A stroke of insight

By Alisa Kim

Stroke—the sudden loss of brain function due to lack of blood flow to the brain or uncontrolled bleeding in the brain—is the third leading cause of death in Canada. Each year there are 50,000 new cases of stroke here. As the country's aging population steadily grows, more people will be living with the effects of stroke, including motor impairment, which afflicts 75% of stroke survivors. 

Dr. George Mochizuki, a scientist in the Brain Sciences Research Program at Sunnybrook Research Institute, hopes to ease the burden of stroke on survivors and their caregivers by developing new rehabilitation strategies to enhance motor recovery. One way he is doing this is by studying the physiological changes that occur in the brain and the muscles following a stroke.

"We recognize stroke as a brain injury, but what's less often considered is the extent to which stroke impacts muscle. For people to interact with their environment and perform everyday activities, they need their muscles to work. We need to understand what changes occur in stroke-affected muscles and to develop appropriate strategies to help enhance recovery," he says.

Although disuse accounts for some of the muscle changes that occur after stroke, other changes, including alterations in the force-generating capacity of the muscle and changes in the way muscles use energy, also contribute to the extent of disability, says Mochizuki, who is also a scientist at the Heart and Stroke Foundation Centre for Stroke Recovery . "These are changes that are unique to stroke. These markers, in conjunction with brain-level changes, reveal characteristics of motor dysfunction that can be targeted with therapy."

To help Mochizuki characterize changes in brain and muscle properties, the Canada Foundation for Innovation awarded him $111,113 through its Leaders Opportunity Fund. He will use the award to buy systems for stimulation and testing of the brain and stroke-affected muscles, as well as muscle training equipment.

He will use transcranial magnetic stimulation to measure changes in brain excitability in people who have had a stroke, which indicates the strength of connection between brain and muscle. Mochizuki will also use muscle stimulation equipment to engage muscles that are affected by stroke. "By applying peripheral stimulation, we can get those muscles active, which may induce changes in brain activity as a result that contribute to future activation of these muscles," he says.

He will also use exercise equipment to improve range of motion and speed of movement in the arm and leg muscles of study participants with the aim of effecting longer-term change.

One of his goals is to determine whether motor recovery can be enhanced through different combinations of therapies. He will investigate whether pairing certain drugs with exercise or brain stimulation yields better results than one type of therapy alone. For example, Mochizuki is investigating the use of Botox—a drug that reduces muscle tightness in people who experience spasticity after stroke—in combination with different types of therapy.

He says that having precise measurements of brain and muscle changes following a stroke will enable practitioners to fine-tune treatment according to individual need. "If we can be really specific in our understanding of what's happening at both of those sites, we'll also have the ability to deliver therapies that are specific to the individual's capacity to generate movement. There's a lot of utility in having that information so that we can develop therapies that are optimized to the individual patient."