Although patients are known to recover from paralysis of one side of the body after a stroke, the mechanism by which this recovery occurs is not understood. But a Columbia Presbyterian neurologist has used an imaging technique called functional MRI (fMRI) to observe the parts of the brain activated in this recovery process, shedding light on how the brain reorganizes itself to restore motor function.
Dr. Randolph S. Marshall, assistant professor of neurology at Columbia University College of Physicians & Surgeons and Attending Physician at the Columbia Presbyterian Medical Center of NewYork-Presbyterian Hospital, compared eight patients who had suffered strokes with six healthy controls. The stroke patients had fMRIs within the first few days after the stroke occurred and at again three to six months after the stroke. Their brains were imaged as they performed a simple motor task using the weak hand.
Paralysis occurs on the opposite side of the body from the site of a stroke, because the left hemisphere of the brain generally controls the right side of the body and vice versa. In a healthy person, the right side of the brain is activated while a person performs a task with his or her left hand. In Dr. Marshall’s study, the stroke patients showed heightened brain activity on the same side of the body as the hand that they were using to perform the tasks. But as they began to recover full use of the paralyzed hand, the opposite side of the brain– in the hemisphere where the stroke occurred– began to show more and more activity.
Dr. Marshall’s results suggest that as the brain recovers from stroke, nerve networks within both hemispheres reorganize themselves in a dynamic fashion to compensate for the injury. The study was published in the March 2000 issue of the journal Stroke.