A man suffering complete paralysis in both legs has regained the ability to walk again using electrical signals generated by his own brain. Unlike similar efforts that have seen paralyzed subjects walk again by using their own brainwaves to manually control robotic limbs, the researchers say this is the first time a person with complete paralysis in both legs due to spinal cord injury was able to walk again under their own power and demonstrates the potential for noninvasive therapies to restore control over paralyzed limbs.
The subject of the research, carried out by scientists at the University of California, Irvine, had been paralyzed for five years. The work began with a stint of mental training designed to reengage the brain's walking ability, which saw the subject don an electroencephalogram (EEG) cap (a piece of headwear fitted with electrodes that monitor the brain's electrical impulses). The man was first made to control an avatar in a virtual environment, which was then followed with physical training to build up the strength of his leg muscles.
With a system that delivers the electrical signals from his brain to electrodes placed around his knees to initiate movement, he began practising walking in the air, suspended around 5 cm (2 in) above the ground. This allowed him to become accustomed to the walking motion without his legs actually needing to support the weight of his body. On his 20th visit, equipped with a support system to avoid falls and take some of his body weight, he managed to put one foot after the other along a 3.66 m (12 ft) walking course. The researchers report that across a 19 week testing period, he developed better control of his limbs.
This work builds on previous research carried out at UCLA where electrode arrays have been used to stimulate motion in sufferers of paralysis. In 2011, its researchers managed to restore voluntary leg movement in a paralyzed man by applying electrical signals to the spinal cord's own neural network, tapping into the sensory input from the legs rather than the brain to trigger muscle and joint movement.
And earlier this year, UCLA researchers were able to get the paralyzed legs of five men moving again by placing electrodes on the skin of the lower back to stimulate the nerves. Then earlier this month its scientists adapted this technique to allow a completely paralyzed man to control a bionic exoskeleton and take thousands of steps.
But the UC Irvine scientists say this is the first time a person with complete paralysis in both legs has been able to walk without manually controlled robotic limbs.
"Even after years of paralysis the brain can still generate robust brain waves that can be harnessed to enable basic walking," says Dr. An Do, one of the lead researchers. "We showed that you can restore intuitive, brain-controlled walking after a complete spinal cord injury. This non-invasive system for leg muscle stimulation is a promising method and is an advance of our current brain-controlled systems that use virtual reality or a robotic exoskeleton."
Though optimistic, the scientists are urging caution, noting that the study only involved a single patient and further work must be done before they can conclude whether the promising results will translate to others with paraplegia. They also anticipate that implants could improve user control and provide sensation.
"Once we've confirmed the usability of this noninvasive system, we can look into invasive means, such as brain implants," says senior lead researcher Dr. Zoran Nenadic. "We hope that an implant could achieve an even greater level of prosthesis control because brain waves are recorded with higher quality. In addition, such an implant could deliver sensation back to the brain, enabling the user to feel their legs."
The team's research was published in the Journal of Neuroengineering and Rehabilitation.
Source: BioMed Central