o how controlled they could be about their movements," said Angeli.
All participants, including Summers, were able to synchronize leg, ankle, and toe movements in unison with the rise and fall of a wave displayed on a computer screen, and three out of the four were able to change the force at which they flexed their leg, depending on the intensity of three different auditory cues.
“The fact that the brain is able to take advantage of the few connections that may be remaining, and then process this complicated visual, auditory, and perceptual information, is pretty amazing. It tells us that the information from the brain is getting to the right place in the spinal cord, so that the person can control, with fairly impressive accuracy, the nature of the movement,” said Edgerton.
The same tests were also administered following several months of spinal stimulation applied in conjunction with locomotor training. During this time, patients also carried out home-based training, which consisted of hour-long stimulation while practicing intentional movements lying down. At the end of the training, some subjects were able to execute voluntary movements with greater force and with reduced stimulation, while others experienced enhanced movement accuracy. Harkema says it’s unclear whether the improvement was a result of the training or due to the cumulative effects of stimulation over time. They plan to test this distinction in their next study.
“With this study the investigators show that their findings about a motor complete patient regaining movement, reported three years ago in The Lancet, were not an anomaly,” said Susan Howley, executive vice president for research at the Christopher & Dana Reeve Foundation, Short Hills, N.J., which provides patient advocacy and funding for spinal cord injury research. “The implications of this study for the entire field are quite profound and we can now envision a day where epidural stimulation might be part of a cocktail of therapies used to treat paralysis.”
With support from NIBIB, Edgerton, along with collaborators Joel Burdick and Y.C. Tai, professors of mechanical and electrical engineering and bioengineering at Caltech, are also working to develop a new high-density, 27-electrode array in rats to determine if it can provide finer, more robust control of locomotion.
“The technology we used in these four individuals was initially designed for the suppression of back pain, and our animal experiments have told us that we can do much better,” said Edgerton. “For a given type of movement, we want to be able to select exactly where and how to stimulate the spinal cord. We just don’t have that flexibility in the current technology.”
Edgerton is also working with various collaborators on NIBIB-funded projects to explore whether epidural stimulation can be used to help patients with paralysis of the upper limbs. They are also developing a technology that can deliver spinal stimulation through the skin (transcutaneously), which would bypass the need for surgical implantation.
Though there is much work to be done, Harkema believes the results from this newest study already provide enough evidence to challenge currently held beliefs about the prognosis of patients with severe spinal cord injuries.
“Right now, the clinical perspective for individuals with complete motor paralysis is that there is nothing we can do,” said Harkema “I think we need to rethink that. In our study, we demonstrated potential beyond any expectation. We need to relook at what the perceived potential is for this group of individuals.”
“This is a wake-up call for how we see motor complete spinal cord injury,” said Edgerton. “We don’t have to necessarily rely on regrowth of nerves in order to regain function. The fact that we’ve observed this in all four patients suggests that this is actually a common phenomenon in those with complete paralysis.”
This work was supported by the National Institute of Biomedical Imaging and Bioengineering and the National Institute of General Medical Sciences at NIH under the award numbers EB007615