Susan Jeffrey

November 18, 2013

DALLAS, Texas — Researchers have developed a low-cost virtual reality platform that they hope will allow patients with stroke to regain some of their lost arm and hand function by practicing movement in paralyzed limbs by using only their thoughts.

Unlike other rehabilitation approaches that rely on robotic devices or a live therapist to move the patients' affected hand or arm as they imagine trying to move it, this strategy allows patients to train at the terminal on their own time. The researchers hope this type of training will enhance patients' participation in their own recovery.

Alexander J. Doud, MS, chief technology officer at the biomedical engineering and human factors design firm Synaptic Design, and a medical student at the University of Minnesota, Minneapolis, presented their findings here at the American Heart Association (AHA) Scientific Sessions 2013.

"So what we can expect in the future is using these low-cost and affordable components to create something that's going to be able to enter the home, it's going to minimize the care burden on providers, and hopefully, will promote engagement with the rehabilitation process in stroke survivors," Doud told a press conference here.

High Cost, High Stakes

The cost of acute and long-term management of stroke is high; the National Stroke Association estimated these costs for 2012 at around $73.7 billion, the researchers point out. Rehabilitation relies heavily on constraint-induced movement therapy, where a provider moves the arm, and the patient is encouraged to imagine making the motion of the arm that is being moved by someone else.

Virtual reality brain-computer interface for stroke rehabilitation

"What we know is this is expensive," Doud said. "It requires maintenance, it requires meeting with the provider, and sometimes the patient can kind of 'check out,' because whether or not they're actually thinking the appropriate type of thoughts, thinking about moving that arm."

In this pilot study, the researchers present proof of concept of their system that uses electroencephalography readings acquired at 1000 Hz using a 64-channel array cap. He noted, however, that a less expensive 4-channel cap would be sufficient in practice to get the readings required.

"What we're trying to do is create an immersive virtual reality experience that not only allows them to control something on a computer screen, but also something that's meaningful, that's going to target more intentional activation of those neural populations that have been shown in the literature to promote recovery," he noted.

In this study, the system was used by 6 patients with a history of basal ganglia or cortical stroke with residual unilateral hemiparesis and 4 healthy age-matched controls. The aim was to see whether the patients could learn to control the movement of a 1-dimensional standard cursor image or of a virtual cup using 3-dimensional (3D) virtual reality photorealistic human hands.

The patients sat at the terminal and viewed the hands using 3D anaglyph glasses to create the illusion that they were seeing their own arms through the lid of the box, similar to mirror therapy boxes that have been used to help address phantom pain in amputees, Doud noted. "It's important to note that the degree of cortical activation the subjects produced had an immediate feedback on how fast, how much, and to what degree these virtual reality hands reached out."

All participants were tested at random on both sets of images, in three sessions of ten 3-minute trials, for their accuracy and performance manipulating the images.

"What we found was that subjects could control this system with high accuracy," Doud told Medscape Medical News, up to 81% accuracy in some but not all cases, similar to what was achieved with the standard cursor task (87.4% accuracy).

In addition, "many subjects found it very gratifying to be able to see their thoughts and actions manifested in a visual feedback of success for them. So it was an engaging process that we think was something that they would want to do over time."

The visual representation is also a less abstract concept to explain to some older patients, who may already have some cognitive impairment, he noted.

Whether or not the training will actually result in physical rehabilitation is "beyond the scope of this paper," which reports on an initial validation and proof-of-concept study, Doud added, but other research has shown the benefit of motor imagery in promoting recovery after stroke. The researchers' next step is a longer-term study in this patient population using the system to see whether it will translate into recovery of function.

Innovative Approach

Commenting on these findings, Ralph Sacco, MD, American Heart Association past president, Olemberg Family Chair in Neurological Diseases, Miller Professor of Neurology, Epidemiology & Public Health, Human Genetics, and Neurosurgery; and chairman of the Department of Neurology at the Miller School of Medicine at the University of Miami, Florida, called the study small but innovative, using a brain-computer interface that improve rehabilitation after stroke.

"This approach they were using may have potential application if proven in larger numbers of stroke patients," Dr. Sacco said in a statement.

"This kind of brain-computer interface is a way to help to train the brain to recover and improve motor function," he added. "Although we don't have proven effective therapies for motor recovery of function after stroke, it has been shown that physical therapy and more physical therapy — and aggressive physical therapy — can improve outcomes even late after a stroke."

The study was funded by the National Science Foundation and the National Institutes of Health. The authors have disclosed no relevant financial relationships.

American Heart Association (AHA) Scientific Sessions. Abstract #18886. To be presented Monday, November 18, 2013.

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