Study gives new insight into the stages of recovery of hand muscle control after a stroke

May 17 2006

A Queen's study of stroke survivors gives new insight into the stages of recovery of hand muscle control after a stroke, suggesting that patients may benefit from different treatment strategies at different times during the recovery process.

Further, there are different post-stroke patient "profiles" instead of a single common profile for recovery of hand muscle control, according to findings published in the most recent edition of the Archives of Physical Medicine and Rehabilitation. This new discovery paves the way for more effective treatment for stroke survivors based on timing the treatment to the individual's recovery process.

"It is surprising how little is known about the process of physical recovery after stroke," says Brenda Brouwer, the lead researcher and a Rehabilitation Therapy professor. "This is the most comprehensive study we're aware of to date that looks at brain to muscle control outcomes and detailed hand function in stroke patients."

The study found that hand function is directly related to brain activity and that changes in the brain well after the stroke are paralleled by changes in physical ability. The less active the motor cortex -- the part of the brain controlling muscle function -- and the weaker the connections, the less able the stroke survivor is to use their hand muscles.

The findings offer insight into which of the measures currently used to evaluate signals from the brain to the muscle during stroke recovery are most strongly linked to muscle function and therefore which treatment strategies work best for particular patients at early and later stages of recovery.

Interventions including muscle vibration and electrical nerve stimulation in the limbs enhance the motor cortical output to target muscles; mental practice (patient's concentrating on moving the muscle) results in brain cells being more easily activated. With time, the cells in that part of the brain affected by the stroke progressively become more easily activated. The changes in the strength of the connections between the brain and muscles lead to improvements in the ability to use the muscles. "This is a good thing," says Brouwer, explaining that this indicates the circuitry responsible for mediating voluntary movement exists. "We can use this information to maximize a patient's recovery with ongoing therapy."

To examine hand muscle control, participants completed three tests including: tapping a single keyboard key with the index finger; picking up pegs one at a time and placing them into holes on a pegboard; and pushing with their index finger against a metal bar that measures force. Performance on these tests were linked to the ease with which brain cells that control muscle functions can be activated; how active the brain cells are at the time of testing; and the strength of the neural connections between the brain and the muscle.