Washington ? Democratic Sen. Tim Johnson remained in critical condition but was described as recovering and holding his wife’s hand Thursday after emergency overnight surgery to repair bleeding inside his brain.

His sudden illness had raised questions over whether the Democrats would hold their newly won slim control of the Senate.

The South Dakota lawmaker, 59, was on “an uncomplicated postoperative course,” the U.S. Capitol physician said after visiting him Thursday afternoon. Johnson suffered a hemorrhage in his brain caused by a rare and sometimes fatal condition.

“He has been appropriately responsive to both word and touch. No further surgical intervention has been required,” said the physician, Adm. John Eisold. He had said earlier, “The senator is recovering without complication.”

Johnson was responding to the voice of his wife, Barbara, and following directions after the surgery, the senator’s office said in a statement. “He was reaching for and holding her hand.”

Johnson was stricken as Democrats prepared to take fragile 51-49 control of the new Senate when it convenes in three weeks. Democrats seized control of both chambers of Congress from Republicans in November midterm elections.

If Johnson were to leave office, a replacement would be named by South Dakota’s Republican governor, Mike Rounds.

A Republican appointee would create a 50-50 tie and effectively allow the GOP to retain Senate control because of Vice President Dick Cheney’s tie-breaking vote.

Johnson was rushed to George Washington University Hospital at midday Wednesday after becoming disoriented and stammering during a conference call with reporters.

Eisold, the Capitol physician, said doctors stopped bleeding in Johnson’s brain and drained the blood that had accumulated there. “It is premature to determine whether further surgery will be required or to assess any long-term prognosis,” Eisold said.

On Thursday afternoon, Johnson underwent an additional procedure to prevent blood clots. The procedure is standard after surgery, said Julianne Fisher, Johnson’s spokeswoman. Otherwise, she said, there were no new developments. “No news is good news,” she said.

Johnson’s condition, also known as AVM, or arteriovenous malformation, causes arteries and veins to grow abnormally large, become tangled and sometimes burst. The condition is often present from birth.

Johnson spokesman Noah Pinegar said the senator’s diagnosis was a surprise. “No one was aware of it, including Tim,” he said.

Sen. Harry Reid, D-Nev., who is to become majority leader when the new Senate convenes on Jan. 4, said: “We’re all praying for a full recovery. We’re confident that will be the case.”

Reid, who visited Johnson at the hospital Wednesday night and Thursday, told reporters the senator “really looks good.” However, Reid declined to provide any details of Johnson’s medical condition.

Politically, “there isn’t a thing that’s changed,” he said, adding that he was keeping incoming Senate Republican leader Mitch McConnell, of Kentucky, “totally advised” of developments.

Outgoing Senate Majority Leader Bill Frist, R-Tenn., visited the hospital Thursday afternoon.

Senate historian Donald Ritchie said senators serve out their terms unless they resign or die. He said there was precedent for senators remaining in the Senate even though illness kept them away from the chamber for long periods.