Epidural Spinal Cord Stimulation in a Paraplegic Human

This is one of the very exciting and original research articles recently published in The Lancet. This will be game changing in the future management of SCI patients.

Overview

More than 5.6 million Americans live with some form of paralysis, defined as a central nervous system disorder resulting in difficulty or inability to move the upper or lower extremities. More than 1.275 million are spinal cord injured, and of those many are completely paralyzed in the lower extremities. In addition to total loss of motor control, this type of paralysis is also characterized by impairment or loss of bladder control, sphincter control and sexual response.

Epidural stimulation, in the context of paralysis of the lower extremities, is the application of continuous electrical current, at varying frequencies and intensities, applied to specific locations on the lumbosacral spinal cord corresponding to the dense neural bundles that largely control movement of the hips, knees, ankles and toes.

Animal Experiments

In a series of animal experiments beginning in the 1980s, UCLA life scientist V. Reggie Edgerton, Ph.D., Yury Gerasimenko, Ph.D., and colleagues demonstrated conclusively that, even when the spinal cord is completely disconnected from the brain, it is possible to induce stepping motions in the legs of living cats. Further experiments proved the animals could stand, balance and bear weight.

In their most recent animal experiments, published in Nature Neuroscience in 2009, Dr. Edgerton's team demonstrated that while being stimulated epidurally, the spinal cord's neural networks can initiate and sustain weight bearing and relatively coordinated stepping without cortical involvement. One of the novel findings was that the spinal cord neural networks that can generate stepping could be controlled or directed by the sensory information from the legs.

The First Human Test (2009-2010)

In 2009, the FDA approved a human research protocol. The initial subject selected was completely paralyzed in his lower extremities following a hit and run accident in July 2006. Formerly an athlete in extraordinary physical condition, he suffered a complete motor injury at the C7/T1 level, classified ASIA B.

Prior to implantation of the epidural stimulator, the subject underwent 170 Locomotor Training sessions with no stimulation over a period of 26 months — with no measurable effect — in order to ensure that LT alone was not responsible for any subsequent improvements.

Key Research Findings

In the initial phase of the research experiment, the subject was able to reach a standing position, supplying the muscular push himself while his spinal cord was being stimulated electrically. He can stand independently, bearing full weight, for up to four minutes at a time (up to an hour with periodic assistance when he weakened). He also developed the capacity to voluntarily move his toes, ankles, knees and hips while being stimulated. In addition, he experienced improved temperature regulation and some recovery of autonomic function.

Future Potential

"While these results are obviously encouraging, we need to be cautious, and there is much work to be done," says Dr. Edgerton. Only one subject has been studied so far; the results need to be replicated.

Nonetheless, the investigators envision a day when at least some individuals with complete spinal cord injuries will be able to use a portable stimulation unit and, with the assistance of a walker, stand independently, maintain balance and execute some effective stepping. Possibly even more importantly, the secondary complications associated with spinal cord injury may be greatly affected, improving the quality of life of these individuals.

"This is a significant breakthrough," notes Dr. Harkema. "It opens up a huge potential to improve the daily functioning of individuals."

"We now have proof of concept," adds Susan Howley, Executive Vice President for Research at the Christopher & Dana Reeve Foundation. "It's an exciting development. Where it leads to from here is fundamentally a matter of time and money."