Sahil Kapur January 23, 2012, 12:23 PM

Updated 1:47 p.m. ET

Sen. Mark Kirk (R-IL) suffered a stroke over the weekend and is recovering after successful surgery Monday morning, his office said. Kirk’s physician told reporters that the senator will remain in intensive care for several days, but is expected to make a full mental recovery — which could take weeks or longer — and resume his duties in Congress.

“His prospects for a full mental recovery are good,” Dr. Richard Fessler, the physician who performed the surgery, told reporters in Illinois. “His prospects for a full physical recovery, particularly on his left side, are not great.”

He said Kirk’s stroke was on the “the right side of his brain,” and could “affect his ability to move his left arm and possibly his left leg.” He added that it might also result in some facial paralysis.

Fessler said it’s “way too soon to try and predict” how much time he may need to take off from legislative business — but it could be weeks or months, not days. “Senator Kirk’s job is cerebral,” he added. “And I believe the functions he requires to do his job will be fine.”

“We do not know what caused the stroke,” the doctor said. He added that the senator “was beginning to deteriorate neurologically” after checking in to the hospital on Saturday, “which forced us to go into surgery Monday morning.” It lasted 3 hours.

Fessler said Kirk is briskly responsive to commands and recognizes those around him when taken off sedation, but will remain in intensive care “over the next several days.”

Kirk’s spokesperson announced the news in a statement Monday morning:

On Saturday, Senator Kirk checked himself into Lake Forest Hospital, where doctors discovered a carotid artery dissection in the right side of his neck. 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, was elected to the Senate in November 2010, after first having won a seat in the House in 2000. His Senate seat is the one Barack Obama vacated after winning the presidency, and was held in the interim by Roland Burris.

Kirk enlisted in the navy reserve in 1989 and was called to active duty during the 1999 NATO action over Kosovo. He currently holds the rank of commander. He is currently unmarried, having finalized a divorce of an eight-year marriage in 2009.

Mark Kirk