CHICAGO (AP) — Nearly a year after a stroke left him barely able to move the left side of his body, U.S. Sen. 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.