Senator Joe Manchin of West Virginia left the seat empty to honor his colleague.
Kirk's doctor, Northwester Memorial Hospital neurosurgeon Richard Fessler, says the senator recently asked for his Blackberry and that Kirk is doing better than he expected at this point.
But Fessler says Kirk may never regain full movement, even after a long rehabilitation.
"He's breathing on his own. He's answering questions appropriately and quickly, so mentally he is doing well," Fessler said.
Fessler says the stroke affected Kirk's left side, particularly movement of his left arm and face, and currently the senator is speaking with a slight slur.
The 52-year-old remains in intensive care.