Seemingly the stuff of science fiction, a laboratory in Grenoble, France, has developed an implantable wireless device which has enabled a 28-year old tetraplegic patient to walk and control both arms using a brain computer interface and exoskeleton. 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 return mobility to patients with this disability, medical doctors, physicians and researchers at Clinatec, the CEA laboratory in Grenoble operated within Grenoble university hospital, have developed a device to control a four-limb exoskeleton that records and decodes brain signals. The device, developed at CEA, is an implant; it records brain activity in real-time and those impulses are used to drive the exoskeleton.

For the first time, the tetraplegic patient was able to walk and control both arms using this neuroprosthetic which records, transmits, and decodes brain signals. The results of the clinical study under the Brain Computer Interface (BCI) Project at Clinatec were published last week in The Lancet Neurology journal.

Wimagine chip

The WIMAGINE implant (Source: Clinatec)

The major innovation is the device’s ability to provide chronic high-resolution recording of the brain’s electrical activity; the activity related to 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. Recording electrical activity in the sensorimotor cortex required development of an implantable medical device, called WIMAGINE. The device was designed for semi-invasive implantation in the cranium in order to record electrocorticograms (ECoG) using an array of 64 electrodes in contact with the dura mater (a membrane that surrounds the brain and part of the spinal cord).

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.

Predicting imagined movement
The recorded electrocorticograms are decoded in real-time to identify the deliberate movement the patient imagines; the decoded transmissions control the corresponding limb of an exoskeleton. Decoding electrocorticograms required the development of highly sophisticated algorithms based on artificial intelligence (AI) and machine learning (ML), and software to control the movements of the exoskeleton in real-time. The WIMAGINE device also involved research engineers from CEA-List, which specializizes in smart digital systems, who developed the four-limb exoskeleton. The design specifically took into account the interaction of a quadriplegic person with the exoskeleton to be able to mobilize it safely.

Clinatec Exoskeleton

Clinatec’s exoskeleton

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.

Alim-Louis Benabid, a neurosurgeon and chair of the board at Clinatec, worked with a team to design the WIMAGINE implantable device 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. He commented, “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.”

Three more patients will be trial the system
With the authorization of regulatory authorities, the clinical trial to test the device on the 28-year-old tetraplegic patient with a lesion on his spinal cord started when two WIMAGINE devices were implanted in June 2017 on the right and left sides of the upper sensorimotor area of his brain, above the his 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 also can rotate his wrists while sitting or standing.

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 coming years, according to the press release from CEA.