Sen. Mark Kirk (R - Ill.) has a "pretty good chance of continuing a very vibrant life," a doctor said Monday, hours after the Republican underwent surgery to relieve swelling around his brain from a stroke.
Kirk, 52, checked himself into Lake Forest Hospital on Saturday after telling his staff he wasn't feeling well, Kirk's office said in a statement. He was transferred to Northwestern Memorial Hospital in Chicago, where further tests revealed he had suffered an ischemic stroke.
"Sen. Kirk has had a stroke to the right side of his brain," Dr. Richard Fessler said Monday at Northwestern. "What that means is that it will affect his ability to move his left arm, possibly his left leg and possibly can involve some facial paralysis."
Kirk suffered swelling in his brain Sunday night, forcing doctors to take him into surgery to remove a four-inch-by-eight-inch portion of his skull.
While there may be some permanent physical consequences, Fessler said he was optimistic about the senator's mental recovery.
"Since it's the right side of the brain and not the left side of the brain, he's got a pretty good chance," he said. "Most of our cognitive functions -- that is, our ability to speak, understand and have higher order of thinking -- are located on the left side of the brain, and I believe that when we are all through this, the left side of his brain will be fine."
Kirk's aides said they'll continue to provide constituent services as they always have while the senator recovers.
However, Kirk will not be able to cast any votes in the Senate as long as he is unable to return to Washington, D.C.
Politicians from both sides of the aisle offered words of encouragement for the senator.
"Senator Kirk and I have served on different sides of the aisle, but the entire City of Chicago is by his side today," said Mayor Rahm Emanuel. "He remains in our thoughts and prayers as he recovers."
"He is young and in good physical condition and I have no doubt he will make a speedy recovery," said Sen. Dick Durbin. "I have reached out to his staff and offered to do anything I can to help with his Senate duties. Loretta and I will keep Mark and his family in our prayers.”
Illinois Comptroller Judy Baar Topinka said in a statement she was stunned and saddened by the news.
"If there is one thing I have learned about Mark over the years, it's that he is a fighter and relentless in his efforts to accomplish a goal," Topinka said. "Those attributes will serve him well in working toward a rapid recovery. My thoughts and prayers are with him."
In separate statements, Reps. Randy Hultgren, Robert Dold, Peter Roskam and Joe Walsh, as well as Illinois House Republican Leader Tom Cross and former Illinois Treasurer Alexi Giannoulias, who lost to Kirk in the campaign for Senate, expressed well wishes and their hopes for a "speedy recovery."
Gov. Pat Quinn said his thoughts and prayers were with Kirk and his family.
"We can all take comfort knowing that as a Navy commander, Sen. Kirk knows how to fight and he will fight through this to return to his work on behalf of the people of Illinois as quickly as possible," he said.
Illinois GOP Chairman Pat Brady called Kirk a "tireless fighter."
"I join all Illinoisans today in praying for Senator Mark Kirk and his family and staff. Mark has always been a tireless fighter in our military and in Congress, and I know that continues today with his recovery."
Republican presidential candidate Mitt Romney, who received Kirk's endorsement in the presidential campaign, said he was "extremely distressed" by the news.
"I wish him a speedy recovery and a swift return to the U.S. Senate chamber, so he can continue his important work for the people of Illinois and all the people of the United States," said Romney.
NBC Chicago has reached out to The White House seeking comment.