At the very least, Dr. Sofroniew hopes the discovery helps change the current, "pessimistic" perspective about spinal cord damage.
"When I was a medical student, my professors taught that the brain and spinal cord were hardwired at birth and could not adapt to damage. Severe injury to the spinal cord meant permanent paralysis.Our findings add to a growing body of research showing that the nervous system can reorganize after injury. What we demonstrate here is that the body can use alternate nerve pathways to deliver instructions that control walking."
Written by Neil Majithia
Reviewed by Brittany Raffa
Published by Pooja Ghatalia