Illinois Republican Sen. Mark Kirk is recovering at a Chicago hospital after suffering a stroke over the weekend, his office announced Monday morning.

Kirk, 52, is a former five-term House member who in November 2010 won election to the Senate seat formerly held by President Obama.

Kirk’s office said that on Saturday, the senator “checked himself into Lake Forest Hospital, where doctors discovered a carotid artery dissection in the right side of his neck.”

He then was transferred to Chicago’s Northwestern Memorial Hospital, where doctors discovered that he had suffered an ischemic stroke, which occurs when an obstruction in an artery prevents blood flow to the brain.

“Early this morning the Senator underwent surgery to relieve swelling around his brain stemming from the stroke,” Kirk’s office said. “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.”

UPDATE, 1:22 P.M.: Richard Fessler, a neurosurgeon at Northwestern Memorial Hospital, told reporters at a news conference Monday afternoon that the physical effects of Kirk’s stroke could be long-lasting.

“I think his prospects for a full mental recovery are pretty good,” Fessler said of Kirk. “I think the prospects for his full physical recovery, particularly on the left side of his body, are not great. . . . I think the use of his left arm is going to be very difficult. I’m hopeful for the use of his left leg.”

Fessler added that to allow Kirk’s brain to swell without being compressed, doctors removed a four-by-eight-inch piece of the senator’s skull over the part of his brain that was swelling.

For the next several days, Fessler said, Kirk will be in intensive care, where doctors will be treating him to keep the pressure on his brain as low as possible.

Asked when the senator might be back to work, Fessler said it’s “way too soon to try and predict.”

“It’s not going to be days,” Fessler said.