A process known as epidural stimulation helped three out of five paralysis patients independently walk again.

Two separate studies, both published on Monday, reported successful cases of total paralysis patients recovering walking ability after receiving spinal cord implants and intense walking training.

One study by UCLA and the Mayo Clinic published in the journal Nature Medicine, detailed how 29-year-old Jered Chinnock was able to walk without assistance on a treadmill while holding on to the rails. Chinnock had been paralyzed in a snowmobile accident and left with no lower body sensation or voluntary motion. While Chinnock could walk independently on a treadmill, he did not regain sensation in his legs.

In another study by Kentucky Spinal Cord Injury Research and published in the New England Journal of Medicine two out of four patients with complete loss of lower body motor function were able to walk unassisted. The other two were able to sit and stand independently, and one was able to make stepping motions while supported on a treadmill. The fourth suffered a hip fracture which set back his training.

Epidural Stimulation Amplifies Brain Signals

Both studies use a spinal cord implant and a procedure called epidural stimulation. Researchers believe after paralysis there are still some small signals between the brain and the areas of paralysis. However, they are not strong enough to create independent movement.

Epidural stimulation works by making the spinal cord more alert and excitable and, thus, more aware of the existing signals. The device was first developed years earlier for pain control.

According to the Guardian, the device was placed below the site of injury covering regions that send sensorimotor signals to the legs and a battery was implanted in the abdominal allow, where the frequence and intensity of the signal could be tweaked. Researchers monitored electrical activity in the legs during the training sessions.

“We know the spinal cord has the ability to organize very detailed motor activity,” said Dr. Claudia Angeli of the Kentucky Cord Injury Research Center and co-author of one of the studies. “But before the injury it was getting commands from the brain and it was getting information from the environment as well.”

Dr. Claudia Angeli explains the spinal cord uses information from both the brain and the environment to generate movement, but that process is disrupted by paralysis.

“The spinal cord is isolated, it potentially still receives information from the environment, but it is losing the big driver, which was the brain,” Angeli said.

Epidural stimulation helps restore the brain – spinal cord connection.

“It is like it is more aware, it actually can listen to that little whisper from the brain that is still there and it can generate the motor pattern,” said Angeli, adding that training to link movements with these signals is crucial.

Promising, but not Perfect, Technology Helps Paralyzed Patients Walk Again

While the technology is promising it is not without issues. If the device is not on, patients cannot walk. What that means is the current applied to the electrodes must be continuous and thus of low intensity. For some, the intensity that is achievable may not be enough to regenerate movement.

Additionally, finding the right intensity and performing the walking training is an extensive and laborious process. Patients in the study had anywhere from 81 sessions over 15 weeks to 278 sessions over 85 weeks, and the movement regained was far from a complete recovery.

Regardless, seeing formerly paralyzed patients walk again is thrilling and knowing the patients were able to generate that movement using their own brain is revolutionary.

“The patient’s own mind, or thought, was able to drive the movement in the legs,” said Dr. Kendall Lee of the Mayo Clinic, one of the principal investigators of the study, but he stressed that much about the mechanism remained unknown.“You have to deliver a very specific type of stimulation parameters. A random stimulation does not work,” he added.

“It is incredible to be able to be in there and actually see them taking their first steps,” said Dr. Angeli. “It is an emotional time for the individual [themselves] because it is something that they have been told they are never going to be able to do again.”