Sen. Mark Kirk (R-IL) underwent surgery Monday morning at Northwestern Memorial Hospital.
The Chicago Tribune reports that Kirk checked himself into the hospital on Saturday. "On Saturday, Senator Kirk checked himself into Lake Forest Hospital, where doctors discovered a carotid artery dissection in the right side of his neck," his office said in a statement.
Kirk's office continued, "He was transferred to Northwestern Memorial Hospital in Chicago, where further tests revealed that he had suffered an ischemic stroke. Early this morning, the senator underwent surgery to relieve swelling around his brain stemming from the stroke. The surgery was successful.
"Due to his young age, good health and the nature of the stroke, doctors are very confident in the Senator's recovery over the weeks ahead."
Kirk, 52, won President Barack Obama's vacated seat in the U.S. Senate in 2010.
Read more about Sen. Mark Kirk here.