Using Brain Implants to Aid Walking after Spinal Cord Injury


    Last week a new study came out showing how monkeys can fully regain walking and locomotion after paralysis by having electrodes implanted in the brain and spinal cord. The study (Capogrosso et al.) heralds a new way in which a wireless connection can be made from the brain to the spinal cord, by using a brain-spine neural interface. The first electrode is implanted into the motor cortex region that controls leg movement. The second electrode is implanted into the lumbar region of the spinal cord, below the injury site. The brain electrode array detects tiny currents emanating from neurons in the brain and sends them to the lumbar region’s electrode, which stimulates leg muscle contraction, bypassing the lesion.

    Gregoire Courtine showing a model of the monkey brain with the implanted electrode:

    The director of the study, Gregoire Courtine, has been working on ways to use electrical stimulation for regeneration for many years, first using rats and now using macaque monkeys. A brash and charismatic neuroscientist, Courtine started his career in Reggie Edgerton’s lab looking at epidural electrical stimulation and previously gave a TED talk advertising his success in getting spinally injured rats to walk on treadmills. This time, to design the electrode array, Courtine and his team used healthy monkeys to record electrical signals that descend from the brain to the leg and signals from the spinal cord into the leg muscle while in a walking state. These signals were then “replayed” after the spinal cord injury to allow paralyzed monkeys to walk. The signals for muscle movement had to be decoded and sent back in electrical pulses to the spinal cord electrode through a computer.

    The novelty with this device is that the signal can be relayed between electrodes in real-time, something which has hitherto been a challenge. A few years ago I wrote on this blog about a novel clinical trial that used a brain-computer neural interface that can enable a a quadraplegic patient to move a robotic hand, to grasp a drink. It was the first time voluntary hand movement could be restored. That study also resulted from an experiment in monkeys four years before. The new study provides a greater leap, according to Courtine, since it shows that weight-bearing function and muscle coordination can be restored to enable voluntary leg movement, which requires more robust regeneration than the incremental motor movement needed to recover hand grasping. It is hoped that this electrical device will be translated from monkey to human treatments as quickly as the trial using the robotic hand.

    Courtine has been collaborating with a laboratory in Beijing, China in order to carry out the experiments in monkeys. Due to strict ethical and administrative restrictions it has been difficult if not impossible for investigators to use non-human primates in Europe and the US for such experimental trials. The development of this innovative technique in Courtine’s Swiss lab has led to the beginnings of a new human clinical trial, in which two paralyzed patients are already undergoing treatment with implanted electrical pulse generators to re-activate their leg muscles. Given the speed at which these complex clinical trials were translated from monkeys to humans, it raises the possibility that more cures can be developed in China and other emerging-market countries that do not have strict regulations on drug development and medical devices. These new trials come on the heals of a big paralysis trial that saw federal funding withdrawn earlier this year in Louisville Kentucky when the FDA stepped in due to certain violations.

    Regulatory agencies such as the FDA, EMEA and PMDA are frantically scrambling to keep up with innovations and to gain an advantage in the race to approve new treatments in humans. In August the FDA’s medical device division (CDRH) held a workshop with patients and doctors to decide on how best to approve implantable neuro-stimulation devices to treat neurological diseases, diabetes, lupus and macular degeneration. This was just one of several dozen public workshops and committee meetings held this year alone to speed up the delivery of medical devices for patients with neurological problems. The FDA has a research program dedicated to the development of safer and more effective neural interfaces for regulatory approval which will play a crucial part in reviewing applications for electrical stimulation treatments in the coming years, as the field continues to advance.

    FDA neural interface program:


    Brain-Spine Interface paper

    New York Times feature

    Nature feature


    Clinical trial in Louisville Kentucky


    FDA medical devices