Scientists were surprised to find that eight paraplegic people regained some movement following a training program designed to let them use a robotic exoskeleton to move around.
The program involved using a skull cap to control the legs of a virtual avatar, and controlling the exoskeleton using the same method. Scientists think that the program reawakened control over surviving nerves, writes Jonathan Amos for the BBC.
Long-term paralysis seen to improve
The full results of the research were published in Scientific Reports, and detail the progress made by eight subjects paralyzed between 3-13 years before the program began. Long-term paralysis is less receptive to treatment.
“If you’re clinically diagnosed as having a complete lesion, if after 18 months you don’t show any improvement, the chance of regaining any motor or sensory capability below the level of the lesion goes down to zero,” said Miguel Nicolelis of Duke University in the US, who led the study at the AASDAP Neurorehabilitation Laboratory in Sâo Paulo, Brazil.
However tests showed that muscle control and sense of touch improved over the course of the study.
“If you touched them with a pin, or a brush… they would feel something that they didn’t experience before,” Prof Nicolelis told Science in Action on the BBC World Service. “They also experienced a significant visceral improvement. This translated into better bowel and bladder functions – which are very critical for these patients.”
Study shows impressive progress
The system works using a skull cap that records brain waves and two physiotherapy methods that use assisted walking in a harness. It is not clear which of the techniques is responsible for the improvement in the study.
The study had only eight participants and does not compare the treatment with other techniques. As a result it is far from being a clinical trial.
In fact the aim was not to test the improvement in movement and sensation, but rather to see whether a robotic exoskeleton could be used to let paraplegic people learn to walk again. The exoskeleton is controlled via the skull cap, which records brain waves using electrodes, and feedback from the legs is transmitted to vibrating pads on the patient’s arms.
“We use the arms of these patients as transducers, for the brain to perceive signals coming from the feet,” said Prof Nicolelis. “If you adjust these parameters just right, what you produce is some sort of phantom limb sensation. They patients have a feeling that they’re walking by themselves.”
Retraining the brain for movement of legs
Prof Nicolelis says that brain retraining is the key to progress. “In virtually every one of these patients, the brain had erased the notion of having legs. You’re paralysed, you’re not moving, the legs are not providing feedback signals,” he said. “By using a brain-machine interface in a virtual environment, we were able to see this concept gradually re-emerging into the brain.”
It was hoped that the newfound control could control the robotic legs, but progress was so rapid that 4 of the 8 patients were upgraded to partial paraplegia.
Pro Nicolelis says that the brain is making more of an effort to control the legs, but the improvement is also due to a “rekindling” of the remaining nerve connections in the patients’ spines. It is thought that some new nerves may also grow, but evidence is limited to clinical improvement at this stage.
James Fawcett, of the Cambridge Centre for Brain Repair, said that the study was worth talking about. “There’s a lot of interest at the moment in how to make rehabilitation work better,” he told the BBC. “Sometimes it works, and sometimes it doesn’t.”
While the results were impressive, more study is required to work out what happened.
“Some patients do get better anyway. And when you treat them very intensively, there’s a huge placebo effect,” said Fawcett. “This is a basket of manipulations. But in a sense, they all fit together.”
“It’s an important step forward.”