Doctors on Tuesday re-attached the portion of U.S. Sen. Mark Kirk’s skull that was removed after he suffered a stroke more than two weeks ago.

The roughly 4-inch-by-8-inch portion of Kirk’s skull was removed the day after he began experiencing symptoms, in order to make room for swelling caused by the stroke. In a statement Tuesday afternoon, Northwestern Memorial Hospital neurosurgeon Richard Fessler said that swelling “had subsided.”

Fessler previously told reporters that the bone was frozen sterilely, and described how it would be put back on.

“It’s a very simple procedure to go back to surgery, reopen the same incision, which isn’t hard to do because it hasn’t healed very far,” Fessler said during a January 24th press conference. “And you simply put the bone back in its position, connected with titanium plates and screws. And it’s a very firm reconstruction of the skull.”

Fessler in his statement Tuesday called this procedure a “milestone” in Kirk’s recovery.

On Monday, the doctor upgraded Kirk to good condition, from fair, and said the senator watched the Super Bowl on Sunday night.