In a recently published breakthrough, five men suffering from complete motor paralysis were able to generate – voluntarily – step-like movements, using a non-invasive electrical stimulation strategy. The latter is known as ‘transcutaneous stimulation’, and delivers electrical currents via electrodes, placed strategically on the skin of the lower back, to the spinal cord. Previously, all methods of delivering electrical stimulation involved surgically implanting electrodes on the spinal cord – this is the first time this has been done non-invasively.  

Inspiration From Previous Studies: Paralysis Treatment Breakthrough

In a previous study, Edgerton, along with Susan Harkema, Ph.D., and Claudia Angeli, Ph.D., from the University of Louisville, Kentucky claimed that four men, suffering from complete motor paralysis, were able to generate voluntary movements via electrical stimulation of their spinal cords. The stimulation was administered using an epidural stimulator that was implanted surgically onto the surface of the spinal cord.

Based on this remarkable success, Edgerton and the team began working on a non-invasive strategy for delivering stimulation to the spinal cord, on the basis of the tremendous benefits this would bring for paralyzed individuals. Edgerton pointed out that despite undergoing many surgeries, not all paralyzed individuals have the strength to carry on – a non-invasive procedure would remove this problem. Moreover, the cost of this intervention would be one-tenth that of an implanted stimulator.

Developing A Non-Invasive Stimulation Strategy

Five men, who had been paralyzed for more than two years, were administered a series of sessions – 45 minutes each, once weekly – for about 18 weeks. The purpose was to determine whether the non-invasive electrical stimulation could induce the ability to move their legs. During the stimulation, the men were occasionally asked to try moving their legs or to remain stationary.

In the last four weeks, pharmacological treatment in the form of buspirone was also given. This drug mimics the effect of serotonin, and has been successfully used to induce locomotion in mice with spinal cord injuries.

Apart from electrical stimulation, the individuals were also given several minutes of conditioning. This involved moving their legs (manually) in a step-wise pattern. The idea was to see whether physical training coupled with the non-invasive strategy could enhance the desired effects.

Recording The Results

Movements were seen to occur when the legs were suspended, allowing free movement without resistance. Even though this isn’t comparable to walking, the results demonstrated significant progress towards developing a promising therapy.

At the start of the study, the men were only able to move their legs when the electrical stimulation was strong enough to produce involuntary step-like motions. However, with time and effort, the range of the movements increased. After two weeks of the treatment (stimulation and physical training), the range of voluntary movements was doubled. Researchers explain that this progress was attributed to electrical reawakening of dormant connections between the brain and the spinal cord.

By the end of the study, and after receiving buspirone, the men could move their legs in a variety of motions without any stimulation, similar to when they were receiving the treatment. This suggests that once the dormant neural networks have been re-established, the men become less dependent, and even independent, of the stimulation.

When the men flexed their feet while receiving stimulation, recordings were made of electrical signals produced in the calf muscle and directly below it. With time, the signals increased in strength, further confirming that a connection had been re-established between the brain and the spinal cord.

Promises For A Better Future

Edgerton is already pursuing a study to see whether non-invasive spinal stimulation can help individuals suffering from motor paralysis fully support their weight and regain control of their autonomic functions, such as bladder control and sexual function. He is also interested to study the strategy with patients of partial paralysis. “What we need to do is maximize the clinical tool box that we have so that the physician and the patient can select a therapy that is best for them.”

“The potential to offer a life-changing therapy to patients without requiring surgery would be a major advance; it could greatly expand the number of individuals who might benefit from spinal stimulation. It’s a wonderful example of the power that comes from combining advances in basic biological research with technological innovation”, stated Roderic Pettigrew, Ph.D., M.D., Director of the National Institute of Biomedical Imaging and Bioengineering at NIH. The results were reported in the Journal of Neurotrauma.