CHICAGO — Nearly a year after a stroke left him barely able to move the left side of his body, Senator Mark Kirk is expected to climb the 45 steps to the Senate’s front door this week — a walk that’s significant not just for Illinois’ junior senator, but also for medical researchers and hundreds of thousands of stroke patients.

It’s estimated only one-third of patients return to work after a stroke, said Dr. Elliot Roth, medical director of the Rehabilitation Institute of Chicago’s New Patient Recovery Unit and AbilityLab, where Kirk recovered.