A paraplegic man can stand up to four minutes at a time or longer with assistance, walk on treadmill with assistance, and move his hips, knees, ankles and toes on command thanks to a remarkable breakthrough by researchers from the California Institute of Technology and the University of Louisville, UCLA. The unprecedented results were achieved by continual direct epidural electrical stimulation of his spinal cord, a treatment that follows 30 years of studies on clinical therapies for paralysis. The study was recently published in The Lancet.
Rob Summers, 25, was the volunteer for this experiment. Summers was left paralyzed from the chest down after a hit-and-run accident in 2006. He underwent the experiment at the Frazier Rehab Institute.
The 11-member research team was led by two prominent neuroscientists: Susan Harkema, Ph.D. of the University of Louisville’s Department of Neurosurgery, Kentucky Spinal Cord Research Center, and Frazier Rehab Institute, and V. Reggie Edgerton, Ph.D. of the Division of Life Sciences and David Geffen School of Medicine at UCLA. Also part of the research team was Joel W. Burdick, Ph.D., Professor of Mechanical Engineering and Bioengineering at Caltech. Burdick developed new computer algorithms and electromechanical technologies that promote locomotive recovery in patients with spinal cord injuries.
The procedure involved applying direct epidural electrical stimulation to the lower spinal cord and mimicking brain signals normally transmitted to induce movement. Once the signal is transmitted, the spinal cord’s neural network, combined with the sensory input from the legs to the spinal cord, can direct muscle and joint movements required to stand and takes steps on a treadmill with assistance.
Epidural stimulation is the application of continuous electrical current, at varying intensities and frequencies to specific locations on the lumbosacral (lower) spinal cord corresponding to the dense neural bundles that largely control movement of the hips, knees, ankles and toes. The electrodes required for this stimulation were implanted at the University of Louisville Hospital by Dr. Jonathan Hodes, chairman of the Department of Neurosurgery at the University of Louisville.
The other component of the experiment involved extensive Locomotor Training during electrical stimulation while the subject was suspended over the treadmill. With assistance from rehabilitation specialists, the neural networks of the spinal cord were retrained to produce muscle movements necessary to stand and take assisted steps.
The research was funded by the National Institutes of Health and the Christopher & Dana Reeve Foundation. Dr. Edgerton is on the Reeve Foundation’s Science Advisory Council and its International Research Consortium on Spinal Cord Injury. Dr. Harkema is Director of the Reeve Foundation’s NeuroRecovery Network.
Drs. Harkema and Edgerton have worked closely together since Harkema began her career as a post-grad student in Dr. Edgerton’s UCLA laboratory, where he pioneered the field of locomotion with extensive animal studies. Dr. Harkema is now the Professor of Neurological Surgery at the University of Louisville and oversees its human research program. Both doctors envision a day when individuals with complete lower-body paralysis will be able to use portable stimulation units or use walkers to stand, maintain balance and take steps. The treatment could also result in more significant relief from complications related to complete spinal injury-related paralysis, such as loss of sexual response or loss of sphincter and bladder control.
“The spinal cord is smart,” notes Dr. Edgerton. “The neural networks in the lumbosacral spinal cord are capable of initiating full weight bearing and relatively coordinated stepping without any input from the brain. This is possible, in part, due to information that is sent back from the legs directly to the spinal cord.”
“This is a breakthrough. It opens up a huge opportunity to improve the daily functioning of these individuals,” concludes Dr. Harkema, lead author of today’s Lancet article. “But we have a long road ahead.”
“While these results are obviously encouraging,” concurs Dr. Edgerton, “we need to be cautious. There is much work to be done.”
The reason for Edgerton’s and Harkema’s cautiousness is the fact that the experiment was conducted on only one human subject to date–Summers. Furthermore, Summers was in exceptional physical condition prior to his injury. In addition, the subject in this case retained some feeling. It is not known how well the experiment will work on patients with entirely no sensation. Another consideration is that earlier experiments on animals involved the use of drug compounds that increased sensitivity and function of the spinal cord’s neural network–drugs not approved for humans. Five new human subjects have been authorized by the Food and Drug Administration to be enrolled in the study.
“Today’s announcement clearly demonstrates proof of concept,” said 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.”
Adds research volunteer Rob Summers, “This procedure has completely changed my life. For someone who for four years was unable to even move a toe, to have the freedom and ability to stand on my own is the most amazing feeling. To be able to pick up my foot and step down again was unbelievable, but beyond all of that my sense of well-being has changed. My physique and muscle tone has improved greatly, so much that most people don’t even believe I am paralyzed. I believe that epidural stimulation will get me out of this chair.”