Technology to enable paralyzed patients to move, and even to feel, their limbs is advancing apace. The latest progress comes from Case Western Reserve University researchers who have worked for months with a man with quadriplegia to enable him to raise a mug to his own lips to sip through a straw.
He made the movement simply through his thoughts due to temporarily implanted, linked brain-recording and muscle-stimulating systems. It took four months of practice with a virtual arm on a computer screen and 45 weeks of physical training for his arm and shoulder to prepare the patient, Bill Kochevar, in advance. He was injured eight years ago in a bicycling accident, paralyzed below his shoulders.
The result is considered to be the first instance of a paralyzed human using technology to enable limb movement via thought. Up next, researchers hope to have miniaturized brain interface that can be fully implanted, a feat thought to be achievable within two or three years. It could be feasible to have a marketed product emerge in roughly a decade.
"This was a science project. The person had connectors bolted to his skull that we connected to," explained Bob Kirsch, chair of Case Western Reserve's department of biomedical engineering and executive director of the FES Center, to Medical Device Daily. He is the principal investigator and senior author of a paper on the research recently published in The Lancet.
"The current challenge of the field is to make it more clinically acceptable, to have a recording device that's miniaturized and implanted in the body. We have colleagues at Brown University and Massachusetts General who are doing this. It's probably two to three years off, demonstrating the safety needs to happen," added Kirsch.
The arrays that go into the brain are very small and tend to have performance that declines rapidly over time. The current iteration lasts up to a few years and is currently being tested in animals. In addition to better enabling these arrays to survive in the body, a longer term ambition is to incorporate a sense of touch.
"There's active research in restoration of sensation. We are recording movement intention signals, but his paralysis is in two directions, so he can't feel that. Having some sense of touch would be an important addition. Others are doing that, and I would be very interested in adding that," said Kirsch.
Another item on his long-term wish list is to enable even more precise movements, perhaps by recording brain signal in different areas of the brain that are associated earlier in the process with the brain signalling the intention to move.
Right now, the area of the brain being monitored is the primary cortex. That's the last step in the brain in a chain of events leading to movement. Earlier in that process, areas such as the premotor cortex and the parietal cortex, which are related to the planning of movement and actually occur in advance of any movement, are activated.
Kirsch expects that capturing signals from these two areas could enable more precise movement since they are thought to better represent patient intention and the actual goal of the movement.
Researchers are focused on enabling simple functions for those who have lost the ability to move their limbs – because doing small, everyday tasks is their top priority. The aim is not to replace caregivers, but to offer increased independence.
"These people are dependent on others for everything. We asked them what was important to them and they say: to scratch my nose, feed myself, attend to personal hygiene. So, we focused on those. We think the brain is able to control a variety of arm movements; we want to extend that so we can let them do more sophisticated movements," said Kirsch.
The brain-computer interface used recording electrodes placed under Kochevar's skull in conjunction with a functional electrical stimulation (FES) system for his arm and hand. The end result was a reconnection of Kochevar's brain to his muscles.
Not only did he raise a glass with his right arm during this initial testing, he also held a makeshift handle piecing a dry sponge to scratch the side of his nose, as well as scooped forkfuls of mashed potatoes from a bowl. He was aided by a mobile arm support that was under his brain control as well to enable him to overcome gravity that would prevent him from raising his arm and reaching.
"It's important to realize that this is a feasibility study. We have shown for the first time that we can take someone with profound paralysis and restore movement in their own arm with the brain. It's not perfect, but it shows it can be done," said Kirsch.
A team of surgeons implanted two, 96-channel electrode assays in his motor cortex on the surface of his brain. Each was about the size of a baby aspirin. The arrays recorded brain signals as Kochevar imagined his arm and hand movements.
After Kochevar went through training with the virtual arm, surgeons implanted 36 FES electrodes to animate muscles in his upper and lower arm. The interface decodes the recorded brain signals into the intended movement command; that is then translated by the FES system into patterns of electrical pulses that trigger muscle movement.
Kochevar is part of the ongoing Braingate2 pilot clinical trial that spans a consortium of academic and Veterans Administration institutions. Earlier Braingate research demonstrated that people with paralysis can control a cursor on a computer screen or a robotic arm.
The Braingate technology that's under investigation was first developed at Brown University in the laboratory of John Donoghue. He is now the founding director of the Wyss Center for Bio and Neuroengineering in Geneva, Switzerland. The implanted recording electrodes are known as the Utah array and were designed originally by Richard Normann, who is a professor of bioengineering at the University of Utah.
"The ultimate hope of any of these individuals is to restore this function," said Benjamin Walter, associate professor of Neurology at Case Western Reserve School of Medicine, clinical principal investigator of the Cleveland Braingate2 trial and medical director of the Deep Brain Stimulation Program at UH Cleveland Medical Center.
He added, "By restoring the communication of the will to move from the brain directly to the body, this work will hopefully begin to restore the hope of millions of paralyzed individuals that someday they will be able to move freely again."