Dogs with severe back injuries may still have their day, thanks to a new method for treating spinal cord trauma. The technique offers hope for canines and could lead to new treatments for preventing paralysis in humans.
Serious trauma to the spinal cord can bring on paralysis even though many nerve cells survive the initial injury. In the days following, dying neurons spew toxic chemicals that overexcite other neurons to death. Cells also leak calcium and sodium, which can flood into and destroy other cells. Scientists think the delayed damage causes the lasting effects of spinal injuries and have focused on therapies that might minimize this biochemical mayhem. Now a harmless chemical cousin of antifreeze, polyethylene glycol, has stepped up to the plate.
About 5 years ago, researchers led by Richard Borgens of Purdue University in West Lafayette, Indiana, discovered that giving guinea pigs a shot of polyethylene glycol right after a serious spine injury repaired much of the initial nerve damage. The mechanism is still poorly understood; scientists speculate that polyethylene glycol forms a soap-bubble-like seal around damaged cells, preventing leakage and intrusion of fluids.
After further investigation, Borgens and his colleagues decided to try the treatment on injured dogs brought into the institutions' veterinary trauma centers. Nineteen paraplegic dogs between 2 and 8 years old were given polyethylene glycol intravenously within 72 hours of their injury, in addition to the usual treatment of steroids, physical therapy, and surgery to remove floating chips of bone. The researchers then compared the dogs' recovery to 24 cases on the books in which dogs had had only the usual treatment. More than half of the dogs receiving polyethylene glycol had noticeably improved mobility within a few days and were standing or walking within 2 weeks, compared to just under a third of regularly treated dogs, the researchers report in the December issue of the Journal of Neurotrauma.
"The results are encouraging," says neurologist Patrick Sullivan of the University of Kentucky, Lexington. "This is an intriguing finding because polyethylene glycol is very safe." Nonetheless, he and other researchers caution that more rigorous studies with better controls will be needed to determine whether polyethylene glycol may be useful for treating human spinal cord injuries. And the differences in how the brain and spinal cord control walking in man versus his best friend will have to be better understood.