An Optimal Period for Motor Recovery After Stroke

Post by Megan McCullough

What's the science?

Stroke recovery studies have used rat models to investigate the impact of motor training at different time periods after the brain injury. These studies have found that adult rats have critical periods of time after stroke where intensive motor retraining leads to the recovery of motor function. These post-injury critical periods are similar to periods of time in early development where there is increased neural plasticity and the brain is more sensitive to external stimuli. Previous research has not uncovered whether these critical periods also occur in human stroke patients. This week in PNAS, Dromerick and colleagues extended these rat model findings to investigate whether human stroke patients also had windows of time after the stroke that coincided with increased sensitivity to intensive motor training.

How did they do it?

Stroke participants received 20 hours of motor therapy in addition to their standardized therapy at either less than 30 days post-stroke (acute), 2-3 months post-stroke (subacute), or 6 months or more post-stroke (chronic). The control group received only standard rehabilitation. The authors conducted pre-tests and post-tests for each participant using the Action Research Arm Test (ARAT), which measures upper extremity movement. The treatment was administered in a controlled clinical setting to create a realistic set of conditions for human stroke patients.

What did they find?

The researchers observed a relationship between the time after the stroke occurred and the rehabilitation therapy specific to this study. Patients in the subacute group showed a significant increase in motor function compared to controls. Patients in the acute group also showed a significant increase in motor function compared to controls; however, it was a smaller improvement than the subacute group. The patients in the chronic group did not show significant improvement in motor function compared to controls. This demonstrates that humans do have critical periods of time after brain injury where targeted treatment leads to increased improvement of motor abilities. 

What's the impact?

This study is the first to show that there are specific windows of time after brain injury where intensive motor therapy leads to an increased recovery of motor function in human stroke patients. Intensive motor therapy performed 2-3 months after stroke led to greater upper extremity motor recovery compared to patients who received this same therapy during different time windows after the stroke and compared to patients in the control group who received standard motor rehabilitation. This study has implications for the development of post-stroke treatments and further validates the translation of previous stroke research in animals to human brain recovery research.

Dromerick et al. Critical period after stroke study (CPASS): A phase II clinical trial testing an optimal time for motor recovery after stroke in humans. PNAS (2021). Access the original scientific publication here.