After receiving an implant that electrically stimulates the spinal cord, four paraplegic men can now voluntarily move their previously paralyzed legs. It's a breakthrough that's poised to revolutionize the treatment of paralysis.
The initial proof-of-concept for this approach came back in May 2011 when a paralyzed patient named Rob Summers had a number of motor functions restored after receiving an epidural electrical stimulator. Summers became paralyzed from the neck down after a car veered into his driveway and hit him as he stood outside his house. Doctors told him he'd never walk again.
The late Superman actor and quadriplegic Christopher Reeve would've been proud; the study was funded in part by the Christopher & Dana Reeve Foundation and the National Institutes of Health (NIH). The new study is the result of research from scientists at the University of Louisville, UCLA, and the Pavlov Institute of Physiology.
Four Out Of Four Ain't Bad
Now, in a new study that appears in the science journal Brain, three more patients with complete paralysis of the legs have received the stimulator and all have responded equally as well — including two patients diagnosed with a motor and sensory complete lesion (an otherwise untreatable disruption of the pathway that sends information about sensation from the legs to the brain). This is amazing because the researchers thought that at least part of the sensory pathway had to be intact for the therapy to work. This suggests that some pathways must still be intact after an injury.
Like Summer, the other three patients — Kent Stephenson, Andrew Meas, and Dustin Shillcox — are paralyzed from the chest down after sustaining injuries from vehicle accidents.
"Now that spinal stimulation has been successful in four out of four patients, there is evidence to suggest that a large cohort of individuals, previously with little realistic hope of any meaningful recovery from spinal cord injury, may benefit from this intervention," noted Roderic Pettigrew in a statement. He's the director of the National Institute of Biomedical Imaging and Bioengineering (NIBIB) at NIH.
Mimicking Brain Signals
The device — a 16-electrode array — works by delivering a continuous electrical current to the patients' lower spinal cords, mimicking signals the brain would normally transmit to initiate movement. When it's active, an electrical current is applied at varying frequencies and intensities to targeted locations on the lumbosacral spinal cord. These locations correspond to the dense neural bundles that control the movement of the hips, knees, ankles and toes. The spinal cord appears to be re-engaging the neural network to control and direct muscle movements when its triggered.
All four participants, each of whom have been paralyzed for more than two years, were able to voluntarily flex their toes, ankles, and knees while the stimulator was active. Some were even able to bear weight on their legs. These capabilities improved over time when performed in conjunction with physical rehabilitation (like walking on a treadmill). An in fact, the patients were able to activate these movements with less stimulation over time, showing that the spinal network is capable of learning and improving nerve functions.
During the study, the researchers also assessed the ability of the participants to control their movements in response to auditory and visual cues. They wanted to know if the patients could voluntarily move in the presence of stimulation and how controlled they could be about their movements.
And indeed, all patients were able to synch leg, ankle, and toe movements in unison with the rise and fall of a wave displayed on a computer screen. Three out of four were able to change the force at which they flexed their legs (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," added study co-author Reggie Edgerton. "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."
The new study shows that the work done on Summers was no fluke.
"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," noted co-author Susan Hawley.
Read the entire study at Brain: "Altering spinal cord excitability enables voluntary movements after chronic complete paralysis in humans."
Images: Susan Harkema/The Lancet/Elsevier; the University of Louisville.