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Stroke Victims Use Minds to Control Robotic Arms
Quadriplegics successfully test out new technology.
By Todd Neale, MedPage Today
Medically Reviewed by Robert Jasmer, MD
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WEDNESDAY, May 16, 2012 (MedPage Today) — Two stroke patients with no function in their arms were able to control robotic limbs by using their minds, according to preliminary results from Brown University.
"I just imagined moving my own arm and [the robotic] arm moved where I wanted it to go," said one patient known as "T2."
Using an "investigational neural interface system" — called BrainGate — the quadriplegics were able to direct robotic arms to touch and grab foam balls, according to Leigh Hochberg, MD, PhD, of Brown University in Providence, R.I., and colleagues.
Another patient was able to grab a bottle of coffee and drink through a straw, the researchers reported in the May 17 issue of Nature.
The patient, Cathy Hutchinson, MSNBC reports, was paralyzed nearly 15 years ago by a brainstem stroke. This new technology — the ability to make an object move just by imagining it would do so — is game-changing for patients with central nervous-system injury.
This was the first time since her stroke that she had been able to bring a vessel to her mouth and drink from it on her own, the authors wrote.
"Although robotic reach-and-grasp actions were not as fast or accurate as those of an able-bodied person, our results demonstrate the feasibility for people with [quadriplegia]," they wrote, "years after injury to the central nervous system.
"Though further developments might enable people with [quadriplegia] to achieve rapid, dexterous actions under neural control, at present, for people who have no or limited volitional movement of their own arm, even the basic reach and grasp actions demonstrated here could be substantially liberating, restoring the ability to eat and drink independently."
Hochberg and colleagues previously reported that patients with long-standing quadriplegia could use a neural interface system to move and click a computer cursor. Additional studies showed that able-bodied monkeys could use neural signals to move a robotic arm.
The BrainGate2 pilot clinical trial began enrolling patients to see whether similar results could be achieved in humans.
The researchers reported results from two participants — Hutchinson, known scientifically as "S3," and a 66-year-old man known as "T2." Both lacked function in all four limbs and could not speak because of a brainstem stroke. Hutchinson entered the study nearly 15 years after her stroke, and the man entered the study 5.5 years after the event.
In both patients, a 96-channel microelectrode array was implanted in the motor cortex, which controls movement. Hutchinson received her implant 5.3 years before the study and T2 received his 5 months before the study.
Neural signals detected by the electrodes were translated by an external computer and used to control two robotic arms — the DLR Light-Weight Robot III, which was designed by the German Aerospace Center as an assistive device, and the DEKA Arm System, which was designed as an advanced upper limb replacement for individuals with an arm amputation.
Both patients tried to use their brain signals to move the robotic arms to grasp foam ball targets flexible supports. Hutchinson performed 158 trials over four sessions and successfully touched the targets in 48.8 percent of DLR trials and 69.2 percent of the DEKA trials. T2, who used only the DEKA system, performed 45 trials in a single session and successfully touched the targets 95.6 percent of the time
Of the successful touches, Hutchinson was able to grasp the target 43.6 percent and 66.7 percent of the time with the DLR and DEKA systems, respectively. T2 grasped the target 65.1 percent of the time.
The robotic arms also showed promise in assisting in the activities of daily living. In four out of six attempts, Hutchinson used the robotic arm to grab a bottle of coffee, bring it to her mouth, drink out of a straw, and place the bottle back on the table.
"This was the first time since the participant's stroke more than 14 years earlier that she had been able to bring any drinking vessel to her mouth and drink from it solely of her own volition," the authors wrote.
"The use of neural interface systems to restore functional movement will become practical only if chronically implanted sensors function for many years," they added. "It is thus notable that S3's [Hutchinson's] reach and grasp control was achieved using signals from an intracortical array implanted over five years earlier."
Additional information to this story contributed by Everyday Health.
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