UGA international

Real-time and wireless

Tetraplegia is caused by a lesion on the spinal cord that prevents the nervous system from controlling all four limbs. To make people with this severe motor handicap less dependent and improve their mobility, the doctors and researchers at Clinatec, a CEA laboratory in Grenoble, have developed a device to control a 4-limb exoskeleton by measuring and decoding brain signals. The major innovation in this device is its ability to provide chronic, high-resolution measurements of the electrical activity in the patient’s brain corresponding to his or her intended movements, and then transmit these measurements in real time and wirelessly to a computer for decoding in order to control the movements of the exoskeleton’s four limbs.

To do this, the team headed by Alim-Louis Benabid, neurosurgeon, Professor Emeritus at the Université Grenoble Alpes, lead author of the publication in the journal The Lancet Neurology [1] and chairman of the board at Clinatec, designed an implantable device (WIMAGINE®) that collects the brain signals emitted in the sensorimotor cortex when an individual imagines a movement. The tetraplegic patient can move by mentally controlling the exoskeleton with no need for external controls to trigger the movement. According to Professor Benabid, "This device is an important step forward in helping people with disabilities become self-sufficient. We are extremely proud of this proof of concept and are already considering new applications to make everyday life easier for people with severe motor disabilities."

From technology to clinical trial

With authorization from the regulatory authorities, Clinatec is conducting a clinical trial to test the device on a 28-year-old tetraplegic patient with a lesion on his spinal cord. The results were published on 3 October 2019 in the journal The Lancet Neurology.

Two WIMAGINE® devices were implanted in June 2017 on the right and left sides of the upper sensorimotor area of the brain, above the patient's dura mater. The operation was performed at Clinatec by Professor Stephan Chabardes, co-author of the publication, a neurosurgeon at the Grenoble Alpes university hospital, and Medical Director at Clinatec. "Contributing to the success of this project by providing medical care to the patient was an incredible experience," Pr. Chabardes explains.

Since the operation, the patient has spent 27 months performing various types of exercises to practice controlling the exoskeleton. He practices in virtual environments with the exoskeleton avatar at home three days a week and goes to Clinatec to work directly with the exoskeleton one week per month. When fitted with the suspended exoskeleton, he is now able to take several successive steps and control his two upper limbs in three dimensions. He also can rotate his wrists while sitting or standing.

These sensors have been working for more than two years, an exceptional feat given the plasticity of the brain, which makes keeping information stable a difficult and complex task.

This patient will continue his involvement in this research protocol at Clinatec and participate actively in future developments. This proof of concept for a neuroprosthetic providing this level of freedom will open the door to new applications for use at home by patients in their everyday lives. To achieve this, the Clinatec team is working on integrating new effectors, such as a wheelchair, and is also developing even more robust and precise algorithms to perform more complex movements, with the hope of later enabling tasks such as holding an object. Three other tetraplegic patients will also be included in this clinical trial in the coming years.

Recording brain signals to recreate movement with the WIMAGINE® machine

Recording electrical activity in the motor cortex required development of an innovative implantable medical device: WIMAGINE®. The device was designed for semi-invasive implantation in the cranium in order to record electrocorticograms (ECoG) over the long term using an array of 64 electrodes in contact with the dura mater.



Electronic boards contain the electrocorticogram acquisition and digitalization systems, designed by microelectronics experts at CEA-Leti, together with a remote power supply and wireless systems transferring data via secure radio link to an external base station. The implant packaging was designed to ensure long-term biocompatibility and safety. The implants underwent rigorous testing to verify their compliance with the standards required by EU Directives for Active Implantable Medical Devices.

The electrocorticograms recorded are then decoded in real time to predict the deliberate movement imagined by the patient to control, for example, the trajectory of the corresponding limb of an exoskeleton. Decoding electrocorticograms required the development of highly sophisticated algorithms based on Artificial Intelligence methods (Machine Learning) and software to be able to control the movements of the exoskeleton in real time. The WIMAGINE® device also involved research engineers from the CEA-List institute specializing in smart digital systems. These developed the four-limb exoskeleton based on their reversible actuation and control-command bricks. This design specifically took into account the interaction of a tetraplegic person with the exoskeleton to be able to mobilize it safely.

The long-term goal is to identify fields in which the brain-machine interface could be used to compensate for various types of motor disability and give patients more independence in their everyday lives, for example by controlling a wheelchair or an articulated arm.