U.S. Sen. Mark Kirk was recovering from a stroke on Monday. Doctors say he suffered an ischemic stroke, the most common type of stroke, on the right side of his brain.

Stroke is a disease that affects the arteries leading to and within the brain. It is the No. 4 cause of death and a leading cause of disability in the United States.

For more information on the different types of stroke, the effects of a stroke, the warning signs and treatment, click here.