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Mind-reading exoskeleton allows disabled man to move

07 October 2019

For the first time, a quadriplegic patient was able to move and control both upper limbs through a neuroprosthesis, which collects, transmits and decodes brain signals in real time to control an exoskeleton.

Clinatec - Juliette Treillet (Image courtesy of University of Grenoble Alpes)

Published on October 4, 2019 in The Lancet Neurology, the results of the clinical study of the Brain Computer Interface (BCI) project, carried out at Clinatec (CEA, CHU Grenoble Alpes), validate the proof of concept of piloting an exoskeleton for specific members. This piloting is enabled by the long-term implantation of a semi-invasive medical device for measuring brain activity, developed at CEA. This technology is intended, ultimately, to give greater mobility to people with motor disabilities.

Real time and wireless

Tetraplegia is characterised by a lesion of the spinal cord making it impossible to control nerves to the four limbs. To limit the dependence and facilitate the mobility of these people with severe motor disabilities, the doctors and researchers of Clinatec, CEA laboratory in Grenoble, have developed a device to control a 4-member exoskeleton through measurement and decoding brain signals. The great innovation of this device is to be able to chronically measure in high resolution the electrical activity in the brain corresponding to the patient's movement intentions and then transmit them in real time and wirelessly to a computer to decode them in order to control the movements of the 4 members of the exoskeleton.

To do this, the team of Emeritus Professor at the University of Grenoble Alpes, Alim-Louis Benabid, first author of the publication in the journal Lancet Neurology and President of the Board of Clinatec, designed an implantable device (WIMAGINE) that collects, at the level of the sensorimotor cortex, the cerebral signals emitted during a person's movement intentions. Without the need for external control to provoke the movement, the quadriplegic person can move thanks to the mental control of the exoskeleton. According to Professor Benabid, “this device is an important step forward for the autonomy of people with disabilities. We are very proud of this proof of concept and are already thinking about new applications to make life easier for people with severe motor disabilities.”

From technology to clinical trial

Clinatec, with the approval of the regulatory authorities, is conducting the clinical trial of this device, the results of which were published on October 3, 2019 in The Lancet Neurology, in a 28-year-old quadriplegic patient with spinal cord. 

Two WIMAGINE devices were implanted, in June 2017, bilaterally at the level of the upper sensorimotor zones of the brain, that is to say on the top of the patient's dura mater. This intervention was performed at Clinatec by Professor Stephan Chabardes, co-author of the publication, neurosurgeon at CHU Grenoble Alpes and clinical director of Clinatec. "Participating in the success of this project, through medical support dedicated to the patient has been very rewarding," says Professor Stephan Chabardes. 

Following the operation, the patient performs for 27 months different types of exercises to train to control the exoskeleton. Three days a week, from his home, he trains in virtual environments, like the avatar of the exoskeleton and one week a month he goes to Clinatec to work directly with the exoskeleton. Equipped with the suspended exoskeleton, he is now able to follow a few steps and control his two upper limbs in three dimensions, while having control of the rotation of his wrists, sitting or standing. 

The breach (Image courtesy of University of Grenoble Alpes)

These sensors have been running for more than two years, which is exceptional given the plasticity of the brain that makes the stability of information very difficult and complex.

This patient will continue to be involved in this research protocol at Clinatec and will actively participate in future developments. Indeed, this proof of concept of a neuroprosthesis with a large number of degrees of freedom, makes it possible to envisage new applications for use in the home of the patients as part of their daily life. For this, the Clinatec team is working on the integration of new effectors, such as a wheelchair, but also on the creation of algorithms even more robust and accurate to perform more complex gestures and allow, for example, to term object grasping. It is also planned to include three more tetraplegic patients in this clinical trial over the next few years.

Capturing signals from the brain to restore movement - the WIMAGINE device

Capturing electrical activity in the motor cortex has necessitated the development of an implantable medical device unique in the world: WIMAGINE. This device has been specified to be implanted semi-invasively on the skull, in order to measure electrocorticograms (ECoG) through a matrix of 64 electrodes in contact with the dura, and this in the long term.

Electronic cards include the electrocorticogram acquisition and digitisation bricks designed by CEA-Leti's microelectronics experts, as well as bricks for remote power and wireless data transmission via secure radio link to an external terminal. The implant packaging has been designed to ensure its biocompatibility and long-term safety. The implants have been rigorously tested for compliance with the essential requirements of the European directives for active implantable medical devices.

The electrocorticograms thus captured are then decoded in real time to predict the voluntary movement imagined by the patient. The latter can then control, for example, the trajectory of the member of the corresponding exoskeleton. The decoding of electrocorticograms necessitated the development of very sophisticated algorithms, based on machine learning methods and software allowing real-time control of exoskeleton movements. This device mobilised the research engineers of CEA-List, an institute dedicated to intelligent digital systems. These developed the four-limb exoskeleton based on their reversible actuation and control-command bricks.

The ambition, ultimately, is to decline the fields of use of the brain-machine interface to compensate for different types of motor disability and give more autonomy to patients in their daily lives by driving such an armchair rolling or articulated arm. 

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