Mobility after paraplegia due to spinal cord injury (SCI) is primarily achieved by substituting the lost function with a wheelchair. However, the sedentary lifestyle associated with excessive wheelchair reliance can lead to medical co-morbidities, such as osteoporosis, heart disease, respiratory illnesses, and pressure ulcers. These conditions contribute to the bulk of SCI-related medical care cost. Therefore, restoration of walking after SCI remains a clinical need of high priority.

Now, novel brain-computer interface technology created by University of California, Irvine researchers has allowed a paraplegic man to walk for a short distance.  In the preliminary proof-of-concept study, a patient with complete paralysis in both legs due to spinal cord injury was able, for the first time, to take steps without relying on manually controlled robotic limbs.  The opensource study is published in the Journal of NeuroEngineering & Rehabilitation.

Previous studies show that current approaches to restoring ambulation after SCI include the use of robotic exoskeletons and functional electrical stimulation (FES) systems. These devices, however, lack intuitive able-body-like supraspinal control, as they typically rely on manually controlled switches. In addition, these systems cannot exploit the neuroplasticity of residual or spared pathways between the brain and spinal motor pools. Hence, novel means of restoring intuitive, brain-controlled ambulation after SCI are needed. If successful, such novel approaches may drastically reduce SCI-related medical costs and improve quality of life after paraplegia due to SCI.

In the current study the male participant, whose legs had been paralyzed for five years, walked along a 12-foot course using an electroencephalogram-based system that lets the brain bypass the spinal cord to send messages to the legs. Data findings show that it takes electrical signals from the subject’s brain, processes them through a computer algorithm, and fires them off to electrodes placed around the knees that trigger movement in the leg muscles.

The team explain that even after years of paralysis, the brain can still generate robust brain waves that can be harnessed to enable basic walking. Results showed that researchers can restore intuitive, brain-controlled walking after a complete spinal cord injury; with this noninvasive system for leg muscle stimulation showing promise as an advance of current brain-controlled systems that use virtual reality or a robotic exoskeleton.

The researchers stress that months of mental training to reactivate the brain’s walking ability and physical therapy were needed for the study participant to reach the stage where he could take steps. Wearing an EEG cap to read the patient’s brain waves, the male participant was first asked to think about moving his legs. The brain waves this created were processed through a computer algorithm to isolate those related to leg movement. The subject later was trained to control an avatar in a virtual reality environment, which validated the specific brain wave signals produced by the algorithm.

Data findings show that this training process yielded a custom-made system, so that when the participant sought to initiate leg movement, the computer algorithm could process the brain waves into signals that could stimulate his leg muscles.  To make this work, the subject required extensive physical therapy to recondition and strengthen his leg muscles. Then, with the EEG cap on, the patient practiced walking while suspended 5 centimeters above the floor, so they could freely move their legs without having to support himself. Finally, the patient translated these skills to the ground, wearing a body-weight support system and pausing to prevent falls.  The group conclude that since this proof-of-concept study involved a single patient further research is needed to establish whether the results can be duplicated in a larger population of individuals with paraplegia.

The team surmise that once they have confirmed the usability of this noninvasive system, they can look into invasive means, such as brain implants.  For the future, the researchers hope that an implant could achieve an even greater level of prosthesis control because brain waves are recorded with higher quality and even deliver sensation back to the brain, enabling the user to feel their legs.

Source: University of California, Irvine