The results of a clinical study under the Brain Computer Interface (BCI) Project at Clinatec were published in The Lancet Neurology journal and provide proof of concept for controlling a four-limb exoskeleton. The system is driven via the long-term implant of a semi-invasive medical device to record brain activity developed at CEA in Grenoble. In the long term, this technology is expected to give greater mobility to individuals with severe motor disabilities.
Tetraplegia is caused by a lesion on the spinal cord that prevents the nervous system from controlling all four limbs. To limit dependency and facilitate the mobility of patients with this severe disability, medical doctors, physicians and researchers at Clinatec, the CEA laboratory in Grenoble operated with the Grenoble university hospital, have developed a device to control a four-limb exoskeleton that records and decodes brain signals.
The major innovation in this device is its ability to provide chronic high-resolution recording of the brain’s electrical activity. This activity related to the moving intention is transmitted it in real-time wirelessly to a computer for decoding in order to control the movements of the exoskeleton’s four limbs.
Alim-Louis Benabid, neurosurgeon, Professor Emeritus at Université Grenoble Alpes, lead author of the publication in The Lancet Neurology journal, and Chair of the Board at Clinatec, worked with a team to design the implantable device (WIMAGINE®) that collects brain signals in the sensorimotor cortex emitted when an individual imagines moving. The tetraplegic patient can move by mentally controlling the exoskeleton: external controls are unnecessary. 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 trials
With the authorisation of 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. 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 at Clinatec was performed by Professor Stephan Chabardes, co-author of the publication, a neurosurgeon at CHU Grenoble Alpes, and Medical Director at Clinatec. “Contributing to the success of this project by providing medical care to the patient was an incredible experience,” Dr. 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 times a week and works directly with the exoskeleton at Clinatec one week every month. When fitted with the suspended exoskeleton, he is 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.
This patient will continue his involvement in this research protocol at Clinatec and will actively participate 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. The Clinatec team is working on integrating new effectors, such as a wheelchair, and developing even robust and more 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
Recording electrical activity in the sensorimotor 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 data-transfer systems via secure radio link to an external base station. The implant packaging was designed to ensure long-term biocompatibility and safety. The implants have undergone rigorous testing to verify their compliance with 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 and then, for example, to control 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 CEA-List, the institute specialised 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 quadriplegic 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 create compensatory systems for various types of motor disabilities and give patients more independence in their everyday lives, for example, by driving a wheelchair or controlling an articulated arm.