Because of a series of breakthroughs sparked by the study of sleep apnea, Gordon Mitchell, professor and chair of Comparative Biosciences, is examining an unusual treatment for spinal cord injuries.
The study looks at patients with partially damaged spinal cords, focusing on ways to improve the use their surviving neural pathways. Mitchell’s method, of “intermittent hypoxia treatment,” gives patients brief and repeated periods of low oxygen to increase spinal cord plasticity, essentially training the spinal cord to achieve functions that had been lost. “As long as there are some spinal pathways left, we can tap into that,” said Mitchell.
Mitchell’s research team is an interdisciplinary group including Randy Trumbower at Emory University, Zev Rymer, director of research at the Physical Rehabilitation Institute in Chicago, and Gillian Muir, a professor of veterinary biomedical sciences from the Western College of Veterinary Medicine in Saskatchewan, Canada. These collaborators, which include a neuroscientist, a neurologists, a physical therapist, and a veterinarian, form a perfect team to study spinal cord injuries, with research spanning both animal and human trials.
Their studies began after Mitchell noticed a curious effect while simulating sleep apnea patients, who are subjected every night to repeated, short periods of low oxygen. He wanted to test the idea that the body fights this problem through natural processes of compensation. As Mitchell expected, initial rat studies showed plasticity of respiratory motor neurons, meaning the body reacted by training its own motor nerve cells to improve breathing. Once his group realized that intermittent hypoxia triggered plasticity in the spinal cord, they wondered if it would be of use in treating individuals with spinal injuries in the neck, where breathing is greatly impaired. In a pioneering study on rats with spinal injuries, his group demonstrated that intentionally exposing the rats to intermittent hypoxia had beneficial effects. “We restored a lot of their capacity to take a breath,” said Mitchell. But that wasn’t the only change in the rats. A follow-up study with Muir showed that the same treatment induced plasticity in other motor neurons, restoring function in the forelimb as well. “That kind of recovery, there’s almost no precedent for that,” said Mitchell, encouraged by the dramatic results. “It’s such a simple procedure,” said Mitchell. “It’s like holding your breath for 20 seconds” every five minutes.
Now moving into human trials, Mitchell is working with Trumbower and Rymer to test their therapy on people with chronic injuries, averaging 15 years post-injury. These same patients have little or no prognisis for functional improvement; according to Mitchell, in most people with spinal cord injuries, “There’s a period of about six months where they’re improving,” said Mitchell. “After that, they’re stuck on this plateau” with little hope for further improvement. Mitchell and his team hope that intermittent hypoxia therapy can improve this grim outlook.
The set-up involves a breathing mask that distributes the proper amounts of oxygen, then brief periods of lowered oxygen. Shortly after, patients test their ankle strength by pressing on something like a gas pedal. The results are impressive, showing 80 percent improvement after just one treatment. “If you treat them with air, nothing happens,” said Mitchell. “If you treat them with intermittent hypoxia, you can increase their strength.” The team is now moving on to more complex movements, and are investigating improvements in walking.
Cautiously optimistic, Mitchell is eager to investigate further the causes and effects behind the treatment. “There’s a long way to go,” he said, seeing a great potential for future studies. He hopes to pair intermittent hypoxia with physical therapy to improve results and give physical therapy the boost it needs to further improve function.
Mitchell also thinks their research could come full circle and help sleep apnea patients. “We’re making so much progress with the neurochemicals that cause this effect,” said Mitchell. “This could come back and suggest drugs for sleep apnea.”
As with all research, a promising breakthrough raises as many questions as it answers. “All we know is it looks interesting so far,” said Mitchell. “There’s a long way to go.”