(Updates with Mrs. Johnson statement, paragraph 9) By Thomas Ferraro and Richard Cowan WASHINGTON, Dec 14 (Reuters) - U.S. Sen. Tim Johnson of South Dakota was critically ill but stable on Thursday after brain surgery for a potentially deadly bleeding that could deprive his fellow Democrats of their razor-thin hold on the new Senate. Doctors said Johnson had needed no additional surgery and was having an uncomplicated recovery. A Johnson spokesman cautioned that could change and the next 24 to 48 hours was "a critical benchmark." Democrats narrowly wrested control of the U.S. Congress from President George W. Bush's Republicans in last month's elections, gaining a thin 51-49 majority in the Senate when it convenes in three weeks. If Johnson, 59, were to leave office, Republicans could gain control of the Senate, with Vice President Dick Cheney having the power to break tie votes. "We're all praying for a full recovery, we're confident that will be the case," said Senate Democratic leader Harry Reid of Nevada. Adm. John Eisold, attending physician of the U.S. Capitol, said Johnson had brain surgery for a rare and often fatal condition, and was in critical condition at George Washington University Hospital. Johnson underwent about five hours of surgery that ended shortly after midnight on Thursday. Eisold said later in a statement: "Senator Tim Johnson has continued to have an uncomplicated post-operative course. ... He has been appropriately responsive to both word and touch. No further surgical intervention has been required." The senator's wife, Barbara Johnson, said in a separate statement that Johnson was responding to her voice and following directions after the surgery and that by morning, he was reaching for and holding her hand. Eisold's announcement for the moment calmed the atmosphere in Congress where Johnson's condition had set off speculation over Democrats' hold on the new Senate coming into power in January. Dr. Richard Sullivan, a neurologist in Scarborough, Maine, said, "Often times the outcome is good." "If you survive the hemorrhage within the first day or two, that's great," added Dr. Richard Harvey of the Rehabilitation Institute of Chicago. Eisold said Johnson had an intracerebral bleed caused by a congenital malformation. SURPRISE DEVELOPMENT Johnson, who had prostate surgery in 2004, was hospitalized on Wednesday with stroke-like symptoms after he verbally stumbled and seemed confused in a radio interview with reporters. If the senator had to be replaced, South Dakota Republican Gov. Michael Rounds would name someone to finish the final two years of his six-year term. An election for a successor would be held in November 2008, when Johnson's term ends. If Rounds named a Republican, that would put the Senate at 50-50, with Cheney breaking any tie because he presides over the Senate. Bush's party could then continue to set the agenda in the Senate, undermining Democrats' hopes of more influence over his policies, particularly on the Iraq war. Democrats would still control the House of Representatives. Republican Sen. Trent Lott of Mississippi told Fox News: "My expectation and hope is that Tim will recover fully and come back and we'll go to work. You know I'd like to be in the majority, but I don't want to do it that way." The Senate historian's office said the only way the seat could change hands was if Johnson died or resigned, since even if incapacitated, he could remain in office. According to the historian, at least nine senators since 1942 had taken extended absences -- from a month to a few years -- for health reasons. Johnson's surgery involved a congenital arteriovenous malformation, which means he was born with a tangle of malformed blood vessels, in this case in his brain. When they burst and bleed, such tangles often kill patients before they can get to the hospital, but quick surgery can correct the defect. Brain damage can result from the pressure of the bleeding, just as it can from a stroke. (Additional reporting by Jeremy Pelofsky and Maggie Fox)
