Wireless neural probe allows tetraplegic patient to walk an exoskeleton
during the BCI project at Clinatec ©FDD Clinatec.
And for the first time, a tetraplegic patient implanted with a set of neural probes and wearing an exoskeleton was able to walk and control both arms solely through brain control. The paper “An exoskeleton controlled by an epidural wireless brain–machine interface in a tetraplegic patient: a proof-of-concept demonstration” published in The Lancet Neurology journal describes a system driven via the long-term implant of a semi-invasive medical device dubbed Wimagine.
electrodes to record electrocorticograms (EcoG). It is powered
wirelessly and transmits recorded EcoGs wirelessly too.
Developed at CEA in Grenoble, Wimagine collects brain signals in the sensorimotor cortex emitted when an individual imagines moving. Wimagine 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, 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 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. Hence a tetraplegic patient fitted with this neuroprosthetic implant can move by mentally controlling the exoskeleton, without external controls.
Decoding electrocorticograms required the development of highly sophisticated algorithms based on Artificial Intelligence methods 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.
“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”, said neurosurgeon Alim-Louis Benabid, lead author of the publication in The Lancet Neurology journal and Chair of the Board at Clinatec.
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. 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 can also 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. The Clinatec team is working on integrating new effectors, such as a wheelchair, and developing even more robust and precise algorithms to perform more complex movements such as holding an object.
Clinatec – www.clinatec.fr
CEA-Leti – www.leti-cea.fr
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