Using functional electrical stimulation (FES) and an intracortical brain–computer interface (iBCI), researchers have restored arm and hand function in a patient with an almost complete spinal cord injury (SCI).
The approach allowed the patient to repeatedly drink coffee and to feed himself with his own arm and hand, solely of his own volition.
The results represent a neurotechnology-based circumvention of spinal cord injury, the researchers say.
"Other options for patients with long-term paralysis use eye movements or voice recognition, which we call 'command interfaces,' but these are limited for commanding highly functioning arm and hand movements," lead author, A. Bolu Ajiboye, PhD, Department of Biomedical Engineering and School of Medicine, Case Western University, Cleveland, Ohio, told Medscape Medical News.
Dr A. Bolu Ajiboye
"We thought maybe these patients could use their head to command the system."
The report was published online March 28 in The Lancet.
The patient, a 53-year-old man, had experienced a traumatic high-cervical SCI (cervical level 4, American Spinal Injury Association [ASIA] Impairment Scale category A) during a bicycle accident 8 years before the study.
The accident left him essentially paralyzed from the neck down. On his dominant right side, he retained restricted and nonfunctional voluntary shoulder girdle motion, but no voluntary glenohumeral, elbow, or hand function, and no sensation below the shoulder.
To circumvent the SCI, researchers implanted micro–electric arrays in the area of the motor cortex related to movement. Each of these arrays has 96 recording electrodes that are connected by wire to a pedestal that sits on the patient's scalp, explained Dr Ajiboye.
After receiving the muscle-stimulating electrodes, the patient trained by using a virtual reality system for 4 months. During these sessions, while immersed in the virtual environment and wearing three-dimensional glasses, he learned to move the arm to various parts of the computer screen.
"Even very early on, he was able to acquire all those targets with an accuracy of 95% to 100%," reported Dr Ajiboye.
After 4 months, the patient received 36 percutaneous muscle-stimulating electrodes in his right upper and lower arm, including percutaneous anodic current return electrodes to restore finger and thumb, wrist, elbow, and shoulder movements.
Neural Decoder
During experiments, the pedestal was attached to a cable that connects to computers that record and process data. Researchers have created a mathematical algorithm they call a "neural decoder" that maps brain activity.
"It extracts movement-related information from patterns of cortical signals, and sends it to the FES system, which determines the right set of muscles to stimulate to produce the movement that we are estimating that our participant is trying to do," said Dr Ajiboye.
Source: Cleveland FES Center
He stressed that delays in carrying out the current study had nothing to do with the need for training and more to do with the logistics of planning the surgery.
"The patient was actually able to do the brain task on day 1, and the more he does it, he gets progressively better."
Using the FES + iBCI system, the patient was able to grasp a cup of coffee and drink it with a straw. This required him to extend his elbow, open his hand, grasp the cup securely, flex his elbow to transport it close to his mouth and drink it, and then extend his elbow to return the cup and release his grasp. It took him between 20 and 40 seconds to complete this task and was successful in 11 of 12 attempts.
The patient also was able to feed himself using the system. He consistently and repeatedly scooped forkfuls of mashed potatoes and navigated his hand to his mouth to take several bites.
The patient reported that "he simply thinks about moving his arm and hand and they move in the way he intends, so to him it's invisible; it's seamless," said Dr Ajiboye.
With the FES system turned off, the participant was completely unable to perform meaningful movements. According to the authors, this indicates that no substantial motor recovery occurred as a result of FES or iBCI.
Over the course of the study, from December 1, 2014, when the patient received the intracortical implant, to November 7, 2016, the patient had four device-related adverse events. However, all were treated and resolved.
For example, in one case, he bumped his head where the pedestal lay on the back of his bed. This caused a minor headache, which went away when he took aspirin, said Dr Ajiboye.
"The key point is that there were no serious adverse events and nothing related to the device or to the study, which gives us confidence that this device is safe."
This new FES-iBCI system has several advantages over other approaches to overcome paralysis, for example, a robotic arm.
"People with paralysis don't care for the robotic arm," because it's cumbersome and has to be small enough to be mounted to a wheelchair and to go through a door, said another study author, Robert F. Kirsch, PhD, Department of Biomedical Engineering and School of Medicine, Case Western University.
Dr Robert F. Kirsch
"A number of other systems provide some independence; for example, voice recognition to control TVs and telephones, et cetera, but the big advantage of what we're doing is that it restores movement using the patient's own body and muscles."
To translate this system into clinical practice, the brain interface part would require a recording device that doesn't involve a connector mounted to the skull, said Dr Kirsch.
"It needs to have a wireless device that can stream the information out of the head."
Researchers are already working on this in animals, and it's "not so far off — maybe 2 to 3 years" before it's available for patients, said Dr Kirsch.
"That would make the system much more practical for clinical deployment because everything would be inside the body and there would be no external devices."
Proof of Principle
But while the study is "ground-breaking," the treatment "is not nearly ready for use outside the lab," said Steve Perlmutter, PhD, Department of Physiology and Biophysics and Washington National Primate Research Center, University of Washington, Seattle, in an accompanying editorial.
"The movements were rough and slow and required continuous visual feedback, as is the case for most available brain–machine interfaces, and had restricted range due to the use of a motorized device to assist shoulder movements. Stimulation of nerves or the spinal cord, rather than muscles, and more sophisticated stimulation technology might provide substantial improvements."
The study did not attempt to address the many hurdles that all motor neuroprostheses must overcome, said Dr Perlmutter. These include recording stability over long periods; optimal decoding and control algorithms; and development of devices that are small enough, robust enough, and cheap enough to be fully mobile and widely available.
"Thus, the study is a proof-of-principle demonstration of what is possible, rather than a fundamental advance in neuroprosthetic concepts or technology. But it is an exciting demonstration nonetheless, and the future of motor neuroprosthetics to overcome paralysis is brighter."
Approached for his comment on the study, An Do, MD, assistant professor, Department of Neurology, University of California, Irvine, said it "represents a significant step forward in using neural technologies to restore function after catastrophic neurological conditions such as SCI."
Dr Do has reported on a brain–computer interface system that bypasses a damaged spinal cord to send electrical signals directly to leg muscles and has enabled a patient with SPI to walk.
Whereas many prior studies relied on the use of a robotic arm to execute the patient's desired movements, this study demonstrates the control of the patient's own arm, Dr Do told Medscape Medical News.
"This accomplishment represents a drastic improvement in the patient's overall function. A person with a cervical ASIA A SCI is dependent on others for almost all activities of daily living. In this case, this patient's functional capacity essentially improved to 'modified independent' from a 'dependent' level."
Dr Do also noted that relying on FES rather than robotic arms can drastically reduce cost and overall size of the BCI system. As well, the use of FES may have many secondary health benefits for patients with SCI, such as improving cardiovascular health and reducing spasticity.
But he pointed out that there are still many challenges moving forward. For example, he said, the current electrode arrays used to acquire brain signals are transcranial.
"While they have been implanted for about 2 years with no major adverse effects, the risk of a central nervous system infection is always present. A similar infection risk also applies to the percutaneous FES electrodes."
Some patients with SCI may also find such a system aesthetically objectionable, added Dr Do.
"Significant engineering efforts will need to be overcome to design new systems that address these issues," he said. "It will also be necessary to determine if this system will work across a larger population of patients with SCI and if the system can maintain proper function over extended periods of time. A number of other improvements to increase the movement speed and accuracy will also be necessary."
The authors and editorial writer have disclosed no relevant financial relationships.
Lancet. Published online March 28, 2017. Abstract, Comment
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Cite this: Paralyzed Patient Moves With Brain-Controlled Stimulation - Medscape - Mar 30, 2017.
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