The paralyzed could walk again with a “prosthetic exoskeleton”

By Dr. Ananya Mandal, MDOct 9 2011

If Dr. Miguel Nicolelis along with his international group of researchers succeed, the paralyzed could walk again.

The team claims that they have cleared a hurdle to the construction of a prosthetic suit that will enable the paralyzed to walk, as well as restore their sense of touch. They are working towards the opening day of the 2014 World Cup soccer tournament in Brazil when they hope to send in a young quadriplegic striding out to playing fields to open the games.

Their contraption is like a “prosthetic exoskeleton”. Nicolelis with collaborators, neuroscientists and physiologists from Brazil, Switzerland, Germany and the United States have reported success with lab monkeys with it.

In laboratory tests, electrical messages conveying sensation could be sent directly to the monkeys' brains. Both animals could distinguish among three identical circles by virtually “feeling” their differing textures. Specially coded electrical currents were delivered straight to each monkey's sensory cortex by four filaments the breadth of a hair. Both Mango and Nectarine (the two female monkeys in the experiment) quickly learned to discern one circle from another to complete a task. The study appeared in the journal Nature.

For a person with a spinal cord injury, sending such orchestrated bursts of electrical information to the brain could do more than allow a patient who has lost sensation to experience the pleasures of touch again. The breakthrough would also provide the necessary sensory feedback for the user of a prosthetic walker to navigate uneven terrain and steer clear of dangers such as hot or slippery surfaces. By adding sensory feedback, the latest experiment creates a loop of command and control that could make the complex act of walking possible.

“The remarkable success with nonhuman primates is what makes us believe that humans could accomplish the same task much more easily in the near future,” Nicolelis said. “We hope that in the next few years this technology could help to restore a more autonomous life to many patients who are currently locked in without being able to move or experience any tactile sensation of the surrounding world.”

Dr. Bruce Volpe, a professor of neurology at Weill Cornell Medical College calls the breakthrough a “remarkable use of sensory information” that “opens novel ... possibilities” for patients who have lost movement and sensation to injury or illness. Following injury or stroke, patients' recoveries are often hampered by the “noisy, unresponsive or absent sensory information” making its way to their brains, Volpe says. “These data suggest new options for generating that missing and crucially informative sensory information,” he said. “We are trying to provide the patient a new body, and we believe the patient's brain will assimilate the new body as part of the sense of self of the patient,” Nicolelis said. “It would be just like a car…only a little tighter.”

UCLA physiologist V. Reggie Edgerton, who was not involved in Nicolelis' work but has pioneered the use of electrical stimulation to initiate movement in paralyzed patients, said that the brain's innate flexibility — its ability to take in electrical signals and learn to attach meaning to them — makes approaches like that of the Walk Again Project highly promising.