Regaining Leg Control with Spinal Stimulation

National Institute of Biomedical Imaging and Bioengineering Bethesda, MD

According to a new NIH-funded study, five men with complete motor paralysis were able to voluntarily generate steplike movements using a new technology that non-invasively delivers electrical stimulation to their spinal cords. The technology, called transcutaneous stimulation, delivers electrical current to the spinal cord using electrodes placed on the skin of the lower back. While another four paralyzed individuals had previously achieved voluntary movement while receiving spinal stimulation, their electrical stimulation device had been surgically implanted on their spinal cords. This marks the first time the stimulation was delivered non-invasively.

In this study, the men achieved leg movement while their legs were suspended in braces hanging from the ceiling, which allowed them to move freely without resistance from gravity. Although this type of movement is not comparable to walking, still, the results signal significant progress towards the eventual goal of developing a therapy for a wide range of individuals with spinal cord injury, the researchers say.

The study was conducted by a team of researchers at the University of California, Los Angeles; University of California, San Francisco; and the Pavlov Institute, St. Petersburg, Russia.

“These encouraging results provide continued evidence that spinal cord injury may no longer mean a life-long sentence of paralysis and support the need for more research,” said Roderic Pettigrew, PhD, MD, director of the National Institute of Biomedical Imaging and Bioengineering at NIH. “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.”

During this recent study, the 5 men, all of whom were paralyzed for more than 2 years, underwent a series of 45 minute sessions, once a week, for approximately 18 weeks, to determine the effects of non-invasive electrical stimulation on their ability to move their legs.

In addition to stimulation, they each received several minutes of physical training, having their legs moved manually for them in a step-like pattern. The goal of this conditioning was to assess whether physical training combined with electrical stimulation could enhance efforts to move voluntarily.

For the final four weeks of the study, the men were given the pharmacological drug buspirone, which mimics the action of serotonin and has been shown to induce locomotion in mice with spinal cord injuries. While receiving the stimulation, the men were instructed at different points to either try to move their legs or to remain passive.

At the start of the study, the men’s legs only moved when the spinal stimulation was strong enough to generate involuntary movements. But, when the men attempted to move their legs further while receiving stimulation, their range of movement significantly increased. After just four weeks of receiving stimulation and physical training, the men were able to double their range of motion when voluntarily moving their legs while receiving stimulation. The researchers believe that the electrical stimulation was able to reawaken dormant connections that may exist between the brain and the spinal cord of patients with complete motor paralysis. (See Figure 1)

Surprisingly, the researchers said, by the end of the study, the men were able to move their legs with no stimulation at all and their range of movement was, on average, the same as when they were moving while receiving stimulation.

Going Forward

A new study has already been initiated to see whether these same men can be trained with non-invasive spinal stimulation to fully bear their weight, a feat that the four men with surgically implanted stimulators have already achieved. In addition, they hope to determine whether non-invasive stimulation can help individuals regain some autonomic functions lost due to paralysis such as the ability to sweat, regulate blood pressure, and control bladder, bowel, and sexual function.

Although a non-invasive stimulation could offer advantages over a surgically implanted device, they say both should continue to be developed as all patients are going to need something slightly different, with non-invasive stimulation best in some cases while implanted stimulation will work best for others.

For more information, visit www.nibib.nih.gov. 

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