Spinal cord injury is the most common cause of paralysis today, leaving patients immobilized, with bleak chances of recovery. Now, scientists have provided new hope for patients with this condition, by making paralyzed rats walk again with a normal coordinated gait, using electrical stimulation.
Spinal cord injury is the leading cause of paralysis today, followed closely by stroke, head injury and multiple sclerosis. The spinal cord is a necessary component for movement, since it provides a connection between the brain and the rest of the body. It basically acts to transport information to the peripheral nervous system, thus allowing us to move our limbs. If this flow of information is disrupted in any way, due to severe injury, then the information required by the rest of the body in order to move, cannot be transmitted. This can result in partial or complete paralysis. Unfortunately, for such injuries there has been no effective treatment so far, leaving many spinal cord injury patients with permanent paralysis of the limbs.
Now, Grégoire Courtine and his colleagues at the Swiss Federal Institute of Technology in Lausanne (EPFL) have provided new hope for the recovery of spinal cord injury patients. By using a combination of electrical stimulation and neurotransmitters, they managed to make paralyzed rats with severed spinal cords walk again, with a normal humanlike gait.
Mimicking walking using electrical stimulation
In the past few years, there have been major developments in the treatment of paralyzed patients with spinal cord injury, as scientists have figured out ways to mimic the signals required for limb movement. A promising technique that has emerged from these studies, is the stimulation of the spinal cord with electrical pulses in order to transmit signals to patients limbs and compel them to move. This therapy, which is still at its experimental stages, has remarkably allowed four paraplegic patients to regain some voluntary movement in their limbs.
However, this method, known as epidural electrical stimulation (EES), is far from perfect, since the electrical impulses require constant adjustment, in order to achieve a natural, coordinated gait. Up until now, these limitations have restricted the use of EES to an exercise aid that helps spinal cord injury patients regain some movement in their extremities.
How can we achieve a more natural walking gait using electrical stimulation?
In order to improve on this method and achieve a more natural and coordinated walking gait for paralyzed patients, researchers at the EPFL developed algorithms that were able to automatically regulate the electrical pulses in realtime, allowing for more natural movement.
More specifically, the scientists used paralyzed rats with severed spinal cords and surgically implanted electrodes in their spines. The animals were treated with serotonin agonists (5HT1A/2/7), which prime the spinal cord to communicate with the legs, since this is not possible after a spinal cord injury. The rats were then placed on a treadmill, or on a runway with obstacles supported by a robotic harness and their movement patterns were monitored under a number of different electric pulses.
Taking advantage of the information they collected in this experiment, the scientists then developed an algorithm that could constantly monitor the rats movement and adjust the electrical stimulation in realtime, continuously and automatically, mimicking natural brain signals. Using this method, the rats were able to walk at least 1000 steps on a treadmill, with a much more natural and coordinated gait. They were even able to succesfully climb rat-sized stairs!
What are the prospects of this method in the treatment of patients with spinal cord injury?
The technique developed in this study is the first of its kind, since it makes limb movement adjustment in realtime possible. However, this method is still far from allowing paralyzed patients to walk completely on their own, even though at its current state, it may help them partly restore broken connections in the brain by exercising the spinal cord and limbs. Since making rats walk again versus making humans walk again is quite different, as rats unlike humans are quadrupeds, the research team of Grégoire Courtine is now already planning on testing this new exciting method in human trials in the very near future. They plan to use a scaled up system to control electric pulses in human patients paralyzed by spinal cord injury.
Although these exciting new developments do not yet provide a miracle treatment, it is hoped and believed by scientists that in the near future walking alone again may become possible for spinal cord injury patients. This may be achieved by taking advantage of these new findings to build a neuroprosthesis that will act as a brain-machine interface. This will potentially allow thoughts from the motor cortex of the brain to be transmitted through implanted electrodes to a spinal cord stimulator. By controlling this stimulator through their thoughts, spinal cord injury patients may eventually be able to control their own leg movement and thus hopefully walk again.
Sci. Transl. Med. 6, 255ra133 (2014)