Singer Gloria Estefan sustained a severe spinal injury when her tour bus was hit by a tractor trailer in 1990. Since then, she’s been an advocate for people with spinal cord injury by supporting the Miami Project to Cure Paralysis.
The Miami Project is exploring ways to regenerate cells to allow people to walk again. Now a study in The New England Journal of Medicine in 2018 provides fresh hope.
Two of the four participants in the study—both of whom had complete motor paralysis, meaning no motor function below the point of injury—walked over ground (as opposed to stepping on a treadmill) without assistance from trainers after undergoing intensive locomotor training. This type of therapy allows people with spinal cord injuries to practice standing and stepping repeatedly on a treadmill while wearing a supportive harness and being aided by therapists and technicians. The repetitive standing and stepping helps retrain the spinal cord to remember walking.
The participants, who’d sustained their injuries roughly three years prior to the study, also had a device to receive electrical impulses implanted on certain segments of the spinal cord where the circuitry for walking and standing is located. The device was then connected to a neurostimulator implanted in the abdomen or lower back, which delivered electrical impulses at different frequencies and intensities to those sections of the spinal cord. The resulting electrical field generated increased excitability, or awareness, to locations in the spinal cord corresponding to neural networks largely responsible for movement of the hips, knees, ankles, and toes.
“The spinal cord is then able to ‘hear’ the signal coming down from the brain,” explains Claudia Angeli, PhD, assistant professor at Kentucky Spinal Cord Research Center and the study’s lead author. While the brain continues to send signals to move, stand, and walk even after paralyzing injury occurs, “the [injured] spinal cord isn’t strong enough to notice them. The stimulator raises awareness in this area.” Meanwhile, locomotor training, she says, “prepares the spinal cord to relearn to integrate this signal with all the other signals that are coming through.”
The 2018 study is “a continuation of a previous study,” Dr. Angeli notes. In the earlier one, four patients with complete motor paralysis learned to stand first, then to step on a treadmill. After receiving the implanted stimulator, all four were able to stand, but none could walk over ground.
Dr. Angeli believes she knows why. “There’s evidence that the first thing you train is what gets ingrained the most, with functionality also improving the most. For this new set of four individuals—who were selected to closely match the first four in level of injury and age—we trained both tasks simultaneously, training them to stand for an hour, then training them to step for an hour, concurrently.”
The training was also more extensive. Participants trained five days a week for two hours a day over eight or nine weeks. Only then did they undergo surgery to implant the stimulator devices. After recovering from surgery for 20 days, the subjects renewed locomotor training along with electrical stimulation.
Researchers are just beginning to analyze the results. “We have a lot of questions to answer,” says Dr. Angeli, “like ‘Why did only two of the four [subjects] respond?’” She thinks it may be because the two who walked still have limited sensation below the area of injury. The other two are sensory complete—they have no sensation at all below the level of injury. “It may be that the sensory complete participants just need more training to reach functional recovery,” she says.
It may turn out that this type of therapy is optimal for some injuries and not for others, Dr. Angeli says. In addition, the US Food and Drug Administration originally approved the implanted stimulator devices for pain management, not spinal cord injury.
Still, the results are encouraging, says Dr. Angeli. “In this trial, we’ve shown that the spinal cord has the potential for relearning and retraining. Just because someone has been injured for two, three, or four years doesn’t mean the capacity is gone.”
The study’s results could potentially yield “an amazing boon to all aspects to society,” says A.M. Barrett, MD, FAAN, director of stroke rehabilitation research at the Kessler Foundation in East Hanover, NJ. Now that researchers are actively pursuing this type of rehabilitation, Dr. Barrett expects many with spinal cord injury will seek it out—and be undaunted by the hard work it entails. “People will be willing to put in the time” to gain the benefits, she predicts. “Even standing again, with trunk stability, is significant.” It could lead to improved psychological health, bone health, and integrated social connection, she says.
The results are exciting, Dr. Angeli says, but the study was limited to four patients, and thus must be considered preliminary, Dr. Angeli says, “We have many more steps to go before this type of therapy exists outside limited—and costly—clinical trials.”
Still, the future is looking bright, says Dr. Angeli. “We’re hoping to use increased, targeted technology to better suit our needs” she says. “But the potential is there. We can start to change the way individuals think of spinal cord injury.”
