The prosethetic device records, transmits and decodes brain signals in real time to control an exoskeleton.
The WIMAGINE device means that, for the first time, a tetraplegic patient has been able to walk and control both arms using this neuroprosthetic.
Tetraplegia is caused by a lesion on the spinal cord that prevents the nervous system from controlling all four limbs. Clinatec, working with the Grenoble university hospital, developed the device to control a four-limb exoskeleton that records and decodes brain signals.
The device has the ability to provide chronic high-resolution recording of the brain’s electrical activity. This activity related to the moving intention is transmitted in real-time wirelessly to a computer for decoding in order to control the movements of the exoskeleton’s four limbs.
The implantable device collects brain signals in the sensorimotor cortex which are emitted when an individual imagines moving. The tetraplegic patient is able to move by mentally controlling the exoskeleton – no external controls are necessary.
According to Professor Benabid, Chair of the Board at Clinatec and a neurosurgeon, “This device is an important step forward in helping people with disabilities become self-sufficient. We are already considering new applications to make everyday life easier for people with severe motor disabilities.”
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 devices were implanted in June 2017 and since the operation, the patient has spent 27 months performing various types of exercises to practice controlling the exoskeleton.
When fitted with the exoskeleton, the patient 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.
The Clinatec team is currently working on integrating new effectors and developing more robust and precise algorithms to perform more complex movements, with the hope of later enabling tasks such as holding an object.
The WIMAGINE 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 digitalisation systems, together with a remote power supply and wireless data-transfer systems via secure radio link to an external base station. 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.
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 mobilise 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.
