The experimental application of electrical stimulation has let some people who are paralyzed regain motion. Two different research groups recently demonstrated that the electrical stimulation of the spinal cord could give some paralyzed people the ability to walk again.
One should note that it was not only the electrical stimulation of the spinal column that let the patients regain movement, there was also a large amount of intense training and physical therapy that the patients underwent. Despite this, the electrical stimulation of the spinal cord did let three patients regain the ability to walk and spine researchers are expressing hope that the therapy could be improved upon and used to help many others. Biomedical engineer from the University of Alberta, Vivian Mushahwar, says that it is likely that a serious milestone has been crossed.
Regaining Movement Through Electrical Stimulation
Previous research on animals has shown that mice with spinal cord injuries can learn to walk again with spinal stimulation, drugs, and physical therapy/training. Furthermore, people who are paralyzed can make movements similar to steps when they are lying down and have their spinal cord stimulated. These facts imply that if the spinal cord is still intact it may be possible to restore movement to those who are paralyzed, and the research team tested this idea.
The two separate studies both utilized a device from medical technology manufacturer Medtronic. The device has been approved to treat pain and it functions by applying an electrical pulse to the spine of the patient. The first study was done by researchers at the Mayo Clinic, was published in the journal Nature Medicine, and the study details how one patient with a spinal cord injury was able to walk with assistance after the stimulator was implanted. After 42 weeks of treatment, the patient was able to walk more or less independently while using a walker, with only occasional assistance.
Researchers at the University of Louisville, Kentucky examined how four different patients responded to electrical stimulation through the device. The study was published in the New England Journal of Medicine, and the study notes that the patients experienced two months of standing and stepping exercise in addition to the electrical stimulation of their spines. While two of the patients did not learn to walk with the device, a third patient was able to move his fingers even though his arms had been paralyzed during an accident while mountain-biking. While the patient does not use the stimulator to walk at home, he was able to start walking in a lab setting with assistance.
The most dramatic example of the effectiveness of the electrical device was patient Kelly Thomas who is able to use the stimulator and a walker to move around her home. Thomas was in an accident four years prior, a vehicle rollover that fractured her spine. Thomas’ doctor had apparently told her there was a 99% chance that she wouldn’t walk again, yet Thomas underwent hundreds of therapy sessions over the course of months to try and regain motion. Thomas learned to use a walker, and after stimulation of the spine is able to walk unaided.
While the technique did not prove helpful for all those who tried it, the two teams of researchers are hoping that the studies will bring more attention and funding to research into the therapeutic effects of the spinal stimulation. Gregoire Courtine, a professor at the Center for Neuroprosthetics and Brain Mind Institute in Lausanne, Switzerland says the results from the data are extremely promising. Courtine explains:
What these data these two papers are showing is that the potential is there. Maybe not for everyone, but I’m becoming convinced that spinal cord stimulation, when optimized, has the potential to be the first treatment to improve recovery after spinal cord injury.
While the data from the study is promising, it also leaves many questions open. The examples presented in the studies are essentially case studies, detailed observations of a small sample size of patients. Larger, more rigorous studies must be conducted to see if the effects hold constant across different populations of patients. It’s also not entirely clear why the electrical stimulation helped the patients move, just that it did.
One theory behind why the electrical stimulation device seems to work is that even after a spinal cord injury has occurred, some connections between the brain and the spinal network still exist and that these connections can be restored by an artificial electrical impulse. In other words, it could be that an injury to the spinal column prevents the spinal network signals from reaching the brain and that the spinal stimulator is able to restore enough of a connection that with the intention to move (and lots of practice) it is possible to walk again. Further research will likely aim to discover the mechanism behind the therapeutic effect, and determine who will benefit from the therapy the most, explains Kristin Zhao, director of Mayo Clinic’s Assistive and Restorative Technology Laboratory.
Next Research Steps
Susan Harkema, a neuroscientist at the University of Louisville, says one of the most important next steps is that a therapeutic device explicitly created for therapy of the spine must be made.
“The hurdle is the technology. The technology is just off the shelf for pain. It’s not designed for this use,” says Harkema.
Medtronic or another device manufacturer will have to create devices for spinal cord therapeutic purposes. One type of device that could be meet the needs of researchers is a device that, instead of continuously supplying an electrical current while on, activates as a patient is trying to walk. Claudia Angeli, co-author on the Louisville study, explains that the research team tried to integrate “intent” into every movement made during training. It’s possible that an electro-stimulating device that acts when intentional movements are made could help researchers discern the mechanism behind the therapeutic effect.
Spinal cord stimulators could also target other health issues associated with paralysis like low blood pressure. Harkema’s team is currently planning a randomized controlled trial to investigate how these associated issues are affected by electrical stimulation.