New game-based therapy retrains muscles after a stroke

A customized throw-back video game may offer a surprisingly futuristic path to stroke recovery. 

In a new study, Northwestern University scientists developed a 90s-style video game to help chronic stroke survivors regain lost arm function. While wearing a small device on their impaired arm and using a laptop computer, players use their arm muscles to complete tasks such as flying a helicopter around the screen to hit a moving target. The muscle retraining helps separate the brain's uncoordinated movement signals, enabling muscles to work independently again.

After six weeks of the game-based therapy, chronic stroke survivors improved arm function by as much as 7.8 times as much as those in the control group. They also kept improving even after stopping the therapy. Being able to play the game at home allowed for better access to the therapy and increased reps. Participants performed more than 300 reps per day compared to normal physical therapy in a clinic where they might get only 30 reps three days per week, said co-corresponding author Dr. Marc Slutzky.

Participants also said the game made rehab more fun and engaging. One participant wrote in a survey response, "the whole experience was enjoyable and helpful." Another person wrote, "Definitely I benefitted from the game, both physically and mentally." 

We've been working on this approach to stroke rehab for 15 years, so hearing participants report they're regaining movement in their arm and that it's really helping them in their daily life is so rewarding."

Dr. Marc Slutzky, professor of neurology and neuroscience, Northwestern University Feinberg School of Medicine and Northwestern Medicine physician

The study will be published June 9 in the journal Neurorehabilitation and Neural Repair.

Patients in the study experienced moderate to severe arm impairment (only able to slightly move their arm and extend their elbow) from a stroke at least six months prior to beginning the study. The average patient was 6.4 years out from their stroke while some were 12 years out.

Most stroke rehab today focuses on helping the stroke survivors by having them perform daily tasks, which often leads to survivors compensating for their impaired arm function. For example, leaning forward with the whole body to reach for an object rather than reaching for it with just the arm. While this technique is useful, it doesn't directly aim to improve the movement of the arm. This study, however, found that the therapy improved the range of motion in the participant's arm during reaching tasks, as well as their ability to perform daily activities. 

"Here we're doing something different," Slutzky said. "We're treating the impairment directly and measuring how much the actual arm improved in addition to performing certain functions. We found our conditioning really caused their improvement."

How the gamified rehab works

After a stroke, the brain's movement signals can become disrupted, causing muscles to fire in an uncoordinated way. Called "abnormal co-activation" or "abnormal coupling," this phenomenon makes it difficult for stroke survivors to extend an arm forward with a straight elbow. For instance, someone might try to reach out straight ahead but their elbow bends because their biceps activate at the wrong time.

Called MINT (myoelectric interface for neurorehabilitation) conditioning, the system - designed by a high school student and other members of the Slutzky Neuroprosthetics Lab - identifies abnormally coupled muscles and retrains them to move independently again. To play the game, a stroke survivor wears a small device attached to the impaired arm either at home or in the lab. Then, they use electrical activity of each of the coupled muscles (called electromyograms, or EMGs) to move a cursor in perpendicular directions in a customized video game. For example, their biceps might move the cursor to the right and their deltoids move the cursor up. When the muscles are coupled, the cursor thus moves on a diagonal (up and right, like turning both dials on an Etch-a-Sketch). 

"We have them hit targets that are farther and farther away from that diagonal until they have to separate their muscles and can only hit it by activating one of the muscles and not the other," Slutzky said. The more the muscles decouple, the higher the person's score in the game. 

How the study worked 

The study was a randomized, sham-controlled trial, a rigorous test that evaluates the true effectiveness of a device. Trial organizers divided a group of 59 stroke survivors into three experimental groups and one sham control group. They trained for six weeks total, playing the game for 90 minutes a day, five days a week at home and one day in the lab. 

Each experimental group received a different kind of training regimen to learn how to decouple their co-activating muscles. They first focused on the muscles that were co-activating the most and then moved to the less impaired muscles: 

• The first group trained two muscles at a time, changing the muscles every two weeks
• The second group trained two muscles at a time, changing every two weeks, and were also asked to move their arm as far as they could in the correct direction of the activated muscle.
• The third group was first trained on two muscles at a time, then added a third muscle mapped into the screen (in 3D) when the first two were decoupled. The researchers changed which muscles were being trained every three weeks.
• The fourth group (sham control) followed the same schedule and played a simpler version of the game with just one muscle at a time and did not receive instructions on how to decouple their muscles. 

"We wanted to make the sham group as similar as possible, having them do a similar amount of exercise to what the other groups were doing to receive the motivational and exercise factor of these games but not give them the key ingredient, which was the decoupling," Slutzky said. 

A breakdown of the findings

The study found every group, including the sham group, improved from baseline to the end of the training period, and all experimental groups significantly improved by 4.5 times as much as sham, which was a clinically important amount. The scientists also saw a positive correlation between the amount that co-activation was reduced and the amount that movement improved. The three-muscle group improved significantly more than (7.8 as much as) the sham group at the end of training, while the other two experimental groups did not. 

"It seems most likely that group three improved the most because they received an extra week of training on the muscles that were causing the most impairment," Slutzky said. 

The study measured this improvement using the Wolf Motor Function test, a timed test that measures function in daily activities, such as lifting an arm to a tabletop, straightening an arm, folding a towel, etc. The scientists saw improvements in the speed at which the participants in the experimental groups could complete these tasks. They also saw improvements in the range of motion of the participants' arm during reaching tasks in the experimental groups, but not in the sham group. Participants also kept improving function one month after stopping the therapy.

What's next? 

The team, along with Northwestern bioelectronics pioneer John A. Rogers, is working to make the game's wearable device completely wireless. They're also upgrading the games to be more engaging. Lastly, they plan to test it on stroke survivors' legs. 

Abed Khorasani, Cynthia Gorski, Prashanth Prakash and Richard Harvey, from Northwestern, and Jinsook Roh, from University of Houston, are among the co-authors on the study.