Targeting the 'good' arm after stroke leads to better motor skills

HERSHEY, Pa. — Traditional stroke rehabilitation therapy focuses on restoring strength and movement to the more impaired side of the body, but a new randomized clinical trial has revealed that targeted therapy for the less-impaired arm significantly improved movement and control for stroke survivors. The trial, led by researchers from Penn State and the University of Southern California (USC), compared the new approach to the standard best-practice therapy currently in use. The team said the findings, published today (Feb. 2) in JAMA Neurology, demonstrate that motor skills in the less-affected arm can be improved even years after a stroke occurs and could meaningfully enhance quality of life.

“When we train the less-impaired arm, the individuals got better,” said Candice Maenza, project manager for the Neurorehabilitation Research Laboratory at the Penn State College of Medicine and first author of the study. “This could improve quality of life and reduce the burden of care for caregivers because stroke survivors with severe paralysis on one side rely on this arm for daily tasks like eating or dressing.”

A stroke — when there is an interruption of blood flow to the brain, either due to a blockage or burst blood vessel — can damage parts of the brain that control movement and disrupt communication between the brain and muscles, leading to paralysis, weakness or muscle spasticity that is often focused on one side of the body. Traditional physical rehabilitation focuses on the more impaired side of the body because the lack of strength and movement are so obvious that the arm on the other side of the body may retain function that appears normal, according to study co-author Robert Sainburg, Dorothy F. and J. Lloyd Huck Distinguished Chair in Kinesiology and Neurology at Penn State. Despite the appearance, though, Sainburg said the less-impaired side of the body often loses significant function, resulting in slow and poorly coordinated movements. That’s a challenge when that arm needs to compensate for the reduced ability of the more impaired arm.

“You’re already doing things mostly with one hand and that’s really hard in itself,” Sainburg said. “Now, the effect of the stroke on the less-impaired arm has added an additional deficit on top of that, say a 10-to-25% loss of motor coordination in the hand that has the most function. That’s a big deal in terms of what tasks you can perform for yourself and what tasks require assistance.”

Over the last three decades, however, Sainburg and his colleagues have discovered and demonstrated multiple ways that both sides of the brain contribute to movement, including planning and coordinating movement or correcting movement when an unexpected event occurs. Each side of the brain coordinates different aspects of movement, so an injury on one side of the brain will cause motor deficits in both hands.

While there has been considerable work to understand the performance and deficits of the so-called “bad” arm after stroke rehabilitation, there is no evidence-based intervention that has been shown to benefit the so-called “good” arm, according to the researchers. The research team wanted to know if targeted training of the less-impaired arm could lead to sustained improvements in motor performance in chronic stroke survivors with severe weakness or paralysis on one side of the body.

“This is the first project to use a rigorous randomized clinical trial design to investigate the use of ipsilesional limb training — training the less-impaired arm — in chronic stroke survivors with severe paresis,” said Carolee Winstein, professor emerita and adjunct faculty in biokinesiology and physical therapy at the USC and co-principal investigator of the study.

Conducted at Penn State and USC, the phase II randomized clinical trial builds on a prior pilot study by Sainburg and Maenza. Fifty-three people participated in the trial who were chronic stroke survivors and had experienced stroke at least three months prior and with some having had a stroke many years earlier. At the time of the study, they all had severe impairment in one arm, meaning that they couldn’t grasp and release with their “bad” hand and relied on their “good” hand for daily living tasks.

Participants were randomly assigned to either the treatment or control group and received rehabilitation therapy three times a week for five weeks. All participants were assessed before the start and end of the trial and at three weeks and six months after the end of the trial.

Twenty-five participants received targeted therapy for the less-impaired arm. This included dexterity training focused on real-world activities as well as virtual reality games. Individuals who had experienced a stroke on the left side of their brain performed a shuffleboard-like game where they reached quickly to strike a virtual puck. This activity relied on the brain’s ability to plan and coordinate movement, which is typically impaired after a left-hemisphere brain injury. Those who had experienced a stroke on the right side of their brain played a tracing game where they moved a cursor through various shapes, which required continuous adjustments. That type of precision movement is typically impaired after a right-hemisphere brain injury.

Twenty-eight participants were assigned to the control group and received standard, best-practice therapy for the more-impaired arm. This included warm-up stretching, therapeutic exercises and task-specific practice such as reaching for specific objects.

“What we're doing is remediation that was never done before,” Sainburg said. “We're changing the function of the less-impaired hand so that their activities of daily living can be more efficient.”

Sainburg explained that standard best-practice therapy does involve the less-impaired hand, but typically it is merely to compensate for the loss of use of the other hand during activities of daily living rather than restoring its previous capacity as much as possible.

At the end of the trial period, participants who received targeted training for the less-impaired arm demonstrated significant improvements in arm motor function compared to the control group. They completed a standard dexterity test — that includes tasks like picking up small objects, flipping cards and simulated feeding — 12% or nearly six seconds faster than when they started.

“Stroke patients might have been able to do things like fasten a button, but it took so much time to do it that it wasn't worth it to do it independently. By getting a little bit faster, it makes them want to try to do it by themselves,” Maenza said. “This can be life changing not just for the patient but also for their spouse or caregiver because the burden of care is reduced.”

These improvements persisted for at least six months after the therapy ended. The durability of the results may come from the snowball effect, according to Sainburg.

“The targeted intervention puts patients on what therapists call a virtuous cycle,” Sainburg said. “Once you get a little bit of function, you use it and things continue to improve.”

The researchers plan to continue to investigate how this type of targeted training could be combined with existing therapies and rehabilitation protocols to support everyday function.

“Our results open the door to further research directions such as multi-modal approaches where you combine ipsilesional limb training, as was done here, with training that targets both arms, where each side is controlled in unique ways by the nervous system,” Winstein said.

Other Penn State authors on the paper include Terrence Murphy, professor of public health sciences, and Nick Kitchen, postdoctoral scholar in neurology. Other authors on the paper include Jennifer Tanaka, physical therapist, USC; Jisung Yuk, research associate, Case Western Reserve University School of Medicine; and Rini Varghese, postdoctoral researcher, Johns Hopkins School of Medicine.

Funding from the National Institutes of Health’s Eunice Kennedy Shriver National Institute of Child Health and Human Development supported this work.

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