Paraplegics Take a Step to Regain Movement

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Eight people who have spent years paralyzed from spinal cord injuries have regained partial sensation and muscle control in their lower limbs after training with brain-controlled robotics, according to a study published in Scientific Reports.

The patients used brain-machine interfaces, including a virtual reality system that used their own brain activity to simulate full control of their legs.

The research — led by Duke University neuroscientist Miguel Nicolelis, M.D., Ph.D., as part of the Walk Again Project in São Paulo, Brazil — offers promise for people with spinal cord injury, stroke and other conditions to regain strength, mobility and independence.

“We couldn’t have predicted this surprising clinical outcome when we began the project,” said Nicolelis, co-director of the Duke Center for Neuroengineering who is originally from Brazil.

“What we’re showing in this paper is that patients who used a brain-machine interface for a long period of time experienced improvements in motor behavior, tactile sensations and visceral functions below the level of the spinal cord injury,” he said. “Until now, nobody has seen recovery of these functions in a patient so many years after being diagnosed with complete paralysis.”

Several patients saw changes after seven months of training. After a year, four patients’ sensation and muscle control changed significantly enough that doctors upgraded their diagnoses from complete to partial paralysis.

Most patients saw improvements in their bladder control and bowel function, reducing their reliance on laxatives and catheters, he said. These changes reduce patients’ risk of infections, which are common in patients with chronic paralysis and are a leading cause of death, Nicolelis said.

Brain-machine systems establish direct communication between the brain and computers or often prosthetics, such as robotic limbs. For nearly two decades, Nicolelis has worked to build and hone systems that record hundreds of simultaneous signals from neurons in the brain, extracting motor commands from those signals and translating them into movement.

Nicolelis and colleagues believe with weekly training, the rehab patients re-engaged spinal cord nerves that survived the impact of the car crashes, falls and other trauma that paralyzed their lower limbs. At the beginning of rehabilitation, five participants had been paralyzed at least five years; two had been paralyzed for more than a decade.

One participant, “Patient 1,” was a 32-year-old woman paralyzed for 13 years at the time of the trial who experienced perhaps the most dramatic changes. Early in training, she was unable to stand using braces, but over the course of the study, she walked using a walker, braces and a therapist’s help. At 13 months, she was able to move her legs voluntarily while her body weight was supported in a harness, as seen in a video recorded at the Alberto Santos Dumont Association for Research Support where the neurorehabilitation lab is located.

“One previous study has shown that a large percentage of patients who are diagnosed as having complete paraplegia may still have some spinal nerves left intact,” Nicolelis said. “These nerves may go quiet for many years because there is no signal from the cortex to the muscles. Over time, training with the brain-machine interface could have rekindled these nerves. It may be a small number of fibers that remain, but this may be enough to convey signals from the motor cortical area of the brain to the spinal cord.” 

Building a foundation at Duke

Since the 1990s, Nicolelis has investigated how populations of brain cells represent sensory and motor information and how they generate behavior, including movements of upper and lower limbs.

A computer monitor in the Nicolelis lab displays brain activity from a monkey using a brain-machine interface. Credit: Shawn Rocco/ Duke Health

In one early experiment carried out with fellow neuroscientist John K. Chapin, Ph.D., Nicolelis used brain-implanted microelectrodes to record the brain activity of rats trained to pull a robotic lever to get a sip of water. Through a brain-machine interface, the rats learned to control the lever using only their brain activity.

“They simply produced the correct brain activity and the robotic arm would bring water to the rat’s mouth without them having to move a muscle,” Nicolelis said. “With training, animals stopped producing overt behavior and started relying on brain activity.”

In later endeavors, Nicolelis trained rhesus monkeys to use brain-machine interfaces to control robotic limbs, and later, the 3-D movements of an avatar — animated versions of themselves on a digital screen. The animals soon learned they could control the movements by mentally conceiving them; there was no need to physically move.

The rhesus monkeys later learned to walk on a treadmill with robotic legs controlled by their brains. They also learned they could use thought to propel a small electric wheelchair toward a bowl of grapes.

The Duke experiments with rats and primates built a foundation for the work in human patients, including a 2004 article with Duke neurosurgeon Dennis Turner, M.D., that established a model for recording brain activity in patients when they used a hand to grip a ball with varied force.

“It’s important to understand how the brain codes for movement,” Nicolelis said. “We discovered principles of how the brain operates that we wouldn’t have discovered without getting inside the brain.”

Still, Nicolelis said, the goal of these studies was to open doors for better prosthetics and brain-controlled devices for the severely disabled.

“Nobody expected we would see what we have found, which is partial neurological recovery of sensorimotor and visceral functions,” he said. 

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