By: Steve Siwy for Back1For doctors and patients alike, spinal cord injuries are one of the most profound and intractable of medical problems. Damage to the spinal cord can result in loss of feeling for the patient, as well as decreased mobility to the point of paralysis.
Until recently, few reliable techniques existed for controlling or reversing damage to the spine, but, as Dr. W. Dalton Dietrich, of the Miami Project to Cure Paralysis at the University of Miami, recently told USA Today, “In the last five years, it has never been more exciting in terms of the knowledge we’re obtaining.” The new research is helping doctors to better understand the biology of spinal cord injury, and devise more effective treatments.
In one approach, doctors attempt to retrain the spinal cord to assist with functions that have been lost to injury. The research is based on the idea that the spinal cord alone has enough “computing power” to regulate complex, rhythmic behaviors like walking. Indeed, researchers estimate that some sort of walking motion can be accomplished using as little as 10 to 15 percent of the nerve fibers in the spine. Thus, even if injury has disrupted its connection to the brain, the spinal cord might be retrained to improve limb movement.
At the Miami Project to Cure Paralysis, researchers use treadmills and computer-assisted, robotic harnesses that help patients move their legs in a rhythmic walking pattern. Though scientists still are still unsure how much is due to retraining of the spinal cord, and how much is simply improved muscular and cardiovascular fitness from exercise, patients have shown increased movement and limb strength after several weeks of this robot-assisted rehabilitation.
Regaining lost function isn’t the only goal of research into spinal cord injuries. Doctors also want to mitigate the extent to which function is lost in the first place. In the hours immediately following an injury, secondary damage can occur to nerve tissue, caused by the body’s own reaction to the trauma. Drugs are being sought to halt inflammation, which can aggravate nerve damage, as well as ways to block apoptosis, in which damaged cells perform a kind of “cell suicide.”
The quest to understand secondary damage has also yielded some surprising discoveries. In a recent study, scientists at the University of Rochester Medical Center found that immediately following a spinal cord injury, star-shaped cells called astrocytes flood the injury site with adenosine triphosphate (ATP), the molecule that cells use to store energy. In this case, however, the ATP binds to neurons at the sites of molecules known as “death receptors,” sending signals to the neurons that cause them to die.
Any practical applications for humans are still years away, but doctors hope that by better understanding the mechanism behind ATP flooding, they might eventually be able to slow, or halt, its effects. “There is no good acute treatment now for patients who have a spinal cord injury,” said the Medical Center’s Dr. Maiken Nedergaard, Ph.D., in a press release. “We’re hoping that this work will lead to therapy that could decrease the extent of the secondary damage.”
Nearly 250,000 people in the United States are estimated to be living with some sort of spinal cord injury, and about 11,000 new injuries occur per year. Motor vehicle accidents are the leading cause of spinal cord injuries in the U.S., followed by falls, and most injuries occur to people between the ages of 16 and 30.
